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IB Geography: GEOPHYSICAL HAZARDS
Terms in this set (179)
What is the core made of?
Solid iron and nickel
What is the mantle made of?
Semi molten rock that moves very slowly
Order of the layers on the Earth (starting from the outside)
Crust, mantle, outer core, inner core
Thicker and less dense
Thinner and more dense, older, sometimes up to 200 million years old
Why do the plates move?
Because convection currents in the mantle caused by radioactive decay in the core moves the plates
Destructive plate margin
When two plates are moving towards each other
Example of a destructive plate margin
Along the east coast of Japan
What happens if two continental plates meet at a destructive plate margin?
The plates smash together, but no crust is destroyed
What happens if a continental and an oceanic plate meet at a destructive plate margin?
The heavier more dense oceanic plate sinks underneath the continental plate and forced down into the mantle and melted. This can cause volcanoes and very deep ocean trenches
Constructive plate margin
When two plates are moving away from each other, and magma rises up from the mantle to fill the gap, and cools creating a new crust
Example of a constructive plate margin
The mid Atlantic ridge
Conservative plate margin
When two plates are moving sideways past each other, or are moving in the same direction but at different speeds, crust isn't created or destroyed
Example of a conservative plate margin
Along the west coast of the USA
How are fold mountains formed?
When plates collide at destructive margins, the sedimentary rocks that have built up between them are folded and forced upwards to form mountains
Where are fold mountains found?
At destructive plate margins, or where there used to be a destructive plate margin - such are the west coast of the USA
Example of two continental plates (fold mountains)
Himalayas in Asia
Example of oceanic and continental plates (fold mountains)
Andes in South America
Characteristics of fold mountains
Lots of very high mountains, very rocky and with steep slopes, often snow and glaciers in the highest points and lakes in the valleys
What do humans use fold mountains for?
Farming, hydroelectric power, forestry, tourism, mining
Farming on fold mountains
Higher mountain slopes aren't good for growing crops, so animals are allowed to graze there instead, lower mountain slopes are used for crops, and are sometimes terraced if they are too steep
Mining on fold mountains
Fold mountains are a major source of metal ores, but the steep slopes make it difficult to mine them, so zig zag roads have been built
Tourism on fold mountains
Spectacular scenery, in winter you can do skiing, snowboarding and ice climbing, in summer you can go on walks. To make transport easier, tunnels have been built through the mountains to make transport easier, improving communications
Forestry on fold mountains
Good environment to grow some types of trees like conifers, grown for fuel, building materials and paper and furniture
Hydroelectric power on fold mountains
There are steep sided mountains and high lakes to store water, making it great for HEP
ALPS: Where is it?
Central Europe, stretches across Austria, France, Germany, Italy, Liechtenstein, Slovenia and Switzerland
Formed about 30 million years ago, by the collision between African and European plates
ALPS: Tallest peak?
Mont Blanc at 4810m on the France-Italy border
Used to farm goats high up, which provide milk, cheese and meat, sunnier slopes have been terraced to plant vineyards such as in Lavaux in Switzerland
100 million tourists each year , 70% of tourists go for skiing, snowboarding and ice climbing, in summer people go for walks, mountain biking, paragliding and climbing, new villages have been built for tourists, lots of ski lifts, cable cars, holiday chalets and restaurants built
Narrow valleys are dammed to generate HEP e.g. Berne, Switzerland. Switzerland gets 60% of its electricity from HEP, used locally but also exported
Salt, iron ore, gold, silver and copper were mined, but mining has declined due to cheaper foreign sources
Scots Pine is planted all over as it is very resilient to the munching goats, they are also logged and sold to make furniture
ALPS: Adaptation - steep relief
Goats are farmed because they are well adapted to live high up, also trees are planted as a natural defense against avalanches
ALPS: Adaptation - poor soils
Animals are grazed high up where the soil isn't very good for crops
ALPS: Adaptation - limited communication
Roads have been built over passes (low point between the mountains) but it takes a while to cross, and snow can block them, so tunnels have been built such as the Lotschberg Base Tunnel in Switzerland
Where are volcanoes found?
At constructive and destructive plate margins
How is a volcano formed at a destructive plate margin?
The oceanic plate goes underneath the continental plate, is goes into the mantle and is melted, creating a pool of magma, which rises through the the cracks in the crust called vents, and erupts on the surface
How is a volcano formed at a constructive plate margin?
