TECTONIC PROCESSES AND HAZARDS
Natural hazard: A naturally occurring hazard that has the potential to
harm human life and property
Distribution of natural hazards:
Natural hazards can either be:
geophysical – caused tectonic or geological processes (earthquakes, volcanoes, tsunamis)
or hydrometeorological – caused by hydrological and atmospheric processes (foods, storms,
droughts)
Geophysical hazards (earthquakes, volcanic eruptons) tend to occur on plate boundaries,
especially destructve plate boundaries [because you have plates colliding causing earthquakes
and magma rising causing eruptonss
e.g. boundary between North American plate [contnentals and Pacifc plate [oceanics is
destructve
e.g. Indian and Australian plate are both on a collision and constructve plate boundary. Parts
of the two plates are colliding causing earthquakes but other parts are moving away from each
other releasing lava in gentle eruptons.
-> This causes tsunamis which afects those on the coast of India, Bangladesh, Thailand and
Australia
Geophysical hazards also occur in the middle of large plates – known as intra-plate
earthquakes / volcanic actvity
-> Perhaps due to smaller tectonic plates existng within major plates
Eruptons in partcular also occur at hotspots – not necessarily in associaton with plate
boundaries. Hotspots are small areas of the Earth’s crust with an unusually high temperature
that are associated with volcanic actvity.
e.g. Hawaii ; Iceland ; USA
[more on hotspots laters
Plate Tectonic Theory:
TIMELINE OF EVIDENCE FOR PLATE TECTONICS:
1915: Wegener’s Contnental Drif heory
- Collected fossil, rock and mountain evidence
-> Found animal and plant fossils of the same type in several countries that are separated by
oceans – especially on coasts of contnents that are separated by an ocean
e.g. Rock strata in E coast of South America and W coast of Africa match
e.g. Fossils of tropical plants found in Antarctca
-> Glacial evidence found in lines on mountains where glaciers moved through Africa, South
America, Australia and India
-> Shape of American coast and African coast ft together
- Theory states that all contnents were once a supercontnent known as Pangea. Over tme
Pangea split and parts of the contnent drifed apart creatng new contnents
-> The evidence he found all supports this theory
, WWI: Sonar technology
- Sonar tech developed for use in WWI involved sound waves being sent down to the ocean
foor and refected back. The refecton revealed that the ocean foor has geological features –
contrary to their previous belief that the ocean foor was fat
1919: Convecton Current heory
- Determined that mantle is semi-plastc – the material itself is solid but fows like a liquid.
Convecton current in the mantle move the crust above it
1946: Ocean foor mapped
- Sonar tech used by scientsts was used to map the ocean foor – revealed the mid-ocean
ridge, mountains, volcanoes and trenches on the ocean foor
1954: Volcanoes and earthquakes mapped
- Eruptons and EQ epicentres of previous hazards revealed a world-wide patern in which they
are occurring in similar places and in the same place as where the ocean ridges and trenches
were previously mapped
1960: Sea-foor spreading theory
- States that due to magma rising at constructve boundaries, new sea foor is being created
and the ocean is getng larger
-> e.g. North America is moving away from Europe slowly [Mid-Atlantc Ridges
1963: Palaeomagnetsm
- Occasionally the Earth’s magnetc feld fips. Basalt released from basaltc volcanoes on the
MAR contains magnetc minerals. When released, the minerals take on the directon of the
Earth’s magnetc feld.
-> Polarity reversals of the Earth have been recorded in rock that has been formed at the MAR
as magnetc stripes
-> This is evidence of sea-foor spreading as new crust is constantly forming at the MAR and
takes on the magnetc feld, records it, and appears striped
(Also allows for identfying the age of oceanic crust as younger rock is closer to the ridge)
1965: Plate tectonics
- Theorised that the Earth’s crust is made of chunks of rock called plates – the edges of which
are where the EQs and volcanoes previously mapped lay
1983: GPS
- GPS monitoring devices placed around the world and tracked movements of the Earth’s crust
e.g. how the MAR is expanding
PLATE TECTONICS:
The lithosphere is the Earth’s crust and is split up into major and minor tectonic plates.
-> there are oceanic plates which are thin and dense, and contnental plates which are thick
They move over the asthenosphere (semi-molten layer of rock in the upper mantle) and their
movement causes geophysical hazards – earthquakes and volcanic eruptons.
