Restless Earth Flashcards
What is a plate
A section of the earths crust
What is a plate margin
The boundary where 2 plates meet
What is the mantle
The dense mostly solid later between the outer core and the crust
What is a convection current
The circular currents of heat in the mantle
What is the earths core
The centre of the earth, it is split into the solid inner core and the molten outer core
What is the earths crust unstable
Because the plates are moving due to them floating on he upper mantle and convection currents create the movement deciding which way the plates will move
What does the movement of plates lead to
Earthquakes, volcanoes and fold mountains
What are the four types of plate boundary
Constructive
Destructive
Collision
Conservative
Characteristics of constructive plate margins
They move apart
Mostly under the ocean
Magma rises up to the surface through cracks and new land is formed
Magma is made of basalt so hot and runny
What is formed on a constructive plate margin
Lava flows
very shallow sided volcanoes, they aren’t explosive or dangerous.
Ridges are built up from sea bed
Earthquakes are small and caused by friction as plates pull apart
Characteristics of collision plate margin
Destructive boundary
Two continental plates collide
What are formed on collision boundaries
Destructive earthquakes also happen on faults (huge cracks in the crust)
Fold mountains
Characteristics of conservative plate margins
Plates slide past each other
Moving in similar direction at slighting different angles and speed
Rare but very destructive earthquakes. (Close to surface)
How do earthquakes form on conservative plate margins
One plate is moving faster in a different direction than the other so they tend to snag.
The movement of the plate causes friction and pressure builds up along the fault.
Eventually pressure is too much and one plate jerks past the other.
Characteristics of destructive plate margins
Plates move together
One plate is oceanic and other is continental the denser oceanic crust sinks under the lighter continental - known as subduction.
What is formed at a destructive by subduction plate boundary
Subduction zone is oceanic trench
Composite volcanoes
Earthquakes when plates jerk which are often devastating
How does a composite volcano form
Oceanic plate sinks under continental so there is great pressure.
Oceanic plate melts.
The magma may then rise upwards as it is less dense and can work its way up through the cracks of continental causing a volcanic eruption leading to the formation of composite volcanoes.
Where are earthquakes and volcanoes usually found
Occur in linear patterns along plate boundaries. Most volcanoes occur in narrow belts or are grouped together in small clumps. Half of them occur around the Pacific ring of fire a destructive plate boundary. Some volcanoes are found away from plate margins in hot spots.
What are fold mountains
Large mountain ranges where rock layers have been crumpled as they have been forced together and form along collision plate boundaries
How do fold mountains form
Sedimentary rock thousands of metres thick formed in big depressions called geosynclines, rivers carried sediment and deposited it here.
Over millions of years this sediment was compressed into sedimentary rock like limestone.
The rock was then forced upwards into s series of folds by collision boundaries.
What is an anticline
Upfold of folded rocks
What is a syncline
Down fold of folded rock
What is an overfold
Where a find has been pushed over on one side
What is an ocean trench
A deep section of the ocean usually where an oceanic plate is sinking below a continental plate. Usually very deep typically 5000-10000 metres.
What is the case study for fold mountains
The Alps
What are the background facts to the Alps case study
- African plate pushing north against Eurasian plate
- highest peak is Mont Blanc
- form border between Italy and France, Switzerland, Austria and Slovenia
What are the four benefits of the Alps and its land use?
Tourism
Farming
Hydro electric power
Forestry
What are key facts about the Alps positive use of hydro electric power
- steep slopes, high precipitation and simmer melting of glaciers produce fast flowing rivers good for generating HEP
- narrow valleys are easy to dam and lakes which store water
- is 60% of switzerlands energy
What are the key facts of tourism positive in the Alps
- all year round
- winter: snow for skiing and winter sports
- summer: lakes, beautiful scenery, walking
- les deux Alps (ski resort)
What are the key positive facts about farming in the Alps
- south facing slopes where it is sunnier
- transhumance where in summer cattle graze on high Alps and in winter cattle return to sheds on valley floor
- dairy farming good for chocolate like lindt
What are the positive key facts about forestry in the Alps
- coniferous trees cover many slopes
- wood , a plentiful local resource, is a main building material and winter fuel
What are the problems of the land use for the Alps
Tourism
- winters warming up
- skiing on worn slopes damages vegetation and surface, increases the number of bare surfaces and the risk of soil erosion
Farming
- farmers but in feed to keep animals on valley floor all year
- cable cars built for tourism are used to get milk to dairies on valley floor
What are the aspects that divide the two types of volcanoes
Depending on the material thrown out during and eruption and the form of the volcano cone produced
What are shield volcanos
Volcanoes on constructive plate margins when the plates move apart and magma rises to fill the gap adding new rock. Some magma could be forced out to the surface through a vent. E.g Hawaii.
