C1.7 Changes in the Earth and its atmosphere Flashcards
What are tectonic plates?
Cracked pieces of the earth’s crust and upper part of the mantle
Why is there convection currents in the mantle and what to the currents cause?
caused by natural radioactive processes
cause the tectonic plates to move at relative speeds, a few cm a year
The mantle is mostly ——– but it is able to————
solid
move slowly
What are the only source of minerals and other resources humans need?
the earth’s crust, atmosphere and oceans
Describe Wegener’s theory of Continental Drift
He said that about 300 million years ago, there had just been 1 super continent. This landmass broke into smaller chunks which moved apart. He claimed that these chunks (our modern day continents) were slowly drifting apart.
What evidence did Wegener have to explain his theory of continental drift?
- Found fossils of very similar plants and animals which were found o opposite sides of the Atlantic Ocean.
- The coastlines of Africa and South America seemed to match like pieces in a jigsaw
- There were matching layers in the rocks in different continents.
Why was Wegener’s theory of Continental Drift not accepted for many years?
- Did not have a convincing reason for why it was happening
- Used inaccurate data so made wild predictions
- He was not a proper geologist
What did scientists once think the features of the earth’s surface was a result of?
The shrinking of the crust as the earth cooled down after its formation
Why cannot scientists accurately predict when earthquakes and volcanic eruptions will occur?
Scientists can not monitor what is happening below the Earth’s crust
not all tremors indicate that a volcano will erupt
plates move suddenly
Where do volcanic eruptions and earthquakes occur?
at the boundaries between plate tectonics.
Describe the proportions of different gasses in the atmosphere
For 200 million years there has been about:
80% nitrogen
20% oxygen
small proportions of various other gasses including: carbon dioxide, water vapour and noble gasses
Describe what happened during the first billion years of the earths existence
- intense volcanic activity
- this released gases that formed the early atmosphere
- water vapour condensed to form oceans
Describe one theory about how the ATMOSPHERE was formed
Early period- mainly carbon dioxide and there would have been little or no oxygen gas. (like atmosphere of venus or mars today). There may also have been some water vapour and small proportions of METHANE and AMMONIA
Describe one theory how LIFE was formed (primordial soup theory)
- Billions of years ago, earth’s atmosphere contained hydrocarbons and ammonia
- LIGHTENING struck- caused chemical reaction between gases resulting in the formation of amino acids
- amino acids combined to produce organic matter- evolved into simple living organisms
What produced the oxygen that is now in the atmosphere?
Plants and algae
through photosynthesis- uses carbon dioxide from atmosphere
Where has most of the carbon dioxide from the early atmosphere gone?
carbon became locked up in sedimentary rocks as carbonates and fossil fuels
carbon dioxide dissolves in the oceans
What is limestone formed from?
shells and skeletons of marine organisms
What do fossil fuels contain?
carbon and hydrocarbons that are the remains of plants and animals.
Why can air be fractionally distilled?
As air is a mixture of gases with different boiling points.
gasses can be used for a variety of industrial processes
What were the results of the experiment to prove the primordial soup theory and what do they suggest?
They found amino acids were made, but not as many as there are on earth.
Suggests the theory is along the right lines, but isn’t quite right
Describe the structure of the Earth
core
mantle
crust - very thin
Why does Iceland have volcanoes?
As Iceland is on a boundary between tectonic plates
Describe how activity within the earth results in earthquakes
Earthquakes are caused by the sudden movement of the earths tectonic plates
The movement is caused by convection currents in the earths mantle
convection currents are caused by the heat released by radioactive processes in the mantle
Describe how volcanic activity during the first billion years of the earths existence led to the formation of oceans
Water vapour was released by the volcanic activity
water vapour condensed to form oceans
Give reasons why the percentage of carbon dioxide decreased in the Earth’s early atmosphere
- Carbon dioxide dissolved in oceans
- marine animals used dissolved carbon dioxide to form their shells/skeletons
- plants absorbed carbon dioxide for photosynthesis
Why did Miller and Urey use methane, ammonia and hydrogen to reconstruct the earth’s early atmosphere?
Because these gases contain the atoms that are in amino acids
Why does the Miller Urey experiment provide weak evidence of how amino acids formed on Earth?
- nobody knows what was in the earth’s early atmosphere- hydrogen, methane and ammonia may not have been in the earth’s early atmosphere
- There may not have been lightening
Miller and Urey only selected gases needed to produce amino acids
What is locked up carbon dioxide?
Carbon dioxide from the earths early atmosphere
which formed sedimentary rocks
Describe how the percentage of carbon dioxide has changed in the last 4500 million years
decreased rapidly at first
then slowly levels off
Should we be concerned about the change in the concentration of carbon dioxide in the atmosphere over the last 200 years?
yes- because percentage is increasing which causes global warming
no- because percentage of carbon dioxide is low compared to millions of years ago.
Describe the layered structure of the earth and the relative sizes of the layers
consists of crust, mantle and core
crust is thinner than mantle and core
suggest why, in 1920, other scientists thought that Wegener’s theory of continental drift was wrong
- he had little evidence to explain why the plates were moving
- Not well respected as did not have a status- not a proper geologist
- other scientists believed the ‘land bridge’ explained the similar rocks and fossils in africa and south america
Deep inside the earth ……………. processes release large amounts of energy. These processes heat up the substances in the Earth’s ………..
radioactive
mantle
In the fractional distillation of liquid air, suggest why the air is filtered before the gases are separated
to remove solid/dust particles
In the factional distillation of liquid air, suggest why water vapour and carbon dioxide are removed before the gases are compressed and cooled at -200 degrees
as at -200 degrees, water and carbon dioxide are solids
this would therefore block pipes
suggest why there are many theories about how life was formed on earth
not enough evidence
Explain how the surface of the earth has changed since the earths formation
number of volcanoes reduced because the Earth cooled forming a crust
continents formed because the earth cooled forming a supercontinent which formed the separate continents
Describe how and explain why continental drift takes place
- earths crust is divided into tectonic plates
- heat is released by radioactive PROCESSES in the mantle
- causes convection currents in the mantle that move the tectonic plates
