When I look at pictures of Meteor Crater near Winslow, it looks kind of squarish, but craters on the moon always seem to be circular. Can you explain this?
My first thought on this one is that this guy had just seen a picture of Meteor Crater shot at an odd angle that made it look like a square because everybody knows craters on Earth or the moon or wherever are always circular.
It turns out, not for the first time, that I was wrong. Meteor Crater does have sort of a square or rectangular shape.
How could a great mass of rock, rounded over the ages, leave behind a square impression?
First, some background: About 50,000 years ago a hunk of space rock weighing around 150 tons and measuring about 134 feet across hit Earth at around 26,800 mph. It gouged out a crater about 570 feet deep and 4,100 feet across.
The shape of a crater like that could be affected by a couple of things – perhaps the angle at which the meteorite struck, and/or just exactly what it hit.
If a meteorite were to strike more or less head-on and throw ejecta – debris – evenly in all directions, it would leave a round crater. If it were to strike at an extremely oblique angle, it could plow stuff in front of it as well as stuff out to the sides, resulting in a more elongated or rectangular sort of crater.
Our meteor struck layers of brittle sandstone and limestone that were already fractured along pressure lines at right angles to one another. That meant the rock was less resistant along those right angles, making a square crater.
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