Restless Earth Notes

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Structure of the Earth

The crust is a thin layer of solid rock floating on the semi molten mantle.

It is made of sections called plates which an be continental or oceanic

Continental plates are older, thicker and less dense, where as oceanic plates are denser, thinner and younger as I s continually being destroyed and rebulit

Convection currents in the mantle cause plates to move creating different plate margins.

Destructive/ Convergent Plate Margins

Two plates move towards each other, when they meet the denser plate (usually oceanic) subducts under the other. I.e South American and Pacific plate.

Composite volcanoes an form on this margin

Plate Margins

Constructive/ Divergent Plate Margins

Two plate move apart crating a gap such as a trench.

Magma can move between the plates to form new crust of a shield volcano

Conservative Plate Margins

Two plate move past each other and the friction generated often causes earthquakes

Volcanoes

Shield Volcanoes

Are made from fluid runny lava.

Usually found at constructive plate margins

Mainly basalt

Have gentle slopes

Have low altitude

Composite Volcanoes

Are made from viscous, sticky lava

Are very common

Have steep slopes

Found at destructive plate margins

Have violent eruptions

Dangers of Living Near Volcanoes

Suffocating ash and fire from heat

Ash and Dust overs schools and homes

Pyroclastic lows of gas and lava

Jojkulhlap (flooding from melted ice)

Destroyed infrastructure, crops and wildlife

Loss of homes and jobs

Advantages of living near Volcanoes

Geothermal energy- In Iceland the steam turning turbines generates electricity and is clean and renewable

Money- Volcanoes attract tourist but can also contain valuable minerals ans metals such as sulphur, copper, silver and gold.

agriculture- The ash from the volcanoes make the soil very fertile and the animals that graze in the area strong.

tomatoes, grapes and nectarines grow well in the area

How to monitor volcanoes

Monitor volume of gas emitted from the volcano

Watch how the top of the volcano bulges.

Listening to magma gurgling from the volcano.

Seismometer to detect movement and tiny earthquakes

Tilt-meter to measure tilt of the volcano's slope changing.

Global positioning system to detect movements and create thermograph to spot changes in temperature

1995 Montserrat Volcanic Eruption (MEDC)

Cause- North and South American plates subduct under Caribbean plate

The melted plates mixed with sea water becoming less dense and rose upwards

The dissolved gases are released and push up old dust and ash causing an eruption

Primary Effects

Deaths and injuries such s burns

Mud pools increase in temperature

Fires and pyroclastic flows

South of island destroyed along with crops and infrastructure

Secondary Effects

Vegetation regrowth

More fertile ground

Less tourism

Starvation of locals

Positive Impacts

New land created

Soil more fertile

Created more awareness of the volcano

Negative Impacts

Loss of jobs and tourism

Wildlife and buildings destroyed

Short Term Responses

Evacuation

Monitoring volcano

Money sent from the UK for temporary buildings, school and water purification systems

Shared facilities

Emergency food

Long Term Responses

People move back

3 year development programme

Continued monitoring of volcano

Super volcanoes

A super volcano is a mega-colossal volcano that erupts at least 1000km2 of material.

Effects of super volcanoes

Produce 1000km2 of ash

Ash can be up to 5m thick 1000km away

Volcanic winter that can last up to 5 years and temperatures drop 5-10 degrees Celsius because of block in solar radiation

Poisonous gas contaminate water

Radius of 500km destroyed

Trigger a tsunami

Plants and crops buried

Climate change

Thousands of deaths

Transport, electricity and farming affects

Mudslides

A fissure- Extends opening along a line of weakness that allows magma to escape

Geothermal- Water heated underground that comes to the surface in a variety of ways

Geyser- A geothermal feature in which water erupts into the air under pressure

Caldera- The depression of a super volcano marking the collapsed magma chamber

Magma cannot escape to the surface and collects under the lower crust.

An 'uplifted bulge' begins to form under the lower crust as the magma chamber enlarges.

Cracks appear on the surface. Gas and ash erupt from the magma chamber through these cracks.

The magma chamber collapses and a depression is formed. This is called a caldera.

Fold Mountains

Fold mountains are formed when two plate of similar densities move towards each other pressing each other to from a mountain such as the Himalayas or the Andes

Andes Case Study

The Andes extends from the north to south of south america formed by the Nazca Plate and south american plate creating fold mountains

School life is basic with limited resources most children end up working the land

There is a large tourism industry due to the natural attractions of the Andes. these include mountain peaks, glaciers , lakes, volcanoes and the famous Inca trail which is a World heritage site, important both naturally and culturally.

Earthquakes are caused by friction between plates, usually by destructive or conversvative plates

The focus of the earth quake is where the Earthquake starts undergroundThe epicenter is directly ontop of the focus, the place on the surface where the biggest seismic waves are felt

Earth Quake Kobe Japan 1995

Cause

Philippines plate subducts under Eurasian Plate.

Pressure released causing earth quake

Effects

6, 434 dead

40,000 injured

300,000 homeless

Gas mains and infrastructure damaged

Homes without water of electricity

Fires

cramped tents

Response

Search for survivors

People sent to hospital

Free telephone connection from Motorola

Essential provided by big retailers

Repairing railways

New buildings with flexible steel frames

Terracing used to grows crops on rocky steep mountain so water doesn't wash soil away. Land is used to grow corn.

Mining using donkeys and llamas suitable for the terrain.

Protecting against earthquakes

Steel frame

Rubber shock absorbers

Open area for people to assemble

Roads for quick access to services

The Andes have a lot of specially adapted plants. However many of the trees are are endangered, and only 10% of the original woodland remains.

There are many species of animals including foxes, cougars and tropical birds.

Llamas and alpacas are kept for wool and meat.

Flamingos and gooses are found near the lakes.

Chinchillas are hunted for their fur making them endangered.

Some humming birds are also endangered.

Earthquakes

Indonesian Tsunami

Effects

Primary

Over 230,00 people killed

Over 94000 people killed in Indonesia. (Half were tourists)

Estimated 50,000 children dead.

5 million people lost their home

Flooding

Infrastructure destroyed

Cars and property destroyed

Tree swept and broken

Entire villages wiped out.

Secondary

Crime

Exploitation

People dying from injuries

Malnutrition

Lack of clean water

Disease

Immediate

Reports

Evacuation

Search for survivors

Bodies collected

$3 billion in international aid

Volunteers for Britain helping

£76 million donated by British

People flown away

Long Term

650 wells cleared in Sri Lanka

Indian Ocean warning system

Monitoring of water quality

Counseling for victims

Rebuilding homes and roads

Response

Tsunami

Plates suddenly move against each other and jolt displacing a lot of water.

Large waves move through the ocean away from the epicenter.

In deep water the waves move quickly with little height

In shallow water the waters slow down and gain height

Water retreats back to sea before hitting.

Tsunamis or tidal waves are caused by shallow earthquakes under the sea that move the entire depth of water above.

Earthquakes

tSUNAMI

Plates and Plate margins

vOLCANOES AND mOUNTAINS