Tectonic Hazards Flashcards
Oceanic crust
Quite thin (5-10km thick), very dense, subducts, so it’s continually destroyed
Continental crust
Very thick(30-50km thick), not very dense, never subducts, so can’t be destroyed
Tectonic plate
It’s slab of rock made up of Earth’s lithosphere
Earthquake
It’s sudden or violent movement within Earth’s crust followed by series of shocks
Volcano
It’s opening in Earth’s crust from which lava, gases + ash erupt from
Plate Margins/Boundaries
They’re place where tectonic plates meet
Crust
It’s Earth’s outermost layer, consists of tectonic plates, upper part of lithosphere + lies above mantle
Mantle
It’s layer of silicate rock between crust + outer core, it’s largest layer + upper mantle is bottom part of lithosphere
Convection Currents
It’s movement of magma within Earth’s mantle caused by heat of core + it causes hot magma to rise as it’s less dense + then fall, currents flow beneath lithosphere, which builds up lateral pressure + carries plates with them
Ridge Push
It happens at constructive margins, oceans ridges form above ocean floor, magma heated by core rises, rising magma reaches lithosphere + cools down to form plate material, as it cools, it forms new plate material, which forces plates apart
Slab Pull
At destructive margins, denser oceanic plate subducts into mantle due to gravity, which pulls rest of plate behind it
Outer core
It’s made up of liquid iron + nickel, it surrounds inner core + it’s below mantle
Inner core
It’s Earth’s innermost layer, it’s extremely hot (it can reach temperatures of up to 5500ºC) + is made up of solid iron + nickel
Destructive boundary
It’s when tectonic plates move towards each other, denser oceanic plate subducts beneath continental plate, friction builds up between them, causing very strong earthquakes, as oceanic plate moves downwards, it melts, creating magma, which is thicker than at constructive boundary + breaks through surface, forming steep-sided composite volcanoes (stratovolcanoes) e.g Pacific + Eurasian Plate
Pyroclastic flow
It’s flow with mixture of steam, ash, rock + dust
Constructive boundary
It’s when tectonic plates move away from each other, magma forces it’s way through overlying crust to surface + breaks through it, causing very small, non-violent earthquakes, magma is very hot + fluid, so lava erupting from broad + flat volcanoes, with gentle but frequent volcanic eruptions, will flow long way before cooling + tectonic plates move apart by ridge push e.g South American Plate + African Plate
Conservative boundary
Plates move past each other or parallel to each other at different speeds, friction between moving plates causes destructive earthquakes, which are released when plates slip + shift, they happen along conservative boundaries as stresses build up over many years e.g Pacific + North American Plate
Distribution of earthquakes + volcanoes
Most happen at plate boundaries (constructive, destructive + conservative)
Focus
Place inside Earth’s crust where pressure is released from earthquake
Epicentre
Point of Earth’s surface directly above focus
Magnitude
Strength of earthquake
Intensity
Measure of violence of earth movement due to earthquake
Seismic Waves
Shockwaves produced by earthquakes in Earth’s crust
New Zealand: Primary effects
7,000 injured, 100,000 buildings damaged, water + sewage pipes damaged
New Zealand: Secondary effects
US $40 billion worth of damage, 10,000 homeless, 10,000 people left Christchurch
New Zealand: Immediate responses
US $7 million received in aid, temporary housing provided, zoning of areas to assess damage + safety
New Zealand: Long term responses
10,000 affordable houses built, water + gas pipes reconnected, buildings demolished, repaired + rebuilt
New Zealand: Causes
Earthquake in Christchurch - 375,000 people, so 1,300 people per square km, Focus - very shallow (5km), Richter Scale Strength - 6.3, Conservative plate boundary, HIC, 22nd February 2011 - 12:50 am
Seismometer
Device that records seismic waves
Nepal: Causes
Earthquake 80km north-west of capital city Kathmandu, 1,200,000 people, so 20,200 people per square km, Focus - 15km below epicentre, Richter Scale Strength - 7.9, Destructive plate boundary (two continental plates), LIC, 25th April 2015 - 11:56am
Nepal: Primary effects
3 million left homeless, cost of damage $5 billion, 7,000 schools destroyed
Nepal: Secondary effects
Landslide that blocked Kali Gandaki River, avalanche on Mount Everest - killed at least 19 people, avalanche in Langtang region, which left 250 people missing
Nepal: Immediate responses
Financial aid pledged from many countries, 500,000 tents needed to provide shelter for homeless, Helicopters rescued many people on Mount Everest
Nepal: Long term responses
$ 200 million from US in aid from Asian Development Bank, over 7,000 schools to be rebuilt or repaired, Repairs to Mount Everest base camp
Reasons for people choosing to live in areas at risk from tectonic hazards: Geothermal energy
In volcanically active areas it’s major source of energy - renewable, so it reduces greenhouse gases emitted, reducing climate change + it won’t run out, e.g Hellisheidi geothermal power plant, Iceland, Environmental
Reasons for people choosing to live in areas at risk from tectonic hazards: Farming
Brings more people + money to area, therefore, buildings built to high standards of earthquake resistance, Soil is fertile due to volcanic eruptions, e.g California, Irrigated fields of crops, Economic
Reasons for people choosing to live in areas at risk from tectonic hazards: Mining
Settlements develop where valuable minerals are found as jobs are created in mining industry, e.g Mining sulphur at Kawasaki Ijen crater, Indonesia, Economic
Reasons for people choosing to live in areas at risk from tectonic hazards: Tourism
Tourist bring money to area which benefits economy, e.g Geysers at Rotorua, New Zealand, Economic
Reasons for people choosing to live in areas at risk from tectonic hazards: Family, friends and feelings
Can see your friends + family more often than if you were to move away from them, e.g Ankara, Turkey, Social
Monitoring
Recording physical changes e.g tracking tropical storm by satellite or using scientific methods to study coastal processes to help inform management options
Protection
Actions taken before hazard strikes to respond to reduce its impact e.g education people or improving building designs
Planning
Actions taken to enable communities to respond to + recover from natural disasters e.g producing hazard map
Prediction
Using historical evidence + monitoring, scientist can make predictions about when + where tectonic hazards may happen
Monitoring: Earthquakes
Scientists can predict where earthquakes usually happen by using historical maps to see where earthquakes have happened before, earthquakes happen on fault lines (cracks in rocks)
Protection: Earthquakes
Buildings: Deep foundation into solid rock, weights on roof to counterbalance shaking, several emergency staircases + exits to speed up evacuations
Planning: Earthquakes
Maps can be produced to show effects of earthquake or to identify areas most at risk from damage so that high value land e.g hospitals can then be protected in these vulnerable areas
Prediction: Earthquakes
Impossible to predict
Monitoring: Volcanoes
Ground deformation: changes to shape of volcano are measured using laser beams, remote sensing: satellites detect heat + changes to volcano’s shape, geophysical measurements: detects changes in gravity as magma rises to surface
Protection: Volcanoes
Earth embankments + explosives can be used to divert lava away from property although not much can be done due to sheer power of volcanic eruption
Planning: Volcanoes
Hazard maps can be produced + they show likely areas to be affected, they can be used to restrict certain land uses or to identify which areas need to be evacuated when eruption is about to happen
Prediction: Volcanoes
Based on scientific monitoring
Volcanoes at a Destructive Plate Margin: Steep-sided composite volcanoes (Stratovolcanoes)
They’re made up of alternating layers of lava + ash, they have pyroclastic flows + they have very violent volcanic eruptions
Lithosphere
It’s made up of Earth’s crust + upper mantle
