Tectonic Processes and Hazards Flashcards
Define natural hazard
They are a natural/geophysical event that has the potential to threaten both life and property.
Define disaster
This is when the natural hazard actually happens and harms people, the environment or the economy
Define vulnerability
How susceptible an area or population is to damage from natural hazard events
What are the factors that influence the vulnerability of a population?
- Population density
- Building quality
- Level of urbanisation
- Wealth
- Quality of emergency/ health services
- Level of education
- Level of corruption
What are the 4 stages of the hazard management cycle?
Response -> recovery -> mitigation -> preparedness
What are the stages of Park’s model (aka the disaster response curve)?
Preparation -> response -> reconstruction -> mitigation
What is the hazard risk equation?
Risk = (hazard x vulnerability)/capacity to cope
What are the headings under vulnerability in the PAR model?
- Root cause e.g. limited access to resources
- Dynamic pressures e.g. lack of education
- Unsafe conditions e.g. fragile economy
Define asthenosphere.
The part of the mantle below the lithosphere where rock is semi-molten.
Define Benioff zone.
The are where friction is created between colliding tectonic plates, resulting in intermediate and deep earthquakes.
Define collision boundary.
When two continental plates collide forming fold mountains as there is no subduction.
Define constructive boundary.
When two plates spread apart causing magma to be released and new land being made.
Define conservative bounday.
When plates move alongside each other in the same or different direction, causing friction to build.
Define convection.
Heat from the core makes magma in the mantle rise towards the crust. As the hot current nears the crust, it begins to cool and sink back towards the core. As the magma sinks, it drags the plates across the surface of the Earth.
What is the core?
The extremely hot centre of the Earth.
What is the crust (continental and oceanic)?
The thinnest chemical layer and the outer layer of the Earth.
Oceanic is denser, made of basalt and thinner while continental is less dense, made of granite and thicker.
What is Degg’s model?
Shows the interaction between hazards and human vulnerability.
Claims disasters only occur when a vulnerable population is exposed to a hazard
Define destructive boundaries.
When the denser oceanic crust sinks beneath the continental crust.
Define epicentre.
The point on the Earths surface directly above the focus of an earthquake.
Define the focus.
The point inside the Earths crust from which pressure is released when as earthquake occurs.
Define geophysical hazard.
A hazard caused by land processes on a large or local scale and include tectonic or geomorphological hazards.
Define governance.
The organisation that controls/oversees a country.
What is a hazard profile?
A diagram that shows the main characteristics of a tectonic hazard.
A single hazard could be plotted or several could be to compare events.
They can help governments develop disaster plans.
Define HILP
High impact Low probability.
Define hotspot.
Points within the middle of a tectonic plate where plumes of hot magma rise and erupt.
Define hydrometeorological hazard.
Natural hazards caused by climate processes (e.g. droughts, floods and storms)
Define intensity.
The measurable amount of a property e.g. force
Define jökulhlaups.
Glacial outburst floods.
Define lahar.
Volcanic mud slides.
Define lava.
Molten or partially molten rock.
Define land-use zoning.
A process by which local government regulates how land in a community may be used.
Define lithosphere.
The solid layer, made from the crust and upper mantle, from which tectonic plates form.
Define liquefaction.
When the violent shaking during an earthquake causes surface rocks to lose strength and become more liquid than solid.
Define logarithmic.
A count that goes up the same amount each time
Define a love wave.
The fastest surface wave, has the longest wavelength and moves side to side while going forward.
Define magma.
Extremely hot liquid & semi-liquid rock located in the mantle.
Define magnitude.
A number that characterises the relative size of a tectonic event.
Define mantle.
The second chemical layer of the Earth that is made of molten magma (iron, magnesium and periodite)q
Define mantle plume.
A rock upwelling from the mantle that is extremely hot. Causes most hot spots.
Define mega-disaster.
A natural disaster of immense magnitude or one that causes severe damage.
Characterised by 2000+ deaths or 200,000+ homeless etc,
What is the Mercalli scale?
A scale of earthquake intensity ranging from I to XII.
Define mesosphere.
The third mechanical layer of the earth. It is solid due to pressure.
Define mid-oceanic ridge.
When two oceanic plates move apart in the ocean.
Define moho.
The boundary between the crust and the mantle.
