Hazards
Earth’s structure and internal energy sources:
Describe the crust.
- Varies in thickness.
- 5-10km under oceans
- 70km under continents
- Oceanic plate (denser) destroyed by plate movement – continental
not.
Compare the inner and outer core.
Inner:
- Solid ball of iron/nickel
- Very hot due to pressure and radioactive decay (uranium gives off
heat when decomposed)
- Responsible for earths internal energy
Outer:
- Semi molten
- Iron/nickel.
- Moves around inner core creating earth’s magnetic field.
Describe the 2 types of heat.
Primordial – heat left from earths formation.
Radiogenic – heat produced by radioactive decay of isotopes.
Describe the mantle.
- Mainly solid rock – high silica content
- However top layer of mantel is semi molten magma
‘asthenosphere’, lithosphere sits on top.
- Mantle becomes denser with depth due to greater pressure.
,Describe the asthenosphere.
- Semi molten layer constantly moves due to flows of heat called
convection currents.
- Movements powered by heat from inner core.
- Lithosphere sits on top.
Describe the lithosphere.
- Broken up into plates.
- Majority within mantle
- Top of lithosphere = crust (land and sea we live on)
Compare continental vs oceanic crust.
Continental Oceanic
Thickness 30-70km 6-10km
Age Over 1,500 mill Less than 200 mill
Density 2.6g/cm3 3.0g/cm3
Composition SiAl SiMg
Outline process of convection currents.
- Heat from inner core convects through mantle into asthenosphere.
- Hot magma rises because it becomes less dense with heat as
particles spread out.
- Magma is cooler at top as its further away from heat source,
becomes denser and sinks back down to bottom.
- Cooler magma is reheated and begins to rise again, creating a loop
called a convection current.
Plate tectonics.
Explain the plate tectonic theory.
- Lithosphere split into large slabs of rock called tectonic plates.
, - Plates move due to convection currents in asthenosphere, pushing
and pulling magma in different directions.
- Convection currents caused when less dense magma rises cools and
sinks.
- Edges where plates meet = plate margins/boundaries
Constructive
C/C – volcanoes,
quakes, rift valleys
O/O – volcanoes,
ocean ridges and
quakes
Plate Conservative
boundaries
Earthquakes
.
Destructive
C/C – fold mts and
quakes
O/O – quakes,
volcanoes, ocean
trenches, island arcs
What occurs at Conservative plate boundaries?
C/O – fold mts,
- Parallel platesquakes
volcanoes, move in diff direction.
- No landforms created.
- 2 plates slide pass each other locked in places.
Earth’s structure and internal energy sources:
Describe the crust.
- Varies in thickness.
- 5-10km under oceans
- 70km under continents
- Oceanic plate (denser) destroyed by plate movement – continental
not.
Compare the inner and outer core.
Inner:
- Solid ball of iron/nickel
- Very hot due to pressure and radioactive decay (uranium gives off
heat when decomposed)
- Responsible for earths internal energy
Outer:
- Semi molten
- Iron/nickel.
- Moves around inner core creating earth’s magnetic field.
Describe the 2 types of heat.
Primordial – heat left from earths formation.
Radiogenic – heat produced by radioactive decay of isotopes.
Describe the mantle.
- Mainly solid rock – high silica content
- However top layer of mantel is semi molten magma
‘asthenosphere’, lithosphere sits on top.
- Mantle becomes denser with depth due to greater pressure.
,Describe the asthenosphere.
- Semi molten layer constantly moves due to flows of heat called
convection currents.
- Movements powered by heat from inner core.
- Lithosphere sits on top.
Describe the lithosphere.
- Broken up into plates.
- Majority within mantle
- Top of lithosphere = crust (land and sea we live on)
Compare continental vs oceanic crust.
Continental Oceanic
Thickness 30-70km 6-10km
Age Over 1,500 mill Less than 200 mill
Density 2.6g/cm3 3.0g/cm3
Composition SiAl SiMg
Outline process of convection currents.
- Heat from inner core convects through mantle into asthenosphere.
- Hot magma rises because it becomes less dense with heat as
particles spread out.
- Magma is cooler at top as its further away from heat source,
becomes denser and sinks back down to bottom.
- Cooler magma is reheated and begins to rise again, creating a loop
called a convection current.
Plate tectonics.
Explain the plate tectonic theory.
- Lithosphere split into large slabs of rock called tectonic plates.
, - Plates move due to convection currents in asthenosphere, pushing
and pulling magma in different directions.
- Convection currents caused when less dense magma rises cools and
sinks.
- Edges where plates meet = plate margins/boundaries
Constructive
C/C – volcanoes,
quakes, rift valleys
O/O – volcanoes,
ocean ridges and
quakes
Plate Conservative
boundaries
Earthquakes
.
Destructive
C/C – fold mts and
quakes
O/O – quakes,
volcanoes, ocean
trenches, island arcs
What occurs at Conservative plate boundaries?
C/O – fold mts,
- Parallel platesquakes
volcanoes, move in diff direction.
- No landforms created.
- 2 plates slide pass each other locked in places.
