Hayward Fault Zone

The Hayward Fault Zone is a geologic fault zone capable of generating destructive earthquakes. This fault is about long, situated mainly along the western base of the hills on the east side of San Francisco Bay. It runs through densely populated areas, including Richmond, El Cerrito, Berkeley, Oakland, San Leandro, Castro Valley, Hayward, Union City, Fremont, and San Jose.
The Hayward Fault is parallel to the San Andreas Fault, which lies offshore and through the San Francisco Peninsula. To the east of the Hayward lies the Calaveras Fault. In 2007, the Hayward Fault was discovered to merge with the Calaveras Fault east of San Jose at a depth of , with the potential of creating earthquakes much larger than previously anticipated. Some geologists have suggested that the Southern Calaveras should be renamed as the Southern Hayward.
North of San Pablo Bay is the Rodgers Creek Fault, which was shown in 2016 to be linked with the Hayward Fault under San Pablo Bay to form a combined Hayward-Rodgers Creek Fault that is 118 miles (190 km) long, stretching from north of Healdsburg through Santa Rosa down to Alum Rock in San Jose. Another fault further north, the Maacama Fault, is also considered to be part of the "Hayward Fault subsystem".
While the San Andreas Fault is the principal transform boundary between the Pacific Plate and the North American Plate, the Hayward-Rodgers Creek Fault takes up its share of the overall displacement of the two plates.
Tectonic setting.
The Pacific Plate is a major section of the Earth's crust, gradually expanding by the eruption of magma along the East Pacific Rise to the southeast. It is also being subducted far to the northwest into the Aleutian Trench. In California, the plate is sliding northwestward along a transform boundary, the San Andreas Fault, toward the subduction zone. At the same time, the North American Plate is moving southwestward relative to the Earth's core, but southeastward relative to the Pacific Plate, due to the latter's much faster northwestward motion. The westward component of the North American Plate's motion results in some compressive force along the San Andreas and its associated faults, thus helping lift the Pacific Coast Ranges and other parallel inland ranges to the west of the Central Valley, in this region most notably the Diablo Range. The Hayward Fault shares the same relative motions of the San Andreas. As with portions of other faults, a large extent of the Hayward Fault trace is formed from a narrow complex zone of deformation which can span hundreds of feet in width.
The transform boundary defined by the San Andreas Fault is not perfectly straight, and the stresses between the Pacific and North American Plates are diffused over a wide region of the West, extending as far as the eastern side of the Sierra Nevada Mountains. The Hayward Fault is one of the secondary faults in this diffuse zone, along with the Calaveras Fault to the east and the San Gregorio Fault, west of the San Andreas.
The complete fault zone, including the Rodgers Creek fault, is divided by seismologists into three segments – Rodgers Creek, Northern Hayward, and Southern Hayward. It is expected that these segments may fail singly or in adjacent pairs, creating earthquakes of varying magnitude. The Association of Bay Area Governments (ABAG) in concert with other government agencies has sponsored the analysis of local conditions and the preparation of maps indicative of the destructive potential of these earthquakes. The various ABAG maps shown below represent some of the more likely possible combinations.
While there are indications that a substantial earthquake on a nearby parallel fault can release stress and so also decrease the near-term probability of an earthquake, the opposite appears to be true concerning sequential segments. A release on a major segment can substantially increase the likelihood of an earthquake on an adjacent fault segment, increasing the likelihood of two major regional earthquakes within a period of a few months.
Rodgers Creek Fault Zone.
The connection between the Rodgers Creek Fault Zone and the Hayward Fault Zone was unclear until 2015 when a survey of the floor of San Pablo Bay found that the ends of the two faults were smoothly linked between Point Pinole and Lower Tubbs Island. An alternate prior hypothesis suggested that the Hayward Fault and Rodgers Creek Fault were probably connected by a series of "en echelon" fault strands beneath San Pablo Bay. The new finding means that the Rodgers-Hayward system together could produce a quake with a magnitude as high as 7.2. It is also considered possible that a major seismic event on either fault may involve movement on the other, either concurrently or within an interval of up to several months. The Association of Bay Area Governments has prepared ground shaking maps that include a possible concurrent scenario (these are shown below).
In October 2016, scientists found definitive evidence that the Rodgers Creek Fault and the Hayward Fault are linked together under San Pablo Bay. A simultaneous rupture of the connected Hayward-Rodgers Creek Fault – about 118 mi (190 km) long from just north of Healdsburg down to Alum Rock in San Jose – could result in a major earthquake of magnitude 7.4 that "would cause extensive damage and loss of life with global economic impact". It has been suggested that the name "Rodgers Creek Fault" be retired and that the entire 118 mi (190 km) fault be known as the "Hayward Fault".
Calaveras Fault.
The Calaveras Fault is continuous from the Sunol area south to Hollister. It was long believed that there was no connection between the Hayward Fault and the Calaveras, but geological studies (particularly the examination of very small and deep earthquakes) suggest that the two may be connected. If true, this link would have significant implications for the potential maximum strength of earthquakes on the Hayward, since this strength is determined by the maximum length of the fault rupture and this rupture could extend beyond the juncture point and so include some portion of the Calaveras. (This potential is not shown in the shake intensity maps shown below.)
Earthquakes.
The largest quake on the Hayward Fault in "recorded" history occurred in 1868, with an estimated magnitude of 7.0. It occurred on the southern segment of the fault, receiving its name (some decades later) from the nascent town of Hayward where it was determined the quake's epicenter was located. However, the 1868 quake caused much damage throughout the then sparsely settled Bay Area, including the city of San Francisco. In fact, the 1868 event became known as the "Great San Francisco earthquake" until the larger tremor in 1906.
Many seismologists believe that the 1906 San Francisco earthquake, which occurred on the San Andreas fault, reduced the stress on many faults in the Bay Area including the Hayward fault, creating an "earthquake shadow": a quiescent period following a major earthquake. Since the 1906 San Andreas event there have been no moderately strong earthquakes on the Hayward fault as were seen before that earthquake. It also appears likely that this quiet period in the earthquake shadow is ending, as projected by the rate of plate motion and the stress state of other faults in the region.
The 1868 earthquake occurred well before the East Bay region was extensively urbanized. The following year, in 1869, the William Meek Estate became one of the first developments in the area, built on 3,000 acres (12 km²) in what became known as the Cherryland district of Eden Township. Recent renovations of the Meek Mansion have revealed that with the 1868 earthquake still fresh in minds of residents of the time, some unusual diagonal bracing was built into the original construction. Although its magnitude was less than the 1906 San Francisco earthquake, the intensity of shaking experienced in the Hayward area may have been greater than in 1906 due to the proximity of the Hayward Fault.
Earlier earthquakes have been detected by trench exposure and associated radiocarbon dating. Combined with the historic record, the last five major events were in 1315, 1470, 1630, 1725, and 1868, which have intervals of about 140 years (note that 2018 is 150 years from the major 1868 event). The longest time was the 160-year period between 1470 and 1630. In 2028, it will have been 160 years since the 1868 event.
Probability of future activity.
United States Geological Survey (USGS) scientists state that a major earthquake occurring on the zone is "increasingly likely". When the next major earthquake occurs on the fault, damage will be catastrophic. More than 1.5 trillion U.S. dollars in property exists in the affected area, and more than 165 billion US dollars in damage would likely result if the 1868 earthquake were to reoccur. Since the fault runs through heavily populated areas, more than 5 million would be affected directly. Water could be cut off to 2.4 million people living in California's San Francisco Bay Area.
For the thirty years following 2014, the probability of there being one or more magnitude 6.7+ earthquakes on the Hayward Fault during that time frame was estimated at 14.3 percent. This is compared to 6.4 percent for the San Andreas Fault, which can have larger earthquakes but is farther away from a significant portion of the urbanized parts of the Bay Area. Earlier (January 2008) assessments suggest that the Hayward, Rodgers Creek, and Calaveras faults may be more likely to fail in the next few decades than previously thought.
The 140th anniversary of the 1868 event was in 2008, and the average time between the last five major events is also averaged at 140 years. Recent estimates of the damage potential of a major Hayward Fault earthquake by a professional risk management firm indicate the potential for huge economic losses, of which only a small percentage is insured against earth movement. (Earthquake insurance is not only quite expensive, it tends to be burdened with large deductibles – at least 15 percent).
Depending upon seasonal weather conditions at the time of a major event a seismic event could be followed by urban wildfires compounded by damage to water systems or massive landslides in saturated soils. In addition to direct damage the effects on commerce due to damaged infrastructure would also be substantial. Experience with large area urban destruction such as caused by earthquake, hurricane, and firestorms has shown that complete rebuilding can take up to a decade, owing to various factors.
The progressively more severe reports and estimates of event probability and consequences have awakened a broad interest in training people for emergency response. It is becoming widely understood that professional fire fighting, police, and medical services will be overwhelmed by a major event and that neighbors will have to assist each other as best they can. Several jurisdictions in the affected area have implemented volunteer Community emergency response team programs to augment the professional response services.
In 2012, USGS scientists said the fault is due for another magnitude 6.8 to 7.0 earthquake, with the California Geological Survey concurring, stating they believe there is a 31 percent chance of a magnitude-6.7 earthquake or greater along the Rodgers Creek-Hayward Fault in the next 30 years.
In March 2015, the United States Geological Survey released "UCERF3: A New Earthquake Forecast for California's Complex Fault System". The UCERF3 represents the best available science to date, and it now considers "multifault ruptures" and "fault readiness", in addition to historical seismicity, in the calculus of earthquake forecasting. The upshot, for those who live in the San Francisco Bay Area, is that experts say there is a 72% chance of experiencing a magnitude 6.7 or greater earthquake in the next 30 years. Moreover, they have a 51% chance of a M≥7 (threshold to be considered a "major" quake), a 20% chance of a M≥7.5 and a 4% chance of a M≥8 (a "great" quake) when all the mapped faults in the region are taken in to account.