The magma rises up through the the gap between the tow plates moving apart
Example of a hotspot volcano
In Hawaii volcanoes have formed over ares of very hot magma
Made up of ash and lava that has erupted and cooled and hardened into layers, the lava is usually thicc and flows slowly and hardens quickly forming a steep sided volcano
Example of a composite volcano
Mount Fuji, Japan
Made up of only lava, which is runny, flows quickly and spreads over a large area, forming a low, flat volcano
Example of a shield volcano
Mauna Loa, Hawaiian islands
Made up of only lava, lava is thick and flows slowly and hardens fast, forming a steep sided volcano
Example of a dome volcano
Mount Pelee in the Caribbean
How can scientists try to predict when a volcano will erupt?
Monitor volcano for things such as tiny earthquakes, escaping gas and changes in the shape of the volcano by using satellite images
The Soufreire Hills in Montserrat,a small island in the Caribbean Sea
June 25th, 1997 (small eruptions started in July 1995)
The Soufriere Hills volcano
4 - 5 milion m3 of rock and gas was released
MONTSERRAT: Death toll?
19 people killed
It is above a destructive plate margin, where the Atlanic plate is being forced under the Caribbean plate, magma rose up through the cracks forming and underground pool of magma. The rock above the pool collapsed causing an eruption
MONTSERRAT: Primary effects?
Large areas covered with volcanic material, capital city Plymouth covered in 12m of mud and ash, over 20 villages and two thirds of homes destroyed by pryroclastic flows, 19 people died and 7 injured
MONTSERRAT: Secondary effects?
Fires destroyed many buildings including local government offices, police headquarters and the central petrol station. Tourists stayed away and businesses were destroyed, disrupting the economy, population decline - 8000 of the 12000 inhabitants have left since 1995, improved soil fertility
MONTSERRAT: Immediate response?
People were evacuated from the south to safe areas in the north, shelters were built, UK provided £17 million of emergency aid, rescue services were sent to find survivors
MONTSERRAT: Long term responses?
A risk map was created, and the south of the island is off limits whilst the volcano is active, UK has provided £41 million to develop the north of the island, new docks, homes, and airport, volcano observatory has been set up
Where do supervolcanoes form?
At destructive plate margins and over parts of the mantle that are really hot (hotspot)
How do supervolcanoes form over hotspots?
Magma rises up through the crust to form a large magma basin below the surface, the pressure of the magma causes a bulge on the surface, several kilometers wide, the bulge eventually cracks creating vents for lava to escape through, the lava erupts out of the vents causing earthquakes, and sending up loads of ash
What happens after a supervolcano has erupted?
There is no longer anything in the magma basin, so the rock collapses, causing a caldera
Example of a supervolcano
Yellowstone National Park or Lake Toba in Indonesia
Characteristics of a supervolcano
Flat, cover a large area, have a caldera
What will happen if a supervolcano erupts?
It will throw out thousands of cubic kilometres of rock, ash and lava (a normal volcano will only produce a couple of cubic kilometres), everything within ten miles will be dead, because a huge super heated cloud of ash and gas will flow at high speed, ash will block out sunlight over whole continents, triggering a mini ice age
Where do earthquakes occur?
At all three plate margins
How do earthquakes occur at destructive plate margins?
Tension builds up when one plate gets stuck when moving down past the other
How do earthquakes occur at constructive plate margins?
Tension builds along cracks within plates as they move away from each other
How do earthquakes occur at conservative plate margins?
Tension builds up when plates that are grindin past each other get stuck
How does the Richter scale work?
An earthquake with a magnitude of 5 is 10 times one that has a magnitude of 4
What counts as a "major earthquake"?
An earthquake that ha a magnitude greater than 5
How does the Mercalli scale work?
Measures the effects of an earthquake, by asking eye witnesses about what happened
6th April 2009
8th October 2005
6.3 Richter scale
7.6 Richter scale
Destructive plate margin
Destructive plate margin
Laws on construction standards, but some modern buildings weren't built to withstand earthquakes, Civil Protection Department that trains people to help with rescue operations
No local disaster planning was in place, buildings were not designed to withstand earthquakes, poor communications and roads
ITALY: Primary effects?
290 deaths from collapsed buildings, hundreds injured, thousands of buildings damaged or destroyed, thousands made homeless, water pipe broken
PAKISTAN: Primary effects?
80, 000 deaths from collapsed buildings, hundreds of thousands injured, entire villages destroyed, 3 million homeless, water pipes and electricity were cut off
ITALY: Secondary effects?
Fires caused more damage, broken water pipe in Paganica caused a landslide, aftershocks hindered rescue services
PAKISTAN: Secondary effects?
