Plate tectonics Flashcards
Oceanic crust
Very dense and therefore is forced under continental crust at destructive plate margins. It is made of basaltic rock, which is younger rock that the rock in continental crust.
Continental crust
Not as dense as oceanic crust, therefore oceanic crust if forced under the continental crust at destructive plate margins. It is made of indigenous rock, which is older than basaltic rock, and is 4000 million years old.
Constructive/divergent plate margin
Creates crust as plates pull away from each other, allowing magma to rise in the volcanic vent created by the gap between the plates. Convection currents drive plates apart. An example, is the Eurasian and North American plate.
Destructive plate boundary
Destroys crust, as the oceanic crust is turned into basaltic magma in the subduction zone that leads to the magma chamber of a stratocone volcano. Both plates are moving towards each other, and because oceanic plate is denser than Continental crust, the Oceanic crust is forced beneath the Continental crust at the trench. Volcanoes on destructive margins are very active as lots of magma is produced from the subduction zone, and the magma produced is very gaseous from the steam and methane from water in the Oceanic plate. Also, due to the huge pressure in the subduction zone from the melting Oceanic plate, lots of seismic energy is released to produce huge earthquakes.
Conservative plate margin
No crust is destroyed or created. The two plates either slide past each other in opposite directions or in the same direction, like at the San Andreas fault which is the boundary between the North American and Pacific plate. Due to the plates moving in a stick-slip fashion, huge amounts of seismic energy is produced in a small time period with a shallow focus, causing huge earthquakes.
Collision plate boundary
No crust is destroyed or created. Two continental crusts move towards each other, but neither is denser. Therefore, due to the pressure from the rocks of the plates, the two crusts fold on top of each other to form a mountain range, which are called fold mountain ranges. An example is the Himalayas, which is the boundary between the Eurasian and Indian plate.
What is a tectonic plate?
A segment of the Earths crust that is moving above the asthenosphere.
How does the mantle move?
In a convection current, as the mantle is heated from the radiation from the outer crust. The mantle then cools as it reaches the asthenosphere, and resultantly drops down to the outer core again.
What is the lithosphere?
The rigid layer of crust and upper-most solid mantle, that cracks under pressure. These cracks are tectonic plates and they move on the asthenosphere.
What is the asthenosphere?
The upper mantle layer that is semi molten and moves the crust segments/tectonic plates.
What is the mantle?
Deformable part of earths structure that moves in huge convection currents, heated by the core. The outmost layer of the mantle (Lithosphere) is solid and also the lower mantle, but otherwise the mantle is molten.
What is the core?
It is the Earths heat engine, that causes the mantle to move. It consists of two parts, the outer core and the inner core. The outer core is liquid and made of iron and nickel. The inner core is extremely hot due to the huge amounts of pressure, and is estimated to be around 5000 Fahrenheit.
