Geography Revision 1 - Restless Earth

Crust - outer layer of the earth, solid, tectonic plates.

Mantle - liquid, convection currents.

Outer Core - made out of molten rock, liquid.

Inner Core - amde out of iron and nickle, solid.

When 2 plates move away from each other.

As the plates move apart the gap if filled by magma rising up from the mantle below.

The rising magma creates shield volcanoes.

When 2 plates push together but neither one will be pushed under the other.

The 2 edges crumple upwards to form mountain ranges - The Himalayas.

When 2 plates move together and one plate slides under the other.

The oceanic crust sinks under the continental because it is thinner.

The plate sinks into the mantle where it melt in the subduction zone.

It forms an ocean trench on the ocean floor.

Energy builds up in the subduction zone and can cause an earthquake.

If the molten rock from the subduction zone rises upwards it can cause the making of a composite volcano.

When 2 plates slide past each other.

Pressure builds up along the plate boundaries until one jerks creating an earthquake.

Earthquakes and volcanoes tend to have a linear distribution.

There is a line of earthquakes down the middle of the Atlantic Ocean.

There can also be clusters of earthquakes and volcanoes.

Earthquakes and volcanoes tend to happen along the edges of tectonic plates.

Sediments accumulates on the sea bed.

Over millions of years the sediments compress to form sedimentary rocks.

The rocks are pushed together as the plates on either side of the ocean push together.

Meaning that the sedimentary rock folds up.

Constructive - gentle slopes, wide base, frequent eruptions, made of lava, form at constructive plate margins.

Destructive - tall cone, steep slopes, narrow base, made of ash and lava, irregular eruptions, violent explosions, form at destructive plate boundaries.

Where - Montserrat

Primary Effects - ash could caused buildings covered and ruined, no airport, no roads, no communication, 23 people dead, everything ruined, no electricity, no clean water, lives ruined.

Secondary Effects - loss of homes, grief, unemployment, loss of tourism,

Responses - evacuation, temporary shelters, given clean water, rescue services, helicopters, emergency food and medical resourse, aid from other countries, reconstruction.

Where - Kobe, Japan

Primary effects - building collapsed, 5,000+ dead, fires started, liquefaction, no food, water pipes burst, gas pipes burst.

Secondary Effects - transport links disturbed, 230,00 people homeless, no clean water, blocked roads, electricity supplies disrupted, closing of industries.

Responses - emergency services, rescuers, water, gas and electricity supplies restored, reconstruction.

Earthquakes happen when stress builds up inside the earths mantle and the energy realeased is an earthquake.

Earthquakes also happen at passive plate boudaries and the testion builds up beteween 2 plates and on suddenly jerks causing an earthquake.

Earthquakres are measured on a richtar scare or a mecalli scale.

Rictar Scale - no upper limit, measured using a size-mograph, logarithmic scale meaning from 1 to 2 it would be 100 ime stronger.

Mercalli Scale - measured from I to XII on the efffects of an earthquake, it describes the damaged caused by an earthquake.

Normally waves are wind-driven and may hae a length of 100m.

Tsunami waves can be 200km at length.

As a tsunami wave travles to the shore it gets bigger and travels extremely fast.

Where - Indian Ocean

Most Affected - Sumatra,