What is the characteristic of a shield volcanoes lava and why
Basic Lava from within the mantle has a low silica content so it pours out easily, is runny and flows long distances before cooling
Characteristics of a shield volcano
- cone with wide base and gentle slopes
- made of lava only
- regular and frequent eruptions
- lava pours out with little violence
What is a composite cone volcano
One formed at a destructive plate margin.
denser oceanic plate under continental plate, forms a pool of magma and great heat and pressure forced the magma up along a gap where it erupts to form the volcano.
What are the characteristics of a composite volcanoes lava
- acid lava has high silica content so more vicious so travels a shorter distance before cooling
Why are composite volcano eruptions so violent
The vent becomes blocked which leads to great pressure building up before the next eruption and when this happens lava us shattered into pieces to form bombs and ash and dust are showered over a wide area
Characteristics of a composite volcano
- tall cone with narrow base and steep sides
- made or alternate layers of lava and ash
- irregular with long dormant periods
- violent explosions
What is a natural hazard
An occurrence over which people have little control which poses a threat to people’s lives and possessions
What is the difference between a natural hazard and a natural event
Because things can occur in unpopulated areas so it is not a hazard
What are the primary effects (the immediate effects after caused directly by it) of a volcanic eruption
People injured and killed
Buildings, property and farmland destroyed
Communications and public services disrupted
What are the secondary effects (after effects that occur as an indirect effect on a longer timescale) of a volcanic eruption
Shortage of drinking water, food and shelter
Spread of disease from contamination
Economic problems from the cost of rebuilding and loss of land
Social problems from family loses and stress
Lahars and pyroclastic flows
Dust in atmosphere can affect global temperature
What is a lahar
Mudflows resulting from ash mixing with melting ice or water
What can loss of life in a volcanic eruption be due to
Falling debris, suffocation from poisonous gases or being buried in mud flows
What are the immediate responses to a volcanic eruption
Evacuation from area directly after or if predicted before
Emergency services deployed
International aid sent e.g tents, bottled water, medical supplies
What are the long term responses after a volcanic eruption
Rebuilding settlements
Redeveloping conic activities affected like farming and tourism
What is a case study for a volcanic eruption
Mt St. Helens
What are background facts to the Mt St. Helens case study
In USA
Juan de fuca subducted under North American plate
Mini earthquakes and small eruptions as an after effect
What are the primary effects of the Mt St. Helens case study
- 61 deaths
- 10 million trees destroyed
- spirit lake filled with ash and mud
- floodwater washed away several roads and railway bridges
- electricity supplies were interrupted and telephone wires cut
- ash encircled the world after a few days
What are the secondary effects of the Mt St. Helens case study
- money lost as businesses were destroyed, crops and livestock, logging camps and fisheries
- ash in atmosphere though to have affect UKs weather
What were the responses to the Mt St. Helens eruption
Shorterm - Evacuation of area before main eruption but predication of area was not completely accurate Long term- Need for rebuilding 10 million trees replanted
Why do people live near volcanoes
- volcanic soils are very fertile
- many attractions for tourists e.g hot springs and mud pools, watching geysers and trips to the crater
- selling souvenirs or bus trips
- hot water has economic uses e.g domestic heating or geothermal energy
- valuable minerals e.g sulphur
What is the earth crust
The outer layer of the earth
What are the advanced warning signs of volcanic eruptions
Small earthquake shocks, increased emission of steam and gases and visual signs of bulging around the crater
What do electronic tilt metres do
Measure very small changes in the profile of the mountain
What do global positioning systems (GPS) do
Use satellites to detect small movement in the earth and changes in the surface temperature can also be seen by satellites
How do you measure the gases that are being released before an eruption
Gases emitted from the bent increases the amount of sulphur dioxide and robots can be used to monitor these changes
How do past eruptions help monitor volcanoes
The gap between their patterns of lava flow and ash movement give info about how a volcano is likely to behave
How are volcanoes near large populations managed
Organising evacuations and arranging supplies if the signs of an eruption occur, Land use zoning and hazard mapping can be used to limit the impact on people.
Lava can be cooled during an eruption by being sprayed with water and lava flows can be diverted with concrete blocks.
What is a super volcano and where do they occur
A mega colossal volcano that erupts at least 1000km3 of material. Occur at hot spots not on plate boundaries
What is a hot spot
A section of the earths crust where plumes of magma rise weakening the crust
Characteristics of a super volcano
Occur in large depressions called calderas often marked by a rim of higher land around the edges
How is a super volcano formed
Magma in the earth rises into the crust from a hot spot but is unable to break through the crust.
