Plate Tectonics

Question 1

Types of crust

Answer 1

Continental crust is thicker(30-70km thick) and less dense.
Oceanic crust is thinner(6-10km thick) and more dense

Question 2

Convection currents

Answer 2

1)The Earth’s mantle is hottest close to the core, so lower parts of the asthenosphere, heat up, become less dense and slowly rise
2)As they move towards the top of the asthenosphere they cool down, become more dense and slowly sink.
3)These circular movements of semi-molten rock are called convection currents 4)They create drag on the base of the tectonic plates, causing them to move

Question 3

Slab pull

Answer 3

1)At destructive plate margins, denser crust is forced under less dense crust
2)The sinking of the plate edge pulls the rest of the plate towards the boundary

Question 4

Ridge Push

Answer 4

1)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
2)The new crust cools and becomes denser. Gravity causes the denser rock to move downslope, away from the plate margin
3) This puts pressure on the tectonic plates, causing them to move apart.
4) Ridge push is also known as gravitational sliding

Question 5

Sea-floor spreading

Answer 5

1)As tectonic plates diverge (move apart), magma rises up to fill the gap created, then cools to form new crust.
2)Over time, the new crust is dragged apart and even more new crust forms between it.
3)When this happens at a plate margin under the sea the sea floor gets wider.
4)This process is called seafloor spreading
5)It creates structures called mid-ocean ridges- ridges of higher terrain on either side of the margin.