Flashcards in Restless Earth Deck (103):
Describe the background of Eyjafjallajökul
-The caldera at the top of the volcano is 2.5Km wide
-The volcano is 1,666m tall
-The volcanic land mass has built up over time due to frequent volcanic activity
Describe the location of Eyjafjallajökul
-It is on the island of Iceland, which is part of Europe and is situated immediately South of the Artic Circle
-Iceland is located in the North American Plate (moving west) and the Eurasian plant (moving East), creating a divergent plate boundary (move apart at 1-5cm every year)
-On constructive plate boundary
Describe the tectonic history of Eyjafjallajökul
-The island has 30 active volcanic systems, of which 13 have erupted since the settlement of Iceland in AD 874
-A study of the last 11 centuries reveals over 200 eruptions, with around three quarters of these explosive and which and average frequency of 20-25 events per 100 years
What were some of the short term impacts of the Icelandic volcano?
1. The 150m thick ice cap melted, which caused major flooding go Iceland, 800 people evacuated
2. 20 farms were destroyed by the flooding and the ash
3. Airspace closed across Europe with at least 17,000 flights a day being cancelled , 6 flightless days
4. Ash blocked out sun turning day into night
5. Local water supplies were contaminated with fluoride
1. Temporary reduction of aircraft noise
2. 2.8 million less tonnes of CO2 emitted
Describe the Earth's layers (state, temperature)
1. Crust: solid, <300 degrees, 20Km(thin), divided into tectonic plates
2. Mantle: Semi-Molten Rock, 870 degrees, moves very slowly
3. Outer Core: Liquid, 3,600 degrees, movements responsible for the Earth's magnetic field
4. Inner Core: Solid iron and nickel, 5,500 degrees, immense pressure
What is the difference between the Continental and Oceanic crust?
-They are the two types of crust
-Continental crust is thicker and less dense
-Oceanic crust is thinner and more dense
Why are the tectonic plates moving?
Because the rock in the mantle underneath them is moving
What are the places that the plates meet called?
Boundaries or plate margins
Describe Destructive Margins (Subduction)
1. Two plates move toward each other due to the convection currents in the mantle, one oceanic and one continental
2. The denser, heavier oceanic crust subducts under the lighter, less dense continental crust, this creates a subduction zone and an ocean trench
3. In the subduction zone, friction from the contact of the two plates can cause earthquakes (when they lock and release) and heat
4. As the oceanic crust sinks further into the mantle, it melts to produce magma. Because of this increase in volume or magma some rises through the weaknesses in the continental crust
5. Eventually the magma will erupt on the surface as a volcano
6. Where the oceanic crust subducts under the continental crust, ocean sediment is scraped off the ocean bed and onto the continental crust. It is pushed up and folded to form fold mountains.
Describe Destructive Margins (Collision)
1. Two plates of the same density move toward each other
2. Due to their similarity, little or no subduction takes place but instead the sediment and rocks at the plate margin crumple and fold and no crust is destroyed
3. This creates mountain ridges, such as the Himalayas
4. Over time, these mountains may be weathered and eroded by the effects of glaciers and rain
Describe Conservative Margins
1. Two plates moving in either the opposite or same directions (at different speeds). There is no subduction or creation of new rock
2. Movement is not smooth and friction is generated between the two plates
3. Sometimes friction can cause the plates to lock together. However, the plates are still being forced to move, so there is an increase in potential energy
4. At some point, pressure overcomes friction and the plates are suddenly released, jolting past one another
5. This sudden release of energy causes earthquakes
Describe Constructive Margins
1. Two plates of oceanic crust pull apart (diverge), in this case the North American plate and the Eurasian plate
2. The rising magma plume forces the ends of the plate to push up and buckle. This creates tensional cracks on the underside of the plates
3. Magma is squeezed into the gap between the two plates and is cooled by the ocean to form new, solidified rock (basalt)
4. Rising magma forces its way through the tensional cracks, and forms submarine volcanoes (shield) on the ocean floor
5. With successive eruptions over millions of year, they can crow until they break the surface of the ocean, and become a volcanic island (Iceland)
What is a fold mountain?
