Plate Tectonics And Associated Hazards

a layer of the mantle below the lithosphere comprised of relatively fluid material referrd to as plastic

at the centre of the Earth and is formed of the densest material mainly iron and nickel

two types (oceanic and continental) that have contrasting characteristics such as density and material

layer comprised of the crust and the top layer of the mantle which is made of solid and rigid material

middle layer of the Earth formed of less dense, silicate rocks rich in iron and magnesium and is the second thickest layer

the boundary between the crust and the mantle named after the scientist who discovered it

the study of the history of the Earth's magnetic field

theory that the Earth's crust is made up of different rigid plates/slabs that form the lithosphere which float on the asthenosphere powered by convection currents from the Earth's core

new crust is formed at plate boundaries causing the sea floor to expand/get wider

dense rocks containing iron and nickel alloys

silicate rocks (rocks with lots of silicon in them) and oxygen

1. radioactive decay of some elements in the mantle and core generate heat

2. lower parts of asthenosphere heat up and rise

3. as they rise, they cool and then sink

4. this current creates drag on the base of the tectonic plates causing movement

1. rising current diverge at the base of lithosphere creating drag so plates diverge also

2. magma rises to fill gap and cools to form new crust

3. this is repeated over time

when new crust is created due to convection currents it causes the sea floor to expand

mid-ocean ridges

mid-Atlantic ridge

1912

Pangaea

geological evidence and fossils

he couldn't back it up with a mechanism for how the continents moved

palaeomagnetism

sea floor spreading - mechanism

the theory of plate tectonics

- areas of S. America and Africa have rocks of same age and composition and distribution when matched up

- mountain ranges in Scotland and Nordic countries are similar to East coast of N. America

- matching fossils can be found when some continents are matched up

- it is unlikely these species migrated or evolved separately

- living organisms can also be found on different continents

- unlikely they migrated/evolved

- glacial deposits in Antarctica, Africa and Australia match in deposition when matched up

- coal deposits formed in tropical conditions found in N. America and Europe suggest they were closer to the equator

- the Earth's magnetic field changes every 200,000 years or so

- when magma erupts from the crust magnetic minerals align themselves with the direction of the magnetic field

- the alternating magnetic stripes show crust is older the further away from the ridge

Gondwanaland - in the south

Laurasia - in the north

a point on the surface of the Earth located above a plume of rising magma, the Hawaiian Islands lie above such a spot

shock waves released by the rupture of rock strata at the focus of an earthquake

over 5,000 degrees Celcius

light elements, the most abundant being silicon, aluminium, potassium, sodium and oxygen

6-10 km

30-40 km

80-90km thick

seven very large ones and a number of small ones

continental

- 30-70km

- over 1,500 million years

- 2.6 (lighter)

- mainly granite, silicon, aluminium, oxygen (SIAL)

oceanic

- 6-10km

- less than 200 million years

- 3.0 (heavier)

- mainly basalt, silicon, magnesium, oxygen (SIAM)

mid- ocean ridges

rift valleys

basaltic lava

3

5

below the asthenosphere which is less liquid

name given to the total mass of water on the surface of the planet

sometimes uses to describe the part of the earth where life exists

two continental plates collide and neither can sink so they are forced upwards

fold mountains

earthquakes

two plates move away from each other and so the magma moves up to fill the space

mid-ocean ridges and sometimes shield volcanoes

oceanic and continental plates move towards each other and the oceanic gets submerged under the continental where it melts in the subduction zone

volcanoes

fold mountains

deep ocean trenches

two plates slide past each other without creating or destroying any crust but do create pressure

volcanoes

fault lines - San Andreas

place where two lithospheric plates come together, one sinking underneath the other

a curved chain of volcanic islands located at a tectonic plate margin, typically with a deep ocean trench on the convex side

low land region formed by the interaction of Earth's tectonic plates with a typical formation of long, narrow and deep

when the oceanic plate is subducted and partially melted, it creates gases and molten rock which move upwards through faults in the continental rock above

