Supervolcanoes

Characteristics of a Supervolcano 

A supervolcano is a very large volcano with the potential to erupt catastrophically and with enormous power. 

Supervolcanoes develop on a handful of places around the globe and are located on destructive plate margins or over parts of the mantle that are really hot called hotspots. Three super volcanoes are located in South America. A super volcano is also found in Japan, Aira Caldera. There are also super volcanoes in Indonesia, New Zealand and Siberia. 

Differences between volcanoes and super volcanoes

Supervolcanoes 

• EMISSIONS: 1000km cubed of material (av)
• APPEARANCE: Large depressions (calderas) 

Volcanoes 

• EMISSIONS: 1km cubed of material (av)
• APPEARANCE: Cones

Formation of a super volcano:

• Rising magma cannot escape, and a large bulge appears on the surface
• Cracks appear in the surface and gas and ash erupt from the magma chamber
• The magma chamber collapses, forming a depression called a caldera. 

Monitoring and predicting volcanic eruptions

Earthquake activity 

An increase in earthquake activity is an indication that magma is rising beneath a volcano causing, causing rocks to crack and fracture. Seisometerss are used to detect earthquakes. They pick up the vibrations in the earth's crust. An increase in vibrations may indicate a possible earthquake. 

Tiltmeters

Tiltmeters can be placed on the ground to measure slight changes in the tilt of the ground caused by rising magma. Global positioning systems (GPS) use satellite technology to measure very slight changes in distance of as little as 1mm. Laser beams can also be used to measure changes in distance between two fixed points on a volcano. If a volcano swells, the distance between two places will increase. 

Digital cameras

Digital cameras can be placed on the rim of craters to record small eruptions or landslides that may indicate rising magma. (e.g White island, New Zealand) Controlled from a distance, this is a safe way to monitor crater activity. Thermal imaging techniques and satellite cameras can be used to detect heat around a volcano. As activity increases, the temperature around the volcano increases. 

Gas Monitoring Stations

Gases emitted from a volcano, such as sulphur dioxide, can change in concentration prior to an eruption. Continuous gas monitoring stations are used by scientists to monitor activity at Kilauea volcano on Hawaii. The higher the sulphur content of the gases released, the closer the volcano is to erupting. A sudden increase in radon gas may suggest an earthquake. 

Historic information 

Historic information from previous eruptions can be used to construct hazard maps. This includes history of ash falls, lava flows and lahars. Hazard maps are used to identify zones at risk from particular hazards. They can be used to decide which areas are safe for developments such as housing and also in making plans for evacuations. 

Mount Merapi October 2010 Case Study

Causes 

The volcano and its eruptions were caused by the Indo Australian plate being sub ducted beneath the Eurasian plate. This caused great pressure and heat from friction between the plates which melted the Indo-Australian plate to form magma. The magma was lighter than its surrounding area so rose to the surface and caused a violent volcanic eruption. 
Furthermore, the volcanic eruption was particularly violent because Mount Merapi is a composite volcano with viscus lava that is more resistant to moving quickly, which in turn leads to the build up of pressure. 

The volcano is located on a destructive plate margin at a subduction zone and is part of the 'Pacific Ring of Fire' 

Primary effects

• On 25th October there were three major eruptive moments and hundreds of tremors. 
• On 26th October there was more explosive events. Pyroclastic flows spread 3km down the mountain.
• On 30th October there were further eruptions and lava continued to push into the dome. 
• Ash fell up to 30km away and 5km into the sky 15km away, villages were under 30cm of ash. The city of Yogyakarta was covered in ash. 
• Volcanic bombs and hot gases of up to 800 degrees Celsius spread over 11km away
• Sulphur dioxide was blown across indonesia and as far south as Australia. 

Secondary effects

• Vegetable prices increased because of the damage to crops
• Planes were grounded in Western Australia because of the risk of damage to aircraft from the ash cloud. 
• Ash, rock and lava deposited on the sides of the volcano washed down into towns by rainfall creating a lahar. 
• 4000 dairy cows and large areas of agricultural land were lost as they were damaged by heavy falls of ash. 
• Food shortages due to lost crops. 
• 34 people died as a result of pyroclastic flows. 
• Homes, roads, water supplies were destroyed
• 273 people died overall and 360,557 people were forced to flee their homes. 

