C1.7 Changes in the Earth and its atmosphere Flashcards
What was Alfred Wegener’s theory?
Continental drift, at one time all the continents were joined together but over time they have slowly drifted apart to form the modern day continents we know today
What was his evidence of continental drift?
He found fossils of very similar plants and animals on opposite sides of the atlantic ocean. He also found other cases of this. Additionally he notice that Africa and South America seemed to fit together like a jigsaw. Their were matching rocks in different continents. Some fossils were found in the wrong continents, i.e. where they wouldn’t have survived.
What was the name Wegener gave to the original ‘supercontinent’?
Pangaea
Why was Wegener’s theory rejected?
Geologists thought it was impossible and one calculated that the forces needed to move the continents would have stopped the earth rotating. Wegener had used inaccurate data in his calculations. Wegener wasn’t a ‘proper’ geologist
By when was the theory accepted?
1960’s
Which part of the earth do we live on?
The crust
What are the properties of the crust?
It is very thin. From 5km to 50km. It is surrounded by the atmosphere
What is below the crust?
The mantle
What are the properties of the mantle?
It has the properties of a solid except it can flow very slowly. Radioactive decay takes place, producing a lot of heat
What occurs in the mantle?
Convection currents
What is at the centre of the earth?
The core
What is the inner core made of?
It is made up of solid iron and nickel
What is the outer core made up of?
It is made up of liquid iron and nickel
Which part of the earth is the hottest?
The inner core, with temperatures up to 5,500 degrees celsius
How thick is the mantle?
Approximately 2,900 km
What are the crust and the upper part of the mantle cracked into?
Tectonic plates which float on the mantle
Why do tectonic plates drift?
Because of convection currents in the mantle. The large amounts of heat released through radioactive processes cause convection currents to form
What causes convection currents in the mantle?
The heat released from radioactive processes causes the mantle to heat at the bottom. As heat rises the mantle also slowly rises until it loses energy and cools, causing it to fall back down again. This forms a steady current of movement in the mantle, causing the tectonic plates to move
How much do tectonic plates move each year?
A couple of centimetres
What happens when the tectonic plates move very suddenly?
An earthquake
Where do volcanoes and earthquakes often occur?
At the boundaries between two tectonic plates (fault lines)
Are volcanoes and earthquakes easy to predict?
No, they are very sudden and disastrous. However there are some methods of detection but they can sometimes lead to a false alarm
How was the atmosphere formed?
Volcanoes gave out a lot of gas
What was the early atmosphere?
Mostly CO2, water vapour and small amounts of methane and ammonia
How were the oceans formed?
When the water vapour condensed
What is the proportions of different gases in the current atmosphere?
80% Nitrogen
20% Oxygen
Small proportions of other gases such as carbon dioxide, water vapour and noble gases
What was Earth’s surface originally like?
Molten and so hot any atmosphere ‘boiled away.’ Eventually it cooled down a bit and a thin crust formed
Why did green plants and algae evolve over the earth?
The were happy in the CO2 atmosphere
What happened to the early CO2?
A lot of it was dissolved into the ocean and the green plants and algae absorbed some of the CO2, producing O2 by photosynthesis
What happened to the dead plants and algae?
It was buried under layers of sediment along with other dead organisms. The carbon and hydrocarbons inside them became locked up in sedimentary rocks as insoluble rocks and fossil fuels
What happens when we burn fossil fuels?
The ‘locked-up’ carbon is released and the concentration of CO2 in the atmosphere increases
What happened as a result of the build-up of oxygen?
Many of the earlier organisms died as they could not tolerate it, but other more complex organisms were allowed to evolve
What did the oxygen create
The Ozone, which blocks harmful rays
How much carbon dioxide is there in the atmosphere now?
Very little
What did the oceans act as?
A reservoir for carbon dioxide
Give an example of an insoluble carbonate
Limestone, formed by shells and skeletons of marine organisms
Name the theory surrounding how life was formed by interaction between hydrocarbons, ammonia and lightning
The primordial soup theory
What is the primordial soup theory?
The earth’s atmosphere was once rich in nitrogen, hydrogen, ammonia and methane. Lightning struck, causing a chemical reaction between the gases resulting in the formation of amino acids. The amino acids collected a a ‘primordial soup’ and gradually combined to produce organic matter which eventually evolved into simple living organisms
Who carried out an experiment to prove this theory?
Miller and Urey
What experiment did Miller and Urey do?
They sealed the gases in their apparatus, heated them and applied an electrical charge for a week. They found that amino acids were made, but not quite as much as there are on earth
Can we fractionally distill air?
Yes as the mixtures of gases have different boiling points. By fractionally distilling air we can get a variety of products for use in the industry
What is the process of Fraction Distillation with air?
- The air is filtered to remove dust
- It is then cooled to -200 degrees and becomes a liquid
- During cooling the water vapour condenses and is removed
- Carbon dioxide freezes and is removed
- The liquified air then enters the column and is heated slowly
- The remaining gases are separated by fractional distillation. (Oxygen and argon come out together so another column is used to separate them)