Fault effects.
Fault creep.
The surface of the fault is creeping at less than 0.5 cm (0.2 in) per year in the regions of concern. Extreme southern regions of the fault are creeping more quickly, perhaps sufficiently to prevent fault rupture there, but mostly the creep is insufficient to relieve the accumulating forces upon most of the fault and so will not prevent a large earthquake. The creep is sufficient to displace roads, curbs, and sidewalks and so visibly reveal the surface trace in many locations. Creep damage to asphalt road surfaces will usually appear as a series of echelon cracks. Creep effects may be seen also in older structures crossing the fault, some of which have been fitted with expansion joints to accommodate this slow motion.
Earthquake shaking.
The magnitude of an earthquake, as indicated on a seismic scale, is roughly proportional to the length of the rupture, while the ground motion in the region surrounding the fault is highly dependent upon the local soil conditions, somewhat upon the distance and relationship to the progression of the fault rupture, and (as recently recognized in the 1989 Loma Prieta earthquake) reflected energy from deep discontinuities in the Earth's structure. The area affected by an earthquake is also dependent upon the density and uniformity of the soils surrounding the fault.
Bayside soil conditions.
The Hayward fault is considered to be particularly dangerous due to the poor soil conditions in the alluvial plain that drops from the East Bay Hills to the eastern shoreline of San Francisco Bay. At the lower elevations near the bay the soil is mostly water saturated mud and sand, placed in the early 20th century as fill in marsh areas. This soil tends to amplify the effects of an earthquake and so producing significantly greater ground motion. Additionally, the soil itself can fail, turning into a liquid mud from the agitation, a mud unable to support buildings erected upon once-firm soil. This region is also covered with dense low-rise urban development, most of which was built soon after the 1906 San Francisco earthquake, and long before even moderately earthquake resistant construction practices had been developed in the late 1920s.
Further improvement in the construction of resistant structures and the development of retrofitting method have only recently been developed, largely in response to the effects of the 1971 Sylmar, 1989 Loma Prieta, and 1994 Northridge events in California – none of which were hugely catastrophic, but each of which caused loss of life in structures not thought to be vulnerable, and so increased public, engineering, and government awareness of the need for specific remediations and construction methods required for improved life safety.
Although many structures have undergone seismic retrofitting there are a large number of dangerous unreinforced masonry (mostly brick) structures and chimneys, which can be extremely hazardous to occupants in a large earthquake, and a large number of buildings which are either not bolted to their foundations or with soft stories that are insufficiently resistant to shear forces. Foundation and soft story weaknesses are easily remediated in most cases, but this is only effective if the work is competently done, with proper attention to minor details such as nailing patterns and proper connections. Local surveys of recently completed work have exposed deficient workmanship in a number of cases involving household retrofits.
Landslides.
There are many small active landslides and evidence of numerous large archaic landslides in the Berkeley Hills. Such areas may be stable only under present conditions. There is the possibility that a large earthquake could trigger very large earth flows, particularly if the soils are seasonally saturated with water, possibly rendering extensive areas unbuildable. (See the Virtual tour – Google Earth Flyover below.)
Potentially impacted structures and features.
Many structures near the bay shore on either side would probably be severely affected by either a major Hayward Fault rupture or a nearby San Andreas Fault rupture. Severe effects were seen in both Oakland and northern San Francisco from the 1989 Loma Prieta earthquake, even though this event was not extremely large and was centered a significant distance away in the Santa Cruz Mountains. Most of the severe effects of that event were due to poorly responding soil conditions and design deficiencies in large structures. Only a portion of the structural deficiencies in the larger area have been addressed, and the surface motion effects of a large event are likely to be far more severe than seen in the Loma Prieta event.
Freeways and overcrossings.
Many modifications have been made to freeway structures to reduce life hazards during seismic events. Significant adverse conditions remain which can cause disruption with possible long-term effects upon critical traffic infrastructure despite these modifications.
Warren Freeway portion of Highway 13
In its northern extent, the Hayward Fault lies directly beneath the portion of Highway 13 (the "Warren Freeway") that is south of its intersection with Highway 24 and north of its terminal connection with Interstate 580 (the "MacArthur Freeway"). In this rift valley there are a number of elevated street crossings in the Montclair District that cross the fault.
Highway 24
State Highway 24, connecting Oakland to Orinda, Lafayette, and Walnut Creek through the Caldecott Tunnel, is composed of extensive earth fill at the location where the fault is crossed. An earthquake may cause minor landsliding on some slopes of the freeway, and the plastic movement of the fill would likely disrupt the pavement if the movement here of the surface displacement is substantial, possibly presenting a hazard to motorists and shutting down the highway for a while. More extensive disruption and greater hazard could be caused by the failure of elevated structures, both those over which the highway passes and overcrossings of the freeway, of which there are two nearby. As elsewhere in the area, such structures have undergone extensive retrofitting for safety.
Highways 80 and 880 and the Port of Oakland
A severe earthquake is more likely to disable the offshore causeway portions of Interstate Highway 80 (the Eastshore Freeway), since it is built on fill placed in the 1930s atop mudflats whose upper layers were deposited in the 19th century as a result of extensive hydraulic gold mining in the distant Sierra Nevada mountain foothills. This soft mud is expected to amplify earthquake shaking, and the mud supporting the heavy fill may liquefy, and so possibly cause major disruption of the highway due to failure by sinking of the highway and by differential movement of large sections. (More modern construction for these conditions employs linked and "floating" – in mud – lightweight concrete and plastic foam box structures to support a road.) Similar conditions underlie the eastern approach roads to the Bay Bridge. Better, but still locally poor soils underlie the portion of Interstate Highway 880 that extends to the South Bay region from the MacArthur Maze. As the bulk of cargo containers from the Port of Oakland travel on these two roads, the disabling of both would cause severe disruption of West Coast import and export goods, owing to the consequent overloading of other West Coast container handling ports.
Highway 580
A major route for commuters traveling from Southern Alameda County, the San Joaquin Valley and the East Bay hills to downtown Oakland and San Francisco, Interstate 580 crosses the fault twice, and runs very close to the fault between the intersections with State Route 13 (the Warren Freeway) and Interstate 238.
San Francisco–Oakland Bay Bridge.
The 1989 Loma Prieta earthquake caused a failure of a single section of the upper deck of the eastern span of the San Francisco–Oakland Bay Bridge, which closed the bridge for 30 days. A replacement of the eastern span was completed in August 2013. Engineers and much of the public had long recognized that a strong earthquake centered close to the bridge on either the Hayward or San Andreas faults could cause a complete collapse of the eastern span.
Railroads.
Parallel to the Eastshore Freeway and inland only two blocks is a four-track railroad route used for general freight traffic, including that generated by the Port of Oakland (Union Pacific and BNSF railroads) and by Amtrak passenger traffic to the Pacific Northwest and eastward through Reno and Salt Lake City. Along the north shore of Contra Costa County, substantial amounts of pressurized liquid gas, flammable liquids, caustic materials, and various toxics are stored temporarily in bulk railcars adjacent to passenger and freight traffic mainlines, with great potential hazards should a derailment occur. Derailments have often occurred during major earthquakes, both directly by tipping and by roadbed failures; industrial accidents involving these materials have caused extensive health hazards in the mixed residential–industrial areas of Richmond.
Bay Area Rapid Transit.
In addition to extensive modifications to over crossings and elevated structures, largely to prevent dismantling due to shaking or destruction by soil failure, several other unique system feature require special treatment.
Transbay tube
BART trains travel between San Francisco and Oakland through an underwater tube structure. The tube is composed of welded plate steel segments. Each oval outer section carries two inner train tubes of circular cross section and a central rectangular access and rescue tunnel, with the void between elements filled with concrete. The segments were sunk into a ditch dredged through bay mud and covered with rock fill, and then pumped free of water upon completion, making the resulting tube somewhat buoyant, but held in place with a rock overfill. Subsequent seismic analysis indicated the possibility that the overfill could fail due to agitation, allowing the buoyant tube to float upward, misaligning the tracks and possibly overstressing the bolted connections. This potential problem has been addressed by vibratory compaction of the overfill covering the tube. Additional stabilization includes the driving of large pilings and the connection of additional restraints.
Slip joint
The transbay tube terminates at an under-bay slip joint near the Embarcadero Station in San Francisco. The designed slip margin has been reduced by half due to unforeseen settlement of the tube structure. The projected worst-case motion at this joint has been determined to be beyond that for which the joint is presently capable, which could cause severe structural problems and mud and water entry into the tube and adjacent subway systems. This is to be corrected at great expense – first estimated at $142 million but expected to cost far more – probably the largest single cost item in the list of BART seismic retrofits.
Berkeley Hills Tunnel
In June 2006 Bay Area Rapid Transit (BART) management announced that they have elected not to modify the Berkeley Hills Tunnel, which actually penetrates the Hayward Fault, arguing that it would be cheaper (and less disruptive to current operations) to rebore a misaligned portion after the fact than to protect riders (either by extensive modifications of the tunnel or by replacing it with a higher bore) against the small likelihood that a train (or two) would crash into or be cut in two by a major slippage of the fault. Modified train scheduling to prevent multiple train exposure at faults has been determined by BART engineers to be impractical due to variations in train passage, but automated event-related realtime train operational response is considered practical (see below).