1. Highland areas, formed along plate boundaries where great compressive Earth movement take place at collision boundaries
2. They are formed over millions of years from sedimentary rocks which have been forced upward into a series of folds by the movement of tectonic plates
3. At a destructive subduction boundary, where the oceanic plate subduct beneath the continental, ocean sediment is scraped off the ocean bed and onto the continental crust. This is pushed upwards, also forming fold mountains.
Describe the formation of fold mountains
1. Rivers carry and deposit sediments into huge depressions in the sea called geosynclines (a large-scale depression in the Earth's crust containing a thick series of sediments)
2. There are long periods of quiet between earth movements during which sediment, thousands of meters thick, build up in these geosynclines
3. These sediments are then forced upwards into a series of folds by the compressive movement of tectonic plates
4. These folds can be upfolds (anticlines) or downfolds (synclines). The ricks can also be fractured or faulted
5. Examples of Fold Mountains are the Alps, Rockies, Himalayas and Andes
Describe the location of the Alps
Fold Mountain Range
-Formed about 30 million years ago by the collision between the African and European plates
-Mont Blanc at 4810m on the Italian-French border is the tallest peak
-Population around 12 million people
How do people use the Alps for Farming?
1. The steep upland areas are used to farm goats, which provide, milk, cheese and meat
2. Some sunnier slopes have been terraced for plat vineyards (e.g. Lavaux and Switzerland)
How do people use the Alps for Hydro-Electric Power (HEP)?
1. The narrow valleys are dammed to generate HEP e.g. in the Berne area in Switzerland. Switzerland get 60% of its electricity from HEP stations in the Alps
2. The electricity produced is used locally to power homes and businesses and it is also exported to towns and cities further away
How do people use the Alps for Tourism?
1. 100 million tourists visit the Alps each year making tourism a huge part of the economy
2. 70% of tourists visit the steep, snow covered mountains in the winter for skiing, snowboarding and ice climbing and in the summer tourists visit for walking, mountain biking, paragliding and climbing
3. New villages have been built to cater for the quantity of tourists e.g. Tignes in France
4. Ski runs, ski lifts, cable cars and holiday chalets and restaurant pepper up the landscape
How do people use the Alps for Mining?
1. Salt, iron ore, gold, solver and copper were mined in the Alps, but the mining has declined dramatically due to cheaper foreign sources
How do people use the Alps for Forestry?
1. Scots Pine is planted all over the Alps because it is more resilient to the munching goats, which kill native tree saplings. The trees are logged and sold to make things like furniture
How have people adapted to the steep relief in the Alps?
1. Goats are farmed there because they are well adapted to live on steep mountains. trees and man-made defences are used to protect against avalanches and rick slides
How do humans use fold mountains for farming?
-Higher Mountain slopes are not great for growing crops (as cold?) so they are used to graze animals e.g. mountain goats
-Lower slopes are used to grow crops
-Steep slopes are sometimes terraced to make growing crops easier
How do humans use fold mountains for mining?
-Fold mountains are a major source of metal ores, so there is a lot of mining going on
-The steep slopes make access to the mines difficult, so zig-zag roads have been carved out on the sides of some mountains to get to them
How do humans use fold mountains for Tourism?
Fold Mountains have spectacular scenery, which attracts tourists
-In winter people visit to do sports like skiing, snowboarding and ice climbing
-In summer, walkers come to enjoy the scenery
-Tunnels have been drilled through some fold mountains to make straight, fast roads.
-This improves communications for tourists and people who live in the area as it is quicker to get to places
How do humans use fold mountains for Hydro-Electric Power (HEP)?
Steep sided mountains and high lakes (to store water) make fold mountains ideal for generating hydro-electric power
How do humans use fold mountains for forestry?
-Fold Mountain ranges are a good environment to grow some types of tree (e.g. conifers)
-They are grown on the steep valley slopes and are used for things like fuel, building materials, and to make things like paper and furniture
What is an earthquake?
-A sudden release of energy or pressure from the Earth's crust that produces seismic shock waves
-These shock waves cause the ground to shake very intensely and can cause a lot of damage
-Earthquakes are vibrations caused by earth movements at plate boundaries and at major fault lines (cracks in the Earth's surface)
How are earthquakes measured using the Ritcher scale?
