Fragile Planet- Plate Tectonics Flashcards
What is the structure of the Earth, starting from the outside in order?
Crust, mantle, outer core, inner core
What is the crust of the earth?
This is the thinnest layer of the Earth. It is between 8 and 40km thick. In comparison to the whole earth radius, the crust is very thin, like and egg shell. Its thinner under ocean than on land. It contains rock and minerals. Under the oceans, the crust is mainly basalt but under the continents it’s mainly granite.
What is the mantle of the earth?
This is the thickest layer of the Earth. This is made of solid rock that can flow-plastic rock. It moves in slow, big circles caused by convection currents. As the magma closest to the inner core is heated it rises are cools closer to the surface, causing movements.
What is the outer core of the earth?
The outer core is semi liquid iron. Temperature are about 5300 degrees celsius. 2200km thick. The fact that iron is liquid here and iron is magnetic means that the earth’s magnetic field is formed here which protects us from harmful solar winds and allows life on our planet.
What is the inner core of the earth?
Is the inner most part of the earth. 1200km thick (from 6300km deep to 5100km) . It is the hottest part of the earth, temperature over 5500 degrees celsius. Mainly made of iron and nickel- the material is under lots of pressure. The material is very dense. The rock is solid in the inner core due to the pressure.
What was Pangea?
All the rocks were formed when the land was a single continent.
What was Wegner’s theory about plate tectonics?
Alfred Wegner proposed that countries were once joined together and had then moved apart. In fact he believed that all continents were once joined together as one big land mass called Pangea, which stayed in tact until about 200 million years ago.
What is continental drift?
The idea that continents are slowly shifting their positions is called continental drift.
What is plate tectonics.
The Earth’s crust is made up of a number of large plates that are moving
in constant, slow motion.
Convection currents in the mantle move the plates. The source of heat driving the convection currents is radioactive decay which is happening deep in the Earth.
The ocean floors are continually moving, spreading from the centre and sinking at the edges.
At the edges of these plates (plate boundaries) earthquakes and volcanoes occur.
How does convection currents support the idea of plate tectonics?
In the Mantle, Convection Currents
were found to be slow yet extremely powerful movements of volcanic rock in the
mantle. The magma is heated to 5,5000*C in the mantle and rises to the crust where they cool and descend only to be heated. This was powerful enough to move the
earth’s plates.
How does the study of fossils support plate tectonics?
Similar fossils are found on different continents. This is evidence that these regions were once very close or joined together. Such species could not have crossed
oceans, so they must have lived on the same land mass at some time in the past.
Give an example of a fossil of an animal that supports the study of fossils as evidence for plate tectonics?
The mesosaurus fossil was found in South America and the Western part of Africa.
How do geological patterns support plate tectonics?
Similar pattern of rock layers on different continents is evidence that the rocks were once close together or joined. Similar geology groups have been found in Australia,
S. America Antarctica and Africa.
Coal has been found in Antarctica. Coal requires warm climates to form. This indicates that it was once near the equator.
How does palaeomagnetism support plate tectonics?
A discovery of a ridge of mountains running along the middle of the Atlantic Ocean. known as the Mid Atlantic Ridge was made - these were formed by underwater
volcanoes and lava cooling. As lava cools the magnetic iron points to the north pole. It was known at the time that the earth’s polarity switches approximately every 100mill years and when this reversed from north to south, the iron particles in the erupting magma aligned themselves with the Earth’s new polarity at that time – this creates evidence of seafloor spreading.
What are the seven major plates on Earth?
The seven major plates are the African plate, Antarctic plate, Eurasian plate, Indo-Australian plate, North American plate, Pacific plate and South American plate.