Landslides buried buildings and people, blocked roads and cut off water, electricity and phone lines, diarrhea spread due to little clean water, freezing winter conditions caused more casualties and made rescuing more difficult
ITALY: Immediate response?
Camps were set up for the homeless, ambulances, rescue dogs and the army were sent to rescue survivors, cranes and diggers removed rubble
PAKISTAN: Immediate response?
Help didn't reach many areas for days or even weeks, people had to be rescued by hand without equipment or emergency services, tents, blankets and medical supplies were distributed within a month, but not to all areas, helicopters and rescue dogs were brought in from other countries
ITALY: Long term response?
Prime Minister promised to build a new town to replace L'Aquila, investigation as to why the buildings collapsed
PAKISTAN: Long term response?
40, 000 relocated to new town of Balakot, government money has been given to those whose homes were destroyed so they can rebuild them, homes are being built more resistant, new health centres have been set up
INDIAN OCEAN: When?
Boxing Day 2004
INDIAN OCEAN: Cause?
Destructive plate margin, the plate that was moving down into the mantle cracked and moved very quickly
INDIAN OCEAN: Tsunami size?
9.1 on the Richter scale, 30m high waves
INDIAN OCEAN: Where did it affect?
Indonesia, Thailand, India, Sri Lanky
INDIAN OCEAN: Primary effects?
230, 000 people killed or still missing, whole towns and villages were destroyed, over 1.7 million lost their homes, infrastructure severely damaged, 5 - 6 million needed emergency food, water and medical supplies
INDIAN OCEAN: Secondary effects?
Tourism industry suffered, fishermen couldn't fish, salt from sea water meant that plants can't grow in many areas, mangroves, coral reefs, forests and sand dunes were also destroyed
INDIAN OCEAN: Short term responses?
Within days hundreds of millions of pounds had been pledged by foreign governments, charities, etc to give water food, shelter and medical attention, ships and planes were sent and teams of specialists to rescue people from other countries
INDIAN OCEAN: Long term responses?
Billions of pounds have been pledged to help rebuild the infrastructure, programmes have been set up to help people rebuild homes and get back to work, tsunami warning system has been put in place, disaster management and volunteers have been trained
Heat lost by the Earth as it cools
Made of fragments of solid material, forming a steep conical hill, not very high
Example of a cinder volcano
Volcano Du Fuego, Guatemala
The occurrence of a hazard, the effects of which change demographic, economic and/or environmental conditions
An event that causes great damage or harm
The probability of a hazard occurring
The geographic conditions that increase the susceptibility of a community to a hazard or to the impacts of a hazard event
Two sources of Earth's heat?
Radioactive decay in the core and primordial heat
How do the plates move?
Convection currents in the mantle caused by radioactive decay drags the plates and moves them
The soft layer of the mantle on which the tectonic plates move
Very hot, upward channels of material that can cause igneous activity
Where are most plumes found?
Near plate margins and may be responsible for the original rifting of the crust
What is a primary hazard of a volcano?
The direct impacts of the eruption e.g. pyroclastic flows, lava flows, ash clouds
What is a secondary hazard of a volcano?
Hazards that arise due to the way the ejected material reacts e.g. ash may join with rainwater to form mudflows, or lahars
Volcanic mudflows that form from condensed steam, rain, or melted ice, plus ash, mud and other debris
Scalding avalanche of ash and hot, toxic expanding gas, traveling very fast down the side of a volcano
What makes lava more viscous?
P wave (primary)
Fastest and can move through solids and liquids, shake BACK AND FORWARD
S waves (secondary)
Slower, and can move through solids only, makes the ground move SIDE TO SIDE
S waves that make the ground move sideways
Surface waves whose matter moves in a circular motion
Hawaiian lava eruption
Involve a central vent, lava flows relatively gently, low level eruption, basaltic magmas with low viscosity, high vent temp
Vulcanian pyroclastic eruptions
Violent and occur when trapped gases build enough pressure to blow of the overlying layer of crust
Icelandic lava eruptions
Persistent fissure eruption, lots of basaltic lava
Stombolian pyroclastic eruptions
Explosive eruptions, white cloud of steam, run lava erupted into sky
Vesuvian pyroclastic eruptions
Very powerful blasts of gas that push ash clouds into the sky, lava, and ash falls
Plinian pyroclastic eruptions
Extremely violent, huge clouds of pulverised rock and ash that are kilometres thick, part of the volcano can be blasted away
The point on the surface directly above the focus
The point at which plates release their tension or compression suddenly
What type of waves cause more damage?
