Book 20, Question 112
Why Do Some Mountain Rocks Look Like Wavy Ribbons?
Some mountain rocks look like wavy ribbons because their layers were folded. Earth's crust squeezed them from the sides, like pushing on a rug. It happened slowly, over millions of years, and those folds are still there today.
More fun facts
- Folding happens when Earth's forces put stress on rock and the rock bends instead of breaking.
- Folds shaped like an arch are called anticlines, and folds shaped like the letter U are called synclines.
- In a syncline, the youngest rock sits in the middle with older rocks on either side, and an anticline is the opposite.
- The Valley and Ridge province of the Appalachians is a long series of anticlines and synclines.
- Those folds formed from squeezing during the assembly of the supercontinent Pangea.
- There, soft limestones and shales wore down into valleys, while tough sandstones form the ridges.
- Where rivers cut through these ridges, they make narrow water gaps.
Sources: National Park Service, National Park Service
Questions kids ask
What is an anticline?
An anticline is a fold in rock layers shaped like an arch.