Pressure builds up in a large and growing magma pool until the crust can’t contain the pressure.
Cracks appear in the surface and gas and ash erupt from magma chamber.
Magma chamber collapses causing a super volcano and caldera.
What are the effects of a super volcano
It effects the landscape over hundreds if not thousands of kilometres, it can lead to a volcanic winter because of all the dust in the atmosphere - lowers temperature because less sunlight is reaching the earth.
What six ways are super volcanos different to normal volcanos
- much bigger
- emit huge amounts of material (1000km3 compared to Mt St. Helens 1km3)
- don’t look like a volcano as no volcano characteristic cone
- large depressions called calderas
- rim of higher land around their edges
- don’t occur on plate boundaries
What is the case study for a super volcano
Yellowstone
What are the background facts to yellow stone
- last eruptions were 2 million years ago, 1.3 million years ago and 630000 years ago
What are the primary effects if the Yellowstone volcano was to erupt
Destroy 10,000km3 of land
Kill 87000 people
Within 1000km 15cm of ash would cover buildings
1 in 3 affected would die
Ash would affect transport, electricity, water and farming
What are the secondary effects if the Yellowstone super volcano erupted
Lahars likely The U.K. Would await the arrival of ash 5 days later Global climate would change Crops would fail A volcanic winter
What is an earthquake
The shaking and vibration of the crust due to movement of the earths plates and can happen along any plate boundary
How do earthquakes form in general
When tension is released from inside the crust .
Happens because plates don’t move smoothly so sometimes they get stuck when this happens lots of pressure builds up and when it is released earthquakes occur.
How does a destructive plate margin cause earthquakes
The pressure from the sinking of the subduction plateand it’s subsequent melting can trigger strong earthquakes as this pressure is periodically released
What is the focus of an earthquake
The point in the earths crust where the earthquake originates the shaking is worse on the surface if the focus is shallow
What is the epicentre of an earthquake
The point on the earths surface directly above the focus
What is a shock wave of an earthquake
Seismic waves generated by an earthquake that pass through the earths crust
What are the stages of the seismic waves
- Primary waves,relatively weak and causes surface to move forward and back in the direction of that wave
- Secondary waves, stronger and at right angles to the outward movement of the main wave. Both are below the surface
- Final waves travel near to the surface and are most powerful
What are the two different types of waves
Longitudinal waves causing up and down movement
Transverse waves causing side to side movement which is more damaging
What is the magnitude (size of the earthquake) measured by
Seismograph
How do seismographs work
They record the extent of shaking by a pen and identify the trace of movement on a rotating drum
What is a graph produced by a seismograph called
Seismogram
What is the Richter scale and how is it used
Used for measuring earthquakes based on scientific recordings of the amount of movement. It is logarithmic so everyone on it goes up is actually ten times bigger e.g an earthquake a 2 is 10 times bigger than one at 1.
What is the mercalli scale and what does it take into account
It is used to identify the intensity of an earthquake. It classifies using Roman numerals and takes into account the visible effects of the earths surface, people and buildings
What does the value of the mercalli scale depend on
The distance to the earthquake as the highest scoring will be around the epicentre
What are the primary effects of an earthquake
Collapsing buildings roads and bridges
People killed e.g being trapped in homes, places of work and cars
People injured e.g falling buildings
What are the secondary effects of an earthquake
Fires caused by earthquakes breaking gas pipes and bringing down electricity wires
Tsunamis caused by earthquake on the sea floor
Landslides likely on steep slopes and in areas of weak rocks
Diseases like cholera spread easily when burst pipes lead to shortages and contamination from sewers
How do physical factors of an earthquake make it a high level of damage
If it has a high magnitude on Richter scale
If it has a shallow focus
Sands and clays as they vibrate more
How do physical factors of an earthquake make it a low level of damage
If it is a low magnitude
If it has a deep focus
And if the place is made of a hard rock surface
How do human factors mean earthquakes have a high level of damage
High density of population Residential area of a city Self built housing Lack of emergency procedures Also effected by the time and day and how close people are to epicentre
How do human factors mean an earthquake has a low level of damage
Low density of population
Urban areas with open spaces
Earthquake proof buildings
Regular earthquake drills
Why is the impact of an earthquake much more severe in poor countries
Because earthquake resistant buildings are too expensive.where building regulations exist they may he ignored because builders want to make more money and people can only afford cheap houses. People less prepared.
What are the three Ps
Prediction, protection and preparation
What is Prediction against an earthquake and how useful is it
Attempting to forecast an event based on current knowledge.
Not very useful as experts know when earthquakes are likely but not definite, time between earthquakes doesn’t seem to works, watching animal behaviour is viewed sceptically, foreshocks happen but not on a useful timescale.