1. This measures the amount of energy released by an earthquake (called the magnitude)
2. Magnitude is measured using a seismometer which is a machine with an arm that moves with the vibrations of the earth
3. The Richter scale does not have an upper limit and it is logarithmic, this means that an earthquake with a magnitude of 5 is TEN TIMES more powerful than one with a magnitude of 4 (goes up in powers of ten)
4. Most people do not feel earthquakes of magnitude 1-2
5. Major earthquakes are above 5
6. Quantitive measure
How are earthquakes measured using the Mercalli scale?
1. This measure the effects of an earthquake
2. Effects are measured by asking eye witnesses for observations of what happened. Observations can be in the form of words or photos
3. It is a scale of 1 to 12
4. Qualitative measure
Describe primary waves (P waves) (A seismic wave)
-Causing back and forth movement
-Go through solids and liquids
Describe secondary waves (S waves) (A seismic wave)
-Causes side to side movement
-Travel through solids
Describe surface waves (P waves) (A seismic wave)
1. Longitudinal: cause up and down movement
2. Transverse: cause side to side movement and cause the most damage
Where do earthquakes occur?
They can occur at all major plate boundaries but the most severe earthquakes are normally found at Destructive (Subduction and Collision) and Conservative boundaries
Describe the causes of earthquakes at destructive margins
1. Subduction exerts pressure on the crust
2. Pressure from the subduction and melting
3. Broad belt of earthquakes, depth increasing with distance from margin
4. Strong, high magnitude earthquakes
Describe the causes of earthquakes at conservative boundaries
1. Pressure and tension builds up due to friction as the plates move past each other and get stuck
2. Narrow zone of usually shallow-depth earthquakes
3. Moderate to high magnitude earthquakes infrequent
Describe the causes of earthquakes and constructive boundaries
1. Tension from the gentle extension of the plates and margin
2. Earthquakes close to the surface and narrowly concentrated
3. High frequency but low magnitude earthquakes
-Haiti Earthquake 12th January 2010
-In the Caribbean
What were the causes of the Haiti Earthquake
1. Conservative fault through Haiti is between Caribbean and North American plate
2. Caused by release of seismic stresses that had built around two tectonic plates, C was moving eastward with respect tot eh North american plate
3. Focus was 9.97 Km below the surface (very shallow)
4. Epicentre was 10 km southwest from Haiti's Capital, Port-au-Prince
5. The motions of these plates create what are know as strike slip faults, where two sections of the Earth's crust are grinding past each other in opposite directions.
What were the primary impacts of the Haiti Earthquake?
1. Over 188,383 houses were badly damaged and the earthquake destroyed 105,000
2. Roads and docks in Port-au-Prince were also destroyed. This made it difficult to transport food, clean drinking water, clothes, temporary shelters, cooking utensils and most importantly drugs and medicine for the people affected by the earthquake
3. After the Earthquake there were 19 million cubic meters of rubble and debris in Port au Prince
What were the secondary impacts of the Haiti Earthquake?
1. Diseases: due to no clean drinking water and dead bodies rotting, there was a Cholera outbreak in October 2010 which affected more as so many homeless or already injured, it killed 5,899 and infected 216,000
2. 4,000 schools were damaged or destroyed (long term impacts for education prospects)
3. At its peak one and a half million people were living in camps including over 100,000 at critical risk from storms and flooding
4. ECONOMIC PROBLEMS:
-people trying to rebuild their houses and business without the availability of money to buy such materials
-1 in 5 jobs were lost due to the earthquake
5. SOCIAL PROBLEMS:
-people who may have lost all their relatives including children who have been left with no one to care for them (trauma, stress, grief)
-Generation of amputees left due to lack of medical attention, meaning many wounds went gangrenous and meant they had to be amputated
-Lots of doctors and nurses had to do surgery outside because the hospitals were full of people and some hospitals were destroyed
What were the immediate responses to the Haiti Earthquake?
