Geography GCSE: Unit 1A - Tectonic Plates

↳ The crust is divided into tectonic plates – they are made of continental and oceanic plates.

↳Continental – thicker and less dense.

↳Oceanic – thinner and more dense.

↳ Destructive – two plates are moving towards each other.

·         Where an oceanic plate meets a continental plate, the denser oceanic plate is forced into the mantle and destroyed – this creates volcanoes in the ocean trench.

·         Where two continental plates meet and they smash together, but no crust is destroyed.

↳ Constructive – two plates moving away from each other.

·         The magma rises from the mantle which fills the gap and cools therefore, creating a new crust.

↳ Conservative – two plates are moving sideways or past each other.

·         The crust isn’t created nor destroyed.

↳ When tectonic plates collide, the sedimentary rocks are forced upwards to form mountains.

↳ Therefore, fold mountains are found at destructive plate margins.

↳ You can also get fold mountain where a continental and oceanic plate collide. (The Andes, South America)

↳ You can also get fold mountains where two continental plates collide. (The Himalayas, Asia)

Location – Central Europe (Austria, France, Germany, Italy, Liechtenstein, Slovenia and Switzerland).

Formation – By collision between the African and European plates.

The Alps are used for:

↳ Farming

·         Steep uplands are used for: farming goats which provide milk, cheese and meat.

·         To plant vineyards (Lavaux, Switzerland)

↳ Hydro-Electric Power (HEP)

·         Narrow valleys = dammed = generate HEP. (Berne, Switzerland)

·         Electricity produced for locals, powering homes and businesses. Also, exported to towns and cities further away.

↳ Tourism

·         100  million + tourists visit The Alps a year.

·         70% visit steep, snow covered mountains for extreme sport (skiing, snowboarding ect)

·         Villages are built for tourists (Tigenes, France)

↳ Forestry

·         Scots Pine is planted all over the Alps which make it more resilient to goats and also, the trees are logged and sold to make furniture.

People have also adapted to the conditions in the Alps:

↳ Steep relief

·         The goats are farmed as they are well adapted to steep mountains. Also, the trees and any other man-made defences are used to protect against avalanches.

↳ Poor soils

·         The animals are grazes in high areas due to the fact that the soil isn’t as capable for growing crops.

↳ Limited communication

·         Roads have been built at lower points of the mountains. (The Brenner Pass between Austria and Italy)

↳ Composite volcanoes (Mt. Fuji, Japan):

·         This is made of lava and ash which has erupted over the years and is cooled and hardened down to form layers.

·         The lava is thick and flows slowly therefore, it hardens quickly resulting to form a sleep-sided volcano.

↳ Shield volcanoes (Mauna Loa, Hawaii):

·         This is made up of only lava.

·         The lava is runny; therefore it flows quickly and spreads over a wide area hence forming a low, flat volcano.

↳ Dome volcanoes (Mt. Pelée, the Caribbean):

·         This is also only made of lava.

·         The lava is thick therefore, it flows slowly and hardens quickly and so, it forms into a steep-sided volcano.

Date of eruption – 25^th June 1997

Size of eruption – 4-5 million m³ of rocks and gas released 

Death toll – 19 killed

Cause – the Atlantic plate was forced under the Caribbean plate

↳ Primary impacts:

·         Large areas were covered with volcanic material.

·         Over 20 villages and about two thirds of homes were destroyed by the pyroclastic flows.

·         Schools, hospitals, the airport and port were destroyed.

↳ Secondary impacts:

·         Fires destroyed many building such as government offices and police headquarters.

·         There was a population decline – 8,000 of the 12,000 inhabitants left.

·         Volcanic ash improved soil fertility

↳ Immediate response:

·         People evacuated from the south area to safe areas in the north.

·         Temporary infrastructure was built

·         Shelters were built to house evacuees

↳ Long-term response:

·         A risk map was created.

·         The south of the island is off-limits as it is still active.

·         The Montserrat Volcano Observatory has been set up and tries to predict future eruptions.

 ↳ The magma rises up through cracks in the crust which form a magma basin below the surface. So, the pressure of the magma causes a circular bulge on the surface.

↳ Then, the bulge eventually cracks which creates vents for lava to escape through resulting the lava to erupt out of the vents which causes earthquakes

↳ The magma basin empties and the bulge is no longer supported therefore, this causes more lava to spew as the bulge has collapsed.

↳ When the eruption is finished, a caldera is left – these often form large lakes.

 A super volcano:

↳ Is flat.

↳ They cover a large surface area.

↳ They have a caldera.

The possible consequences if a super volcano erupts:

↳ A thick cloud of gas and ash will form burning and burying everything in its path.

↳ It would trigger mini ice ages as the ash will block out daylight.

↳ The ash will settle over large areas burying fields and buildings.

Earthquakes occur at all three types of plate margins.

↳ Destructive margins

·         Tension is built when one plate gets stuck as it’s moving down past the other into the mantle.

↳ Constructive margins

·         Tension is built along cracks within the plates as they move away from each other.

↳ Conservative margins

·         Tension is built when the plates which are grinding past each other gets stuck.

Earthquakes can be measured by using:

·         The Richter Scale

·         The Mercalli Scale

Place – Indian Ocean

Date –2004

Size – 9.1 on the Richter Scale (earthquake off the west coast of Sumatra on 26^th December 2004)

Cause – there’s a destructive plate margin along the west coast of Indonesia in the Indian Ocean.

↳ Around 230,000 people killed or missing.

↳ Towns or villages destroyed (1.7 million people lost their homes).

↳ Infrastructure damaged.

↳ 5 – 6 million people needed emergency food, water and medical supplies.

↳ Massive economic damage. (Millions of fishermen lost their livelihoods)

↳ Massive environmental damage caused. (Coral reefs destroyed by waves)

Short-term responses:

·         Millions of pounds was pledged by foreign governments, charities ect.

• Foreign countries sent ships, planes and teams of specialists to help rescue people, distribute food and water.

Long-term responses:

·         Billions of pounds was pledged to help re-build infrastructure.

·         A tsunami warning system was put in place.

• Disaster management plans were put in place in some countries.