The Mush Zone: A slurpy layer lurks deep inside the planet

摘要

If you were to take a supersonic elevator down toward the center of the globe, it wouldn't take long to feel the heat. Just after the start of the journey, at the meager depth of 200 kilometers, the temperature rises to 1,000℃. This is the base of Earth's lithosphere, its outermost skin. Leaving the lithosphere, the elevator enters the mantle—the great rocky domain that makes up 84 percent of the planet's volume. If the heat doesn't do you in, the boredom certainly will. The shaft descends through thousands of kilometers of mostly featureless, solid rock. It's like enduring a crosscountry bus ride that rolls past the same flat scenery for days on end.