Impacts

Negative 

• 273 people were killed - 176 died on the spot from pyroclastic gas, and 97 from accidents or other causes after being hospitalised 
• 577 people were injured with many suffering severe burns and chronic respiratory problems
• 360,000 people were displaced from their homes
• People, particularly farmers, lost their homes and livelihoods 
• The evacuation centres were overcrowded leading to poor sanitation, no privacy and serious disease risk
• Toursits will be put off visiting the location, which will affect the local economy

Positive 

• Ash from the volcano will eventually lead to more fertile soils in the area. 
• A conservation area has been set up around the volcano where it is unsafe to live. 

Responses 

Immediate 

• 210 evacuation centres were set up, either as tents, in schools, churches, stadiums or government offices.
• 1,600 people, either volunteers or military were part of the national aid response and distributed food, medicine and blankets.
• International aid was offered from organisations such as the Red Cross as a result of growing food shortage. 

Long Term

• Formal evacuation centres were eventually set up because buildings, such as schools and government offices, were needed for their official uses. 
• 2,682 people have had to be moved to new, safer houses permanently.
• The government is making money available to farmers to help replace their livestock. There is funding for more than 4000 dairy cattle
• The government has set up a special task force to support people that have been affected by the volcano either by family issues, or because they have lost their jobs. 
• They are also rebuilding infrastructure, roads, railways and reconstructing water supplies. 
• Further research is being carried out to find better ways of monitoring future eruptions. 

Volcanoes

Characteristics of volcanoes 

Location

Volcanoes are distributed close to plate margins, particularly constructive plate margins. Many volcanoes have formed along the mid atlantic ridge between the South American plate and the African plate, and The North American Plate and the Eurasian Plate. The area around the Pacific ocean is especially prone to volcanoes and is called 'The Pacific ring of fire'. This ring stretches from the Andes in South America, northwards to California in North America and all the way to the Philippines. Many islands in the Philippine archipelago are volcanic islands. They also occur in destructive Plate Margins, shown by the volcanoes in the Andes regions. 

Key Terms: 

Natural Hazard: An event over which people have little control, which threatens people's lives and possessions. This is different from a natural event as volcanoes can erupt without being a hazard. 

Primary effects: The immediate effects of the eruption, caused directly by it. 

Secondary effects: The after effects that occur as an indirect effect of the eruption on a longer timescale. 

Aid: Money, food, training, and technology given by richer countries to poorer ones, either to help with an emergency or for long term development. 

Immediate response: How people react during a disaster and straight afterwards.

Long-term Response: Later reactions that happen in the weeks, months and years after the event. 

Lahar: Mudflows resulting from ash mixing with melting ice or water - a secondary effect of a volcano. 

Hazard map: A map that shows areas that are at risk from hazards such as earthquakes, volcanoes, landslides, floods and tsunamis. 

The Andes Case study

The andes

Background

The Andes is a range of young fold mountains formed around 65 million years ago. It is the longest range of fold mountains in the the world, extending the length of South America. The Andes are a result of a head on collision between two tectonic plates; the Nazca Plate and the South America plate. 

South American countries; Venezuala, Colombia, Ecuador, Peru, Bolivia, Chile, and Argentina. 

How are the mountains used for: 

Farming

Farmers grow a variety of crops on the steep slopes of the Andes (E.g Farmers in Bolivia grow potatoes. The use of terraces creates areas of flat land on the slopes, enabling inhabitants to overcome the steep relief and erosion. Additionally, terracing ensures the soil has enough moisture for crops to grow. Some cash crops are produced in the Andes, for example, soy beans, rice and cotton. Most of the crops are crown in the lower valleys. 

Hydroelectric Power

The steep relief and narrow valleys that limit farming are an advantage for hydroelectric power. They can be more easily dammed than wider valleys and the relief encourages the rapid flow of water used to generate electricity. Additionally, the melting snow in spring increases the supply of water. For example, in 2009, the El Plantanal HEP plant began to generate electricity using a Dam across the Canete River. The project cost $200 million. 

