What are the four main layers of the Earth?
Enjoying Flashcards?
Tell us what you think
What are the four main layers of the Earth?
The four main layers of the Earth are:
Crust.
Mantle.
Outer core.
Inner core.
Define continental crust.
The continental crust is a thicker (up to 70km), less dense layer than the oceanic crust. It is mainly composed of granite.
What is the asthenosphere?
The asthenosphere is a plastic-type layer in the upper mantle that moves slowly under high pressure and carries the lithosphere on top.
True or False?
The lower mantle is cooler and less dense than the upper mantle.
False.
The lower mantle is hotter and more dense than the upper mantle.
What is the composition of the inner core?
The inner core is a solid centre, mostly composed of iron.
Define the term lithosphere.
The lithosphere is the rigid layer above the asthenosphere, together with the crust. Together, they float on top of the asthenosphere.
What are the two key causes of extreme heat in the Earth's core?
The two key causes of extreme heat in the Earth's core are:
Radioactive decay of elements such as uranium and potassium
Residual heat from the collisions of asteroids and other small bodies resulted in the formation of Earth.
True or False?
There are only seven tectonic plates.
False.
There are seven major tectonic plates and several minor ones.
Define oceanic crust.
Oceanic crust is a thinner (5–10 km) and denser layer mainly composed of basalt.
What is the main driver of tectonic activity?
The main driver of tectonic activity is the heat from the Earth's core.
What is the theory of plate tectonics?
The theory of plate tectonics is a scientific theory that revolutionised people's understanding and study of geological processes and the Earth, explaining phenomena such as earthquakes, volcanic eruptions, mountain formations and continental movement.
Who proposed the Continental Drift Theory?
Alfred Wegener proposed the Continental Drift Theory.
What is convection current theory?
Convection current theory explains tectonic plate movement as the result of heat from radioactive decay in the core moving upwards in the mantle, creating currents that carry the lithospheric plates above.
Define slab pull.
Slab pull is the process where gravity pulls a subducting plate down into the mantle at a subduction zone.
True or False?
Slab pull is less important than ridge push in causing plate movement.
False.
Slab pull is much more important than ridge push in causing the movement of tectonic plates.
True or False?
Wegener's Continental Drift Theory explained how tectonic plates move.
False.
Wegener's theory stated that the continents had moved but was unable to suggest how or why.
What is palaeomagnetism?
Palaeomagnetism is evidence that the sea floor has gradually moved apart at a mid-ocean ridge. It is shown by the alignment of minerals in cooled lava with the Earth's magnetic field.
What is seafloor spreading?
Seafloor spreading is the process by which new oceanic crust is formed at mid-ocean ridges and moves away from the ridge over time.
What evidence did Wegener use to support his Continental Drift Theory?
Wegener used evidence such as:
The fit of continents.
Fossil distributions.
Rock type and structural similarities.
Past climatic evidence.
What is gravitational sliding (or ridge push)?
Gravitational sliding (or ridge push) is the process where gravity pulls the lithosphere down the slope created as new oceanic crust cools and becomes denser. This pushes the crust forward.
What are the three main types of plate boundaries?
The three main types of plate boundaries are:
Constructive (divergent).
Destructive (convergent).
Conservative (transform).
Define constructive plate boundary.
A constructive plate boundary is where plates move apart or diverge. This leads to new crust being formed.
What is a rift valley?
A rift valley is a landform that forms when diverging plates are beneath the land, causing the crust to stretch and fracture, with areas of crust dropping down between faults to create a valley.
True or False?
Deep sea trenches only form at destructive boundaries between oceanic and continental plates.
False.
Deep sea trenches can form at destructive boundaries between oceanic-continental plates and between oceanic-oceanic plates.
What is the Benioff Zone?
The Benioff Zone is the zone where earthquakes occur along the subduction slab at a destructive plate boundary.
Define conservative plate boundary.
A conservative plate boundary is where plates slide past each other in opposite directions or in the same direction at different speeds.
What type of volcanoes typically form at destructive plate boundaries?
Steep-sided, composite volcanoes with andesitic and rhyolitic lava flows typically form at destructive plate boundaries.
True or False?
Volcanic activity occurs at all types of plate boundaries.
False.
There is no volcanic activity at conservative plate boundaries or at continental-continental collision boundaries.
What is an island arc?
An island arc is a curved chain of volcanic islands forming where submarine volcanic eruptions lead to crust building up and rising above sea level at oceanic-oceanic destructive boundaries.
How do fold mountains form at a continental-continental collision boundary?
Fold mountains form at continental-continental collision boundaries when two plates of similar density move towards each other and neither is dense enough to subduct, pushing the land upward.
What are hot spots?
Hot spots are areas around the core of the Earth where radioactive decay is concentrated, creating extreme heat.
Define the term magma plume.
Magma plumes are upwellings of superheated rock that rise from deep within the Earth's mantle towards the surface.
True or False?
Magma plumes only cause volcanic activity at plate boundaries.
False.
Magma plumes can break through the middle of a tectonic plate to reach the surface, causing volcanic activity and earthquakes far away from the plate margins.
What is an island chain?
An island chain is a series of volcanic islands formed when a tectonic plate moves over a stationary magma plume.
How are island chains formed?
Island chains are formed when a tectonic plate moves over a stationary magma plume, creating a series of volcanoes that become active when above the plume and extinct as they move away.
True or False?
The oldest island in a hot spot chain is closest to the magma plume.
False.
The oldest island in a hot spot chain is the one furthest away from the magma plume.
Give an example of an island chain formed by a hot spot?
Hawaii is an example of an island chain formed by a hot spot.
How do magma plumes differ from other sources of volcanic activity?
Magma plumes differ from other sources of volcanic activity as they can cause volcanism within tectonic plates, not just at plate boundaries.
True or False?
Magma plumes move with tectonic plates.
False.
Magma plumes are stationary while tectonic plates move over them.
What happens to volcanoes in an island chain as they move away from the magma plume?
Volcanoes in an island chain become extinct as they move away from the magma plume.