The restless earth

The earth as it appeared 65 million years ago Early Geologists missed the most obvious observation that Africa’s coast line closely matched the coast line of South America

The mantel behaves like a solid but can flow slowly like a liquid A moving plate 1915 Alfred Wegener first put forward the idea of continental drift but he could not explain it. It was rejected by the other geologists! Heat from radioactive decay in the core

Heat from radioactive decay in the core

One land mass ‘Pangeae’

Pangaea splits in two

Land masses move apart - 4cm year? India moves North and pushes up the Himalayas

Land masses are cracked into a large number of tectonic plates The distribution of volcanoes largely follows the plate boundaries

If earthquakes happen under the sea, huge tidal waves called tsunamis may occur.

If earthquakes happen under the sea, huge tidal waves called tsunamis may occur.

If earthquakes happen under the sea, huge tidal waves called tsunamis may occur.

Problems e Problems emerged with the cooling earth idea Too much heat existed in the core from radioactive elements to allow for cooling effect 2. Eventually all mountains should be eroded and all dips filled in and be of a similar age 3. Where did all the eroded river sediment go? million tons of it each year! - a 20km high ! coverage around the planet ! 1. Similar fossils and rocks appeared on coasts of South America and Africa 5. How did identical snails turn up in Norway and Canada and how did marsupials travel from South America to Australia?

Problems e Problems emerged with the cooling earth idea Too much heat existed in the core from radioactive elements to allow for cooling effect 2. Eventually all mountains should be eroded and all dips filled in and be of a similar age 3. Where did all the eroded river sediment go? million tons of it each year! - a 20km high ! coverage around the planet ! 1. Similar fossils and rocks appeared on coasts of South America and Africa 2. Identical snails turn up in Norway and Canada and marsupials end up in South America and Australia.

Problems e Problems emerged with the cooling earth idea Too much heat existed in the core from radioactive elements to allow for cooling effect 2. Eventually all mountains should be eroded and all dips filled in and be of a similar age 3. Where did all the eroded river sediment go? million tons of it each year! - a 20km high ! coverage around the planet ! 1. Similar fossils and rocks appeared on coasts of South America and Africa 2. Identical snails turn up in Norway and Canada and marsupials end up in South America and Australia. 3. There coal seams from tropical forests in Spitzbergen in the arctic circle.

Problems e Problems emerged with the cooling earth idea Too much heat existed in the core from radioactive elements to allow for cooling effect 2. Eventually all mountains should be eroded and all dips filled in and be of a similar age 3. Where did all the eroded river sediment go? million tons of it each year! - a 20km high ! coverage around the planet ! 1. Similar fossils and rocks appeared on coasts of South America and Africa 2. Identical snails turn up in Norway and Canada and marsupials end up in South America and Australia. 3. There coal seams from tropical forests in Spitzbergen in the arctic circle. Early geologists invented “ land bridges” across prehistoric seas to allow animal migration which since have disappeared!! (No evidence existed for this at all)

Tectonic theory People once thought that the oceans and the continents were formed by shrinkage from when the Earth cooled down after being formed. Alfred Wegener proposed something different. Consider Africa and South America: These continents look like they “fit” together. They also have similar rock patterns and fossil records. These two pieces of evidence led me to believe that there was once a single land mass. This is my TECTONIC THEORY.

Forming mountains The formation of mountain ranges can be explained by tectonic theory. Consider the Himalayas at the top of India: This is where India is now This is where India was millions of years ago The intense heat and pressure from this process causes the rocks to change structure into metamorphic rocks.

The Answer: 1)Scientists discovered 50 years later that the Earth generates massive amounts of heat through radioactive decay in the core. This heat generated convection currents in the mantle causing the crust to move 2)We also now know that the sea floor is spreading outwards from plate boundaries Tectonic theory The Evidence: 1)Some continents look like they used to “fit” together 2)Similar rock patterns and fossil records The Problems: Wegener couldn't explain how continental drift happened so nobody believed him Conclusion – scientists now believe Wegener’s Tectonic Theory