There are many processes occurring in the lithosphere:
- MANTLE CONVECTION:
In the Earth’s core the decay of radioactve elements produces heat which heats the
lower mantle. This creates convecton currents in the mantle where hot magma has a
Natural hazard: A naturally occurring hazard that has the potential to
harm human life and property
Distribution of natural hazards:
Natural hazards can either be:
geophysical – caused tectonic or geological processes (earthquakes, volcanoes, tsunamis)
or hydrometeorological – caused by hydrological and atmospheric processes (foods, storms,
droughts)
Geophysical hazards (earthquakes, volcanic eruptons) tend to occur on plate boundaries,
especially destructve plate boundaries [because you have plates colliding causing earthquakes
and magma rising causing eruptonss
e.g. boundary between North American plate [contnentals and Pacifc plate [oceanics is
destructve
e.g. Indian and Australian plate are both on a collision and constructve plate boundary. Parts
of the two plates are colliding causing earthquakes but other parts are moving away from each
other releasing lava in gentle eruptons.
-> This causes tsunamis which afects those on the coast of India, Bangladesh, Thailand and
Australia
Geophysical hazards also occur in the middle of large plates – known as intra-plate
earthquakes / volcanic actvity
-> Perhaps due to smaller tectonic plates existng within major plates
Eruptons in partcular also occur at hotspots – not necessarily in associaton with plate
boundaries. Hotspots are small areas of the Earth’s crust with an unusually high temperature
that are associated with volcanic actvity.
e.g. Hawaii ; Iceland ; USA
[more on hotspots laters
Plate Tectonic Theory:
TIMELINE OF EVIDENCE FOR PLATE TECTONICS:
1915: Wegener’s Contnental Drif heory
- Collected fossil, rock and mountain evidence
-> Found animal and plant fossils of the same type in several countries that are separated by
oceans – especially on coasts of contnents that are separated by an ocean
e.g. Rock strata in E coast of South America and W coast of Africa match
e.g. Fossils of tropical plants found in Antarctca
-> Glacial evidence found in lines on mountains where glaciers moved through Africa, South
America, Australia and India
-> Shape of American coast and African coast ft together
- Theory states that all contnents were once a supercontnent known as Pangea. Over tme
Pangea split and parts of the contnent drifed apart creatng new contnents
-> The evidence he found all supports this theory
, WWI: Sonar technology
- Sonar tech developed for use in WWI involved sound waves being sent down to the ocean
foor and refected back. The refecton revealed that the ocean foor has geological features –
contrary to their previous belief that the ocean foor was fat
1919: Convecton Current heory
- Determined that mantle is semi-plastc – the material itself is solid but fows like a liquid.
Convecton current in the mantle move the crust above it
1946: Ocean foor mapped
- Sonar tech used by scientsts was used to map the ocean foor – revealed the mid-ocean
ridge, mountains, volcanoes and trenches on the ocean foor
1954: Volcanoes and earthquakes mapped
- Eruptons and EQ epicentres of previous hazards revealed a world-wide patern in which they
are occurring in similar places and in the same place as where the ocean ridges and trenches
were previously mapped
1960: Sea-foor spreading theory
- States that due to magma rising at constructve boundaries, new sea foor is being created
and the ocean is getng larger
-> e.g. North America is moving away from Europe slowly [Mid-Atlantc Ridges
1963: Palaeomagnetsm
- Occasionally the Earth’s magnetc feld fips. Basalt released from basaltc volcanoes on the
MAR contains magnetc minerals. When released, the minerals take on the directon of the
Earth’s magnetc feld.
-> Polarity reversals of the Earth have been recorded in rock that has been formed at the MAR
as magnetc stripes
-> This is evidence of sea-foor spreading as new crust is constantly forming at the MAR and
takes on the magnetc feld, records it, and appears striped
(Also allows for identfying the age of oceanic crust as younger rock is closer to the ridge)
1965: Plate tectonics
- Theorised that the Earth’s crust is made of chunks of rock called plates – the edges of which
are where the EQs and volcanoes previously mapped lay
1983: GPS
- GPS monitoring devices placed around the world and tracked movements of the Earth’s crust
e.g. how the MAR is expanding
PLATE TECTONICS:
The lithosphere is the Earth’s crust and is split up into major and minor tectonic plates.
-> there are oceanic plates which are thin and dense, and contnental plates which are thick
They move over the asthenosphere (semi-molten layer of rock in the upper mantle) and their
movement causes geophysical hazards – earthquakes and volcanic eruptons.
There are many processes occurring in the lithosphere:
- MANTLE CONVECTION:
In the Earth’s core the decay of radioactve elements produces heat which heats the
lower mantle. This creates convecton currents in the mantle where hot magma has a
