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Tuesday, November 15, 2011

Ancient piece in the rock garden - by Dan Hathaway

I discovered four different types of interesting rock during my visit to Fugitive's Drift. All four of them tell very different stories.

These are my observations about the rock I am holding in the photograph.
It isn't often I get to hold a piece of import breccia in my hand. In fact, I have never done it before.
This is so because impact breccia is formed by the collision of meteorite with the surface of the earth. This is a very rare occurrence.

There are really only a few places in the world where this has happened.
So to be holding a piece of evidence of cosmic collision is all the more exciting.

If you look closely at impact breccia you can see the shattered fragments of the earth's crust that the meteorite slammed into. I was thinking that it looked like someone seriously tore into a rock pile with a sledgehammer. The whole thing is glued together in a matrix of something called melt rock. Melt rock is caused by the tremendous amount of heat liberated by the impact. The breccia then cools and solidifies.

Did anything get hurt by the meteorite? Probably not, because the age of a nearby crater is about 2 billion years old. The only things living back then were single cell bacteria. It was a really different world.

Who would have thought that a walk in your beautiful rock garden would extend back that far.

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