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The One Minute Geographer: This Fragile Earth (14) The Earth’s Relief
Elevation is called “relief” on a globe. We saw in earlier posts that the tallest mountain, however defined — Everest, Mauna Kea or Chimborazo — is less than 7 miles tall. The deepest ocean trench, Challenger Deep, the southern end of the Mariana Trench in the Pacific southwest of Guam, is actually deeper than any mountain is tall. It’s 36,200 feet or 6.9 miles deep.
In what follows, to make the math simple, I’m going to call those highest and lowest points on the earth less than 8 miles of relief. Now recall that the diameter of the earth is about 8,000 miles. The highest and lowest points, 8 miles up or down, represent less than 8/8000 miles. That is 1/1000 (one one-thousandth) of the diameter of the earth.
When you buy a relief globe and you can “feel” the mountains on it, that’s all for show. If you look at the legend on the globe you will see that it says something like “vertical exaggeration 20x” or more. Instead of 5 miles tall, Mount Everest would have to be 100 miles tall for you to actually feel it like that on a typical 16-inch diameter globe.
So suppose you wanted to make an accurate 16-inch diameter globe to show mountains and ocean trenches in proper portion. You’ve got your exacto knife out and you are ready to start carving. Are you ready for this?
