Geography - TECTONICS

Accretion wedge

The accumulation of material at the point of subduction.

Aseismic buildings

Buildings designed to withstand or minimise destruction during an earthquake.

Asthenosphere

The soft layer of the mantle on which the tectonic plates move

Continental crust

Crust that forms the continents of the lithosphere, on average 35km thick

Continental drift

The movement of tectonic plates, due to varying weights of crust. It was originally thought that convection currents caused the movement of the plates, but now Slab Pull is thought of as the primary driving force.

Convection currents

The circulation of magma within the mantle (asthenosphere). Magma is heated by radioactive processes in the core and cools at the surface, and so circulates between the two places.

Degg's Model

This model shows that a hazard becomes a disaster if it affects a vulnerable population.

Epicentre

the point on the Earth's surface directly above the focus of an earthquake

Focus

The place in the crust where the pressure/seismic energy is released.

Hazard mitigation cycle

The sequence of governance of a natural hazard: monitoring & prediction, mitigation, preparedness.

Hot spot

volcanoes found away from the plate boundary due to a magma plume

Jokulhaup

A sudden glacial flood caused by a glacier on top of or near a volcano melting due to the heat from the eruption.

Lahar

flow of mud and debris

Lithosphere

A rigid layer made up of the uppermost part of the mantle and the crust.

Love waves

Surface waves that shear the ground in a horizontal direction. Can only travel through solids. Third to arrive.

Mid ocean ridge

An undersea mountain chain where new ocean floor is produced; a divergent plate boundary.

Moment magnitude scale

A measure of an earthquake's energy released, considered the most accurate measure.

Oceanic crust

Crust, usually thinner than continental crust, that forms the sea floor. It is on average 7km thick.

Paleomagnetism

The alternating polarisation of new land created. As magma cools, the magnetic elements within will align with the Earth's magnetic field, which can alternate over thousands of years

Park's model

A model describing the decline and recovery of a country over time, following a natural disaster.

Partial melting

Elements within the lithosphere have different melting points, and so rock is partially melted, partially solid.

Primary waves

1st wave, P, travels the fastest, compressional/longitudinal, move through solids, liquids, and gases

Pyroclastic flow

the flow of ash, cinders, bombs, and gases down the side of a volcano during an explosive eruption

Rayleigh waves

A surface wave (type of L-wave) that reaches the surface with up and down movement

Richter scale

a logarithmic scale of 1 to 10 used to express the energy released by an earthquake

Secondary waves

seismic wave that moves rock particles at right angles to the direction of the wave (transverse)

Seismic waves

The energy released during an earthquake, in the form of Primary, Secondary, Love and Rayleigh Waves.

Slab pull

Slab pull occurs where older, denser tectonic plates sink into the mantle at subduction zones. As these older sections of plates sink, newer and less dense sections of plate are pulled along behind.

Ridge push

the process in which new material at a ridge or rift pushes older material aside, moving the tectonic plates away from the ridge

Subduction

The process by which oceanic crust sinks beneath a deep-ocean trench and back into the mantle at a convergent plate boundary.

Tsunami

.Initial vertical water displacement (often from a submarine earthquake) creates waves, with large destructive power.

Volcanic explosivity index

An intensity scale that rates a volcano's destructiveness and explosive power on the amount of matter it ejects during an eruption.

Volcanic island arc

A series of volcanoes that are formed consecutively, as a tectonic plate moves across a magma plume.

Wadati-benioff zone

A region of the subducting plate, most affected by pressure and friction, where most destructive margin earthquakes originate.

Convergent boundary

A tectonic plate boundary where two plates collide, come together, or crash into each other.

Divergent boundary

A plate boundary where two plates move away from each other.

Conservative boundary

Where two tectonic plates slide past each other, but where crust is neither formed or destroyed

How are deep ocean trenches formed

denser oceanic plate subducts beneath the continental plate- trenches form where this happens

formation of fold mountains

Fold mountains are found on plate boundaries where two plates have collided. As the two plates push against each other, the pressure forces the land to buckle upwards into folds.

collision margin

2 CONTINENTAL plates move TOWARDS; fold up to form mountains, e.g. Himalayas

Rift valley

steep sided valley formed when 2 continental plates move apart

fault

a crack in the earth's crust

transform fault

tectonic plates sliding past one another (ex. San Andreas fault).

hypocentre

same thing as the focus

body waves

seismic waves that travel through the Earth's interior - p and s waves

surface waves

seismic waves that travel along the Earth's surface - love waves

seismometer

Instrument used to measure horizontal or vertical motion during an earthquake.

seismic moment

energy released by an earthquake at the moment it occurs

modified mercalli intensity scale

A scale with values from I to XII used to characterize earthquakes based on damage.

