Structure of the earth

1. Structure of the earth WALT: The structure of the Earth WILF: Identify the structure of the Earth Describe the evidence that explains how the Earth is changing Explain how volcanoes and earthquakes are formed

2. Structure of the earth atmosphere

3. Structure of the earth The core is a mixture of magnetic metals. The inner core is solid and the outer core is a liquid The mantle is a solid but in places behaves like a liquid The crust is a very thin layer, as thin as 5km in some places. The atmosphere is a thin layer of gases about 10km All the minerals we depend on in our lives come from the atmosphere, oceans and crust.

4. Tectonic plates The Earths’ crust and the upper part of the mantle are cracked into huge pieces, known as tectonic plates. Tectonic plates move very slowly and scientists believe that the world map was different millions of years ago. South America was thought to be attached to Africa from their jigsaw like coastlines. A scientists called Wegener put forward the idea of continental drift in 1915. No one believed him at first then fossils and rocks showing the same species were found on both continents. Other scientists started to believe his theory and now continental drift is widely accepted

5. http://www.youtube.com/watch?v=QDqskltCixA

6. Pangaea- Super continent

7. Tectonic plates Tectonic plates move very slowly a few centimetres every year. This is because deep inside the Earth radioactive atoms decay releasing huge amounts of energy. This heats up molten minerals in the mantle which expand. They become less dense and rise up. When they cool they sink and are replaced by warm minerals. Forces created by these convection current move the tectonic plates.

8. Tectonic plates http://www.youtube.com/watch?v=p0dWF_3PYh4

9. Tectonic plates At the boundaries of the plates, huge stresses build up. These forces make the plates buckle and deform, mountains can be formed in the way. The plates may also slip past each other. These sudden movements may cause earthquakes.

10. Tectonic plates • Tectonic plates move a few centimetres every year because inside the Earth radioactive atoms decay releasing huge amounts of energy. This causes convection currents which move the plates • Stress build up at the boundaries, • buckled plates = mountains. • Plates slipping past each other = earthquakes.

11. The Earths Atmosphere For about 200 million years, the proportions of the different gases in the atmosphere have been much the same as they are today: • 80% nitrogen • 20% oxygen • Small amounts of carbon dioxide, water vapour and noble gases.

12. The Earths Atmosphere During the first 200 billion years there was intense volcanic activity which released the gases (carbon dioxide, water vapour and nitrogen) that formed the early atmosphere and water vapour which condensed to form the oceans.

13. The earths atmosphere • First billion years - Intense volcanic activity which released carbon dioxide, water vapour andnitrogenthat formed the early atmosphere. The water vapour condensed to form the oceans. • One theory of how the atmosphere began – atmosphere mainly CO2with little oxygen (Like Venus and Mars). There was also small amounts of water vapour, ammonia and methane

14. How life began There are many theories about how life began on Earth. Scientists think that life began about 3.4 billion years ago as a simple organism that could make its own food. This was thought to have evolved into algae. As the oxygen levels increased the algae evolved into plants. As more oxygen was available, animals were able to survive. The oxygen that plants and algae produced through photosynthesis is now in our atmosphere.

15. Life on earth The atmosphere is explained by the oxygen being produced from plants during photosynthesis. But where did the molecules that make up the cells of even the simplest living things come from? The answers are only theories, they are based on assumptions, the most widely accepted theories will have the most evidence to support them.

16. Carbon locked into rocks Carbon dioxide is taken up by plants, animals eat plants so it ends being transferred to animal tissue, bones and teeth. Over millions of years the dead bodies of the huge numbers of animals built up in the oceans. Eventually they formed sedimentary carbonate rocks like limestone (containing mainly calcium carbonate) Some of these rocks were crushed and formed fossil fuels. In this way most of the carbon dioxide from the atmosphere ended up locked up within the Earth’s crust Carbon dioxide also dissolved in the oceans. It reacted and made insoluble carbonate compounds. These fell to the seabed and helped form more carbonate rocks.

17. Carbon locked into rocks • Plants use CO2, animals eat plants. CO2 ends up in animal tissue, bones and teeth. • Dead plants and animals form sedimentary carbonate rocks in the oceans (like limestone)(coal) • Some of these rocks were crushed and formed fossil fuels. Fossil fuels are the remains of plants and animals and are made of hydrogen and carbon • In this way most of the carbon dioxide from the atmosphere ended up locked up within the Earth’s crust

18. Carbon dioxide in the atmosphere • Over the last 200 million years the levels of carbon dioxide in the atmosphere have not changed very much • This is due to the natural cycle of the carbon in which carbon moves between the oceans, rocks and the atmosphere. • The cycle is self-regulating, so left to itself it the carbon levels remained balanced. • The levels only change with human interaction • The oceans act like a reservoir for carbon dioxide. They absorb excess it when it is produced and release it when there is a shortage

20. Carbon dioxide in the atmosphere • The oceans act as a reservoir for carbon dioxide. • Increased amounts of carbon dioxide that are absorbed by the oceans has an impact on the marine environment. The more CO2 in the oceans the more acidic the water is. Some plants cannot cope with acidic water. Photosynthesis removes CO2 from the atmosphere • Carbon dioxide levels are being increased by burning fossil fuels as this releases the carbon stored within the fossil fuel & respiration

21. Revision • Make a mind map on each topic, covering all the key points • Work through the chemistry unit in the text book either making notes or answering the summary/exam questions. This is your revision, do what is best for you • This is your time to ask questions and use the text. • Use your time wisely!!!