Restless Earth Flashcards
What are the three main layers from which the Earth is made?
Crust - made from thin layers of tectonic plates
Mantle - divided into solid upper part and semi-liquid lower part, which can flow
Core - consists of a liquid outer core and solid inner core
How do convection currents cause plate movement?
Give the four stages.
1) The decay of radioactive material in the core heats up molten rock in the mantle to create a convection current.
2) The heated rock from the mantle rises to the earth’s surface.
3) At the surface the convection currents move the tectonic plates in the crust.
4) Molten rock cools and flows back down to its original position to be reheated once more.
Give one example of a destructive plate boundary.
Describe what happens at this type of boundary and detail which two plates are involved.
What are the hazards at a destructive plate boundary? (3)
Andes Mountains, Peru
Where an oceanic plate meets a continental plate, the denser oceanic plate is subducted beneath the less dense continental plate.
Many earthquakes and volcanoes and possible tsunamis.
Give one example of a constructive plate boundary and describe what happens at this type of boundary.
What are the hazards at a constructive plate boundary? (2)
Mid-atlantic ridge, Iceland
Two oceanic plates move apart from each other, magma rises constantly between the two plates as it cools, new oceanic crust is formed.
Small earthquakes and volcanoes that are not very explosive.
Give one example of a conservative plate boundary and describe what happens at this type of boundary.
What are the hazards at a conservative plate boundary? (2)
San Andreas Fault, California
Two plates slide past each other.
Destructive earthquakes and small earth tremors daily.
Give one example of a collision zone and describe what happens at this type of destructive boundary.
What are the hazards at this type of boundary?
Himalayas
A collision zone is a type of destructive plate boundary where two continental plates move towards each other, as they meet they push upwards forming mountain ranges.
Many Earthquakes, landslides and rare volcanos.
Give 4 features of a shield volcano.
Describe their eruption patterns.
Give an example of a shield volcano.
1) Found on constructive plate boundaries
2) Formed by eruptions of thin, runny lava which flows a long way before it solidifies
3) Have gently sloping sides and a wide base
4) Contain basaltic magma which is very hot with low silica and gas content
Erupt frequently but not violently
Mauna Loa
Give 5 features of a composite volcano.
Describe their eruption patterns.
Example.
1) Found on destructive plate boundaries
2) Formed by eruptions of viscous, sticky lava and ash that don’t flow far.
3) Have steep sloping sides and a narrow base
4) Made up of layers of thick lava and ash
5) Contain andesitic magma which is lees hot but contains lots of silica and gas.
Erupt infrequently but violently, including pyroclastic flows (mix of ash, gases and rock.)
Mount Fuji
What is needed after an earthquake or volcanic eruption? (6)
1) Trained volunteers to help the injured and clear away debris.
2) Clean water to prevent the spread of disease
3) Food because often roads, shops, towns and farms have been damaged
4) Radio communication as phones often don’t work
5) Medical help to care for the injured people
6) A plan to evacuate the area if needed
Earthquake case study - facts and impacts (6)
Haiti - January 12th 2010
1) 316,000 dead - injured and dead trapped under rubble
2) Homes, offices and factories destroyed or so badly damaged they had to be demolished - people sleeping in the streets for fear of more earthquakes
3) Mortuaries unable to deal with the dead so mass graves were dug to bury people.
4) Phone and power lines down
5) Roads blocked by rubble
6) Nursing and midwifery school destroyed along with the presidential palace
Volcanic eruption case study - what happened (2) and impacts (3).
Eyafjallajokull, Iceland 2010
What happened:
1) Eruption occurred under a glacier which caused the ice to melt.
2) Ash cloud 6000-10000 metres in height.
Impacts:
1) Flash flooding
2) Ash fall coated surrounding areas
3) People evacuated
4) 95,000 flights cancelled - $2 billion cost to airlines and £102 million cost to London in tourist income.
5) Disruption to air freight - the UK imports 95% of its fruit.
What is the oceanic crust?
The Oceanic crust is found under the oceans and is thin but dense and is made out of basalt with no crystals in it, as it cooled very quickly.
What is the continental crust?
The continental crust is the land, it is thick but less dense, it is made out of granite which contains crystals as it cooled slowly.
What is the Volcanic explosivity index a measure of?
What is a seismograph or seismometer?
It is a measure of the destructive power of a volcano from 1 to 8.
An instrument used to detect and record earthquakes.
Give five main reasons why people in developed countries are at greater risk from tectonic hazards than people in developed countries.
1) More people live in risky conditions near to possible hazards such as volcanoes and mountain ranges.
2) People can’t afford safe, well-built houses.
3) People don’t have insurance
4) Government don’t have the money to provide aid.
5) Poor communication, no warning or evacuation.
