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 MarginsTwo 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
Constructive/ Divergent Plate MarginsTwo 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 MarginsTwo plate move past each other and the friction generated often causes earthquakes
Shield VolcanoesAre made from fluid runny lava.Usually found at constructive plate marginsMainly basaltHave gentle slopesHave low altitude
Composite VolcanoesAre made from viscous, sticky lavaAre very commonHave steep slopesFound at destructive plate marginsHave violent eruptions
Dangers of Living Near VolcanoesSuffocating ash and fire from heatAsh and Dust overs schools and homesPyroclastic lows of gas and lavaJojkulhlap (flooding from melted ice)Destroyed infrastructure, crops and wildlifeLoss of homes and jobs
Advantages of living near VolcanoesGeothermal energy- In Iceland the steam turning turbines generates electricity and is clean and renewableMoney- 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 volcanoesMonitor volume of gas emitted from the volcanoWatch how the top of the volcano bulges.Listening to magma gurgling from the volcano.Seismometer to detect movement and tiny earthquakesTilt-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 plateThe melted plates mixed with sea water becoming less dense and rose upwardsThe dissolved gases are released and push up old dust and ash causing an eruptionPrimary EffectsDeaths and injuries such s burnsMud pools increase in temperatureFires and pyroclastic flowsSouth of island destroyed along with crops and infrastructureSecondary EffectsVegetation regrowthMore fertile groundLess tourismStarvation of locals
Positive ImpactsNew land createdSoil more fertileCreated more awareness of the volcanoNegative ImpactsLoss of jobs and tourismWildlife and buildings destroyedShort Term ResponsesEvacuationMonitoring volcanoMoney sent from the UK for temporary buildings, school and water purification systemsShared facilitiesEmergency foodLong Term ResponsesPeople move back3 year development programmeContinued monitoring of volcano
A super volcano is a mega-colossal volcano that erupts at least 1000km2 of material.Effects of super volcanoesProduce 1000km2 of ashAsh can be up to 5m thick 1000km awayVolcanic winter that can last up to 5 years and temperatures drop 5-10 degrees Celsius because of block in solar radiationPoisonous gas contaminate waterRadius of 500km destroyedTrigger a tsunamiPlants and crops buriedClimate changeThousands of deathsTransport, electricity and farming affectsMudslides
A fissure- Extends opening along a line of weakness that allows magma to escapeGeothermal- Water heated underground that comes to the surface in a variety of waysGeyser- A geothermal feature in which water erupts into the air under pressureCaldera- 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 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 underground. The epicenter is directly ontop of the focus, the place on the surface where the biggest seismic waves are felt
Earth Quake Kobe Japan 1995
CausePhilippines 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.
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
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.
Plates and Plate margins
vOLCANOES AND mOUNTAINS