Plate Tectonics Flashcards
What does the inner and outer core contain a lot of?
Iron and nickel
What is the mantle made of?
Silicate rocks
What is the asthenosphere?
The layer above the mantle nearest to the core and is semi molten.
What is the lithosphere?
The rigid top part of the mantle and the crust together.
What are the two types of crust?
Continental and Oceanic
What are the features of an continental crust?
Its thicker (30 - 70km thick) and less dense.
What are the features of an oceanic crust?
It is thinner (6-10km thick) and more dense.
How hot is the inner core?
6000 degrees
How hot is the mantle?
Around 1000- 3500 degrees
Describe the process of convection currents in relation to plate movement?
The Earths mantle is hottest close to the core, so lower parts of the asthenosphere heat up, become less dense and slowly rise. As they move towards the top of the asthenosphere they cool down, become denser and slowly sink. These circular movements of semi molten rock are called convection currents. They create drag on the base of the tectonic plates, causing them to move.
Describe the process of slab pull in relation to plate movement?
At destructive plate margins, denser crust is forced under less dense crust. The sinking of the plate edge pulls the rest of the plate towards the boundary.
Describe the process of ridge push in relation to plate movement?
At constructive plate margins magma rises to the surface and forms new crust which is very hot. It heats the surrounding rocks which expand and rise above the surface of the surrounding crust, forming a slope. The new crust cools and becomes denser. Gravity causes the denser rock to move downslope, away from the plate margin. This puts pressure on the tectonic plates, causing them to move apart. Ridge push is also known as gravitational sliding.
Describe sea floor spreading?
As tectonic plants diverge, magma rises up to fill the gap created, then cools to form new crust. Over time, the new crust is dragged apart and even more new crust forms between it. When this happens at a plate margin under the sea the sea floor gets wider. This process is called sea floor spreading, it creates structures called mid ocean ridges.