S waves, but they are slower
Example of an earthquake triggered by a dam
7.9 Sichuan in May 2008
What is a mass movement?
Movement of material under the influence of gravity alone
Human causes of earthquakes
Dams, reservoirs, mining, fracking and nuclear testing
Secondary hazards of earthquakes
Landslides, liquefaction, tsunamis
Quickly moving downhill flow of soil and rock fragments containing a large amount of water
The process by which an earthquake's violent movement suddenly turns loose soil into liquid mud
Where does liquefaction take place?
In saturated soils
How does liquefaction occur?
In saturated soils, the gaps between water particles are filled with water. When the soil particles are vibrated, they lose contact with each other and act like a liquid
What is a tsunami?
A huge wave or waves caused by seismic activity
Occurs when a lump of rock fractures
Stress that pushes rocks in parallel but opposite directions - the force that pulls the slope down
Very slow MM
Very fast MM
Most important factors of mass movement
Gravity, slope angle and pore pressure
What causes slope failure?
Reduction in internal resistance, or shear strength of the slope, increase in shear stress
The resistance to the shear stress
Factors increasing shear stress
- Removal of underlying support
- Loading of slope
- Lateral pressure
- Transient stress
Factors contributing o reduced shear strength
- Weathering effects
- Changes in pore water
- Changes of structure (creation of fissures in clays)
- Organic effects (burrowing of animals, decay of roots)
What type of boundaries are associated with broad belts of earthquakes?
Destructive, where there are subduction zones
What type of boundaries are associated with narrow belts of earthquakes?
Example of a volcano formed over a hotspot?
The volcanoes in Hawaii
Rapid, free fall of rock from a steep cliff face. Made worse by freeze thaw. Scree slope is formed at the bottom
Landslips / landslumps
The occasional rapid movement of a mass of earth or rock sliding along a concave plane
What causes landslips?
Occurs after periods of heavy rain, the water saturates the overlying rock, making it able to slide.
Very slow movement, occurring on gentle slopes, because the soil particles expand and contract in wet and dry periods
NEPAL LANDSLIDES: When?
NEPAL: Why is Nepal at risk of lots of landslides?
- Seismic activity occurs there
- Has lots of steep slopes
- Seasonal rainfall
- Road constructions
- The slopes are weakened by previous slides
NEPAL: What caused it?
Gorkha earthquake in April 2015
NEPAL: Vertical distance?
NEPAL: Horizontal distance?
Whole settlements were buried, many died
The expected frequency that an event will occur
What effects the severity of a hazard? (9)
6. Speed of onset
8. Areal extent
9. Number of hazards
How can earthquakes be predicted?
- Micro earthquakes
- Changes in rock stress
- Ground subsidence
- Changes in magnetic field
- Animal behaviour
- Seismic activity
Economic factors affecting vulnerability
- Quality of housing
- Access to technology (to communicate and predict)
- Insurance cover
Social factors affecting vulnerability
- Education, leads to more money and better homes
- Awareness of hazards and how to deal with them
Demographic factors affecting vulnerability
- Population density
Political factors affecting vulnerability
- Government action e.g. the failure of the Burmese government to allow aid to the cyclone in 2008 increased death tolls
Why do people live near hazard locations?
Fertile soils are found volcanoes, ancestral land, not enough money to move away
Physical facts affecting the impact of a tectonic even (8)
1. Distance from epicentre
2. Richter scale
6. Time of day
7. Time of year and climate
Definition of a hazard event
The occurrence of a hazard, the effects of which change demographic, economic and or environmental conditions
Definition of risk
The probability of a hazard event causing harmful consequences (expected losses in terms of death, injuries, property damage, economy and environment)
Definition of vulnerability
The geographic conditions that increase the susceptibility of of a community to a hazard of impacts of a hazard event
Definition of a disaster
A major hazard event that causes widespread disruption to a community or region with significant demographic, economic, and environmental losses and which the affected community is unable to deal with without outside help
Heat that is produced from the radioactive decay of materials
The process by which Earth's crust breaks apart; can occur within continental crust or oceanic crust
The deepest part of the ocean floor; made up of rolling hills and flat plains.
An explosive eruption of thick lava and steam or gas
An eruption composed of bursts of dark ash, steam, and gas
Pyroclastics-ash clouds and flows, usually large magma volume, sustained violence, lasts hours to days
An eruption characterized by hot ash clouds, deadly pyroclastic flows, or both
THIS SET IS OFTEN IN FOLDERS WITH...
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