1. Many countries responded to appeals for aid , pledging funds and dispatching rescue and medical teams, engineers and support personnel. The British public donated £107m
2. $5 billion US donated in the first few weeks
3. 1.3 million people were put in homeless shelters
4. Communications systems, air, land and sea transport facilities, hospitals and electrical networks had been damaged by the earthquake with slowed the rescue and aid efforts
4. There was much confusion over who was in charge, air traffic congestion, and problems with prioritisation of flights further complicated early relief work
5 Port-au-Prince's morgues were quickly overwhelmed with many tens of thousands of bodies having to be buried in mass graves
What were the long term responses to the Haiti Earthquake?
1. Training has been provided for 13,149 teachers and 7,842 teaching staff
2. 1000s of earthquake affected families were provided with agricultural assistance during the past three cropping seasons, this included 4,000 tons of crop seeds, 2,378 million roots and tubers, 179,000 banana plants, 16.5 tons of vegetable seeds, 239,000 hand tools, 24,000 tons of fertilisers and 170 tons of compost
3. As of June 2011, 1.2. million people had benefited from water provision receiving more than 4,200 cubic meters of water daily
4. A million children receive daily meals through the National School Feeding Programme
5. Nearly 500,000 people have been provided with improved temporary shelter
6. The EU gave $330 million and the World Bank waived (cancelled) the country's debt repayments for 5 years
7. The Senegalese offered land in Senegal to any Haitians who wanted it
8. Six months after the Earthquake, 98% of the rubble remained uncleared, some still blocking vital access roads
Describe the Earthquake in New Zealand
-Christchurch, New Zealand 22nd February 2011
-Focus Depth: 5km
-Epicentre location: 10Km Southeast of Christchurch in the Port Hills
-Time of event: 12.51pm
What were the causes of the Christchurch Earthquake?
1. New Zealand is directly on the border between the pacific and Indo-Austrailian plate. Therefore it is on the Pacific Ring of fire responsible for the frequent Earthquakes that occur in New Zealand including the Christchurch one
2. There is a Destructive subduction boundary
3. The 2011 earthquake occurred along a previously unknown strike-slip boundary, where the fault moved east-west but also upwards (reverse thrust)
4. The fault line is southeast of Christchurch
What were the prediction strategies put in place for the Christchurch Earthquake?
-A nation wide network of Earthquake detecting and monitoring centres called Geonet was created
-On average, magnitude 7 earthquakes occur once every 10 years, and magnitude 8 earthquakes occur once a century
What were the protection strategies put in place for the Christchurch Earthquake?
-The six-storey Canterbury TV building which collapsed was designed by an inexperienced engineer, inadequately constructed and should never have been issued with a building permit
-Building standards and the severity of building inspections are playing a major role in the reconstruction process
-A 1935 building code made many buildings earthquake resistant and to also prevent the buildings from collapsing so people can escape
-Building foundations should be improved to prevent or lessen the effects of liquefaction
What are the preparation strategies put in place for the Christchurch Earthquake?
-Geonet is able to provide emergency services with information moments after an earthquake or hazardous event has occurred
-The Earthquake Commission has provided funds to educate civilians on how to 'Quake safe' their homes
What were the primary impacts of the Christchurch Earthquake?
1. The CBD of Christchurch suffered particularly devastating damage (negative SEE)
2. 70% of the buildings in the CBD were demolished in the Earthquake (or would have to be torn down afterwards due to their instability) (negative social and economic)
3. 165,000 of the area's 220,000 homes were affected in some way, with many homes made uninhabitable (negative SEE)
4. 181 people were killed (negative social)
5. Liquefaction occurred in many areas throwing buildings off tilt and drastically altering land shapes (negative social and environmental)
What were the secondary impacts of the Christchurch Earthquake?
