Plate tectonics🌋 Flashcards
What is the Earth’s crust and the 2 types?
The crust is the outer most layer, also known as the lithosphere. It is solid rock split into tectonic plates. The 2 types are: continental crust(granite)which forms the land, and oceanic crust(basalt)which is under the oceans.
Which of the 2 types of crust are denser, and how does this affect plate boundaries?
The continental crust has a low density and is 30-50km in thickness. Whereas the oceanic crust is more dense and between 6-8km in thickness. At a destructive plate boundary , the oceanic plate is forced under the continental plate because it is denser; this process is known as subduction. (Causes severe earthquakes and heat due to the friction).
What is Earth’s mantle?
Earth’s mantle is our planet’s thickest layer and lies between the crust and core. The top layer is known as the asthenosphere, which is semi molten (jam) on which tectonic plates float. The bottom of the mantle is solid.
What are the features of the inner core of Earth?
It is around 1000km thick and composed of iron and nickel. Under extremely high-pressure conditions, the core is solid, and extremely hot due to the heat from the decay of radioactive elements.
What surrounds the inner core?
The outer core. It is also composed of iron and nickel but it is a liquid. The pressure in the outer core is not high enough to make it solid. It is less dense.
Why do plates move?
Convection currents in the mantle move plate tectonics. Heat generated from the radioactive decay of metals in the earths core, create magma in the asthenosphere (upper mantle) that moves in a circular motion. This moves the plates on the surface. Tectonics are constantly moving.
What is “Pangea”?
200 million years ago, the Earth’s continents were all joined up to create 1 supercontinent, known as Pangea. The theory of continental drift became accepted in the 1960s. This is evidenced by the way continents fit together-almost perfectly, e.g. South America and Africa.
- extra note :) Its name is derived from the Greek pangaia, meaning “all the Earth.”
What are plate boundaries?
Also known as plate margins, plate boundaries are the edges of tectonic plates, where earthquakes and volcanoes occur.
What are the major plate boundaries?
North American plate, Pacific plate(oceanic), Nazca plate(oceanic), South American plate, African plate, Eurasian plate and the Indo- Australian plate
What occurs at a collision plate boundary?
At a collision boundary(a type of convergent boundary) two continental plates a pushed towards each other. Because the plates are the same density, subduction does not occur, however the plates buckle upwards. They rise and form fold mountains. No volcanoes form but friction can cause large earthquakes.
The Himalayan mountain range have formed as a result of the collision between the Indian Plate and Eurasian Plate.
What occurs at conservative plate boundaries?
Conservative plate boundaries exist where 2 plates do not collide but slide past each other along a fault line. This occurs at the boundary between the pacific and North American plate. The friction caused by the abrasive motion results in severe earthquakes. The San Andreas fault in California has caused several devastating earthquakes.
What occurs at a divergent plate margin/ constructive plate boundary?
At a constructive plate boundary, the plates are pushed apart by the convection currents that rise up within the mantle. An example is the North American and Eurasian plates. As the plates slowly move apart, magma rises and erupts through the crust. This process happens over a very long period of time until enough new crust has formed to create a volcano.
The mid Atlantic ridge is the best known example, underwater. *See photo online. Earthquakes are fairly small and volcanoes are less forceful.
What occurs at a convergent plate boundary?
A convergent (also known as destructive) plate boundary is found where a continental and oceanic plate move towards each other. An example is the Nazca and South American plate. The oceanic plate is forced under the continental plate because it is denser;this process is known as subduction. The friction causes some severe earthquakes and also causes the oceanic plate to heat up. As it melts, magma is formed and then a magma chamber. If the magma reaches the surface it forms a volcano. Volcanic eruptions tend for be explosive due to the extreme pressure release.
What are hotspot volcanoes
Hotspot volcanoes occur where heat rises as hot plumes of magma from earth’s interior. High heat and lower pressure at the base of the crust enables the melting of rock(magma). Magma rises upwards through cracks and erupts to form active volcanoes on the earths surface. E.g. Hawaiian islands
What is the pacific ring of fire?
The pacific ring of fire is region where many volcanic eruptions and earthquakes occur. It is along the pacific and Nazca plate(surrounding the 2).
