Tectonic hazards Flashcards
what is accretion wedge
-the accumulation of material at the point of subduction
what is aseismic building
buildings designed to withstand or minimise destruction during an earthquake
what is the asthenosphere
the upper mantle layer of the earth . its semi molten and approximately 200km wide
what is ash
fine particles and dust ejected during an eruption , which can remain airborne as clouds or accumulate on the ground
what is the continental crust
crust that forms the continents of the lithosphere , on average 35km thick
what is continental drift
the movement of tectonic plates , due to varying weights of crust . it was originally though convection currents moved plates but now slab pull is though of as the primary driving force.
what is Degg’s model
model shows that a hazard becomes a disaster if it affects a vulnerable population.
what is the epicentre
the point on the surface , directly above the earth quakes origin
what is the focus
the place in the crust where the pressure / seismic energy is released
what is the hazard mitigation cycle
the sequence of governance of a natural hazard: monitoring and prediction, mitigation, preparedness.
what is a hot spot
volcanoes found away from the plate boundary , due to magma plume closer to the surface.
what is Jokulhaup
a sudden glacial flood caused by a glacier on top of or near a volcano melting due to heat from the eruption
what is a lahar
a flow of mud and debris
what is the lithosphere
the upper crust of the earth.
what is a love wave
a surface earthquake wave with horizontal displacement
what is a mid ocean ridge
Partin oceanic plates at a constructive plate boundary creates a ridge , with new land at the base of the oceanic valley
what is the oceanic crust
crust, usually thinner than continental crust , that forms the sea floor . it is on average 7km thick
what is paleomagnetism
the alternating polarisation of new land created.
as magma cools, the magnetic elements within will align with the earths magnetic field , which can alternate over thousands of years.
what is the park model
a model describing the decline and recovery of a country over time, following a natural disaster
what are primary waves
an earthquake wave causing compressions within the body of the rock
what is pyroclastic flow
a mixture of gases and rock fragments , at high temperatures travelling at rapid speeds.
what is a Rayleigh wave
a surface earthquake wave causing both horizontal vertical displacement
what is a Richter scale
a logarithmic measure of earthquakes intensity.
what is a secondary wave
an earthquake wave causing vertical displacement within the body of rock
what is a seismic wave
the energy relesed during an earthquake in the forms of primary , secondary , love and Rayleigh waves
what is slab pull
the force contributing to the movement of tectonic plates . slab pull is due to the weight of the plate.
what is subduction
oceanic plate is forced below continental plate , due to the oceanic plate being more dense than the continental plate.
what is a tsunami
initial vertical water displacement creates waves, with large destructive power.
what is the volcanic explosivity index
a measure of magnitude of a volcanos eruption
what is the wadati-benioff zone
a region of the subducting plate , most affected by pressure and friction, where most destructive margin earthquakes originate
what is a destructive plate boundary
Continental and oceanic:
● Denser oceanic plate subducts below
the continental.
● The plate subducting leaves a deep
ocean trench.
● Built up pressure from the melting
plate cause explosive volcanoes
bursting through the continental plate
what is a constructive boundary
Oceanic and oceanic:
● Magma rises in between the gap left by
the two plates separating, forming
new land when it cools.
● Less explosive underwater volcanoes
formed as magma rises.
● New land forming on the ocean floor by
lava filling the gaps is known as sea
floor spreading (as the floor spreads
and gets wider).
Continental to continental:
● Any land in the middle of the separation
is forced apart, causing a rift valley.
● Volcanoes form where the magma
rises.
● Eventually the gap will most likely fill
with water and separate completely
from the main island.
what is ridge push
The slope created when plates move apart has
gravity acting upon it as it is at a higher
elevation. Gravity pushes the plates further
away, widening the gap (as this movement is
influenced by gravity, it is known as
gravitational sliding).
what plate boundary does earthquakes occur at
The most powerful earthquakes occur at destructive and conservative
boundaries
what plate boundary does Tsunami occur at
occur at destructive
boundaries
what plate boundary does Volcanic hazards occur at
The world’s active volcanoes are found at constructive and destructive plate
boundaries, and at hotspots
what is the equation for risk
Risk = hazard x vulnerability / capacity to cope
what is the PAR model
Root causes - dynamic pressures - unsafe conditions- disaster( risk - hazard x vulnerability) - natural hazard
what are the steps to the park’s model
step 1 - Relief ( hours-day)
Immediate local response ,foreign aid
step 2- Rehabilitation ( days or weeks )
Services ,Temporary shelters ,hospitals set up Food and water
step 3-Reconstruction ( weeks - years)
Restoring , Infrastructure , future event
What did believe Alfred Wegener 1912
All continents were once joined in a super continent called Pangea. Continental drift caused Pangea to move apart.