1. Aftershocks delayed the assessment of damaged buildings and slowed down the reconstruction process (negative social and economic)
2. There was a great deal of uncertainty about the state of the economy in the period after the earthquake - many households and businesses came under significant financial stress (negative economic)
3. There was a big decline in electronic payments because of damage to ATMSs or because of a lack of access to them - many were in cordoned off areas (negative economic)
4. The loss of hotels and other visitor accommodation had a significant impact on the tourism industry and female employment was disproportionately affected because of the high % of women working in this sector (negative economic and social)
5. Some communities were broken apart as people were forced to move elsewhere in New Zealand or to Australia (negative social)
6. 13 schools closed and 18 schools merged as a result of the Earthquake , 4,500 pupils were lost due to out-migration (negative social)
7. Psychological impact as people live in fear of another earthquake and it has a deep and long lasting impact on their lives. It impacts their decisions to invest in the region (negative social)
8. 15% fewer exports and 1% fewer imports went through Christchurch airport in October 2012 compared to the previous year (negative economic)
What were the immediate responses to the Christchurch Earthquake?
1. The CBD of Christchurch was evacuated
2. The day after the Earthquake, the New Zealand prime minister declared a state of national emergency in the Christchurch region
3. The maintenance of payment systems including the supply of additional cash was vital, $150 million NZ cash was sent to Christchurch the week following the Earthquake
What were the long terms responses to the Christchurch Earthquake?
1. The Christchurch Central Recovery Plan set out the way in which the central area of the city will be redeveloped
2. The cost of rebuilding is equivalent to more than 10% of New Zealand's GDP
3. Nearly $1 billion NZ of building consents were granted in the first six months of 2012, to help people and businesses rebuild their homes and livelihoods
4. The government intends to spend $1 billion NZ in the next 10 years renewing the education system in the affected areas
5. The Canterbury Earthquake recovery Authority are to spearhead reconstruction activities in Christchurch, the estimated cost is £13 billion and it is to be divided into four zone depending upon damage levels
-The red zone, the worst affected area will have 5000 of the worst affected insured properties or their land bought
-The orange zone, which is home to 10,000 homes had an undecided fate
-The green zone has 100,000 residences which are likely to all be rebuilt
What are predication strategies?
Attempts to forecast an event - where and when it will happen - based on current knowledge
What are protection strategies?
Constructing buildings and other structures so they are safe to live in and will not collapse
What are preparation strategies?
Organising activities and drills so that people know what to do in the event of an earthquake
What is a volcano?
-A volcano is an opening or vent in the Earth's surface through which material (magma, ash, gas) erupts
-They are a tectonic hazard
What are the three states of a volcano?
1. Active: one that has erupted since the last ice age (in the past 10,000 years roughly)
2. Dormant: One that has not erupted in the past 10,000 years, but which is expected to erupt again
3. Extinct: One that nobody expects to ever erupt again
What are the properties of shield volcanoes?
1. Found on constructive boundaries
2. Gentle sloping sides, lava flows quickly and spreads over a wide area, made up of only lava
3. Thin and runny lava ('basic') - hotter so travels further before cools
4. Gentle explosion
5. Hazards: Gases and lava flows
7. E.G. Mauna Loa (Hawaii, USA) and Nyiragongo (DRCongo)
What are the properties of composite volcanoes?
1. Found on destructive (subduction) boundaries
2. Steep sides, lava cannot flow far and flows slowly, alternating layers of lava and ash
3. Viscous, thick lava ('acidic') - less hot so hardens quicker
4. Violent explosion: hardening rock blocks vents and builds up pressure
5. Hazards: Pyrocastic flows and lahars
7. E.g. Mt Fuji (Japan), Mt St Helens (USA)
What are the properties of dome volcanoes?
1. Made up of only lava
2. The lava is thick
3. The lava flows slowly and hardens quickly, forming a steep-sided volcano
How do scientists try to predict volcanic eruptions in advance?
-Millions of people live in places where volcanic eruptions can happen
-With so many lives at risks it is important to try and predict eruptions, so the damage caused can be minimised
-Scientists can monitor the tell-tale signs that come before a volcanic eruption, such as:
1. Tiny earthquakes
2. Escaping gas
3. Changes in the shape of the volcano (e.g. bulges in the land where magma had built up under it)
All mean an eruption is likely
What is a tsunami?
-An enormous sea wave generated by disturbances on the sea floor. They are most often triggered by earthquakes and submarine (underwater) landslides. They can be described as 'a wall of water'
-A special type of wave, where an event, often an earthquake, moves the entire depth of water above it
How does a tsunami form?
