Book 20, Question 19
Do Mountains Have Roots?
Yes, in a way, mountains have roots! Earth's crust floats on the softer rock below it, like an iceberg in water. Tall mountains have deep roots of crust pushing down underneath them.
More fun facts
- Scientists call the balance between mountains and the rock beneath them isostasy.
- One classic idea, the Airy model, says mountains have thick roots of crust, like a floating iceberg.
- Another idea, the Pratt model, says the density of the crust changes instead of its thickness.
- Under the Sierra Nevada in California, the crust thickens to more than 50 kilometers.
- The crust under the Basin and Range country east of the Sierra Nevada is only about 35 kilometers thick.
- The European Alps also have crustal roots.
- The crust under the Rocky Mountains is as thin as or thinner than the crust under the Great Plains, so not every range has a deep root.
Sources: U.S. Geological Survey
Questions kids ask
Do all mountains have deep roots?
No. Some ranges, like the Sierra Nevada and the Alps, have thick crustal roots, but others, like the Rockies, do not.