Plate Tectonics

Question 1

Structure of the Earth

Answer 1

1 - At the centre of the earth is the core which is split into the inner core and outer core. The inner core is a solid ball containing lots of iron and nickel and the outer core is semi molten also contains lots of iron and nickel
2 - around the core is the mantle which is mostly made of silicate rocks. The part nearest the core is rigid, the next layer is the asthenosphere which is semi molten and can flow and the rigid top part of the mantle and crust together is the lithosphere
3 - the outer layer of earth is is the crust. There are two types of crust - thin dense oceanic and thick less dense continental

Question 2

How is the earth divided into tectonic plates

Answer 2

The lithosphere is divided into lots of slabs called tectonic plates which move in relation to each other. The places where the plates meet are known as plate boundaries or margins.

Question 3

How do tectonic plates move - CONVECTION CURRENTS

Answer 3

1 - the earths mantle is hottest close to the core so the 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 4

How do tectonic plates move - SLAB PULL

Answer 4

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 5

How do tectonic plates move - RIDGE PUSH

Answer 5

1- at constructive plate margins magma rises to the surface and forms new crust which is very hot. It heats the surrounding rocks that expand and rise above 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 6

Process of Sea Floor Spreading

Answer 6

1 - As tectonic plates diverge, magma rises to fill the gap created the cools to form a 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 - it creates structures called mid ocean ridges