Restless Earth

Igneous- composed of crystal minerals that form from cooling and solidification of molten magma from within the earth.

Sedimentary- layers of materials formed from the debris of other rocks broken down by weathering and erosion. Some have fossils.

Metamorphic- rocks altered by increased temperature and/or pressure.   

Granite- magma rises from the earth's mantle and slowly cools within the earth's crust . Slow rate of cooling produces large crystals.

Basalt- magma reaches earth's surface as lava from a volcano and cools quickly. Rapid cooling causes small crystals.

Limestone- Remains of shells and skeletons of small marine organisms.

Sandstone- Results from grains of sand being compressed and cemented together.

Slate- Shales and clays changed by pressure

Marble- limestone changed by heat and pressure

 Core- centre of the earth, found below the mantle. It is extremely not and may be made of metal.

Mantle- Layer above the core, makes up 80% of earth's mass. Behaves like liquid rocks.

Crust- Upper layer of earth on which we live. Solid, but is split into sections called plates.

Oceanic crust- lies underneath planet's ocean, consists of heavier rocks such as basalt. These rocks are much thinner and are about one-twentieth the age of continental rocks.

Continental crust- forms the great landmasses of the world and consists of relatively light substances such as granite. These rocks can be up to 4000 million years old and are between 25 and 90 km thick.

Plate- Sections of the Earth's crust which are constantly moving due to convection currents set up in the mantle.

Convection currents- Repetitive movements set up in the mantle due to heating by the core. These currents make the crust move.

• At constructive plate boundaries, currents rise to the surface, they spread out and pull plates apart.
• At destructive plate boundaries, currents collide and pull plates together.
  

Plate margin/ boundary- zone where 2 plates meet. May be described as constructive, destructive, conservative or collison.

When plates are pushed apart, so they move away from one another and new crust is created.

Mid-Ocean ridges- Where two plates made of oceanic crust move apart, the magma of the mantle rises to fill the gap, causing the crust to rise and form a ridge.

They are where new crust is being formed and are formed along mid-oceanic ridges, where 2 plates are forced apart by rising molten rock or magma from the mantle. Atlantic Ocean is widening by 3cm per year. Smaller earthquakes and larger volcanoes, of which the large volcanoes form volcanic islands.

When one plate is subducted below another, the plates crash together and the crust is destroyed.

Subduction Zone- an area where crust is being forced down into the mantle.

Ocean trench- a feature of a destructive plate margin which involves oceanic crust where the oceanic crust is forced down into the mantle it sinks below its normal level to create a deep trench in the ocean.

At a destructive plate margin the oceanic plate is forced down, an Ocean Trench is formed the plate moves and the pressure triggers severe earthquakes.