x dating y com - Dating terrestrial impact structures

Terrestrial planets have hard surfaces that can be re-shaped by several different processes: impact cratering, volcanism, erosion, and tectonics.

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The craters on all of the moons except Io, Mercury, and most of the ones on Mars are from impacts.

The kinetic energy of the impacting meteorite or asteroid is converted into heat, sound, and mechanical energy---the projectile explodes on impact.

To become complex, a crater must have a large enough diameter.

On Earth the transition diameter lies between two and four kilometers.

Sometimes the impact site reveals an abundance of siderophile elements such as iridium, osmium, platinum, and palladium.

Other tell-tale signs of an impact are products of shock metamorphism such as shatter cones, planar features in quartz and feldspar, diaplectic glass, and a high-pressure form of quartz called stishovite.At such speeds, the projecticle explodes on impact and carves out a round bowl-shaped depression on the surface. How can you distinguish an impact crater from a volcanic crater?Volcano craters are above the surrounding area on mountaintops while the craters from impacts are below the surrounding area with raised rims.I actually live within the boundaries of an ancient buried impact structure located in Des Plaines, Illinois, USA.This eight kilometer diameter crater is about 280 million years old.Because the Earth is so active geologically, most traces of impact craters have been erased by erosion and tectonic activity.

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