Mining

The Andes has a range of important minerals and the Andean countries rank in the top 10 for tin (Peru and Bolivia), nickel (Columbia), silver (Peru and Chile) and gold (Peru). More than half of Peru's exports are from mining. For example, The Yanacochla gold mine is the largest gold mine in the world - It is an open pit and the gold bearing rock is loosened by daily dynamite blasts. This brings jobs to nearby towns - E.g Cajamarca. 

Tourism

The Andes is home to many natural attractions such as mountain peaks, volcanoes, glaciers and lakes. Many tourist attractions show how people settled in these inhospitable places - E.g Machu Picchu - This site is of interest as it shows how people lived in such a harsh environment. Machu Picchu is the remains of a settlement built by the Inca's. A popular tourist activity is following The Inca Trail, a set of three routes that meet at Machu Picchu. These destinations are popular to tourists as they combine different cultures and history, as well as stunning scenery. 

How have the local people adapted to: 

Limited communications

The local people have adapted to limited communication by using llamas as pack animals to reach inaccessible areas. They are able to carry 25% of their body weight, meaning they can carry materials for irrigation and buildings. The mining industry often relied on them as a form of transport. Today, mostly male llamas are used for transport. The females are used for meat and milk, and their wool is used for clothes and rugs. 

There are plans to build a tunnel linking Chile and Argentina under the Andes.

Steep relief

Throughout the ages the local people have used a system of terraces to overcome steep relief. A terrace is an area of cultivation whose slopes are levelled or raised and stabilized  by a small wall made of stones. Terracing helps retain water in an area that receives little. Additionally, they limit the downward movement of soil in areas where the soil is thin, meaning there is consistently good soil at every level. Terraces also maintain soil humidity and reduce the risk of frosts. 

Poor Soils

The local people have dealt with the problem of poor soils by implementing an irrigation system. This means the land is artificially watered, combating the issue of water shortages. The use of terraces also helps poor soil as it helps retain water in an area that receives little additionally. Where soil is thin, the terraces prevent soil moving down. 

Key terms

Subsistence: Farming to provide food and other resource's for the farmers own family. 

Terraces: Steps cut into hillsides to provide flat land

Irrigation: artificial watering of the land 

Hydroelectric power: The use of flowing water to turn turbines to generate electricity

Landforms at Plate Margins

Fold Mountains and Ocean Trenches 

• Both Fold Mountains and Ocean Trenches form at destructive subduction plate margins
• Only Fold Mountains form at destructive collision plate margins

Formation of Fold Mountains

• Fold mountains form at destructive plate margins - either collision or subduction zones
• Rivers deposit sediment at the bottom of the ocean forming sequential layers. Over time, repeated deposition leads to layers of sedimentary rock forming. 
• As the plates begin to move together, the layers of rock are pushed up and down - the crumpling producing anticlines and synclines of fold mountains. 
• This continues, even when the ocean has been removed.
• For example, the himalayas. 

Formation of Ocean Trenches

• Ocean trenches only occur at destructive subduction plate margins. Convection currents cause continental crust to move towards oceanic crust. 
• The denser oceanic crust sinks beneath the lighter continental crust forming an ocean trench at the point where the ocean 'dives' beneath the continental crust creating a deep section of the ocean. 
• For example, the Mariana trench formed where the Pacific sub ducts beneath the Philippine plate. 

Composite and Shield Volcanoes 

Composite Volcanoes

• Steep slopes and narrow base 
• Secondary cones
• Layers of thick ash and lava
• Viscus Magma
• Eruptions infrequent but often violent

Shield Volcanoes

• Wide base and gentle slopes 
• Low, rounded peak
• Layers of runny lava with little ash
• Eruptions frequent and non violent

Past exam question:

Compare and contrast a composite and shield volcano

• Similarities: Magma chambers, vent, crater
• Differences: Composite; destructive plate margin, infrequent but violent eruptions, steep sides and narrow base, layers of thick ash and lava / Shield; constructive plate margin, frequent but non violent eruptions, wide base and gentle slopes, layers of runny lava with little ash

Key terms:

Fold mountains: Large mountain ranges where rock layers have been crumpled as they have been forced together

Ocean trenches: Deep sections of the ocean, usually where an oceanic plate is sinking beneath a continental plate. 

