restless earth Flashcards
name the layers of the earth , what are they made out of and what are there physical states
crust - Granite - solid
lithosphere- basalt -solid
mantle - silica based materials-solid
outer core- iron/nickel-liquid very dense
inner core- iron/ nickel-solid very dense
what are the two types of crust
continental crust and oceanic crust
what are the features of continental crusts and oceanic crusts
continental- Makes up most of the land area of the earth . It is dominated by rocks which cooled below the surface , such as granite. it is between 25km and 80 km thick
oceanic crust -much thinner than continental , between 6km and 8km, and made up of rocks such as basalt .
how do the earths tectonic plates move ?
high temperature in the core cause radioactive decay causing materials to rise in the mantle called convection currents. These cool and spread out before sinking again. some of the rising and moving material moves in sheets , creating movement in the crusts above which is pulled apart to create new crust. in other places it rises as columns creating hotspots .
what are constructive margins ?
they are formed by rising magma splitting up continental crusts and forming new oceans. This is happening in east Africa today in its continental rift zone.
what are destructive margins and how is subduction involved ?
as oceanic crust meets the continental crust the heavier oceanic crust is subducted beneath the lighter continental crust. An increase of pressure as movement occurs , leads to violent earth quake activity. The oceanic plate melts into the mantle , due to heat and friction . The magma then rises through the continental crust causing it to explode through causing an violent earthquake.
how does a deep oceanic trench occur?
A deep oceanic trench always exists where the two plates meets.
what are conservative plate margins ?
the two plates ( oceanic and constructive) slide past each other. No land is lost or gained therefore no volcanic activity. pressure builds up when the plates stick and then serve earthquakes occur as the pressure is released
what is the Richter scale ?
the Richter scale is a logarithmic scale . This means that each level is 10 times greater than the one before . A magnitude 6 earthquake is therefore ten times bigger than a 5 and so on
CASE STUDY: name two examples of earthquakes. tell details and primary and secondary impacts.
1st Haiti- details- magnitude of 7.0 , depth 13km and struck at 5pm . PRIMARY impacts 316,000 deaths and 300,000 injured. economic losses of £8.5 billion . poverty and slums made people vulnerable to building collapses. SECONDARY- over 7000 people killed. estimated 100 million were made homeless. damage to roads and ports made it unable to make trade.
2nd Canterbury New Zealand - details- magnitude of 7.1 , depth 10km and it stuck at 4.30 am. PRIMARY impacts no deaths about 100 injured. total damage to property costs about 1.8 billion to cost . Deaths were low because most people were sleeping and building were strong . SECONDARY impacts a major after shock with a magnitude of 6.3 , killing 185 people.
how do people prepare for an earthquake ?
1 cross bracing prevents stops floors collapse
2 A strong steel frame which is flexible , stops cracking
3 Strong double glazed windows stops broken glass showering down
4 very deep foundations to prevent collapses
5 shock absorbers built into cross bracers
how do tsunamis occur?
1 ruptures in the seafloors pushing water upward causing waves to take place.
2 Waves move rapidly in deep ocean reaching speeds of up to 500km/h.
3 as the waves nears land it slows to about 45 km but is squeezed upwards , increasing in height.
4 Waves heads inland destroying all in its paths.
What are composite volcanoes?
forms form alternating layers of rock fragments. that’s why they are called composite. they produce thick , viscous lava called andesite. that clogs up the vents causing a build up of pressure and leads to very violent eruptions. They are found at DESTRUCTIVE plate margins.
what are shield volcanoes ?
they re huge in size. They are made up of many layers of runny , basaltic lava flows. Lava spills out of a central vent . A broad shaped , gently sloping cone is formed. This is caused by the very fluid , basaltic lava which cant be piled up into steep mounds . They are found at CONSTRUCTIVE plate margins.
CASE STUDY: name two examples of volcano eruptions and talk about form , magma type , explosively and frequency .
1st MT Pinatubo - composite -steep sided small area alternative layers of ash and lava - viscous and sticky flows slowly . often freezes inn thee central vent Granitic or andesitic magma - infrequent and sometimes unpredictable, Pressure builds up over time.
2nd Mauna Loa - shield - gentle slopes large area almost all lava - Fluid flows quickly from many fissures basaltic magma - very frequent and generally gentle eruptions.