Seismic sensor network
BART has installed and continues to enhance a network of seismic sensors (an earthquake warning system) to trigger a system halt in the event of a major event, this to include automated event progression analysis to determine the best action with regard to individual trains for maximum safety (a fault rip can take up to several tens of seconds to completely propagate from the epicenter to the more distant affected locations). Such sensor networks and warning devices have a potential to reduce the hazards from falling objects and furnishings provided that the people notified are well trained in appropriate responses (similar to the Cold War's "duck and cover" training of schoolchildren).
Refineries.
Of primary concern with respect to the Hayward Fault is the huge Chevron Richmond Refinery in Richmond. Although founded on better ground than most of the shoreline, this refinery has extensive crude oil and finished product docks and pipelines extending into the bay, which could produce catastrophic spills into the bay, with the potential to adversely affect hundreds of miles of sensitive wetlands. Dismantling of high pressure and temperature process units and the consequent fire danger to personnel and equipment could produce substantial economic consequences for the western states. Large liquid storage tanks are protected by berms that are designed to contain the contents should a tank fail under normal conditions. Similar process and product conditions exist at other refineries further inland near Martinez, but mostly these plants are exposed to earthquakes from other faults.
Fuel pipelines.
Gasoline is continuously shipped under pressure from Richmond and Martinez area refineries through Kinder Morgan Energy Partners pipelines which run under heavily populated East Bay urban areas to tank terminals near San Jose Airport in North San Jose. Aviation fuels are piped from these same refineries to the Oakland Airport. A number of spills have previously occurred due to landslides and such spill and related toxic and flammable material release may be prevalent in a major seismic event. A November 9, 2004, construction accident on this pipeline system in Walnut Creek killed five people. As seen in other worldwide pipeline ruptures, even an instantaneous stop of pumping would take several minutes to significantly lower pipeline pressure after a break, and would likely result in the release of significant amounts of flammable liquid fuels. Chevron also has a petroleum products pipeline that crosses the fault.
Pacific Gas & Electric Company has numerous gas distribution lines crossing or near the Hayward Fault. Several PG&E gas transmission pipelines also cross the fault. After the San Bruno pipeline explosion, which was unrelated to seismic activity, it took PG&E crews 95 minutes to stop the gas flow to both ends of that failed pipeline.
Bay Area water supplies.
East Bay Municipal Utility District (EBMUD) supplies water to 800,000 East Bay customers who live west of the Berkeley Hills. Prior to the adoption and implementation of a $200 million seismic improvement project all of the water for these customers went through one vulnerable tunnel that crosses the Hayward Fault near the Caldecott Tunnel. As part of this project, that tunnel – the Claremont Tunnel – was seismically retrofitted. Additionally, EBMUD created a second route to bring water to these west-of-the-hills customers through the Southern Loop Bypass near Castro Valley. The Southern Loop was completed in 2002, while the seismic retrofitting of the Claremont tunnel was completed in February 2007.
The Hetch Hetchy Aqueduct, which supplies 270 to 315 million gallons of water per day to the City of San Francisco and other Bay Area communities, directly crosses the Hayward Fault in Fremont. A 2002 report by the Bay Area Economic Forum suggests that a breakdown in the aqueduct due to an earthquake could cut off Hetch Hetchy water to the Bay Area for 60 days. In addition to depriving 85% of San Francisco residents of their drinking water, this would cut off supplies for firefighting and water-intensive industry, causing economic damage of $17.2–28.7 billion. Extensive reconstruction work at the Hayward Fault crossing includes a multi-sectioned tunnel structure to allow shear without collapse, this is to contain a section of water pipe with ball joints and a slip joint.
Lake Temescal.
The fault continues north under the eastern margin of Lake Temescal and its dam, which is unlikely to fail since it has been completely reinforced by the extensive earth fill supporting the subsequently improved Highway 24.
University of California, Berkeley.
Many of the structures at the UC Berkeley academic campus have been self-rated as having "poor" earthquake performance. Numerous chemical, radiological, and biohazardous materials are present (in relatively small quantities) on campus and on the associated Lawrence Berkeley National Laboratory, in the hills above the university. However, the University has undertaken an extensive retrofitting project over the past decade to systematically retrofit all academic buildings on Campus to withstand a significant earthquake.
Memorial Stadium
Further north the fault passes under the lengthwise midline of the football field of California Memorial Stadium at the University of California, Berkeley. Fault creep since 1923 offset the original walls at the north and south ends 13 inches (33 cm).
Extensive upgrades over a recent eighteen-month interval have addressed the life safety issues, including replacement of the football players' facilities, and an extensive seismic retrofit of those sections not subject to fault shearing. The work was the subject of several lawsuits from neighborhood and environmental groups, who were concerned about such extensive construction on top of a major fault. During the reconstruction, the Cal Bears have played at AT&T Park in San Francisco for one season. The modifications completed in Summer 2012 involved the cutting of the stadium into four independent sections, followed by the demolition of the two segments directly over the rubble zone. The north and south ends are formed of new bridging sections that rest upon floating mats (foundations that do not penetrate the surface, rather sitting upon plastic sheets over level graded gravel and sand) where they pass over and near the fault, with appropriate sliding connections between the sections for the safety of spectators and the ability to absorb the relative rotation between the east and west fixed sections and the new north and south mobile sections.
Electrical and communication system disruption.
Affected areas are likely to be without electrical power for an extensive period. This in turn can make fuel supplies for vehicles and emergency generators unavailable locally and impact both domestic water, industrial water, sewage plants, and drainage pumping. Due to the extensive use of point of sale scanners and registers in supermarkets this could also impact the ability of stores to sell essential items such as groceries and to preserve frozen food items, as well as terminating cable TV and most internet access.
Cellphone and most landline telephone service, while theoretically survivable for a short time on battery and emergency power, could instead suffer immediate disruption from ground shaking effects.
Cities affected.
Some of the cities in the eastern bay shore and south bay region near this fault include Richmond, El Cerrito, Berkeley, Albany, Emeryville, Kensington, Oakland, Piedmont, San Leandro, San Lorenzo, Castro Valley, Hayward, Union City, Fremont, Newark, Milpitas, Niles, and portions of San Jose.
Similar dangerous soil conditions and insufficiently resistant buildings are also on the southern, western and northern boundaries of San Francisco and San Pablo bays and would also be severely affected by a major earthquake on the Hayward fault. As that portion includes the so-called Silicon Valley, the potential economic disruption due to destruction of works in progress and the dismantling of microelectronics fabrication plants could have an economic effect extending worldwide. The current estimates of the probability of a major earthquake on any of the numerous regional faults range up to 70 percent within the thirty-year period 2000–2029. A recent "quiet period" following many years of minor activity is considered to be particularly ominous by many, although geologists have not yet been able to predict earthquakes with any useful accuracy. They do warn that all residents of the region should be prepared for a large event and its subsequent effects (e. g., lack of water, firefighting, first aid, electricity, motor and heating fuels, etc.) and that much life-safety protective work remains to be done.
Retrofits for survivability.
It is primarily the likelihood of a severe earthquake on the Hayward or San Andreas faults that has spurred a substantial effort to retrofit and sometimes replace large structures at risk, particularly the eastern and western spans of the San Francisco–Oakland Bay Bridge, the San Francisco and Oakland city halls, and numerous elevated rail, road, and pedestrian structures and overpasses. Much work remains to be done in the region and progress is being hampered by budget constraints imposed by trickle down federal-state-regional deficits, design and construction delays due to state and local political bickering over design, and unexpectedly high steel and cement costs due to the extensive construction work being done in China. Nonetheless, Bay area cities and counties have long expected a major earthquake and as a result all building in the past 30 years has been required to adhere to strict guidelines regarding earthquake resistance. Of all the earthquake prone regions of the world, the San Francisco Bay Area is among the most prepared structurally for the eventuality of a major quake while remaining grossly unprepared in both civil response planning and in the retrofitting of older buildings.
Further information.
Virtual tour.
The Google Earth website, in cooperation with the United States Geological Survey, has prepared a virtual helicopter tour of the fault, with much additional information available through the tour. Potentially dangerous landslide areas are also marked, showing great areas beyond the fault that could be rendered uninhabitable by a major event.
Special exhibit.
Fremont Earthquake Exhibit: "The Hayward Fault Exposed"
This geotourism exhibit (April through October 2006, now closed) featured a 12- to deep pit exposing the Hayward Fault, which could be viewed "face to face" from a shaded platform by descending a staircase. Significant features were noted and marked. Similar trench excavations are used in the determination of the frequency and magnitude of prehistoric earthquakes and to determine the location of latent faults as part of the science of Paleoseismology
In popular culture.
The Tom Wolfe novel "A Man in Full" features a fictional major earthquake on the Hayward Fault as a deus ex machina method (freeing a major character from prison) and plot development point.
The James Bond movie "A View to a Kill" (1985) involved a plot, referred as "Main Strike", by Max Zorin to detonate explosives along the Hayward Fault, San Andreas Fault and at the "geological lock" to flood the two faults with water from nearby lakes and cause both faults to move causing a "double earthquake" that would destroy Silicon Valley, all in order for Zorin to monopolize the microchip market.
References.
Sources


