7 Our Changing Planet Flashcards
(54 cards)
What materials are inside the mantle? 3
- magnetic metals
- nickel
- iron
Is the outer core liquid or solid?
Liquid
What is the structure of the earth? 4
- starting from the surface there is the crust
- the mantle
- the core in the centre
- a thin layer of gases called the atmosphere surrounds the earth
Why do the tectonic plates move?2
The moving of the tectonic plates is caused by convection currents in the mantle, due to radioactive decay
What evidence is there Africa and South America were once joined to each other?3
The fossils and rock structures that we find are similar
Fossils show the same reptiles and plants once lived on both continents
The layers of rock in the two continents have been built up in the same sequence
What happens when the boundaries of the plates meet?3
- Huge stresses build up
- These forces make the plates buckle and deform and mountains may form
- these plates may also suddenly slip past eachother these sudden movements cause earthquakes
Why is it difficult for scientists to predict when earthquakes and volcanic eruptions will occur?3
- Earthquakes and volcanoes happen when tectonic plates meet
- it is difficult to know when the plates may slip past eachother
- this makes it difficult to predict accurately when and where earthquakes will happen
How was oxygen produced?2
As plants spread over the earth, the levels of oxygen in the atmosphere increased
How were the gases in the earths atmosphere produced?3
- It probably consisted mainly of carbon dioxide
- there may also have been water vapour together with traces of methane and ammonia
Why does one theory involve hydrocarbons, ammonia and Lightning? 3
- one theory states that the compounds needed for life on Earth
- came from reactions involving hydrocarbons such as methane and ammonia
- the energy required for the reaction could have been provided by lightning
How can the gases in the air be separated?2
The main gases in the air can be separated by fractional distillation
These gases are used in industry as useful raw materials
What are the main gases in the atmosphere today and what are their relative proportions?2
About 80% of the atmosphere is nitrogen
About 20% is oxygen
What are the main gases in the earths atmosphere?2
Oxygen
Nitrogen
How does carbon move in and out of the atmosphere?4
Plants
Animals
The oceans
Rocks
Why has the amount of carbon dioxide in the atmosphere increased recently?
Due to the amount of fossils fuels we are now burning
When do we get earthquakes?
An earthquake is what happens when two blocks of the earth suddenly slip past each other
When do we get tsunamis?5
- they are caused by sudden movement of the ocean due to: earthquakes,
- landslides on the sea floor,
- large volcanic eruptions
- meteorite impact
in the ocean which causes water to be displaced and this water forms the start of a tsunami
Name how mountains can be formed by tectonic plates?
- when earths tectonic plates crash together because of the large amount of energy involved the sides of the plates crumple like in cars
How can mountains be formed along fault lines?3
- blocks of earth are uplifted and tilted over as two plates grind together
- the uplifted part forms a mountain and the lowered parts are filled in with eroded material
eg Sierra Nevada mountain range in California
How can mountains be formed from magma?3
- magma beneath the earths surface is pushed up but dosent actually crack through
- this bulge of magma cools eventually and gardens into hard rock like granite
- the layers of softer rock above the magma erode away and is left with a large dome shaped mountain
What is a plateau?
Flat high plain
What theory did Wegner propose?
That the earths continents were once joined together, but gradually moved apart over millions of years
How far away is the earths atmosphere?2
- most of it is within 10km of the surface
- the rest is within 100km roughly
How thick is the crust?
6km under the oceans
35km under continental areas