1. Tectonic upthrust in the from of earthquakes (and submarine volcanoes) cause a vast quantity of water to be displaced in a very short time generating a huge amount of energy
2. In the open sea, tsunamis travel at up to 800km/h and commonly go unnoticed as they pass beneath ships because they are usually less than 1m high and the distance between the wave crests is typically hundreds of kilometres
3. As the tsunami waves approach the coastline they are slowed dramatically by friction to around 40 Km/h. The wavelength becomes shortened and the wave amplitude increases. One of nature's warning signs of a tsunami approaching are a sudden withdrawal of the sea from a coastal region. Water near the coast is pulled back into the growing wave
4. Finally with the wavelength compresses and heightens to 5-10 meters the wave collides with the shore causing huge damage.
Tsunami consists of a series of waves that pour on shore for as long as 30 minutes. The succeeding outflow continues the destruction causing more damage to people and property. Furthermore, after the first wave hits, more waves follow at 20-60 minuets intervals
What are the causes of tsunamis? (in ascending commonness)
2. (submarine) landslides
3. (submarine) volcanic eruptions
4. Meteorite impacts in the ocean
What is a supervolcano?
A mega colossal volcano that erupts at least 1,000 km cubed of material. They are rare and devastating eruptions that have global consequences
Describe the formation of a supervolcano
1. Magma rises up through cracks in the curst to form a large magma basin below the surface. The pressure of the magma cause a circular bulge on the surface several kilometres wide.
(Rising magma cannot escape and a large bulge appears on the surface)
2. The bulge eventually cracks, creating vents for lava to escape through. Lava erupts out of the vents causing earthquakes and sending up gigantic plumes of ash and rock
3. As the magma basin empties, the bulge is no longer supported so it collapses (spewing up more lava). This forms a large depression called a caldera
4. Sometimes these fill with water to from a large lake e.g. Lake Toba in Indonesia
What are the differences of supervolcanoes and volcanoes?
1. Supervolcanoes are flat with depressions called calderas, often marked by a rim of higher land around the edges. Volcanoes are like mountains, cone shaped with a crater
2. They cover a large area, much bigger than volcanoes
3. They emit at least 1,000km cubed of material and at eruption from Mt St Helens (a volcano) erupted some 1Lm cubed
4. Supervolcanoes erupt less frequently, eruptions are 100,000 years apart
What are the likely effects of a supervolcano eruption?
1. A supervolcano will erupt 1000s of cubic kilometres of rock and ash and lava, which is much more than normal volcanoes which usually produces a couple cubic kilometres
2. A thick cloud of super-heated gas and ash will flow at high speed form the volcanoes, killing, burning and burying everything it touches. Everything within 10s of miles will be destroyed
3. Ash will shoot kilometres into the air and block out almost all daylight over whole continents. This can trigger mini ice ages as less heat energy from the sun gets to Earth
4. The ash will also settle over hundreds of square kilometres burying field and buildings (ash from normal volcanoes usually covers a couple of square kilometres)
What are the current supervolcanoes? When was the last supervolcano eruption?
1. They develop at destructive plate margins or over hotspots
2. Yellowstone National Park, Wyoming, USSA
3. 74,000 years ago Lake Toba (Indonesia) supervolcano
What were some of the long term impacts if the Icelandic volcano?
1. Fine ash silted the rivers and caused blockages a year on
2. Shares in air travel and Tourism Agencies dropped by 4% and so less fuel was needed so, 1.87 million barrels were not in demand causing a loss of money in the oil industry
1. The eruption may boost Iceland's tourist industry on the longer term. A new visitor centre has just opened close to the volcano
What were the immediate responses to the Icelandic volcano?
1. 800 people evacuated from homes and villages
2. Rescuers wore face masks to prevent them form chocking on the dense cloud of ash
What were the long term responses to the Icelandic volcano?