Subcontinental lithospheric mantle

The subcontinental lithospheric mantle (SCLM) is the uppermost solid part of Earth's mantle associated with the continental lithosphere.
The modern understanding of the Earth's upper mantle is that there are two distinct components - the lithospheric part and the asthenosphere. The lithosphere, which includes the continental plates, acts as a brittle solid whereas the asthenosphere is hotter and weaker due to mantle convection. The boundary between these two layers is rheologically based and is not necessarily a strict function of depth. Specifically, oceanic lithosphere (lithosphere underneath the oceanic plates) and subcontinental lithosphere, is defined as a mechanical boundary layer that heats via conduction and the asthenosphere is a convecting adiabatic layer. In contrast to oceanic lithosphere, which experiences quicker rates of recycling, subcontinental lithosphere is chemically distinct, cold, and older. This translated into the differences between the SCLM and the oceanic lithospheric mantle.
There are two different types of subcontinental lithosphere that formed at different times in Earth's history: Archean and Phanerozoic subcontinental mantle.
Archean subcontinental mantle.
Archean lithosphere is strongly depleted in fertile melt indicators such as CaO and Al2O3. This depletion in major-elements should then be consequence of the Archean lithosphere's formation. Trace-elements are abundant in Archean lithosphere relative to MORB (which samples modern upper mantle) and have been sampled by Re-Os isotope dating of peridotites and ophiolites. The trace element composition of these xenoliths suggest mixing between the two different layers of subcontinental mantle. Particularly, the theory for the removal of Archean subcontinental lithosphere below Archean continental crust via delamination helps to explain mantle-peridotite xenoliths found in the extinct Sierra Nevada arc. Though there is evidence for the preservation of the Archean lithosphere, there is controversy over the preservation of the Archean mantle, for which the Archean lithosphere would have been derived.
The formation of the Archean SCLM is enigmatic. One early theory that komatiite melts formed the Archean SCLM does not explain how komatiites, which form in hot and deep environments, creates a reservoir that is shallow and cool. Another model of Archean SCLM formation suggests that the SCLM formed in a subduction environment in which new Archean crust was created through slab melting. If the primitive mantle is the starting composition for this SCLM formation event, subducting slab would be composed of TTG crust, then the removal of basaltic melt and the enrichment of the mantle wedge with felsic melts could explain the formation of the depleted Archean subcontinental lithosphere. For more information, see Archean subduction.
Phanerozoic subcontinental mantle.
The mechanism of arc subduction is well understood to be the location where new continental crust is formed and is presumably also the site of subcontinental mantle genesis. Firstly, hydrated oceanic crust slabs begin subducting which releases fluids (subduction zone metamorphism) to the mantle wedge above. Continued subduction of the slab leads to further hydration of the mantle which causes partial melting in the mantle wedge. It is expected then that the modern subcontinental mantle is a former, melt-depleted mantle wedge. If the connection between continental crust and the subcontinental lithospheric mantle does not exist, and rather a different Earth process formed both reservoirs, then it further complicates the mechanisms for how the Archean subcontinental mantle formed.


Li Shucai

Li Shucai (; born December 1965) is a Chinese petrologist who is a professor, doctoral superviso and vice-president of Shandong University. He is a member of the Chinese Society for Rock Mechanics & Engineering (CSRME). He is the chief editor of "Tunnelling and Underground Space Technology".
Biography.
Li was born in Laishui County, Hebei, in December 1965. He enrolled at Shandong Mining Institute (now Shandong University of Science and Technology) where he received his B.Eng. degree in 1987 and his M.Eng. degree in 1990. After receiving his D.Eng. degree from the Institute of Rock and Soil Mechanics, Chinese Academy of Sciences (CAS) in 1996, he stayed for researching. He moved to Shandong University in 2000 as dean of the School of Civil Engineering and director of the Geotechnical and Structural Engineering Research Center.


Sonia I. Seneviratne

Sonia Isabelle Seneviratne (born on 5 June 1974 in Lausanne) is a Swiss climate scientist, professor at the Institute for Atmospheric and Climate Science of the ETH Zurich. She is a specialist of extreme climate events.
Biography.
Sonia Seneviratne studied biology at the University of Lausanne and environmental sciences at the ETH Zurich. in 2002, she received a PhD in atmospheric and climate science from ETH Zurich.
She worked as postdoctoral researcher at the National Aeronautics and Space Administration. Since 2007, she is professor at the Institute for Atmospheric and Climate Science of the ETH Zurich.
Sonia Seneviratne is a member of the Intergovernmental Panel on Climate Change (IPCC) and was a lead author of the Special Report on Global Warming of 1.5ºC (2018).
Honours.
Sonia Seneviratne was included in Thomson Reuters's 2015 list of the most cited modern scientists. She was the lead author on a 2014 article in Nature Climate Change that showed no pause in the increase of hot temperature extremes from 1997 to 2012.
She is a Revelle Medal committee member. In 2013, she received the James B. Macelwane Medal from the American Geophysical Union. In 2014, she received a consolidator grant from the European Research Council.


Cala di Labra Formation

The Cala di Labra Formation is a geologic formation in France. It preserves fossils dating back to the Neogene period.


Fowkes Formation

The Fowkes Formation is a geologic formation in Wyoming. It preserves fossils dating back to the Paleogene period.


Porphyroblast

A porphyroblast is a large mineral crystal in a metamorphic rock which has grown within the finer grained matrix. Porphyroblasts are commonly euhedral crystals, but can also be partly to completely irregular in shape.
The most common porphyroblasts in metapelites (metamorphosed mudstones and siltstones) are garnets and staurolites, which stand out in well-foliated metapelites (such as schists) against the platy mica matrix.
A similar type of crystal is a "phenocryst", a large crystal in an igneous rock. Porphyroblasts are often confused with "porphyroclasts", which can also be large outstanding crystals, but which are "older" than the matrix of the rock.
If a porphyroblastic mineral has small inclusions of minerals within it, the mineral is described as poikiloblastic. This observation can help interpret deformation history.
A rock which has many porphyroblasts is described as having a "porphyroblastic texture".
As porphyroblasts grow, the foliation may be preserved as oriented inclusions trapped by the porphyroblast as it overgrows them, and this is helpful for tracking changing deformation planes.
In metamorphic rocks that experience deformation during metamorphism, porphyroblasts may grow before, during, or after the phase of deformation recorded by the matrix minerals. The relationship of porphyroblast growth to deformation is typically evaluated by comparing the shape orientation of trails of mineral inclusions in the porphyroblast to the matrix fabric.
Some garnet porphyroblasts contain curving trails of quartz and other mineral inclusions that record rotation of the crystals relative to their surroundings. However, the question of how much porphyroblasts actually rotate in an external reference frame fixed to the Earth's surface during metamorphism and deformation has long been the subject of debate. The question focused on so-called "spiral garnets", also known as "snowball garnets", whose inclusion trails define spiral patterns. These microstructures are interpreted classically as having formed by shearing induced rotation of a growing garnet crystal. Later research, however, led to an alternative formation model in which a porphyroblast grows over a developing microfold while maintaining a stable position in the external reference frame. Repetition of this process can then produce complex spiral-shaped patterns. Although many researchers continue to adopt the classic rotational model, most researchers who have published research testing both models by measuring the orientations of porphyroblasts have come to support the modern interpretation.


Hasnaa Chennaoui-Aoudjehane


Marathon Formation

The Marathon Formation is a geologic formation in Texas. It preserves fossils dating back to the Ordovician period.


Kechika Formation

The Kechika Formation is a geologic formation in British Columbia. It preserves fossils dating back to the Ordovician period.


Moturoa / Rabbit Island

Moturoa / Rabbit Island is a small island that lies across the southernmost part of Tasman Bay / Te Tai-o-Aorere, on the northern coast of New Zealand's South Island. The long narrow island runs east–west for , and covers .
It lies opposite the mouth of the Waimea River, to the west of Richmond. It was formed about 7000 years ago as several barrier islands accumulated near the mouth of the Waimea River. There is evidence of Maori occupation for over 800 years. The original vegetation comprised tussock, manuka scrub and totara forest further inland.
The Rabbit Island Recreation Reserve contains three islands, Rabbit Island, Rough Island and Bird Island, and became a public reserve in 1908. Rabbit Island, with its long, safe swimming beach, is a popular beach resort to the residents of Motueka, Wakefield, Brightwater, Richmond, Mapua, Stoke and Nelson.
A medium-sized causeway spans a tidal area and joins the mainland to Rabbit Island. There is a large grassed area after this bridge and a Fire Hazard sign ("Keep it Green"). Large areas of the relatively flat islands are covered in pine plantation forest. The beach proper contains vast and mountainous sand dunes topped with masses of cone-bearing pines, with exposed roots, extending for long distances along the island.
The Tasman's Great Taste Trail, a cycleway running from Richmond to Motueka, runs through Rabbit Island. There is also a newly established equestrian area. The reserve area is closed to the public from dusk to 5 am.
In August 2014, the name of the island was officially altered to Moturoa / Rabbit Island.
Others islands with the same name.
The other Rabbit Islands are smaller than or . They are located (north to south):


Calcaire de Blacourt

The Calcaire de Blacourt is a geologic formation in France. It preserves fossils dating back to the Devonian period.