sediments build up in geosynclines and are slowly forced upwards by the steady advance of the plates forming mountains

orogeny

a large column of hot rock rising through the mantle whose heat causes the lower lithosphere to melt

a flat-topped submarine mountain common in the Pacific Ocean, usually an extinct volcano whose summit did not reach above sea level - eroded submerged seamount

an isolated volcanic peak that rises at least 1000 metres above deep ocean floor

- centrifugal force

- gravitational pull of moon

mesosaurus

glossopteris

two continental plates moving towards each other

two plates moving apart

one continental and one oceanic plate moving towards each other

plates move apart

plates move towards each other

Nazca

Pacific

Eurasian

Philippines

Caribbean

porous

circulate

fissures

hydrothermal jets

black smokers

two plates move side by side either in the same direction or in different ones

spreading occurs beneath a major land mass and the heat leads to fracturing and rifting

as the sides of the rift move apart, the central section drops to form a rift valley

either when:

- oceanic crust is subducted by continental crust

OR

- two continental plates move towards each other forcing each of them upwards

at the places where fold mountains are formed and the weight of the sediment can force underlying crust down, forming a 'root'

Himalayas (continental vs. continental)

Andes (oceanic vs. continental)

when two plates diverge, basaltic magma rises to fill the gap and cools forming a ridge on the sea

warms the sea around it enriching it with sulphur producing a rich diversity of life

mid-Atlantic ridge

found at convergent plate boundaries where dense lithosphere is subducted beneath less dense lithosphere

hadalpelagic zone

the deepest zone of the ocean starting at 6,000m

Mariana Trench in the South Pacific Ocean (Pacific under Philippine plate)

outer trench swell

buckle

continental-oceanic

they are the result of oceanic/oceanic convergence when one of the plates is forced under the other where it is melted and eventually rises to form volcanoes

Aleutian Islands of Alaska

Japanese Islands

the angle and rate of subduction and the consistent depth of where melting occurs

the earth's curved surface

triple

120

African Rift Valley which extends 4,000km from Mozambique to the Red Sea

regions deep within the earth's mantle from which heat rises through convection allowing rock in the lithosphere to melt as it pushes against weak crust and forms volcanoes

mantle plumes

hot fluid or semi-fluid material below/within the earth's crust from which lava and other igneous rock is formed upon cooling

hot molten or semi-fluid rock erupted from a volcano or fissure

dark fine grained volcanic rock

dark, fine grained, brown or greyish intermediate rock

a pale fine grained volcanic rock of granitic composition

conical volcano built up of many layers of hardened lava, tephra etc

broad domed volcano with gentle sloping sides,

formed through the cooling and solidification of magma or lava

stat of being thick, sticky and semi-fluid in consistency

basaltic

andesitic

rhyolitic

dissolved gas

explosive

H2O and CO2

B: 1000 -1200

A: 800 - 1000

R: 650 - 800

the composition and temperature

B: low

A: intermediate

R: high

decompressional melting

transfer of heat

flux heating

the geothermal gradient must be raised

the melting temperature of rocks must be lowered

a mechanism to raise the g.g. is convection where hot mantle material rises carrying heat with it. if the g.g. becomes higher than the initial melting temp then partial melting will form.

basaltic

ocean ridges, hot spots, continental rift valleys

when magma intrudes into cold crust, it brings heat with it and transfers it to the surrounding rock when it solidifies. if this is repeated, the local g.g. is increased and melting occurs

rhyolitic

if water or CO2 is added to rock, it lowers the melting point and allows magma to be generated

subduction zones as the plate is force below another, water from the ocean seeps into the pores of the rock and descends into the mantle

less dense

pressure decreases

solution

non-explosive eruption

if the liquid part of the magma has a low viscosity then the gas can expand easily so when it reaches the surface it can burst in a non-explosive eruption

pahoehoe flows

A'A' flows

pillow flows

lava flow

basaltic and andesitic

if the liquid part of the magma has high viscosity then the gas cannot expand easily and so pressure will build inside the gas bubbles meaning explosive bursting will take place when they reach the surface

