C2a - The structure of the Earth Flashcards
Describe the lithosphere(2)
relatively cold, rigid outer part of the Earth that includes the crust and part of the mantle
made of tectonic plates that are less dense than the mantle below
Problems associated with studying the structure of the Earth (3)
crust is too thick to drill through
temps too hot for machinery
information about the earth is collected from seismic waves produced by earthquakes or man-made explosions
Why is the theory of plate tectonics now widely accepted? (2)
theory of plate tectonics explains a wide range of evidence
it has been discussed and tested by a wide range of scientists
Describe the mantle(3)
the zone between the crust and the core
cold and rigid just below the crust
hot and non-rigid at greater depths and therefore able to move
Describe the theory of plate tectonics(4)
energy transfer involving convection currents in the semi-rigid mantle causing the plates to move slowly
oceanic crust more dense than continental crust
when the oceanic plate collides with the continental plate, the oceanic plate, which is cooler at ocean margins sinks and pulls more of the plate down, and partly melts as it reaches the hotter part of the mantle
-subduction and partial melting
Describe the development of the theory of plate tectonics (4)
Originated from Wegener’s continental drift theory (1914)
continental drift theory was not accepted by scientists at the time
new evidence in 1960s about sea floor spreading
theory of plate tectonics slowly accepted by the scientific community as subsequent research has supported the theory
Describe Wegener’s continental drift theory (2)
he noticed that the shapes of the continents fitted together (Africa and South America coastlines) / similar rocks/fossils in different continents
he suggested that the continents were all once joined together, then gradually moved apart
What does the type of volcanic eruption depend on
the composition of the magma
Describe different types of igneous rocks that are formed from lava (2)
iron-rich basalt is formed from runny lava (which flows steadily) from a fairly safe volcanic eruption
silica-rich rhyolite is formed from thick lava from an explosive eruption
Explain why geologists study volcanoes(2)
to be able to forecast future eruptions
to reveal information about the structure of the Earth
Why are geologists now able to better forecast volcanic eruptions but not with 100% certainty
although they can predict volcanic eruptions with greater accuraicies, geologists are still unable to give 100% accurate predictions as volcanic activ ity is very unpredictable
Why does magma rise up through the Earth’s crust
it is less dense than the crust