Dark slope streak

Dark slope streaks are narrow, avalanche-like features common on dust-covered slopes in the equatorial regions of Mars. They form in relatively steep terrain, such as along escarpments and crater walls. Although first recognized in Viking Orbiter images from the late 1970s, dark slope streaks were not studied in detail until higher-resolution images from the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO) spacecraft became available in the late 1990s and 2000s.
The physical process that produces dark slope streaks is still uncertain. They are most likely caused by the mass movement of loose, fine-grained material on oversteepened slopes (i.e., dust avalanches). The avalanching disturbs and removes a bright surface layer of dust to expose a darker substrate. The role that water and other volatiles plays, if any, in streak formation is still debated. Slope streaks are particularly intriguing because they are one of the few geological phenomena that can be observed occurring on Mars in the present day.
Nature of streaks on Mars.
Dark slope streaks are albedo features. They appear to the eye as a brightness difference between the streak and the lighter-toned background slope. Usually no topographic relief is visible to distinguish the streak from its surroundings, except in the very highest resolution (<1 m/pixel) images. In many cases, the original surface texture of the slope is preserved and continuous across the streak, as though unaffected by events involved in dark streak formation (pictured left). The overall effect is equivalent in appearance to a partial shadow cast down the sloping surface. These observations indicate that whatever process forms the streaks, it affects only the very thinnest layer at the surface. Slope streaks are only about 10% darker than their surroundings but often appear black in images because the contrast has been enhanced (stretched).
Albedo features cover the Martian surface at a wide variety of scales. They make up the classical light and dark marking seen on Mars through telescopes. (See Classical albedo features on Mars.) The markings are caused by differing proportions of dust covering the surface. Martian dust is bright reddish ochre in color, while the bedrock and soil (regolith) is dark gray (the color of unaltered basalt). Thus, dusty areas on Mars appear bright (high albedo), and surfaces with a high percentage of rocks and rock fragments are generally dark (low albedo). Most albedo features on Mars are caused by winds, which clear some areas of dust, leaving behind a darker lag. In other areas, dust is deposited to produce a bright surface. The selective removal and deposition of dust is most conspicuous around impact craters and other obstacles where a variety of streaks (wind tails) and blotches are formed.
Dark slope streaks are relatively small features. (See A in Photo Gallery.) They differ from larger albedo features in being produced by gravity rather than wind, although wind may contribute to their initial formation. (See B in Photo Gallery.) The cause of the darkening is uncertain. The particle sizes involved are believed to be very small (sand, silt, and clay-sized particles). No clasts large enough to be imaged are present, and the underlying bedrock slope is never exposed ( i.e., dust is avalanching on a surface of dust). Apparently, other optical, mechanical, or chemical properties are involved in producing the darker tone.
Dark slope streaks commonly share the same slope with other slope streaks of varying tones. The darkest streaks are presumed to be youngest; they have margins that are more sharply defined than streaks that are not as dark. This relationship suggests that streaks lighten and become more diffuse with age, probably because they become covered with fresh dust falling from the atmosphere. Faded dark slope streaks should not be confused with bright slope streaks (discussed below). Dust storms are common on Mars. At times the whole planet is enveloped in a dust storm, as shown in the pictures below.
Morphology and occurrence.
At moderate resolutions (20–50 m/pixel), dark slope streaks appear as thin, parallel filaments aligned downslope along crater rims and escarpments. They are often straight but may also be curved or sigmoid in shape. (See C in Photo Gallery.) Closer up, dark slope streaks typically have elongated, fan-like shapes (pictured right). They range from about 20 to 200 meters in width and are generally several hundred meters to over 1,000 meters long. Dark slope streaks exceeding 2 kilometers in length are uncommon; most terminate on slope and do not extend further out on to level terrain.
A streak commonly starts at a single point (apex) high on the slope. The apex is often associated with an isolated small ridge, knob, or other area of local steepening. In high-resolution images, a tiny impact crater is sometimes visible at the apex. Slope streaks widen downslope from the apex in a triangular fashion, usually reaching their maximum widths short of the halfway point of their lengths. A single slope streak can split into two separate streaks around an obstacle or form an anastamosing (braided) pattern. (See D and E in Photo Gallery.) Slope streaks commonly develop multiple fingers (digitation) at their downslope ends.
Images from the High Resolution Imaging Science Experiment (HiRISE) on MRO have shown that many slope streaks have relief, contrary to earlier descriptions in which no topographic distinction could be seen between the streaked and adjacent, non-streaked surface. The streaked surface is typically about 1 m lower than the non-streaked surface. This relief is only visible in maximum resolution images under optimal viewing conditions.
Dark slope streaks are most common in the equatorial regions of Mars, particularly in Tharsis, Arabia Terra, and Amazonis Planitia (pictured left). They occur between latitudes 39°N and 28°S. At their northern limits, they appear preferentially on warmer, south facing slopes. Curiously, slope streaks are also associated with areas that reach peak temperatures of 275K (2 °C), a temperature close to the triple point of water on Mars. This relationship has led some researchers to suggest that liquid water is involved in dark slope streak formation.
Dark slope streaks do not appear to correlate with elevation or areas of specific bedrock geology. They occur on a wide range of slope textures, including surfaces that are smooth, featureless, and presumably young, as well as older, heavily cratered slopes. However, they are always associated with areas of high surface roughness, high albedo, and low thermal inertia, properties that indicate steep slopes covered with a lot of dust.
It has been suggested that streaks could form when accumulations of dry ice start subliming right after sunrise. Nighttime CO2 frost is widespread in low latitudes.
Formation mechanism.
Researchers have proposed a number of mechanisms for dark slope streak formation. The most widely held view is that the streaks are the result of dust avalanches produced by dry granular flow on oversteepened slopes. Dust avalanches resemble loose snow avalanches on Earth. Loose snow avalanches occur when snow accumulates under cold, nearly windless conditions, producing a dry, powdery snow with little cohesion between individual snow crystals. The process produces a very shallow trough (slough) on the surface of the snow, which from a distance appears slightly darker in tone than the rest of the slope.
Other models involve water, either in the form of spring discharges, wet debris flows, or seasonal percolation of chloride-rich brines. Using data from the Mars Odyssey Neutron Spectrometer, researchers found that slope streaks in the Schiaparelli basin occur in areas predicted to yield between 7.0 and 9.0 weight percent Water Equivalent Hydrogen (WEH) in contrast to typical background values of less than 4% WEH. This relationship suggests a connection between high WEH percentages and the occurrence of dark slope streaks. However, any process that requires voluminous amounts of water (e.g., spring discharges) seems unlikely because of the overall thermodynamic instability of liquid water on Mars.
Another model proposes that dark slope streaks are produced by ground-hugging density currents of dry dust lubricated by carbon dioxide (CO2) gas. In this scenario, a small initial slump at the surface releases CO2 gas adsorbed onto subsurface grains. This release produces a gas-supported dust flow that moves as a tenuous density current downslope. This mechanism may help explain slope streaks that are unusually long.
Some observations suggest that dark slope streaks can be triggered by impacts. Pictures acquired by CTX in 2007 and 2010 showed a new streak appeared in the aureole of Olympus Mons. A follow up image from HiRISE showed that a new crater at the top of the streak. The researchers concluded that the impact triggered the new slope streak. Another streak connected with an impact was found in the Arabia quadrangle.
Research, published in January 2012 in Icarus, found that dark streaks were initiated by airblasts from meteorites traveling at supersonic speeds. The team of scientists was led by Kaylan Burleigh, an undergraduate at the University of Arizona. After counting some 65,000 dark streaks around the impact site of a group of 5 new craters, patterns emerged. The number of streaks was greatest closer to the impact site. So, the impact somehow probably caused the streaks. Also, the distribution of the streaks formed a pattern with two wings extending from the impact site. The curved wings resembled scimitars, curved knives. This pattern suggests that an interaction of airblasts from the group of meteorites shook dust loose enough to start dust avalanches that formed the many dark streaks. At first it was thought that the shaking of the ground from the impact caused the dust avalanches, but if that was the case the dark streaks would have been arranged symmetrically around the impacts, rather than being concentrated into curved shapes.
The crater cluster lies near the equator 510 miles) south of Olympus Mons, on a type of terrain called the Medusae Fossae formation. The formation is coated with dust and contains wind-carved ridges called yardangs. These yardangs have steep slopes thickly covered with dust, so when the sonic boom of the airblast arrived from the impacts dust started to move down the slope.
Using photos from Mars Global Surveyor and HiRISE camera on NASA’s Mars Reconnaissance Orbiter, scientists have found about 20 new impacts each year on Mars. Because the spacecraft have been imaging Mars almost continuously for a span of 14 years, newer images with suspected recent craters can be compared to older images to determine when the craters were formed. Since the craters were spotted in a HiRISE image from February 2006, but were not present in a Mars Global Surveyor image taken in May 2004, the impact occurred in that time frame.
The largest crater in the cluster is about 22 meters (72 feet) in diameter with close to the area of a basketball court. As the meteorite traveled through the Martian atmosphere it probably broke up; hence a tight group of impact craters resulted.
Dark slope streaks have been seen for some time, and many ideas have been advanced to explain them. This research may have finally solved this mystery.
Formation rate.
Slope streaks are one of the few geomorphic features forming on the surface of present-day Mars. New streaks were first identified by comparing images from the Viking Orbiters of the 1970s to images of the same locations taken by the MGS Mars Orbiter Camera (MOC) in the late 1990s. The presence of new streaks showed that slope streaks are actively forming on Mars, on at least annual to decade-long timescales. A later, statistical treatment using overlapping MOC images spaced days to several years apart showed that slope streaks may form on Mars at a rate of about 70 per day. If accurate, this rate suggests that slope streaks are the most dynamic geologic features observed on the surface of Mars.
Dark slope streaks fade and disappear at a much slower rate than new ones appear. Most streaks identified in Viking images are still visible after decades, although a few have vanished. Researchers infer that streaks appear at a rate 10 times faster than they disappear, and that the number of slope streaks on Mars has increased in the last three decades. This imbalance is unlikely to have persisted for geologically significant periods of time. One possible solution to the imbalance is that streaks last for centuries, but are wiped clean "en masse" after extremely rare but fierce dust storms (storms of a magnitude not observed on Mars since Viking). After the storm subsides, a thick layer of fresh dust is deposited to begin a new cycle of streak formation. A recent study published in Icarus found that they last about 40 years. The researchers looked at a region in Lycus Sulci with Viking images and with CTX images from the Mars Reconnaissance Orbiter. The ones first observed with Viking have all gone, but have been replaced with new ones.
Similar and related features.
Dark slope streaks occur in association with or superficially resemble a number of other small-scale, slope-related features on Mars. These include bright slope streaks, avalanche scars, and recurring slope lineae. Water tracks are features that occur in the polar regions of Earth. They resemble dark slope streaks and recurring slope lineae, but have not yet been described on Mars. Many of the slope features on Mars may originate through a continuum of processes with dry mass wasting and minor fluvial (water-related) activity occupying opposite endpoints. Gullies are another feature common on slopes in the mid-latitude southern hemisphere of Mars They have received much attention in the literature but are not discussed here.
Bright slope streaks.
Bright slope streaks are streaks that have a lighter tone (about 2%) than their surroundings. (See F in Photo Gallery.) They are much rarer than dark slope streaks, but both types of streaks have similar morphologies and occur in the same regions of Mars. Evidence suggests that bright slope streaks are older than dark slope streaks. New bright slope streaks have never been observed, and dark slope streaks can be seen overlying bright slope streaks in some images, indicating that the former are younger than the latter. It is likely that bright slope streaks form from old dark slope streaks that have transitioned past a partially faded stage. This supposition is supported by geographical evidence indicating that bright slope streaks are slightly more common in regions where the formation rate of new dark slope streaks is low. In other words, areas with relatively many bright streaks tend to be less active and contain a higher population of old dark streaks.
Avalanche scars.
Areas with abundant slope streaks also contain an apparently distinct class of avalanche scars. The scars resemble slope streaks in morphology and size. (See G in Photo Gallery) They are typically several meters deep and hundreds of meters long. They begin at a single point (sometimes a small, barely resolved impact crater) high on a slope. The edges radiate downslope in a triangular fashion. In about half of the documented examples, a low-lying mound of debris is visible at the downslope end. Originally called "meters-thick avalanche scars," these features were thought to be distinct from slope streaks. However, higher-resolution images from the HiRISE instrument on MRO suggest that meters-thick avalanche scars and slope streaks are related and part of a continuum of active mass wasting features formed by dust avalanches.
Recurring slope lineae (warm-season flows).
In the summer of 2011, a paper appeared in "Science" describing a new class of slope features with characteristics that suggest formation by seasonal releases of liquid water. (See H and I in Photo Gallery.) Called "recurring slope lineae" (RSL), the features received a considerable amount of media attention. RSLs are narrow (0.5 to 5 meters) dark markings that preferentially occur on steep, equator-facing slopes in the southern hemisphere between latitudes 48°S to 32°S. Repeat HiRISE images show that the markings appear and grow incrementally during warm seasons and fade in cold seasons. RSLs bear only a superficial resemblance to dark slope streaks. They are much smaller in width and have a different pattern of geographic occurrence and slope properties than dark slope streaks. RSLs seem to occur on bedrock slopes with seasonally high surface temperatures of 250–300K (-23–27 °C). These location may favor the flow of briney fluids emerging from seeps at certain times of the Martian year. Unlike RSLs, dark slope streaks appear to occur sporadically throughout the Martian year, and their triggering seems unrelated to season or large regional events.
Water tracks.
Water tracks are little-studied slope features common in permafrost-dominated terrains in the arctic and Antarctic regions of Earth. They are zones of enhanced soil moisture that route water downslope over the top of the permanently frozen ground just below the surface (ice table). Although water tracks have not been specifically identified on Mars, several researchers have noted their morphological and spectroscopic similarity to Martian slope streaks. Like dark slope streaks, water tracks are narrow, sublinear features elongated in the downslope direction. They typically display a slight darkness relative to their surroundings and show little or no detectable relief. During peak flow conditions, they appear as damp, darkened, patches of soil that are generally less than 60 m wide and several hundred meters long. The dark surface discoloration vanishes in frozen water tracks during winter, rendering them nearly undetectable.
Photo gallery.
Dark streaks and related features appear in the images below. To see the features described in the caption and text, it may be necessary to enlarge the image by clicking on it.


