Changes In The Earth And Its Atmosphere Flashcards
Earthquakes within the earth’s crust can be sudden and disastrous. Scientists cannot accurately predict when earthquakes will occur. Explain why. To obtain full marks you must support your answer with a description of what causes earthquakes.
Because plate boundaries normally move a few centimetres per year and sudden movement happen to cause earthquakes.
Two hundred years ago, scientists though that the earth was about 400 million years old. This estimate came from the idea that the centre of the Earth was still molten. More recently, measurement of radioactivity in rocks has shown that now know that the Earth is much older than 400 million years.
Radioactivity keeps the core hot.
Suggest two pieces of evidence that could be used to show that the continents had once joined.
The shapes of the two continents fit together like a jigsaw and the same type of rocks have been found.
About fifty years ago, new evidence convinced scientists that the earth’s crust is made up of tectonic plates that are moving very slowly. Give two pieces of evidence that have helped to convince these scientists that the tectonic plates are moving.
Earthquakes and volcanoes
Suggest two reasons why the other scientists in 1920 thought that Wegener was wrong.
Plates cannot move thousands of kilometres and new animals are different.
Explain how earthquakes are caused.
Movement of tectonic plates causes vibration waves in the earth and convection currents in the mantle.
In terms of what is happening Whithorn the Earth, explain the problems of trying to predict earthquakes.
Scientists do not know what happens under the crust and where forces are building up.
Describe what causes the Earth’s tectonic plates to move.
In the mantle convection currents release heat
Give one reason why Wegener’s idea was not accepted in 1915.
No proof.
The theory of plate tectonics is used to explain why earthquakes occur. Explain how earthquakes occur.
Tectonic plates move which is caused by convection currents in the mantle.
Suggest why it is difficult to predict when an earthquake will occur.
Do not kNow what is happening below the Earth’s crust.
In 1915, Alfred Wegener had an idea that the Change shown in the diagram was caused by continental drift. Most scientists could not accept his idea. Suggest why most scientists in 1915 could not accept Wegener’s idea of continental drift.
Wegener had no evidence
The earth has a layered structure and is surrounded by an atmosphere. Use this information and your knowledge and understanding to explain how continents move.
Plates move and heat energy causes convection currents.
Scientists have suggested that the Earth consists of a core, mantle and crust. A ‘traditional’ theory is that the core is made of iron and nickel. A ‘controversial’ theory is that the core is like a nuclear reactor made of the radioactive elements uranium and plutonium. Why can scientists not prove which theory about the core is correct?
Cannot get to see the core.
Suggest two pieces of evidence that may have led Wegener to propose his hypothesis that continents move.
The continents of South America and Africa would have fitted together like a jigsaw.
Suggest why, in 1920, other scientists thought that Wegener’s hypothesis was wrong.
Other scientists thought that continents are fixed.