What is protection
Constructing buildings so they are safe to live in and will not collapse
What are some good ways to earthquake proof your home
- computer controlled weights on roof to restrict movement
- steel frames that can sway
- fire resistant building materials
- automatic window shutters to prevent falling glass
- rubber shock absorbers to absorb earth tremors
- roads
What is preparation and what does it involve
Organising activities and drills so people know what to do in the event of an earthquake.
Hospitals, emergency services, public buildings and individuals practising for major disasters so they are trained and ready.
What is a case study for an MEDC earthquake
Christchurch
Background facts of Christ church earthquake
- 6.3 on Richter scale and was an after shock earthquake
- epicentre 10cm south east of Christchurch
- shallow earthquake focus 5km deep
- liquefaction was wide spread
What were the primary effects of the Christchurch earthquake
- 181 killed
- half the buildings destroyed or damaged
- six storey Canterbury television building collapsed killing 85
- schools closed
- tallest building, hotel grand chancellor, displaced by 0.5 metres
- more than 10,000 homes destroyed or damaged
- power and telephone lines knocked out, burst pipes deluged street in water
What were the secondary effects of the Christ church earthquake
- money lost as businesses closed until buildings confirmed safe
- buildings took months to repair
- insurance claims were made by everyone
- cost of reconstructions £13 billion
- 10,000 migrated away from Christ church
What were the short term responses to the Christchruch earthquake?
- military mobilised to help the rescue effort and the government accepted specialised help from Australia
- fire and ambulance crews and other rescue services searched for survivors
What were the long term responses to the Christ church earthquake
- government set up the Canterbury earthquake recovery authority to reconstruct Christchurch (13 billion)
- city divided into four zones, red zone was worst affected, orange zone was residential, green zone was homes and white zone.
The preparations in case of an earthquake Christ church took
- Geonet detects and monitors earthquakes and provides info in minutes to emergency services
- funding by government to provide earthquake insurance
- public education programs to quake proof they homes
- only older buildings in the north island reinforced to stop damage during an earthquake so Christ church was more vulnerable
What is the case study for an LEDC earthquake
Haiti
What are the background facts to the Haiti earthquake
7 on Richter scale
Tremor lasted one minute
Epicentre 25km from the capital
Focus 13km so shallow and lots of shaking
What were the primary effects of the Haiti earthquake
Over 220,000 deaths Over 300000 injured 1.1 million displaced from homes 90,000 homes destroyed Roads, bridges, telephone lines and electrical systems destroyed Schools and hospitals collapsed
What were the secondary effects of the Haiti earthquake
Fires
Diseases spread due to poor living conditions - lack of sanitation
Small local tsunami
What were the short term responses to the Haiti earthquake
- international aid teams arrive with food, water and medical supplies
- 23000 tents distributed and temporary camps set up
- people dig for survivors with hands and basic tools
- people grieve
What are the long term responses of the Haiti earthquake
- vast areas will need to be rebuilt from scratch (houses, roads schools)
- G7 countries (richest)have written off Haitis debt
- forbid new buildings in high risk area
What is a tsunami
A special type of wage where the entire depth of the sea or ocean is set in motion by an earthquake which displaces the water above it and creates a huge wave
How are tsunamis formed
- earthquakes at sea
- energy from earthquake vertically jolts the seabed (primary effect) a few metres displacing a lot of water (secondary effect)
- large waves begun moving through the ocean away from the epicentre
- in deep water it moves at great speed but as it reaches shallower water it slows but increases in height
How can you tell is a tsunami is coming
If there is no warning system the only sign is just before it strike the waterline suddenly retreats exposing hundreds of metres of beach and seabed
What is a case study for a tsunami
Indian Ocean (the Boxing Day tsunami)
What are the background facts of the Indian Ocean tsunami
- on Boxing Day
- earthquake of 9 on Richter scale
- waves over 20m in places
What are the primary effects of the Boxing Day tsunami
- over 220,000 deaths
- tens of thousands of people injured
- towns and villages swept away
- 2 million people displaced
- bridges and railways destroyed
What are the secondary effects of the Boxing Day tsunami
- disease
- damage to the economies based on agriculture and fishing because people lost crops and boats
- food shortages because of damage to those industries
What are the short term responses to the Indian Ocean tsunami
- people fled from the coast to high land (in Phuket Thailand)
- international aid, blankets, water food and medicine
- £450 million pledged within a week
- troops used bulldozers to create mass graves
- grief as a huge number of deaths
What are the long term responses to the Indian Ocean tsunami
- rebuilding homes and infrastructures
- disaster emergency committee spent £40 million in rebuilding in Sri Lanka and Indonesia
- warning systems have now been put in place in the India ocean