Geology of Pluto

The geology of Pluto consists of the characteristics of the surface, crust, and interior of Pluto. Because of Pluto's distance from Earth, in-depth study from Earth is difficult. Many details about Pluto remained unknown until 14 July 2015, when "New Horizons" flew through the Pluto system and began transmitting data back to Earth. When it did, Pluto was found to have remarkable geologic diversity, with "New Horizons" team member Jeff Moore saying that it "is every bit as complex as that of Mars". The final "New Horizons" Pluto data transmission was received on 25 October 2016. In June 2020, astronomers reported evidence that Pluto may have had a subsurface ocean, and consequently may have been habitable, when it was first formed.
Surface.
More than 98 percent of Pluto's surface consists of solid nitrogen, with traces of methane and carbon monoxide. The face of Pluto oriented toward Charon contains more solid methane, whereas the opposite face contains more nitrogen and solid carbon monoxide. Distribution of volatile ices is thought to be season-dependent and influenced more by solar insolation and topography than by subsurface processes.
Maps produced from images taken by the Hubble Space Telescope (HST), together with Pluto's light curve and the periodic variations in its infrared spectra, indicate that Pluto's surface is very varied, with large differences in both brightness and color, with albedos between 0.49 and 0.66. Pluto is one of the most contrastive bodies in the Solar System, with as much contrast as Saturn's moon Iapetus. The color varies between charcoal black, dark orange and white. Pluto's color is more similar to that of Io with slightly more orange, significantly less red than Mars. "New Horizons" data suggest equally variable surface ages for Pluto, with ancient, dark, mountainous terrain (such as Cthulhu) occurring alongside the bright, flat, effectively craterless Sputnik Planitia and various terrains of intermediate age and color.
Pluto's surface color changed between 1994 and 2003: the northern polar region brightened and the southern hemisphere darkened. Pluto's overall redness also increased substantially between 2000 and 2002. These rapid changes probably relate to seasonal condensation and sublimation of portions of Pluto's atmosphere, amplified by Pluto's extreme axial tilt and high orbital eccentricity.
Soft-ice plains and glaciers.
Sputnik Planitia appears to be composed of ices more volatile, softer and more dense than the water-ice bedrock of Pluto, including nitrogen, carbon monoxide and solid methane. A polygonal convection cell structure is visible over much of the planitia. No craters have been found, indicating that its surface must be less than 10 million years old. A number of mechanisms are proposed to explain the absence of craters, including cryovolcanism (volcanoes erupting volatiles instead of magma), convective overturn, and viscous relaxation – processes that would erase negative topography. Glaciers of what is probably solid nitrogen can be seen flowing from the planitia into adjacent depressions and craters. Nitrogen from the plain appears to have been carried via the atmosphere and deposited in a thin layer of ice on uplands to the east and south of the plain, forming the large bright eastern lobe of Tombaugh Regio. Glaciers appear to be flowing back into the planitia through valleys from these eastern highlands.
Water-ice mountains.
Mountains several kilometres high occur along the southwestern and southern edges of Sputnik Planitia. Water ice is the only ice detected on Pluto that is strong enough at Plutonian temperatures to support such heights.
Ancient cratered terrain.
Cthulhu Regio and other dark areas have many craters and signatures of solid methane. The dark red color is thought to be due to tholins falling out of Pluto's atmosphere.
Northern latitudes.
The mid-northern latitudes display a variety of terrain reminiscent of the surface of Triton. A polar cap consisting of solid methane "diluted in a thick, transparent slab of solid nitrogen" is somewhat darker and redder.
Tartarus Dorsa.
The western part of Pluto's northern hemisphere consists of an extensive, highly distinctive set of 500-meter-high mountains informally named Tartarus Dorsa; the spacing and shape of the mountains looks similar to scales or to tree bark. A January 2017 "Nature" paper by Dr. John Moores and his colleagues identified these icy ridges as penitentes. Penitentes are icy depressions formed by erosion and surrounded by tall spires. Pluto is the only planetary body other than Earth on which penitentes have been identified. Although penitentes have been hypothesized on Jupiter's satellite Europa, current theories suggest they may require an atmosphere to form. Moores and his colleagues hypothesize that Pluto's penitentes grow only during periods of high atmospheric pressure, at a rate of approximately 1 centimeter per orbital cycle. These penitentes appear to have formed in the last few tens-of-millions of years, an idea supported by the sparsity of craters in the region, making Tartarus Dorsa one of the youngest regions on Pluto.
Cutting through both Tartarus Dorsa and Pluto's heavily-cratered northern terrain (and thus formed more recently than both) is a set of six canyons radiating from a single point; the longest, informally named Sleipnir Fossa, is over 580 kilometers long. These chasms are thought to have originated from pressures caused by material upwelling at the center of the formation.
Possible cryovolcanism.
When "New Horizons" first sent back data from Pluto, Pluto was thought to be losing hundreds of tons of its atmosphere an hour to ultraviolet light from the Sun; such an escape rate would be too great to be resupplied by comet impacts. Instead, nitrogen was thought to be resupplied either by cryovolcanism or by geysers bringing it to the surface. Images of structures that imply upwelling of material from within Pluto, and streaks possibly left by geysers, support this view. Subsequent discoveries suggest that Pluto's atmospheric escape was overestimated by several thousand times and thus Pluto could theoretically keep its atmosphere without geological assistance, though evidence of ongoing geology remains strong.
Two possible cryovolcanoes, provisionally named Wright Mons and Piccard Mons, have been identified in topographic maps of the region south of Sputnik Planitia, near the south pole. Both are over 150 km across and at least 4 km high, the tallest peaks known on Pluto at present. They are lightly cratered and thus geologically young, although not as young as Sputnik Planitia. They are characterized by a large summit depression and hummocky flanks. This represents the first time large potentially cryovolcanic constructs have been clearly imaged anywhere in the Solar System.
A 2019 study identified a second likely cryovolcanic structure around Virgil Fossae, a series of troughs in northeastern Cthulu Macula, west of Tombaugh Regio. Ammonia-rich cryolavas appear to have erupted from Virgil Fossae and several nearby sites and covered an area of several thousand square kilometers; the fact that the ammonia's spectral signal was detectable when New Horizons flew by Pluto suggests that Virgil Fossae is no older than one billion years and potentially far younger, as galactic cosmic rays would destroy all the ammonia in the upper meter of the crust in that time and solar radiation could destroy the surface ammonia 10 to 10000 times more quickly. The subsurface reservoir from which this cryomagma emerged may have been separate from Pluto's subsurface ocean.
Internal structure.
Pluto's density is . Because the decay of radioactive elements would eventually heat the ices enough for the rock to separate from them, scientists think that Pluto's internal structure is differentiated, with the rocky material having settled into a dense core surrounded by a mantle of water ice. Pluto's abundant surface volatiles imply that Pluto is either completely differentiated (and thus has liberated all of the volatiles that had been locked away in its water ice) or formed within less than a million years after the circumstellar disk was cleared (when volatiles were still available to be incorporated into Pluto).
The diameter of the core is hypothesized to be approximately , 70% of Pluto's diameter. It is possible that such heating continues today, creating a subsurface ocean layer of liquid water and ammonia some thick at the core–mantle boundary. Studies based on "New Horizon"'s images of Pluto reveal no signs of contraction (as would be expected if Pluto's internal water had all frozen and turned into ice II) and imply that Pluto's interior is still expanding, probably due to this internal ocean; this is the first concrete evidence that Pluto's interior is still liquid. Pluto is proposed to have a thick water-ice lithosphere, based on the length of individual faults and lack of localized uplift. Differing trends in the faults suggest previously active tectonics, though its mechanisms remain unknown. The DLR "Institute of Planetary Research" calculated that Pluto's density-to-radius ratio lies in a transition zone, along with Neptune's moon Triton, between icy satellites like the mid-sized moons of Uranus and Saturn, and rocky satellites such as Jupiter's Io.
Pluto has no magnetic field.


