Geography Mock p1 Flashcards
What are the secondary hazards of an earthquake?
Tsunami, Liquefaction, Landslides
How does a tsunami occur?
Oceanic crust jolted during an earthquake( or volcanic eruption or underwater landslide), causing all the water above to be displaced, and pulled down due to the force of gravity. Energy is transferred to water and travels as a wave. At the start, it has a low amplitude and travels fast. Closer to the coast as the sea level decreases, friction is created between sea bed and waves. The wave slows down and gains height.
Where are tsunamis generally generated?
Subduction zones at convergent boundaries.
Where on Earth do tsunamis generally occur and which continents are most vulnerable?
Pacific ring of fire. Asia and Oceania most vulnerable.
What are factors that affect the impact of a tsunami?
Pop density (more people= bigger effect)
Coastal defences (more defences= less impact)
Wave amplitude
Distance travelled
Gradient of continental shelf (steeper= bigger tsunami)
Shape of land ( bays funnel/ concentrate tsunami waves)
Warning & evacuation systems (less impact)
Economic and human development (less impact)
Tohuku case study
primary hazard- earthquake
secondary hazards- tsunami and liquefaction
11th march 2011
16,000 deaths
9.2 magnitude (equivalent to 600 atomic bombs)
MEDC
6,000 injured
111 hospitals destroyed and sendai airport rendered unusable
aid limited as a result
10 mins for tsunami to reach Japan
millions without electricity due to nuclear power meltdown
Indian ocean case study
primary hazard- earthquake
secondary hazard- tsunami
26th December 2004
9.1 magnitude
220,000 deaths
12 countries affected- many LEDCs including India, Maldives, Indonesia, Malaysia, Thailand, Sri Lanka
650,000 injured
200,000 homeless
spreads of diseases e.g cholera
immediate responses- fresh water, water purification tablets, food, sheeting and tents
uk gov promised £75 million in aid, £100 million raised in donations
long term responses-
Indian Ocean Tsunami Warning system implemented in 2006
plans spending nearly £200 million to rebuild homes
What is liquefaction and what can it cause?
Liquefaction is the water moisture within the soil separating from the soil particles and rising to the surface
Can cause building subsidence and landslides
Christchurch case study
New Zealand
MEDC
6.3 magnitude
185 deaths- 80 as a result of a fallen building
Liquefaction
$40 billion in damage
1 in 5 lost their job
infrastructure sunken into the ground
What is a landslide?
A landslide is unconsolidated material or loose rocks collapsing as a result of shaking caused by an earthquake, weakening cliff faces hills and snow materials
What factors affect the impact of a landslide?
Topography, rainfall, soil and land use
Nepal case study
Earthquake- primary
Landslide- secondary
28th April 2015
7.8 magnitude
9,000 deaths
landslide caused villages to be buried under rubble
What are primary volcanic hazards?
Lava flows, Pyroclastic flows, Tephra and ash flows, Volcanic gases
What are secondary volcanic hazards?
Lahars, Jokulhaup, Acid rain
What is a pyroclastic flow?
Mixture of hot dense rock, lava, ash, and gases which move at high speed along the surface. Extremely dangerous- causes asphyxiation.
What is a lahar?
Combination of mud, rock and water which travel quickly down the sides of volcanoes. Occurs when eruption causes snow and ice to melt, or eruption coincides with rainfall.
What is a Jokulhaup?
snow and ice in glaciers melt after an eruption causing sudden floods.
What are the 4 erosional processes?
Hydraulic Action, Abrasion, Attrition and Corrosion
What is hydraulic action?
Hydraulic action is a large destructive wave breaking on a cliff, and the force of water exerts pressure, loosening pieces of rocks
What is attrition?
boulders, rock particles and pebbles colliding with each other.
What is corrosion?
Sea water and salt spray from waves react with rock minerals and actively dissolve them. Rock minerals carried with solution within sea water.
What is abrasion?
Destructive waves pick up sand, pebbles and/ or boulders and are thrown against a cliff
What is weathering and what are the 3 types?
Weathering is the break down of rock leading to the transfer of material into the littoral zone, where it becomes input to sediment cells.
Mechanical, Chemical, biological
What are sub aerial processes?
Weathering and mass movement
what is mechanical weathering and what are the 3 types?
Mechanical weathering is the breakdown of rock due to physical exertion
Freeze-thaw: Water enters cracks in rocks and freezes, causing it to expand, and increase pressure. Weakens cliff.
Salt crystallisation: Sea water evaporates, leaving salt behind. Crystals grow and exert pressure, casing cracks to widen
Wetting and drying: clay expands when wet and contracts when dried, cycle causes rocks to break up
what is chemical weathering and what are the 3 types?
Chemical weathering is the breakdown of rocks via chemical processes/ reactions
Carbonation: rainwater absorbs C02 creating weak carbonic acid, which reacts with calcium carbonate in rocks to form calcium bicarbonate. This is easily dissolved allowing erosion.
Oxidation: minerals become exposed to air via cracks and fissures, mineral will become oxidised which will increase its volume, causing rock to crumble
Solution: rock minerals such as rock salt are dissolved
what is biological weathering and what are the 3 types?
Biological weathering is the breakdown of plants via plants, bacteria and animals
1) Plant roots- plant roots growing into cracks, causing rock to split
2)Birds- puffins dig burrows into cliffs making erosion more likely
3) seaweed acids- contain sulphuric acids that dissolve rock minerals
What are the 2 types of categories for mass movement?
Flows- material flows and mixes
slides- sediment keeps its same place in material, moving downhill
Explain the 3 mass movement flows
soil creep- slowest but continuous movement of soil particles downhill
solifluction- in tundra areas, top layer thaws but permafrost stays frozen. surface layers flow over frozen.
mudflows- increase in water content of soil can reduce friction, leading to earth and mud to flow over underlying bedrock
Explain the three mass movement slides
Rock falls- sloped cliffs when exposed to mechanical weathering causes rock to fall
Rock slides- water between joints and bedding planes can reduce friction and lead to more sliding
Slumps- soil saturated with water, causing rotation movement of soft materials
Name examples of coastal erosional landforms
Caves, arches stacks & stumps
Wave cut notch
Wave cut platform
Retreating cliffs
Blowhole
How is a cave, arch, stack and stump formed?
Crack formed by hydraulic action and abrasion
Waves continue to erode crack into a cave through hydraulic action and abrasion
Cave becomes larger and eventually breaks through headland to form an arch
Base of arch becomes wider, and roof becomes too heavy and collapses into the sea leaving a stack
Stack undercut at base until it collapses to form a stump
How is a wave cut notch formed?
Destructive waves reach base of cliff, causing abrasion and hydraulic action to wear away rock. curved- wave cut notch forms along base of cliff
How is wave-cut platform formed?
Cliff is eroded at the base, leaving the rock above unsupported and eventually collapses. The cliff retreats and leaves a flat or sloping area.
How are retreating cliffs formed?
Caused by waves undercutting the land at high tide, or constantly if there is no beach. As cliffs undercut, gravity causes mass movement in unsupported rock.
How are blowholes formed?
A pothole on top of a cliff created by chemical weathering and a cave formed by erosion. Cave erodes deeper into cliff face and pothole deepens, they may meet.