1. The EU funded a projected called FutureVolc to install sensors to allow for real-time data analysis. The monitors can detect minute movements of tremors within the ground and detect any curving of the Earth's surface around volcanic sites (know as "inflation") which could be indicative or magma build-up
2. Other experimental sensors will look for changes in gas emissions from active sites, which could suggest the movement of magma up through the Earth's surface
3. A report commissioned by Airbus put the cost to global business of Ey.. eruption as high as $5bn, but estimated vary widely. The airspace restrictions imposed during the eruption were bitterly opposed by many airlines
4. Easyjet and Airbus are currently testing systems that it says will enable planes to detect and circumnavigate ash clouds.
What was the cause of the Icelandic volcano?
1. Location on the MidAtlantic Ridge in North Atlantic Ocean, where the Eurasian and North Atlantic plates are moving apart a few centimetres per year. In Iceland this produces volcanic rift zones and here molten rock or magma rises up and some reaches the surface and erupts as lava and/or ash
2. Eruptions can occur form central summit vents or flank vents of a volcano, or from linear 'fissured' meters to kilometres in length, which develop parallel to the rift zone
-Iceland is also widely considered to be underlain by a mantle plume, such a 'hotspot causes enhanced voclanic activity in addition to that already occurring due to the spreading movement of the plates.
3. The explosive phase started form the summit crater punching through the ice cap, causing meltwaters to mix with the rising magma, the cold meltwater cooled the magma quickly causing it to fragment explosively into large volumes of very fine ash that were ejected high into the atmosphere; a style of eruption known as phreatomagmatic
What was the location of the Tsumani?
The Tohoku tsunami was caused by an earthquake in the Pacific ocean, affecting North-East Japan
What were the specific causes of the Tohoku tsunami?
1. Japan is at the centre of four plates with destructive subduction and conservative boundaries
2. Earthquake occurred on the subduction zone between the Pacific plate and Okhotsk plate
3. 15-45 minuets after the Earthquake struck it caused tectonic upthrust and a large quantity of water was displaced causing a tsunami that hit the East of Japan
Describe the Earthquake and Tsunami
-Earthquake: Magnitude 9.0, 11th March 2:46pm
-Tsunami: Height 5-20m, max vertical shift almost 40m
What were the primary impacts of the Tsunami?
1. 16,000 known deaths
2. 3000 people missing
3. 130,000 buildings destroyed, twice as many damaged
4. Rikuzentakata - 3368 buildings destroyed
5. Ishinomaki - at Okawa Elementary School 74/108 children died nd 10/14 teacher died
6. Estimated 26.7 million tonnes of debris
What were the secondary impacts of the Tsunami?
1. Water flooded cooling systems at Fukushima Daiichi Nuclear power plant:
-systems failed, 3 nuclear units experienced meltdown
-caused immediate evacuation of the area within 20km
-damage caused by harmful pollutants that were emitted
2. Expected acceleration of ageing, low fertility and outmigration of population
What were the immediate responses to the Tsunami?
1. Search and Rescue and stabilisation and prevention of further nuclear disaster by Japanese government
2. Operation USA , sent shelter and medical supplies
-The fist shipment of $1.1 million donation of Gap brand winter clothing was distributed to 10,0000s of People in Miyagi, Fukushima and for the cold winter following the disaster
What were the long term responses to the Tsunami?
1. 11th April 2011 PM, Naoto Kan commissioned a report for the three principles of recovery: safety, sustainability, compassion
2. Took 11 moths to establish Reconstruction Agency due to political infighting
3. 10th Feb 2012 - Reconstruction Agency established with three policies:
-focus on local communities and human linkages within Japan
-base survival of 'self-aid'
-develop conditions for mutual and public aid
What is a volcanic hotspot?
1. A volcanic hotspot is an area in the mantle fromm which heat rises as a thermal plume form deep in the Earth
2. High heat and lower pressure at the base of the lithosphere (tectonic plate) facilitates melting of the rock
3. This melt, called magma, rises through cracks and erupts to form volcanoes
E.G. Hawaii and Iceland
What forms at Constructive boundaries?
1. Ocean ridges
2. Earthquakes (gentle)
3. Shield volcanoes
What forms at Destructive (subduction) boundaries?