What did say Holmes 1929
Convection in the mantle is the force behind continental drift.
What is a Volcanic Hotspot
An area in the mantle from which heat rises as a hot thermal plume from deep in the earth.
What is the lithosphere?
the rigid outer part of the earth, consisting of the crust and upper mantle.
What is the asthenosphere?
the upper layer of the earth’s mantle, below the lithosphere.
Factors affecting earthquake intensity
*Duration of locked fault
*Depth of hypo-centre
*Timing & intensity of seismic waves
What Is basaltic magma
magma that has low viscosity and low silica and gas content; eruption is non-explosive
Rhyolitic Magma
magma that has a high viscosity and high silica and gas content; eruption tends to be very explosive
Explain a Composite volcanoes
large, steep-sided volcanoes that result from explosive eruptions of andesitic and rhyolitic lava and ash along convergent plate boundaries. Poses most danger to Hunan life.
Explain a Shield Volcanoes
Gently sloping mountains formed by thin, runny lava. Frequently eruptive.
What is the “Benoiff zone”
A dipping flat zone where earthquakes are produced by the interaction of a submerging oceanic crustal plate with a continental plate.
What is a fault
A fracture in the rocks that make up the earth’s crust
What is an epicentre?
The point on the Earth’s surface straight above the focus.
What are Secondary Hazards of Earthquakes
*liquefaction
*landslides
*tsunamis
What is soil liquefaction?
When an earthquake causes the ground to shake to the point of making it liquid.
What is a landslide?
the sliding down of a mass of earth or rock from a mountain or cliff.
What is a tsunami?
Convection currents in the mantle move plates towards each-other. Pressure builds up as the denser plate is forced beneath the overriding plate. An EQ occurs. Water is displaced creating a wave which spreads out. As wave approaches shore, height increases and wave length shortens
What are the Primary Hazards of a Volcano?
*pyroclastic flow
*tephra
*volcanic gases
*lava flows
What is tephra?
rock fragments and particles ejected by a volcanic eruption
What are volcanic gases?
Water, sulphur dioxide, hydrogen and CO2.
What are the secondary impacts of a volcano?
*Jokulhlaups
*Lahars
What are Jokulhlaups?
Sudden, violent and short-lived increase in discharge of glacial meltwater
What is community resilience?
The ability to cope with a hazard using your own resources.
Reasons Cumulative Act Effect Model
Acknowledges that pre-existing vulnerabilities in society can exacerbate the impacts of a hazard and make it into a disaster
Governance
The sum of the many ways individuals and institutions, public and private, manage their common affairs
what are the three ways of managing a tectonic hazard.
Modify the Event,
Modify the Vulnerability, Modify the Loss.
Explain Modifying the event .
we can’t control seismic activity. how can control the design of buildings through civil engineering using micro and macro methods.
Micro - strengthening individual buildings and structures.
Macro- large scale support and protective measures designed to protect whole communities.
what are the different types of modifications in modifying the event.
- Land use zoning
- Resistant buildings
- Tsunami defences
- Lava diversion
what are the advantages and disadvantages of Land use zoning
+ low cost
+reduced vulnerability
-stops economic
- development on some high value land
- strict enforcement requirement .
what are the advantages and disadvantages of Resistant buildings
+ can help prevent collapsing
+protects people and property.
- high cost for larger buildings
- Low income families cannot afford this.
what are the advantages and disadvantages of Tsunami defences
+Reduces damages
+ Provides security
- Very high cost
-Doesn’t look nice
- Can be overtopped
what are the advantages and disadvantages of Lava diversion
+ Diverts lava away
+ low cost
-only works for low VEI lava
what are the different modifications for modify vulnerability.
Hi tech scientific monitoring
Community preparedness and education .
Adaptation