andesitic and ryholitic

pyroclasts

tephra

blocks

bombs

ash

basaltic

decompressional melting

effusive

andesitic

rhyolitic

flux melting

transfer of heat

explosive

Hawaiian

Strombolian

Vulcanian

Plinian and ultra-Plinian

horizontal layers of basalt that are formed when lava flows from fissures and solidifies

when erupted cooling basalt lava is formed into distinctive columnar, hexagonal shapes

a broad volcano built up from the repeated non-explosive eruptions of basalt to form low dome/shield, usually with large caldera at top

craggy, steep-sided volcanoes built up of layers of lava typically found near large composite volcanoes

steep conical hills made of loose pyroclastic fragments such as cinders and ash

tall conical volcano built up of many layers (strata) of hardened lava, tephra, pumice and ash

huge depressions in the earths crust surrounded by a rim at a higher relief

mud filled with bubbles of sulphur gas that fills up mud pots

formed when large domes of magma cool underground and are only recognisable after overlaying rocks are eroded

granite with quite large crystals due to slow cooling underground

batholith

pressure

metamorphic aureole

the surface that separates one stratum, layer or bed from another

vertical intrusion that cuts across bedding planes formed when magma intrudes vertically through the crustal rocks

smaller intrusions of magma form a lens shape that intrudes between layers of rock which forces the overlying strata to arch upwards forming a dome which may be exposed by later weathering

type of rock that has been changed by extreme heat or pressure causing physical/chemical change

rock formed by the deposition of material at the earth's surface within bodies of water

horizontal intrusions along that lines of bedding planes that have vertical cooling cracks

volcanic object created when magma hardens within a vent on an active volcano which can cause extreme build up of pressure

two plates moving apart and lava is ejected through a fissure/crack

Mauna Loa, Hawaii

Mount Pinatubo, Mexico

Mount Etna, Sicily

when the build up of gases is extreme, the resulting explosion removes the summit of the cone, down to the magma chamber creating an opening that can be several km wide

later eruptions can create a new cone in the middle of the old one

Santroini, Greece

when magma cools and solidifies before reaching the surface

- because the magma is moving slowly

- the crust is very thick

- if there are only a few weaknesses the magma can move through

because the magma cools slowly as it os not exposed to air

dome

Whin Sill, Northern England

Isle of Arran, Scotland

Devon, South England

- modify the event

- modify the loss

- modify vulnerability

environmental control

hazard-resistant design

- explosives are used to divert the course of lava (1983 Edna)

- water sprays are used to cool the lava (1973 Eldafell)

- artificial barriers and mounds are created to redirect the flow/escape onto (Hilo, Hawaii and Indonesia)

- design may be used to reduce risk posed by ash fall on roofs to stop them from collapsing in

- can't do much in terms of resisting lava flow, pyroclastic flows and lahars

- prediction and warning

- community preparedness

- land use planning

- various physical processes can be measured for changes

- records of past eruptions can be used to determine what and where

- only 20% of volcanoes are currently managed (mainly MEDCs)

- once scientists know, this information can be relayed to governments and media but is sometimes delayed

- evacuations are key to hazard management but require lots of planning and organising e.g. temporary housing and food

- relies on good communication

- maps enforced through legislation

- many LEDCs don't have maps/past records needed

- can be implemented when a volcanic hazards map is drawn up but this can be a difficult and lengthy process

- technical aid

- financial aid

- losses are shared throughout the whole tax-paying population

- support from MEDCs

- relief, rehabilitation and reconstruction

a large column of hot rock rising through the mantle whose heat causes the lower lithosphere to melt

a volcano built up of alternate layers of ash and lava

rock fragment and particles ejected during a volcanic eruption

Volcanic Explosivity Index, measures how violent an eruption is on a scale of 0-8

layer of the earth's atmosphere above the troposphere extending to about 50km above the earths surface