Composite volcano: A steep sided volcano that is made up of a variety of materials, such as lava and ash

Shield volcano: A broad volcano that is mostly made out of lava. 

Plates Key Terms

Crust: The outer layer of the earth 

Plate: A section of the earth's crust 

Plate margin: The boundary where two plates meet 

Mantle: The dense mostly solid layer of the earth between the outer core and the crust. 

Convection currents: The circular currents of heat in the mantle 

Destructive: A plate margin where two plates are moving towards each other, resulting in one plate sinking beneath the other. 

Constructive: Two plates that are moving apart

Conservative: Two plates sliding alongside each other

Earthquake: A sudden, often violent shift in the rocks forming the earth's crust, which is felt at the surface

Volcano: An opening in the earth's crust through which molten lava, ash and gases are ejected. 

Oceanic crust: A tectonic plate made of dense iron rich rock that forms the ocean floor. 

Continental crust: A tectonic plate made of low density continental rock that will not sink under another plate. 

Subduction: When oceanic crust sinks under continental crust at a destructive margin

Collision: When two plates of continental crust meet 'head on' and 'buckle'.

Past exam questions: 

Explain how volcanoes from at destructive plate margins

• Convection currents in the lower mantle cause the plates to move towards each other
• If plates are continental v oceanic crust, the oceanic (denser) crust will sink below the continental (lighter) crust in a process called subduction. 
• Great pressure is exerted and heat is produced from friction between the plates which destroys (melts) the oceanic plate to form magma. 
• The magma is lighter than its surroundings so rises to the surface causing violent volcanic eruptions. 

Explain how earthquakes occur at conservative plate margins

• Plates moving in similar directions (but not the same)
• The pressure builds up as the plates stick 
• Sudden release causing the jerking movement which is the earthquake 
• For example the San Andreas Fault

Types of Plate Margin

Destructive Plate Margins 

• Convection currents in the mantle cause the plates to move together
• If one plate is made of oceanic crust and the other is made of continental crust, the denser oceanic crust sinks under the lighter continental crust in a process know as subduction. 
• Great pressure is exerted and and the oceanic crust is destroyed.
• If two continental crusts meet each other, they collide rather than one sinking beneath the other. This collision boundary is a different type of destructive margin. 

Constructive Plate Margins

• When plates move apart a constructive plate boundary results. This usually happens under oceans.
• As these oceanic plates pull away from each other, cracks and fractures form between the plates where there is no solid crust. 
• Magma forces its way into the cracks and makes its way to the surface to form volcanoes. 
• New land is formed as the plates pull apart. 

Conservative Plate Margins

• At conservative plate margins, the plates are sliding past each other.
• They are moving in a similar (but not the same) direction at slightly different angles and speeds. 
• As one plate is moving faster than the other and in a slightly different direction, they tend to get stuck. 
• Eventually the build up of pressure causes them to be released. 
• This sudden release of pressure causes an earthquake.
• At a conservative plate margin, crust is neither being destroyed or made. With no source of magma, volcanoes are absent. 

The structure of the earth

Convection Currents 

Convection currents are the circular currents of heat in the mantle.

Plates float on the mantle beneath the Earth's surface. Convection currents cause the plates to move. This means some plates are moving apart and some plates are moving together. 

Oceanic and Continental crusts

Oceanic Crust

• Newer - most less than 200 million years old
• Denser
• Can sink
• Can be renewed and destroyed

Continental Crust

• Older - most over 1500 million years oils
• Less dense
• Cannot sink
• Cannot be renewed or destroyed 

Location of plates and margins

Plate Margin: Destructive - subduction

Direction of plate movement: When continental plates move together, the oceanic plate sinks under the continental 

Example: Philippines Plate

Plate Margin: Destrucutive - collision 

Direction of Plate Movement: Plates of continental crust meet head on and 'buckle' 

Example: Indo Australian plate and Eurasian plate

Plate Margin: Constructive 

Direction of Plate Movement: Plates move apart 

Example: Antarctic Plate and Pacific plate 

Plate Margin: Conservative

Direction of Plate Movement: Plates slide past each other moving in the same direction

Example: San Andreas Fault

Where is each plate margin located? 

