2.(and other) Natural Hazard
Quickly: rapid onset hazard
Slowly: slow onset hazard
Natural Disaster
Extreme natural event
Abiotic environment
Biotic environment
Gradational forces
Tectonic forces
Fault
Magma
Lava
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physical event that happens naturally
caused by: changes in atmosphere, earth’s surface sea/body of water
earthquakes, volcanic eruptions, landslides, tsunamis, floods, drought
Local scale: flood, oil spill, fire
Regional scale: volcanic eruption
Global scale: Noah’s flood
effects of a natural disaster cause serious problems for living creatures
economic – crops; social - families
excessive size, frequency, length or damage
non-living things
landforms, soils, rocks, drainage, climate
living things
flora, fauna, humans
Change/ modify landforms made by tectonic forces
weathering and erosion by wind, water and ice
Movement of the earth's crust creates mountains, hills, plateaus.
folding, faulting and volcanism (earthquakes and volcanoes)
A fracture in rock where there has been movement and displacement. One of the major boundaries
between tectonic plates on earth.
The San Andreas Fault is the world's most famous; it splits California between the Pacific Plate
and the North American Plate.
Molten material underneath the earth’s surface
Consists of rock, gases and mineral crystals. Temperatures can get as high as 2,760*C
Molten rock that comes out from a volcano or a fissure in the earth’s surface. Lava is magma that’s
broken through the earth’s surface.
crack in the ground
mudflows of volcanic ash, could be mixed with mud.
formed with the collapse of the top of the volcano into itself
Fissure
Lahar
Caldera
Mitigation processes
People can change and adapt as a result of a natural disaster
 Countries may develop and establish better responses and organisational systems to deal with future emergencies.
 Stress can push others away, it’s too much to handle.
Ridges and trenches
 Ridges form where tectonic plates move apart, the Mid-Atlantic ridge and Iceland.
 Trenches form in some cases where plates meet (The Marianas Trench off Japan's coast)
Fold volcanic formation
 Two plates move together (a compressional plate margin - faulting).
 Can be two continental plates or a continental and oceanic plate.
 Movement forces sedimentary rocks upwards into a series of folds.
 Fold mountains are usually formed from sedimentary rocks and are usually found along the edges continents.
 This is because the thickest deposits of sedimentary rock generally accumulate along the edges of continents. When plates
and the continents riding on them collide, the accumulated layers of rock crumple and fold.
Fault volcanic formation
 When cracks on the earth’s surface are large enough, magma can rise (forces its way up) and volcanoes form.
Volcanic mountain formation
 Expulsion of materials from deep within the earth in the form of enormous amounts of lava or cinders
 These pile up on the earth's surface, forming a mountain.
Constructive plate boundaries
 Magma from the earth's interior rises to the surface and forms volcanoes,
 Forms new crust which pushes away older crust
Destructive plate boundaries
 Oceanic plate slides into the earth's mantle,
where it melts.
 The molten rock then rises to the surface and
forms a chain of volcanoes.
Volcanic eruption for Mt St Helens
 Natural impact
 Cultural impact
 Relation to magnitude and durations
Composite/Stratocone volcano
 Alternating layers of lava and rock fragments
 Often form impressive, snow-caped peaks
 2500+m height
 1000+sq.km surface
 400+km3 volume
Reducing the impact of geomorphic hazards
 Cyclone resistant buildings
 Northern Territory
 Dams and drought-preparation programs
 Australia
 Earthquake resistant buildings
 Japan
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Ring of Fire
 Three-quarters of the earth’s 550 historically active volcanoes lie along the Pacific Ring of Fire.
 This includes most of the world’s recent eruptions
 Where the earth’s tectonic plates are being subducted beneath deep ocean trenches.
Island Arc Volcanoes
 Chain of volcanoes
 “A curved chain of volcanic islands located at a tectonic plate margin, typically with a deep ocean trench on the convex side.”
Hot Spot Volcanoes
 A volcanic centre with a rising plume of hot mantle material.
 Hot spots are not necessarily linked to arcs.
Signals to predict activity
 Earthquakes/seismic activity
 Bulging
 Magma rise means more gas release
Predicting Mt St Helen’s eruption
 Repeated warnings of a large blast prompted the US Forrest Service to evacuate people from certain danger zones
 Earthquakes recorded
 Seismographs and surveying equipment
Living near volcanoes
 Rich earth – farmers
 Rich minerals
 Geothermal activity
 Tourism
Tsunami
 A long, high sea wave caused by an earthquake or other disturbance.
 Usually originate at boundaries of tectonic plates
Predicting future eruptions of volcanoes using:
 Satellite imagery
 Ground deformation – check for bulges/swelling/cracks
 Gas measurement – increases in sulphur indicate magma rise
 Geophysical measurements
 Seismic recording – earthquakes and tremors
 Water testing – chemicals etc. can find their way into nearby water sources