How Colliding Plates Build Mountains

In the picture

1. 1The left plate — a thick slab of layered rock creeping to the right.
2. 2The right plate — the opposing slab pushing back to the left.
3. 3The collision zone — buckled, folded rock layers where the two slabs meet.
4. 4The summit — the highest peak, built from rock stacked up by the folding.

Examples

• Pushing a rug across a floor: the cloth bunches into ridges, just like squeezed rock layers.
• The Himalayas, where India is still pushing into Asia and Everest grows a few millimetres taller each year.

Quiz: How Colliding Plates Build Mountains (Age 12)

1. 1

   Two of Earth’s plates are pushing straight into each other. What builds the mountain range?

   • The rock caught between them is squeezed, folded and pushed upward.
   • The plates melt where they touch, and the melted rock piles up.
   • One plate cracks open and the gap fills with rock from below.
2. 2

   Two plates are creeping side by side in the same direction at the same speed. Is a mountain range likely to grow between them?

   • No, because neither plate is pushing into the other.
   • Yes, because any plate that moves builds mountains as it goes.
   • Yes, because moving plates always squeeze the rock behind them.
3. 3

   Someone stands on the highest peak of a mountain range made by colliding plates. Where did the rock under their boots come from?

   • Layers of rock that were folded and pushed up from lower down.
   • Liquid rock that poured out of the peak and cooled there.
   • Sand and pebbles that wind and rivers piled up on top.

The answers, each with its explanation, are in the app. This lesson has left the free week, so its quiz is part of the subscription.