Barbara Sherwood Lollar

Barbara Sherwood Lollar, (born February 19, 1963) is a Canadian geologist and academic known for her research into billion-year-old water. She is currently a Professor in the Department of Earth Sciences at the University of Toronto. In 2007, she was made a Canada Research Chair in Isotope Geochemistry of the Earth and the Environment. It was renewed in 2014.
Early life and education.
Sherwood Lollar was born in Kingston, Ontario, the daughter of John M Sherwood and Joan Sherwood, historians and academic at Queen's University, Kingston, she joined the University of Toronto in 1992 after receiving a Bachelor of Arts degree in Geological Sciences from Harvard University, a Ph.D. in Earth Sciences from University of Waterloo in 1990, and a postdoctoral fellow at University of Cambridge.
Career.
She has frequently collaborated with Tullis Onstott and Lisa Pratt on large multi-national research projects.
Honours.
In 2004, she was made a Fellow of Royal Society of Canada. In 2010, she was made a Senior Fellow of Massey College. In 2012, she was awarded the ENI award. In 2015, she was made a Fellow of the American Geophysical Union. In 2016, she was awarded the Natural Sciences and Engineering Research Council's John C. Polanyi Award. In 2016, she was invested as a Companion of the Order of Canada "for her revolutionary contributions to geochemistry, notably in the development of innovative mechanisms for groundwater remediation, and for her discovery of ancient fluids that hold implications for life on other planets". Also in 2016, she was awarded the Bancroft Award by the Royal Society of Canada. She received the Logan Medal in 2018.
She was elected a fellow of the Royal Society in 2019.
On 6 May 2019, Lollar received the Gerhard Herzberg Canada Gold Medal for Science and Engineering from the Natural Sciences and Engineering Research Council of Canada.


Ferguson Mountain Formation

The Ferguson Mountain Formation is a geologic formation in Nevada. It preserves fossils dating back to the Permian period.


Creede Formation

The Creede Formation is a geologic formation in Colorado. It preserves fossils dating back to the Paleogene period, particularly many well-preserved fossil plants from Oligocene strata.


Stratigraphic column

A stratigraphic column is a representation used in geology and its subfield of stratigraphy to describe the vertical location of rock units in a particular area. A typical stratigraphic column shows a sequence of sedimentary rocks, with the oldest rocks on the bottom and the youngest on top.
In areas that are more geologically complex, such as those that contain intrusive rocks, faults, and/or metamorphism, stratigraphic columns can still indicate the relative locations of these units with respect to one another. However, in these cases, the stratigraphic column must either be a structural column, in which the units are stacked with respect to how they are observed in the field to have been moved by the faults, or a time column, in which the units are stacked in the order in which they were formed.
Stratigraphy is a branch of geology that concerns the order and relative position of geologic strata and their relationship to the geologic time scale. The relative time sequencing requires the analysis of the order and position of layers of archaeological remains and the structure of a particular set of strata.
The columns can include igneous and metamorphic rocks, however, sedimentary rocks are important geologically because of Classical Laws of Geology and how they relate to the accumulation of sediments and the formation of sedimentary environments. Lithology is a study of bedrock that occurs at a specific location. The strata may contain fossils which aid in determining how old they are and geologist's understanding of sequence and timing. Geologists group together similar lithologies, and call these larger sedimentary sequence formations. There are rules on how formations are named, related to where they are located and what rock type(s) are present. All sedimentary formations shall receive distinctive designations. The most desirable names are binomial, the first part being geographic and the other lithologic. If the rock type is the same, then the formation may be called the "Lyons Sandstone," or the "Benton Shale." When there are several different lithologies within the formation, a more general terminology is used, such as the "Morrison Formation," which contains siltstone, sandstone, and limestone. “For regional studies, geologists will study the stratigraphy of as many separate areas as they can, prepare a stratigraphic column for each, and combine them in an attempt to understand the regional geologic history of the area”.
Laws and principles of geology.
Principle of Uniformitarianism: defined in the authoritative "Glossary of Geology" as "the fundamental principle or doctrine that geologic processes and natural laws now operating to modify the Earth's crust have acted in the same regular manner and with essentially the same intensity throughout geologic time, and that past geologic events can be explained by phenomena and forces observable today; the classical concept that 'the present is the key to the past'.".
Law of Original Horizontality: sedimentary rocks are always deposited as horizontal, or nearly horizontal, strata, although these may be disturbed by later earth movements. This law was proposed by Nicolaus Steno in the mid-17th century.
Law of Superposition: general law upon which all geologic chronology is based: In any sequence of layered rocks, sedimentary or extrusive volcanic, that has not been overturned, the youngest stratum is at the top and the oldest at the base; i.e., each bed is younger than the bed beneath, but older than the bed above it. The law was stated by Steno in 1669.
Cross-cutting relationships: cross-cutting relationships is a principle of geology that states that the geologic feature which cuts another is the younger of the two features. It is a relative dating technique used commonly by geologists.
There are two main processes that are relevant to sedimentary strata formation: tectonic forces which build mountains and the surface, and erosional processes that transport the sediments to lower energy environments where they are then deposited. These processes results in large piles of accumulated sediments whenever there is a change in the depositional environment. The sedimentary particles are deposited dependent on the net energy in the transportation vector, typically water when dealing with sediments clasts.
“Brief descriptions of the units may be lettered to the right of the column, as in the figure, or the column may be accompanied by an explanation consisting of a small box for each lithologic symbol and for the other symbols alongside the column. Columns are constructed from the stratigraphic base upward and should be plotted first in pencil in order to insure spaces for gaps at faults and unconformities. Sections that are thicker than the height of the plate can be broken into two or more segments, with the stratigraphic base at the lower left and the top at the upper right. Bedding and unit boundaries are drawn horizontally, except in detailed sections or generalized sections of distinctly nontabular deposits, as some gravels and volcanic units”.
The following elements of a stratigraphic column are essential and are generally keyed to the figure:
This recorded information from above will give geologist a description of what rocks are in a cliff or underground. This description allows a better understanding to the entire geology of that area. Can be used to decide whether there is potential for oil or natural gas that exists in these rocks. “The differences between rock unit types and fossils observed within the rock determine how these rocks are grouped for diagramming purposes. The column displays what types of rocks these units are composed of in two ways. The unit name itself reveals to geologists the rock type. and displays the relative thickness of the rock units”.


Beechhill Cove Formation

The Beechhill Cove Formation is a geologic formation in Nova Scotia. It preserves fossils dating back to the Silurian period.


Lamar River Formation

The Lamar River Formation is a geologic formation in Wyoming. It preserves fossils dating back to the Paleogene period.


Lime Island Formation

The Lime Island Formation is a geologic formation in Michigan. It preserves fossils dating back to the Silurian period.


Zhang Benren

Zhang Benren (; 28 May 1929 – 1 November 2016) was a Chinese geochemist.
Born on 28 May 1929 in Huaiyuan County, Anhui, Zhang studied geology at Nanjing University, graduating in 1952. He then earned a degree from the Beijing Institute of Geology in 1956 and later became a faculty member. Zhang was elected an academician of the Chinese Academy of Sciences in 1999 and received the State Natural Science Award.
Zhang died at the age of 87 in 2016.


