The document summarizes how the Himalayas and Tibetan Plateau formed through the collision of the Indian and Eurasian tectonic plates starting around 130 million years ago. Sediment deposited on the ocean floor was subducted or squeezed up to form the highest mountains, as evidenced by fossils like ammonites found high in the mountains. The Indian plate drifted northward into Asia, and the continental crust behaved plastically when compressed under pressure, folding and uplifting to create the Himalayan range.

1. What’s this?

4. Can you remember how Tibet / The Himalayas were formed?

5. Amazing Earth – Himalaya Rising

6. (130 Mya)

13. On these two pictures, think about what happens to the sediment in the bottom of the disappearing ocean (can you predict?) So, what has happened to it? Truth is, some has gone down here (subducted), and… … some has been squashed right up here, to the top of the highest mountains

14. Click for animation video

15. Both of these things are important in understanding plate tectonics. The subducted sediment (and water) is what causes the melting (and so the volcanoes), by adding impurities to the mantle (like adding salt to ice) The sediments being squashed to the top result in the amazing truth that the highest mountains are made from material from the bottom of the ocean.

16. What is this fossil called? Ammonites like this are found in the Himalayas. This is how they lived when they were alive. They lived in the oceans. So how come they are found in the highest mountains?

18. After Collision

19. You can see on this slide that the continental rocks get ‘squashed’ when they are put under great pressure (and buried, so they heat up). Geology teachers often say it behaves like plasticine. This is an important thing to understand about continental rocks: when heated and pressurised, they behave plastically (i.e. they squash not snap – unlike the oceanic crust, which does not squash – i.e. it is rigid .)

20. Indian plate Eurasian plate This is getting ‘squished’ sideways! Where is the Indian plate? What is the name of the other plate? Which direction are they moving?