Tectonic Plates

1) At the centre of the Earth is a ball of solid iron and nickel called the core.

2) Around the core is the mantle, which is semi-molten rock that moves very slowly.

3) The outer layer of the Earth is the crust. It's very thin (about 20km).

4) The crust is divided into lots of slabs called tectonic plates (they float on the mantle).

Plates are made up of two types of crust - continental and oceanic:

- continental crust is thicker and less dense

- oceanic crust is thinner and more dense.

5) The plates are moving because the rock in the mantle underneath them is moving.

6) The place where plates meet are caleed boundaries or plate margins.

Destructive Margins

Destructive margins are where two plates are moving towards each other, e.g. along the coast of Japan.

• Where an oceanic plate meets a continental plate, the denser oceanic plate is forced down into the mantle and destroyed. This often creates volcanoes or ocean trenches (very deep sections of the ocean floor where the oceanic plate goes down).
• Where two continental plates meet, the plates smash together, but no crust is destroyed.

Constructive Margins

• Constructive margins can be found where two plates are moving away from each other, e.g. at the Mid-Atlantic ridge.
• Magma (molten rock) rises from the mantle to fill the gap and cools, creating new crust.

Conservative Margins

• Conservative margins are where two plates are moving sideways past each other, or miving in the same direction but at different speeds, e.g. along the West Coast of the USA.
• Crust isn't created or destroyed