1. Ocean trenches
2. Fold mountains
3. Earthquakes (severe)
4. Composite Volcanoes
What forms at Destructive (collision) boundaries?
1. Fold mountains
2. Earthquakes (some severe)
What forms at Conservative boundaries?
1. Upland ridges
2. Earthquakes (some severe)
Describe convection currents in the mantle
1. Radioactive decay in the core heats the molten rock (magma)
2. The heated magma rises as it becomes less dense
3. The magma moves away from the heat source and spreads out
4. The magma cools and starts to sink
5. The cycle of the convection cell restarts
Describe the formation of a shield volcano
1. At constructive margins, the magma rises up into the gap created by the plates moving apart
2. The lava is runny, so flows quickly and spreads over a wide area, forming a low flat volcano
Describe the formation of a composite volcano
1. At a convergent plate margin one plate subducts beneath another
2. It melts in the subduction zone to produce magma
3. This escapes to the surface to form a volcano
4. The subduction zone is at an angle which means that the zone of melting and magma is to one side of the actual plate margin
5. Magma escapes to the surface through the cracks in the crust
What are pyroclastic flows?
Hot volcanic ash and rock, hot expanding gases (600-700 degrees Celsius) move at tremendous velocities - up to 300Km/h
What are lahars?
Ash is liquified by rain or snow melt, hot or cold mudflows, 100Km/h
What are the gases from volcanoes?
Harmful gases can be emitted like carbon dioxide, sulphur dioxide, Radon, killing people and other living things
What are the primary effects of volcanoes? (the immediate effects of the eruption, caused directly by it)
1. Destruction to wildlife and vegetation
2. Air quality
2. Deaths and injuries
3. Damage to infrastructure (communications affected)
4. Immediate decline in tourism
What are the secondary effects of volcanoes? (the after-effects that occur as an indirect effect of the eruption on a longer)
1. Acid rain
3. Pyrocastic flows
4. Fertile soil from ash
1. Food security (shortages)
2. Ash cloud can cause global disruption
3. Can attract tourists
How have people adapted to the poor soils in the Alps?
Animals are grazed in the most high areas as the soil is not great for growing crops
How have people adapted to the limited communications in the Alps?
1. Roads have been built over passes (lower points between mountains) e.g. the Brenner Pass between Austria and Italy.
2. It takes a long time to drive over passes and they can be blocked by snow, so tunnels have been cut through the mountains to provide fast transport links e.g. Lotschberg Base Tunnel has been cut through theBernese Alps in Switzerland
What are the three different ways you can cope with a tectonic hazard?
1. Do nothing
What are the factors which affect which choice is selected?
2. Frequency (how rare)
4. Accuracy of prediction
5. Availability of resources e.g. MEDC v LEDC
6. Economic development (worth saving)
7. Population density
How can you prevent or modify the event?
Earthquakes, volcanoes, and tsunamis cannot be prevented
How can you modify the vulnerability?
1. Hazard resistant design of infrastructure and buildings (protection)
2. Prediction and warning
3. Community preparedness
4. Land use planning
How do you modify the losses after the event?
What are the likely impact of a super volcano? (facts)
1. 90% of people killed within 10,000 km squared
2. Destroy 10,000 km squared of land
3. Ash fall would affect transport, livestock, power line, water quality and communication links disrupted
4. More rainfall as more particulates in the atmosphere
5. Within 5 days ash fall would extend to Europe (UK)
6. In the Tropics a fall of 15 degrees Celsius, failure of monsoon rains and 40% of the planet's population facing starvation
Who studies volcanoes?
-As a volcano becomes active, it gives off a number of warning signs, These warning signs are picked up by volcanologists (experts who study volcanoes)
What are some of the warning signs for volcanic eruptions? How are these monitored?
1. Small earthquakes are caused as magma rises
-Seismometers to detect earthquakes
2. Temperatures around the volcano rise as activity increases
-Thermal imaging to detect heat around a volcano
3. Bulging and ground deformation from magma
-GPS and tilt meters to measure swelling
4. When a volcano is close to erupting it tarts to releases gases. The higher the sulphur content, the closer the volcano is to erupting
-Gas samples to measure sulphur levels