when was the last time yellowstone park erupted
Yellowstone Caldera Non-explosive eruptions of lava and less-violent explosive eruptions have occurred in and near the Yellowstone caldera since the last supereruption.[13][14] The most recent lava flow occurred about 70,000 years ago, while a violent eruption excavated the West Thumb of Lake Yellowstone around 150,000 years ago. Smaller steam explosions occur as well: an explosion 13,800 years ago left a 5 km (3.1 mi) diameter crater at Mary Bay on the edge of Yellowstone Lake (located in the center of the caldera).[15][3] Currently, volcanic activity is exhibited via numerous geothermal vents scattered throughout the region, including the famous Old Faithful Geyser, plus recorded ground-swelling indicating ongoing inflation of the underlying magma chamber.
Mount Mazama Mazama was last active about 4,800 years ago, when an eruption took place near Wizard Island's eastern base.[96] This eruption took place underwater,[93] and it produced viscous lava that created a rhyodacite lava dome, about 2,400 years after the first period of postcaldera activity.[97] Given that Mazama has had periods of sporadic eruptions for 420,000 years, the United States Geological Survey thinks that it is "virtually certain" that Mazama will erupt again in the future.[6][98] Mazama is considered dormant, but it remains monitored by the United States Geological Survey Cascades Volcano Observatory.[21] Future eruptions would likely take place near the western side of the complex and within the caldera rim; they could occur underwater. The ejection of lava rich in gas from shallow water could produce huge ash columns, but submarine eruptions at deeper depths may decrease the explosiveness of the event. Nonetheless, the rapid mixing of water and lava could produce dangerous pyroclastic surges, which are more gaseous and less solid than pyroclastic flows.[6] Such flows could pass over topographic barriers, move rock fragments at rapid speeds of 800 feet per second (240 m/s), and travel several miles from their vent.[99] Mazama is unlikely to produce mudflows far from the caldera, though a nearby vent outside the caldera could erupt and mix with snow. Eruptions are unlikely to produce waves that extend beyond Crater Lake, but powerful explosions could produce tall waves in the caldera.[100] An eruption as explosive as the one 7,700 years ago is unlikely given that it would require larger volumes of magma than are known to be available within the Mazama vicinity.[39] Moreover, landslides could flood adjacent shoreline regions, but they are not likely to induce failure of the caldera's walls, as they rise more than 500 feet (150 m) above the lake's surface.[39] Earthquakes from the nearby West Klamath Lake fault zone could reach magnitudes up to 7.0 on the Richter scale, but these only occur every 3,000 to 10,000 years; they could generate tall waves by creating landslides.[39] Though local earthquakes from volcanic activity would create motion in the lake, they would likely only reach maximum magnitudes of 5.0 on the Richter scale. However, Crater Lake is poorly monitored, and not highly active seismically among the Cascade volcanoes.[101] The largest earthquake threat originates from the Cascadia subduction zone, which could produce earthquakes with a magnitude of 8 or 9 that could lead to huge waves in Crater Lake.[32]
Yellowstone Caldera Volcanism at Yellowstone is relatively recent, with calderas that were created during large eruptions that took place 2.1 million, 1.3 million, and 630,000 years ago. The calderas lie over a hotspot where light, hot, magma (molten rock) from the mantle rises toward the surface. While the Yellowstone hotspot is now under the Yellowstone Plateau, it did help to create the eastern Snake River Plain (to the west of Yellowstone) through a series of huge volcanic eruptions. The hotspot appears to move across terrain in the east-northeast direction, but in fact the hotspot is much deeper than terrain and remains stationary while the North American Plate moves west-southwest over it.[6]
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