What is the moment magnitude scale.
A way to quantify an earthquake’s magnitude.
Define multiple hazard zone.
An area that is at high risk from multiple natural hazards.
Define ocean trench.
Long, narrow depressions on the seafloor as a result of tectonic activity at convergent plate boundaries.
Define palaeomagnetism.
The study of past changes in the Earths magnetic field.
What is the Park’s Model?
It shows how a country or region might respond after a hazard event.
What is the Pressure and Release Model (PAR)?
A tool used to work out how vulnerable a country is to hazards.
The ‘release’ idea represents the reduction of disaster via relieving pressure to reduce vulnerability
Define primary wave.
The fastest body wave which arrives first. It moves through rock and fluid in an accordion movement.
Define a pyroclastic flow.
A flow of tephra and volcanic rock
Define Rayleigh wave.
The slowest, last to arrive wave. Moves only through the crust. Responsible for the movement and shaking felt. Rolling movement.
Define resilience.
The ability to cope and recover
Define rheid.
Partially liquid.
Define ridge-push.
Where lava hardens between ridges push the plates apart.
Define risk.
The probability of a hazard occurring that leads to loss of life or livelihoods
Define sea floor spreading.
Mid-oceanic ridges form new crust when magma cools which pushes plates apart.
Define secondary wave.
The slowest main body wave that arrives second. It only moves through the solid rock and moves up and down.
Define seismic gap theory.
Predicting the magnitude of an earthquake via its frequency.
Define seismic wave.
A wave of energy that travels through the earth.
What is a seimometer?
Measures the movement of the ground to measure an earthquake/volcano
What is a shield volcano?
A short, effusive volcano with effusive explosions that are made only of lava.
Define slab-pull.
When newly formed oceanic crust sinks into the mantle, pulling the rest of the plate further down.
What is a stratovolcano?
A tall, violent volcano of infrequent eruptions made of ash and lava.
Define subduction.
The area in the mantle where a tectonic plate melts.
Define surface wave.
First surface wave that travels through the surface
Define tephra.
Solidified magma (sizes from ash to lava bombs)
Define tsunami.
A sequence of extreme waves due to water displacement.
What is the volcanic explosivity index (VEI)?
It measures the size of explosive volcano eruptions from 0 (non-explosive) to 8 (mega-colossal) and is logarithmic (every increase is by a factor of 10)
Several factors are measured:
- High or eruption column
- Amount of volcanic material
- Duration of explosion
What are some examples of volcanoes measured under VEI?
1 is a Hawaiian style small gentle eruption
5 is a very large eruption with a high eruption column from a composite cone volcano e.g. Mount St. Helens, 1980
The largest ever recorded only reached 8 on the VEI scale
Define volcano.
An opening in the crust that allows lava, ash and gases to escape from magma chamber allow.
Who was Alfred Wegener?
He came up with the Continental Drift Theory in 1912
What are the mechanical layers of the earth?
- Lithosphere
- Asthenosphere
- Mesosphere
- Outer Core
- Inner Core
What are the chemical layers of the earth?
- Crust
- Mantle
- Core
How does mantle convection work?
- Heat from the Earth’s core, caused by radioactive decay, rises to produce convection currents in the molten mantle.
- The lithosphere is broken up into fifteen tectonic plates which ‘float’ on the asthenosphere below.
- Mantle convection causes magma to move, causing the plates to move, bringing them into contact at plate boundaries
What is ridge push?
A plate tectonic process where rising magma in the asthenosphere diverges and pushes plates apart
What is slab pull?
A plate tectonic process where sinking magma, along with gravity, help drag plates down into the mantle.
What is subduction?
A plate tectonic process that is closely related to slab pull at destructive or convergent plate boundaries
What is sea floor spreading?
A plate tectonic process which occurs at constructive as a result of rising magma in the asthenosphere and creates mid-oceanic ridges, as the sea floor spreads apart.
What were the 6 sets of evidence of the Continental Drift Theory?
- Jigsaw Fit
- Geological Fit
- Tectonic Fit
- Glacial Deposits
- Fossil Evidence
- Climatology
What is jigsaw fit?
One set of evidence for the continental drift theory where several continents seem to have a jigsaw like fir, especially South America and Africa. This suggest they were once part of a supercontinent called Pangea.
