Lubricated earthquakes

It’s well known that tectonic plates can slip underneath another plate in subduction zones and that violent earthquakes occur when the plates stick and release. Research is revealing the frequency of potential earthquakes. If it weren’t for ‘lubricated’ sliding, British Columbia would have a major earthquake every fourteen months and Japan every six. I’m not sure whether the lubrication is from melting rock or from seawater or a bit of both.

A map of British Columbia's seacoast shows where earthquakes occur

Cascadia subduction zone


Glenn Morton’s “Why I Left Young-Earth Creationism”

From Old Earth Creation Science Ministry.





A buried river canyon from a geological survey












  1. Go to .
  2. Select ‘publications’.
  3. Select ‘Geoarchives’.
  4. Select ‘1996’.
  5. Select ‘September and October’.



This testimony originally published on Glenn Morton’s website.


Mesa of sedimentary rock coloured by sunset

Rocks rock!

This image from the Grand Canyon comes to you from Schurs Astrophotography.

I like that they refer to the growing dark after sunset as the Earth’s shadow.

Adventures in Science


  • surveyed 25,000 vertical feet of geological strata over two seasons,
  • found the first Precambrian fossils
  • drafted the bill that created the national forest reserves
  • was a science adviser to several U.S. presidents
  • brought the Wright brothers official recognition for their work

The colors of iron

On recent travels, I’ve seen a lot of rocks and soils that are dark grey, purple, red, and ochre. All of these colors come from iron. This monograph explains how one element can cause so many colors, at least in sandstone: Rainbow of Rocks.

Igneous rocks: formation and classification

Here’s a quick link to a good explanation of igneous (“formed by fire”) rocks: Igneous Rocks: Formation and Classification, by by amelianavarro.

Briefly, igneous rocks are formed from melted rock. Higher water content makes it easier for rocks to melt.

Conditions of formation:

  • Intrusive rocks harden inside the earth and tend to cool slowly, forming larger crystals.
  • Extrusive rocks harden on the surface or in air. Usually, it is volcanoes that extrude them as lava, ash, or flying rocks. Extrusive rocks may expand explosively and cool rapidly. They may even be cooled by sea-water.

Classification by texture:

  • Phaneritic rocks have large crystals that are easy to see without magnification, e.g. granite.
  • Aphaneritic rocks have small, sand-like crystals. They may feel smooth. An example is basalt. Their crystals are so small that the human eye cannot see them [easily?] without a lens.
  • Porphryitic rocks have both small and large crystals. One may impulsively assume that large crystals make them phaneritic, so  looks can be deceiving. An example is andesite.
  • Glassy rocks always look shiny. They may feel smooth or greasy. An example is obsidian. They form when molten rock cools very quickly.
  • Vescular rocks have many holes, with holes formed by expanding gasses. They are usually extrusive. A well-known example is pumice.

Classification by silica content :

  • Felsic rocks have more silica. They are usually light in color.
  • Mafic rocks have more iron and magnesium. They are usually dark in color.

I wonder how much silica (SiO2) it takes to be truly “felsic”.

More about the oldest rocks ever

Rocks formed from old mantle were found on Baffin Island in northwestern Canada. The rocks have been seen before, but they awaited dating methods that could distinguish them from the rest of the rocks on Earth. When lava solidifies, elements with their isotopes are frozen into it. We can use them to calculate the age of the rock.

The Earth’s mantle is the hot, stony layer between its crust and the nickel-iron core. Its upper layers can flow, however slowly, but further down it is compressed into a solid by the weight above it.

How can the mantle be modern or primitive? Isn’t it just a ball of molten ooze? Not exactly.

As the Earth formed, it melted from the energy of incoming material. When the loose material in the inner system was mostly accumulated, bombardment slowed and the molten Earth cooled off. In the molten crust, dense material sank to become the core and lighter material floated to the surface. Slow convection currents in the magma probably helped the continents to form in the cooler areas when less dense material was pushed aside by hot, rising plumes. Continents of lightweight silicon-aluminum rock, or sial, float on denser silicon-magnesium rock, or sima. Since the Earth’s crust cooled and solidified it has cracked into several large slabs or plates. The plates slide under or over each other, so that the upper plate is lifted into mountains, as in the U.S. Rockies. They ram into each other, and are compressed, buckling and folding into mountains, as in the Canadian Rockies.  The most spectacular example occurs where India collided with Asia, raising the Himalayas.

Over millions of years, wind, water, ice, and gravity erode the mountains back into rocks and particles, creating new sedimentary rock. However, particles in this rock still have the age signature of the original crust. has the story:

But these rocks contain an early Earth mixture of helium, lead and neodymium isotopes which suggest the mantle rock beneath the crust that yielded them is a virgin pocket of Earth’s original material.That pocket survived for 4.5 billion years under Baffin Island without being mixed by plate tectonics or erupted onto the surface.

“I was surprised that any of the (original) mantle survived,” said geoscientist Matthew Jackson of Boston University. He is the lead author on a paper announcing the discovery in this week’s issue of the journal Nature. “Finding a piece of the original mantle has been a holy grail. The original Earth was a big ball of magma. That’s our (planet’s) original composition.”

The discovery has surprised other researchers as well.


One of the obstacles in finding rocks from such ancient mantle, up to now, has been that researchers had assumed early Earth was composed of rocks with helium and lead isotope matching those of a type of ancient meteorite called a chondrite.

That may be true up to a point, said Jackson. Some recent research by scientists at the Carnegie Institution of Washington has suggested that the Earth’s early mantle would also have tell-tale neodymium isotopes that are unlike chondrites.

“That turns out to be the same as we find in these lavas (from Baffin Island),” said Jackson.

The other signs of untouched ancient mantle material — which has not before lost any of its material to Earth’s surface or been otherwise tainted — is a large amount of the isotopes helium-3 relative to helium-4. There is also an very old lead-isotope signature.

It was these three criteria — the helium, lead and neodymium — that led Jackson and his team to the conclusion that the Baffin Islands’ massive volcanic cliffs are made of the oldest material on the planet.

As for how much of this original mantle might be around, the only way to tell is to look at lava rocks and see if they came from such stuff, said Jackson.

It occurs to me that if there are longstanding downward currents of cooled magma in the mantle, there are places that are between those “downdrafts” and furthest from their influence. Those would be the most likely places for old magma to stay in place near the surface.

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