(literally 'glacier run') is a type of glacier outburst flood caused by the melting of ice during a volcanic eruption

chemical element found in the ash in Iceland 2010 that contaminated crops and water supplies for both humans and livestock

40 mph

Goma Volcano Observatory, scientifically monitors the volcanic activity and predicts levels of risk in the area

a sudden violent shaking of the ground, typically causing great destruction, as a result of movements within the crust or volcanic action

the point where the earthquake originated from beneath the crust, the point within the crust where the pressure release occurs

place on the earths surface immediately above the focus which receives the highest amount of energy

fastest seismic waves that move through solids and liquids, pushing and pulling the rock so the particles move parallel to the direction of the wave

slower and travel through solids only and move rock up and down or side to side perpendicular to the wave direction

travelling through the crust at a low frequency and are almost entirely responsible for the damage caused

love

Rayleigh

point at which energy is released 0-70km below the surface

point at which energy is released 300-700km deep

a measure used to measure the amount of energy released during an earthquake, usually on the Richter Scale

measurement of how often a recurring event occurs

a scale measuring the magnitude of an earthquake

- doesn't have an upper limit

- its logarithmic, each value has a amplitude 10x greater than the previous

- each value represents about 30x more energy released than the previous

scale used to measure impacts of earthquakes using observations

1-12

soil behaves like a liquid due to vibrations or water pressure within the mass of soil particles causing them to lose contact with one another

compressional waves because of the pushing an d pulling action they have

fastest surface wave that moves the ground side to side

surface wave that rolls along the ground like a wave on the ocean moving the ground both side to side and up and down

98%

conservative and subduction

- normal fault

- reverse fault

- strike slip

- found at diverging boundaries

- hanging wall moves down, foot wall moves up

- converging boundaries

- hanging wall moves up, foot wall moves down

- conservative plate boundaries

- horizontal movement

- based on effects above ground

- Mercalli Scale

- no mathematical basis - arbitrary ranking

- more meaningful to non-scientists

- eye-witness/observation surveys

- amount of seismic energy released

- seismographs

- single instrumentally determined value

- release of a build up of pressure b/w plates

- movement of a large amount of magma

- hot spots

- mining

- movements of large amounts of water

term referring to earthquakes that can cause tsunamis

distance between one crest/through and the next

distance between trough and crest

stage where water rushes inland, term also used as a measurement as to how far inland the water went

experienced before the tsunami, the ocean drops back and recedes, happens if trough reaches the land first

the arrangement of natural and artificial features under the ocean off the coast

objects such as boats, vehicles and structures like wooden buildings are lifted and carried in land by the wave

tearing buildings apart, washing away soil, undermining infrastructure foundations

battering by debris carried in the wave

- technological/media advancements

- climate change

- population increase, more people to experience more events

- many happening in MEDCs so more infrastructure is destroyed

- more countries become more developed

- population increases

- technology advancements

- preparation

- science understanding

a naturally occurring process or event which has the potential to cause loss of life or property

lessen the impact of the result

90%

75%

- unpredictability

- lack of alternatives

- changing dangers

- "it won't happen to me"

- costs vs. benefits

- wealth

- technical ability

- education

- organisation of society

- health

- age

- resilience

a reverse fault in which the plain is inclined at an angle equal to or less than 45 degrees

a massive earthquake training drill carried out by the Japan Self-Defence Force (JSDF) based around a 6.0 earthquake involving 18,000 participants in 22 towns

high speed bullet trains in Japan that were fitted with equipment allowing them to stop quickly if earthquakes tremors are detected

an advisory panel set up by the Japanese government in April 2011 which advise about how best to rebuild

the system was designed to reflect the needs and requests of affected communities and offers a range of measures to support reconstruction

British Red Cross opened an appeal within hours of the disaster with the key aims of emergency healthcare/first aid, distributing relief and kitting out 70,000 temporary homes

strategy for providing high ground for communities that lack natural/accessible high ground, residents evacuate vertically rather than horizontally

elevated land based islands have been designed to form entire towns in tsunami affected regions