intensity

an earthquakes effect on people, structures and the natural environment

magnitude

Measure of the energy released during an earthquake

primary effects of an earthquake

ground shaking , crustal fracturing

impacts of ground shaking

causes infrastructure to collapse , killing , injuring or trapping people

crustal fracturing

When energy released during an earthquake causes the Earth's crust to crack

secondary effects of an earthquake

• liquefaction

• landslides and avalanches

• tsunami

liquefaction

occurs when an earthquake's violent shaking suddenly turns loose, soft soil into liquid mud causing buildings and roads to tilt/sink

how does earthquake cause landslides and avalanches

ground shaking places stress on slopes so they fail

aftershocks

a smaller earthquake following the main shock of a large earthquake.

predicting earthquakes

currently no method to accurately predict when or where an earthquake will strike

forecasting earthquakes - precursors (warning signs)

-Mapping earthquakes that happened in the past and notice patterns.

-Detecting changes in the shape of Earth's surface

-Using satellites to monitor Earth's surface for movement and collect data to compare over time.

-foreshocks

Volcano primary hazards

• Lava flows

• Pyroclastic flows

• Ash and tephra fall

• Gas eruptions

Volcano secondary hazards

• Lahars

• Jokulhlaup

Jokulhlaup

GLOF'S caused by snow and ice in glacier melting due to heat from volcanic eruption

Volcanic explosivity index (VEI)

logarithmic scale, 0 to 8, measured on amount and height of volcanic material ejected, duration of eruption

predicting volcanic eruptions

small earthquakes - as magma rises it breaks the rock

volcano surface swelling - magma builds pressure

changes to tilt (slope angle of volcano) as magma moves

How tsunamis form

energy released during EQ causes sea floor to lift displacing water column above, forming tsunami waves

tsunami impacts

• Destruction of land and infrastructure

• Injury and death

• Contaminated drinking water - inland flooding

• Disease

-Wash soil away

predicting tsunami

The inability to predict earthquakes also means there is little way of predicting tsunami.

tsunami early warning systems

DART system uses seabed sensors and surface buoys to monitor changes in sea level and pressure

hazard risk formula

Risk = hazard x vulnerability / capacity to cope

human factors affecting vulnerability and resilience

local and national governance and political conditions

economic and social conditions

physical and environmental conditions

examples of governance and political conditions (regarding tectonic hazards)

building codes/regulations enforcement/existence

infrastructure quality - recovery speed

disaster preparedness plans

emergency services efficiency

communication systems efficiency

education and practised hazard responses

corruption

examples of economic and social conditions

wealth - affects peoples ability to protect themselves

corruption

poor quality housing

poor health care

physical and environmental conditions

high population density eg slums

rapid urbanisation - poor quality housing

accessibility eg nepal eq

disaster pressure and release model

looks at underlying causes of the disaster. processes creating vulnerability (root causes, dynamic pressures, unsafe conditions) interacting with hazards

hazard profiles

A hazard profile is a diagram that shows the main characteristics of different types of tectonic hazards. You could use this to show the characteristics of one natural hazard or you could place multiple profiles on so you can compare and contrast. magnitude, speed of onset, duration, areal extent, spatial predictability,frequency

multiple hazard zones

Places where a number of physical hazards combine to create an increased level of risk for the country and its population.

Hydrometeorological Hazards

Natural hazards caused by climate processes (including droughts, floods, hurricanes and storms)

hazard management cycle

Model for measuring hazard management made up on 4 stages: mitigation, preparedness, response and recovery

park model (hazard-response curve)

Park's hazard-response curve is a model that can be used to assess/compare how well places respond/recover after a hazard event.

hazard mitigation

Strategies meant to avoid, delay or prevent hazard events

hazard adaptation

Strategies designed to reduce the impacts of hazard events

hazard mitigation strategies egs

land use zoning

diverting lava flows (mostly ineffective)

GIS mapping

hazard resistant design and engineering defences

hazard adaptation strategies egs

high tech monitoring eg GIS, early warning systems, satellite and mobile communication

crisis mapping - uses crowd sourced info to map areas struck by disaster

modelling hazard impact

public education

types of aid

emergency

short term

long term

key players in managing loss

• Aid donors

• NGOs

• Insurance

• local Communities

Volcanic eruptions have the greatest magnitude at which type of plate boundary ? Why ?

Destructive/convergent - subduction of old oceanic lithosphere into mantle produces andesitic lava with higher silica content and higher percentage of volatile gases therefore creating more violent eruptions

What are partial wet melts in terms of volcanic eruptions on island arcs?

Water bearing sediment subducted into mantle. As temperatures rise , water released and amount of volatiles increased so scale of hazard increased eg Montserrat

Forecasting

When , where and likely magnitude

Prediction

Where