Back-of-the-Envelope Calculations: Size of KT Meteorite

Barbara Tewksbury
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About 66 million years ago at the end of the Cretaceous Period, a meteorite estimated to have been about 10 km in diameter slammed into the Earth. Let's put the size of this cosmic cannonball into perspective. Suppose we could carefully and quietly lower the meteorite into the Pacific Ocean between Hawaii and the U.S. Once it was sitting on the bottom of the Pacific, how far would the top of the meteorite stick up relative to the surface of the ocean?

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The meteorite would make an island about 10 km across and about 5,000 m high (over 16,000' high, which is higher than Mauna Loa or Mauna Kea on Hawaii!). The Pacific Ocean is deep, between 5,000 and 6,000 meters deep. But, deep as it is, the depth of the Pacific is only about half the diameter of the KT boundary meteorite. Dropping such a meteorite into the Pacific would be rather like dropping a boulder into a puddle (at cosmic velocities)!

References and Resources

This SERC page describes the use of Back of the Envelope Calculations

A View from the Back of the Envelope (more info) : This site has a good number of easy simulations and visualizations of back of the envelope calculations.

The Back of the Envelope : This page outlines one of the essays in the book "Programming Pearls" (ISBN 0-201-65788-0). The book is written for computer science faculty and students, but this portion speaks very well to back of the envelope calculations in general.