- aircraft was in the air quickly surveying the areas needing relief quickly

- Fukushima Power Plant established a 20km evacuation zone

- emergency response teams were overstretched and inadequately supplied

- temporary accommodation was of poor quality e.g. no heating or electricity

- by November 2011, the reactors had been cooled and stabilised

- a month after the disaster, the gov. had set up the Reconstruction Design Council

- wiped 5-10% off the Japanese stock market, global concern they will struggle to recover

- port was operating at 68% capacity

shaking levels may be increased in an area, or amplified, because of the sub-/surface topography

United Nations Development Programme, works to eradicate poverty and help countries in need, after the Haiti 2010 earthquake they helped to improve the socio-economic impacts, education, HIV/AIDS, water supply and general health care

world's largest humanitarian agency fighting hunger, who have set up school meals programmes, cash for assets programmes, helped with emergency preparedness and nutrition

organisation with the goal of soliciting, collecting and otherwise fundraising to provide disaster relief

a system whereby any interior building element is designed to protect and evacuate the building population in emergencies such as earthquakes

vents in the earths surface that emit steam and gases such as CO2 and sulphur dioxide usually found along cracks and fissures

water becomes superheated below ground due to high pressure and temperatures of 100C+ and when it reaches the surface the drop in pressure allows it to vaporise creating steam often accompanied by a roaring sound

Valley of Ten Thousand Smokes in Alaska

formed after the eruption of Novarupta in 1912 leading to thousands of fumaroles erupting in the valley filling it with steam

location

constant

magma chamber

centuries

active volcanism

crystals

like fumaroles but emit sulphurous gases instead

a rare type of hot spring under pressure that intermittently releases hot water and steam

- cone geyser

- fountain geyser

- perpetual spouter

erupts from cone of siliceous sinter in a steady pattern

erupts from pools of water intermittently in intense eruptions

erupt continuously

- geographical location

- underground heat source

- plumbing system

a tube like hole that extends deep into the earths crust becomes filled with water due to porous rock allowing easy groundwater supply and the water deeper in the hole becomes superheated due to it being closer to the mantle until it begins to boil. some of the water is then forced upwards and the boiling water vaporises into steam which moves rapidly towards the surface forcing it and the water out of the tube in an eruption that lasts until all the water is out of the tube or the temp inside the tube drops below 100C. the systems then recharges and the process begins again.

Old Faithful in Yellowstone National Park, Wyoming, USA is a cone geyser that erupts every 45-125 minutes

naturally occurring springs that produce water typically warmer than that of the human body from the earths surface on a regular basis

pressurised

fountains

minerals

calcium

temperature

perfect for bathing or too hot to even enter

water becomes heated as it comes into contacts with magma and a high geothermal gradient may cause superheating

water becomes geothermally heated by percolating deep enough into the crust to reach heated rocks

Grand Prismatic Spring is largest in USA and third largest in the world and is surrounded by awesome colours due to the pigmented bacteria sue to the minerals present

depressions in areas of geothermal activity filled with boiling mud containing sulphurous gas bubbles that burst on reaching the surface

mud volcanoes

2

light grey

pink

iron compounds

20

surface water collects in an impermeable depression lined with clay and under the depression thermal water causes steam to rise through the rock which heats the collected water. Hydrogen sulphide gives the pool an odour and provides energy to the microbes to allow them to break it down into sulphurous acid which turns the rock into clay creating the mud.

Waiotapu is an active geothermal area in New Zealand home to many extrusive features

volcanoes made in different ways involving geo-excreted liquids and gases from the earth and have temperatures inside them that can be as low as freezing

10

700

carbon dioxide

nitrogen

methane

solids

acids

Azerbaijan has the largest concentration in the world with 400 some of which form semi-/permanent islands

decompaction occurs causing gases to be created at a higher rate meaning the mud becomes more buoyant. the pressure created by the mud inside the volcano is higher than that on the outside and so it erupts from fissures and cracks taking some gas with it