Plate tectonics Flashcards
(25 cards)
Define magma
It is the liquid rock in the mantle
Define endogenic forces
Forces from within the earth that cause the crust to move vertically or horizontally
What is mainly responsible for endogenic forces?
Convection currents
What are convection currents?
It is the rising, spreading and sinking of materials in the mantle as it is heated by the core.
What is the asthenosphere?
Weak and ductile part of the mantle lying below the lithosphere
What is the lithosphere?
It is the crust and the solid part of the upper mantle
What is the oceanic crust made from?
Rocks such as basalt made from silica and magnesium- very heavy rocks make it heavy
What is the continental crust made from?
Rocks such as granite are rich in silica and aluminium- lighter rocks so the crust is les heavy than oceanic
Which crust is the thinnest?
Oceanic crust is around 8km thick while the continental is much thicker at around 45km thick
Who proposed the idea of continental drift?
Alfred Wegener
What the land called when all earth continents were as one?
Pangea
Wat composed the main parts of Wegener’s theory?
Matching fossils- the same fossils were found in different continents thousands of miles apart like the Mesosaurus fossil which was found in both Africa and South America. It was a freshwater animal so could not have swam between the two land masses suggesting the continents must have been joined together.
Matching rock folds- Identical rock folds were found along the west of America and the north west of Europe coats suggesting that these were all once a mountain range that broke apart as they are identical and have the same rock type.
seafloor SPREADING-MAKES THE OCEAN FLOOR WIDER MOVING PLATES
Subduction- old seafloor is destroyed and this explains why some plates move faster than others
What is the Moho line and where is it?
It is the boundary that divides a solid upper mantle and the crust
How thick is continental crust on average?
45 km
The rocks that formed the crust are light
It is made up of rocks known as SIAL
What is the thickness of the oceanic crust?
It averages 8 km thick
It is heaviest as it contains rocks like bass salt which are made up of SIMA
Who put forward the tectonic theory?
Alfred Wagner
What did Pangea divide up into?
Gondwanaland and Laurasia
What was the evidence for Continental drift? In terms of plant fossils.
Matching plant fossils found on different continents
Wagner use the plant glossopeteris which he found in South America, India, Australia, Antarctica, Africa to help prove his theory. This plant has a specific climate conditions so the fact that it was found in different continent suggests that they had been joined together in the past.
How did animal fossils help prove wagoners theory correct?
We’re gonna I found fossils of the misosaurus reptile in both South America and Africa. This creature was a freshwater creature so there is no way that it could’ve been found in both continents as they are separated by saltwater. This combined with the distance that the continents are part suggest that they were once joined
How does matching rock folds help identify continental drift?
Identical rock folds were found along the eastern coast of North America and the northern West Coast of Europe. These mountains were all formed roughly 400,000,000 years ago and I made of the same type. Wagner suggested these mountains are once one.
How did matching glacier deposits help prove continental drift?
Wagner found evidence of plastic to glacier around the world in places like Central Africa. These parts of the world would be too hot for glacier suggesting that they must’ve been at a different part of the world at some stage.
How does continental fit prove Wagner correct?
If you observe the South American East Coast, you can see that it fits perfectly into the West Coast of Africa suggesting they were joined together in the past
Where is the age of the sea floor oldest further or closer to the ridge?
The further the rock is from the ridge the older it is