Plessite

Plessite is a meteorite texture consisting of a fine-grained mixture of the minerals kamacite and taenite found in the octahedrite iron meteorites. It occurs in gaps (its name is derived from the Greek "plythos" meaning "filling") between the larger bands of kamacite and taenite which form Widmanstätten patterns.
Many types of plessite exist and vary in formation mechanism and morphology. Some types of plessite as named by Buchwald's "Iron Meteorites" and Massalski's "Speculations about Plessite" are:


Jacks Peak Formation

The Jacks Peak Formation is a geologic formation in Nevada. It preserves fossils dating back to the Ordovician period.


Elaine Anderson

Elaine Anderson (January 8, 1936 – March 26, 2002) was an American paleontologist. She is best known for her work on vertebrate paleontology.
Biography.
Elaine Anderson was born in Salida, Colorado on January 8, 1936. She was the only child of John and Edith Anderson. She was raised in Denver, Colorado.
Anderson graduated from the University of Colorado in 1960. She completed her Master's thesis in 1965. For her Ph.D., she opted to go to Finland, becoming the first Fulbright Scholar to do so. She studied under the Finnish paleontologist Björn Kurtén, then one of the most distinguished authorities on studies on prehistoric mammals. Anderson returned to the United States after completing her Ph.D. and worked as a scientific consultant at the Pleistocene Hall at the Smithsonian Museum of Natural History, Smithsonian Institution. She also worked briefly at the Idaho Museum of Natural History (then known as the Idaho State University Museum of Natural History) and the Maryland Academy of Sciences. She had to leave her latter job in order to return to Denver and care for her ailing mother.
After her mother's death, she stayed in her childhood home, often being visited by other paleontologists, mammalogists and naturalists who were passing through. A frequent visitor of the Denver Museum of Nature & Science (formerly known as the Denver Museum of Natural History), she formally became a member of the staff in 1984. She was elected a Research Associate in 1994. She was also an adjunct professor of Biology at the Colorado State University.
She died on March 26, 2002 in Denver.
Contributions to science.
Anderson specialized in vertebrate paleontology and mammals. Her particular interest in the members of Carnivora earned her the affectionate nickname of "The Carnivore Lady". She was an Associate Editor of the journal "Mammalian Species", published by the American Society of Mammalogists from 1995 until her death. She was also involved in the field of zooarcheology, long before the term was even coined. She was also active in the conservation efforts on North American mammalian fauna.
She was a member of the American Quaternary Association and was elected an Honorary Member of the Society of Vertebrate Paleontology in 2000.
She is best known for her work "Pleistocene Mammals of North America", written in collaboration with Björn Kurtén in 1980.


Gefell Formation

The Gefell Formation is a geologic formation in Germany. It preserves fossils dating back to the Devonian period.


Gazelle Formation

The Gazelle Formation is a geologic formation in California. It preserves fossils dating back to the Silurian period.


Nariva Formation

The Nariva Formation is a geologic formation in Trinidad and Tobago. It preserves fossils dating back to the Paleogene period.


Garrison Formation

The Garrison Formation is a geologic formation in Kansas, U.S.A. It preserves fossils dating back to the Permian period.


Goughs Canyon Formation

The Goughs Canyon Formation is a geologic formation in southeastern Humboldt County, Nevada.
It preserves fossils dating back to the Mississippian stage of the Carboniferous period.


Tessera (Venus)

A tessera (plural tesserae) is a region of heavily deformed terrain on Venus, characterized by two or more intersecting tectonic elements, high topography, and subsequent high radar backscatter. Tesserae often represent the oldest material at any given location and are among the most tectonically deformed terrains on Venus's surface. Diverse types of tessera terrain exist. It is not currently clear if this is due to a variety in the interactions of Venus's mantle with regional crustal or lithospheric stresses, or if these diverse terrains represent different locations in the timeline of crustal plateau formation and fall. Multiple models of tessera formation exist and further extensive studies of Venus's surface are necessary to fully understand this complex terrain.
Exploration.
Pioneer Venus Orbiter detected regions of anomalous radar properties and high backscatter. Using SAR imaging, the Venera 15 and Venera 16 orbiters revealed these regions to be chaotically tiled terrain, which Soviet scientists named "паркет" (parquet), later known as "tesserae." The most recent data concerning tessera terrain comes from the Magellan Mission, in which the majority of Venus's surface was mapped in high resolution (~100 m/pixel). Future missions to Venus would allow for further understanding of tessera terrain.
Locations.
Tesserae are recognized as covering 7.3% of Venus's surface, approximately 33.2×106 km, and occur mostly within a few extensive provinces. They are heavily concentrated between 0°E and 150°E. These longitudes represent a large area between a crustal extension center in the Aphrodite Terra and a crustal convergence center in Ishtar Terra. Tesserae are exposed almost entirely within Venus's crustal plateaus. Tessera inliers, regions of tessera not found within current crustal plateaus are thought to represent regions of collapsed crustal plateaus. Large regions of tessera terrain are labelled based on their latitude. Regions in the equatorial and southern latitudes are labelled as "regio" while regions in the northern latitudes are labelled as "tesserae."
A comprehensive list of regiones and tesserae can be found under List of geological features on Venus. Some well explored regions of tessera include:
Formation.
Tesserae represent an ancient time of globally thin lithosphere on Venus. Tessera Terrain does not participate in the global resurfacing events of Venus. It was thought by many researches that the tesserae might form a global "onion skin" of sorts, and extended beneath Venus's regional plains. However, the currently accepted models support regional formation. Multiple models have been put forward to explain the formation of tessera terrain. Models of formation by mantle downwelling and pulsating continents are the most currently accepted models. A model of formation due to a lava pond via bolide impact was put forth, although it has not currently gained much traction in the scientific community due to skepticism of the ability of a bolide impact to generate sufficient melt. A model of formation due to mantle plumes (upwelling) was persistent for many years, however, it has since been abandoned due to its contradictory prediction of sequences of extension versus the observed cross cutting relationships.
Downwelling.
In the downwelling model, mantle downwelling, possibly due to mantle convection, causes compression and thickening of the crust, creating the compressional elements of tessera terrain. Isostatic rebound occurs due to the crustal thickening. After downwelling ends, a delamination event within the mantle produces extensional elements of tessera. This model does not currently explain tessera's location within crustal plateaus, and instead predicts a domical shape.
Lava pond via giant impact.
In the lava pond via giant impact model, melt due to a bolide impact on a thin lithosphere rises to the surface to form a lava pond. Convection throughout the lava pond resulted in surface deformation that created tessera terrain. Isostatic rebound of the solidified pond creates a crustal plateau structure. This model does not currently explain how convection could transmit enough force to deform several kilometers of brittle material.
Pulsating continents.
In the pulsating continents model, differentiated, low density crust survives early global subduction events forming continental regions. These regions undergo compression due to heating from the surrounding mantle, forming the compressional features of tessera, such as fold and thrust belts, and basin dome terrain. After sufficient crustal thickening has occurred, new lithosphere is generated causing gravitational collapse, producing the extensional features of tessera, such as extensive grabens. During this collapse, decompression causes partial melting, producing the intratessera volcanism seen within the larger regions of tessera terrain. This model requires that the material comprising tessera terrain is continental in nature. Future missions to venus to sample surface compositions are necessary to support this model. This model does not currently explain how a global subduction event could cause the delamination of the entire mantle lithosphere, leaving only low density crust behind.
Variety of tessera terrain.
Individual patterns of tessera terrain record the variations in interactions of the mantle with local regional stresses. This variation manifests itself in a wide array of diverse terrain types. Multiple types of sampled tessera terrain are below, however, they are not meant as a classification scheme, and instead emphasize the variety of terrain types.
Fold Terrain is easily recognizable by its well defined linear fabrics. This type of terrain is composed of long ridges and valleys, greater than 100 km long, that are cross cut by minor extensional fractures that run perpendicular to the fold axes of the ridges. This likely formed due to unidirectional contraction.
Lava Flow Terrain is named such due to its resemblance to Pahoehoe flows found on Earth, with long curving ridges. It is thought that this terrain may be formed due to displacement and deformation due to movement of the material beneath these crustal pieces.
Ribbon Terrain is characterized by ribbons and folds that are typically orthogonal to one another. Ribbons are long and narrow extensional troughs that are separated by narrow ridges. Ribbon terrain can be found both in large crustal plateaus and within tessera inliers.
S-C Terrain is named such due to its geometric similarity to S-C tectonic fabrics on Earth. It consists of two main structures: synchronous folds and small, 5 to 20 km long graben that cross cut the folds perpendicularly. Unlike many other types of tessera terrain, S-C terrain indicates a simple, rather than complex deformation history in which deformation due to widespread motion on Venus is widely distributed. This type of terrain also indicates that strike-slip movement on Venus's surface is possible.
Basin and Dome Terrain, also known as honeycomb terrain, consists of curved ridges and troughs that form a pattern analogous to an egg carton. These structures represent multiple phases of deformation, and are considered the most complex appearing style of tessera. Basin and dome terrain is typically found within the center of crustal plateaus.
Star Terrain is composed of multiple graben and fractures that trend in many directions, but radiate in a star-like pattern. This pattern is thought to be due to doming underneath previously deformed and fractured areas, in which the local uplift causes the radiating pattern.


Palisades Sill (New Mexico)

The Palisades Sill is a fine-grained porphyritic dacite sill which forms spectacular cliffs and palisades in the Cimarron River canyon between Eagle Nest and Cimarron in northern New Mexico. It can be seen in the eastern part of Cimarron Canyon State Park.


Dryden Shale

The Dryden Shale is a geologic formation in Scotland. It preserves fossils dating back to the Devonian period.