Destructive: An example of a destructive plate margin is the Juan de Fuca Plate. The Juan de Fuca plate sub ducts beneath the North American plate off the coast of east america (near the state of Washington) The Nazca plate located in the Pacific Ocean, sub ducts beneath the South American Plate forming a destructive plate margin along the coast of South America (Pacific ocean). Furthermore, where the South American plate meets the Caribbean Plate it sub ducts beneath it. This plate margin is found in Puerto Rico. The indo Australian Plate is colliding with the Eurasian Plate near Japan and the east China sea. 

Constructive: An example of a constructive plate is the Mid - Atlantic Ridge. This constructive margin surfaces at the volcanic island of Iceland. The Mid Atlantic ridge is formed where the North America Plate is moving away from the Eurasian Plate in the Atlantic sea. A constructive plate margin is splitting eastern Africa away from the African continent.Additionally, the Indo Australian Plate is moving away from the Antarctic Plate forming a constructive plate boundary south of Australia in the southern Ocean. 

Conservative: An example of a conservative plate margin is the San Andreas Fault, located on the west Coast of North America in the pacific ocean. The San Andreas Fault is where the North American Plate and the Pacific Plate are moving in the same direction, but at different speeds. 

Water Transfer - Vyrnwy Case study

A traditional solution to an unequal supply of water has been to transfer water from areas of surplus to areas of deficit. In the late 1800s the River Vyrnwy in Powys was dammed to supply Liverpool with Welsh water. 

Construction began in 1881 and was completed in 1888. It was the first stone dam in the UK. In front of the new dam, the Liverpool Corporation built the new village ready for when the valley was going to be flooded. In all, 2 chapels, 3 inns, 10 farmhouses and 37 houses were to be lost under the reservoir. The new village, which retained the name Llanwddyn, was built 3km from the original village. 

Since the dam was built, new transfer schemes have been proposed. In 1973, such an approach was favourably received and three new reservoirs were constructed (Brenig in Wales, Kielder in Northumberland and Carsington in Derbyshire), but the remaining plans never became reality. Predicted demand was never realised and there was over capacity. 

In 1994, the idea of transfer returned, with grand schemes to transfer water from the Severn to the Thames and Trent. However, costs were high and in 2004 it was concluded that local schemes, including small reservoirs, could meet the demand for water in areas such as the south -east. If, in the future, this is not possible, transfers may become a possibility. 

How are rivers in the UK managed to provide our water supply?

Water usage

The north and west of Britain use less water than the south and east of Britain. Households in the north and centre of Britain only use on average 130 - 149 litres per day. London in particular has one of the highest Average household water usage in the country, with a usage of more than 190 litres per household per day. Suffolk has a particularly low average with a usage of less than 130 litres per household per day. 

What increases water usage? 

• Increase in population will increase water usage
• A more affluent lifestyle increases an individuals water usage as a lot of recreational activities use water.
• Demand for food, which is out of season, increases water usage due to watering/irrigation
• Industrial processes utilize a lot of water so usage will increase 
• A rise in temperature will increase water usage for cooling, farming and watering gardens/lawns

Water supply issues and solutions in the UK

Measures must be taken to ensure that the increase in water demand due to population growth and other factors can be met in a sustainable way and that people are encouraged and educated to only use the water they need. There are areas of water surplus such as Scotland and the North of England, which should not have a supply problem in the future. However the Southeast in particular is at risk of water stress where there is insufficient water to supply peak periods due to water deficit. Water conservation is also important and people must be encouraged to reduce their usage. Water meters have been shown to reduce usage by charging people for the exact amount of water they use. People are more likely to take showers rather than baths, not leave taps running, and water their gardens sparingly. Technology is also important. It can assist with more efficient toilets, rain collection systems and water recycling systems.