7 Our Changing Planet Flashcards
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
What is the radius of the core?
3500km
Two reasons why the percentage of carbon dioxide decreased in the earths early atmosphere?
Carbon dioxide dissolves in the oceans
Plants photosynthesis me absorbing carbon dioxide
In an experiment for the earths early atmosphere why use ammonia hydrogen and methane?
The gases contain carbon hydrogen and nitrogen
Why might a country have volcanoes?
On a tectonic boundary
why can’t you know exactly when a volcano will react?
Not all trenors indicate a volcano will erupt
Scientists can’t monitor what goes on below the earths crust in the earths mantle
How does volcanic activity leaf to the formation of volcanos?
Water vapour released by volcanic activity
Condensed to form oceans
How has activity within the earth resulted in earth quake?
Earthquakes are caused by sudden movements of the earths tectonic plates
Caused by convection currents in the earths mantle
Caused by the heat released by radioactive processes within the earth
Describe Wegners idea of how earths continents formed?
They were joined together
The continents then drifted apart
Why did most scientists in 1915 not accept Wegners idea of continental drift?
They would not explain how continents could move
Explain and describe why continental drift takes place?
The earths crust is divided into tectonic plates
The heat released from radioactive processes causes convection currents
In the mantle which then move the tectonic plates
Explain how carbon dioxide is released by limestone?
Calcium carbonated in thermal decomposition produces carbon dioxide
Why did most scientists not accept Wegners idea of continental drift?
No evidence
Other scientist had different views
Didn’t have respect
Why did scientists think Wegner was wrong?
Modern animals different
Continents can’t move thousand of kilometres
What effect of particulates have on the envrionment?
Global dimming
Why are there convection currents in the earths mantle?
They are driven by heat released from natural radioactive processes
What was the early atmosphere supposed to contain?
Methane
Ammonia
Water vapour
Describe the current atmosphere?
80% nitrogen
20% oxygen
Small amounts of water vapour noble gases and carbon dioxide
Describe the first billion years of the earths existence?
There was intense volcanic activity
What did early volcanic activity do?
Released the gases that formed the early atmosphere and water vapour that condensed to form oceans
Why would you fractionally distill air?
To provide a source of raw materials used in a variety of industrial processes
Why are there many theories?
Not enough evidence
Billions of years ago
How does carbon dioxide dissolve in the ocean?
It recasts and makes insoluble carbonate compounds which fall to the sea bed
And help to form more carbonate rocks
Properties of emulsions?
Thicker
Better at coating things
Better texture
Explain cracking?
Heating a fuel to make a vapour The vapour is passed over a hot catalyst Or mixed with steam And heated to a very high temperatures So thermal decomposition happens
Describe a polymerisation reaction?
Many monomers
Bond / join together
What is an alternate theory to the Miller Urey?
Meteors brought organic compounds to earth
Miller Urey experiment?
Water heated
Water vapour travels along tubes into gas mixture
Mixture of water vapour methane hydrogen and ammonia
Electric spark
Condensed
Left for some time
What did water represent in the Miller Urey experiment?
Oceans
What did sparks represent in the Miller Urey experiment?
Lighting
Mixture formed from Miller Urey was known as what?
Primordial soup
Which is a mixture of molecules that could eventually form cells
