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Dynamic Landscapes Topic 1: Tectonic Processes and Hazards Key Terms
All key term definitions can be found in the Geography for Edexcel textbook.
Key term
Natural hazard
Natural disaster
Seismic hazards
Asthenosphere
Lithosphere
Oceanic crust
Continental crust
Mantle plume
Palaeomagnetism
Convection
Slab pull
Convergent
boundary
Definition
A naturally occurring process or event that has the
potential to affect people.
A major natural hazard that causes significant social,
environmental and economic damage.
Generated when rocks within 700km of the Earth’s surface
come under stress that they break and become displaced.
The part on which tectonic plates ‘float’
The surface layer of the Earth is a rigid outer shell
composed of the crust and upper mantle. It is broken up
into huge sections, which are tectonic plates.
A thin dense layer (6-10km thick), which lines the ocean
floors.
An older, thicker layer (usually 45 – 50km thick), which
makes up the Earth’s landmasses. It is less dense than
oceanic crust.
Volcanoes can also form in the middle of plates, where
plumes of hot magma rise upward and erupt onto the sea
floor (at what is called a hotspot).
The study of past changes in the Earth’s magnetic field
(determined from rocks, sediment or archaeological
records).
In the mantle convection, heat produced by decay of
radioactive elements in the earth’s core heats the lower
mantle – creating convection currents. These hot, liquid
magma currents are thought to move in circles in the
asthenosphere – thus causing plates to move.
Newly formed oceanic crust at mid oceanic ridges becomes
dense and thicker as it cools. This causes it to sink into the
mantle under its own weight – pulling the rest of the plate
further down with it forming deep ocean trenches.
Where two plates collide also known as destructive
margins.
Divergent boundary
Where two plates move apart also known as constructive
margins.
Conservative
Where two plates slide past each other, also known as
boundary
transform margins.
Locked fault
A fault that is not slipping because of frictional
resistance on the fault is greater than the sheer stress
across the fault, that is, it is stuck.
Fold Mountains
As two continental plates collide, the plates are folded
and slowly push up, forming chains of Fold Mountains.
Sea floor spreading These are formed when hot magma is forced up from the
asthenosphere and hardens – forming new oceanic crust.
The new crust pushes the tectonic plates apart in a
process called sea floor spreading.
Island arcs
Volcanoes created as a result of subducted plates. These
volcanoes rise above sea level to form separate island
volcanoes, which are usually found in a curved lines.
Subduction
New crust is being created in one place, it is being
destroyed in another by subduction. As two oceanic
plates (or an oceanic and a continental plate) move
towards each other, one slides under the other into the
mantle – where it melts in an area known as the
subduction zone.
Intensity
A measure of the ground shaking. It is the ground
shaking that causes building damage and collapse, and all
the loss of life from the hazard.
Magnitude
The magnitude of an earthquake is related to the amount
of movement, or displacement, in the fault, which is in
turn a measure of energy release.
Benioff zone
The friction created between colliding plates (and
subduction) causes intermediate and deep earthquakes in
an area called the Benioff zone.
Primary waves,
Primary (P) waves – these are the fastest and first to
secondary waves
reach the surface. They travel through both solid and
and surface love
liquid.
waves
Secondary (S) waves – these are slower. They only travel
through solids.
Surface love (L) waves – these are the slowest but cause
the most damage shaking the ground from side to side.
They are larger and focus all their energy on the Earth’s
surface.
Seismic waves
Moment Magnitude
Scale (MMS)
Focus or
hypocentre and
epicentre
Intra-plate
earthquakes
Primary and
secondary effects
Crustal fracturing
Soil Liquefaction
Landslide and
avalanches
Tsunami
Water displacement
Water Column
Gas eruptions
Pyroclastic flows
Shock waves released by tectonic movement and
measured using a seismometer.
The generally preferred scale to measure magnitude
(energy released at the epicentre). It measures total
energy released by an earthquake the moment it occurs.
Focus or hypocentre - The point within the ground where
the strain energy of the earthquake stored in the rock is
first released. The distance between this and the
epicentre on the surface is called the focal length.
Epicentre – the location on the Earth’s surface that is
directly above the earthquakes focus.
Earthquakes which occur in the middle interior of
tectonic plates and are much rarer than boundary
earthquakes.
Primary – happen as a direct result of a hazard.
Secondary – happen as an indirect result of a hazard.
When energy released during an earthquake causes the
Earth’s crust to crack.
Secondary hazard -The process by which watersaturated material can temporarily lose normal strength
and behave like a liquid under the pressure of strong
shaking. Occurs in saturated soils.
Secondary hazard - The ground shaking places stress on
the slopes, so they may fall resulting in landslides, rock
slide, mudslide and avalanches.
Secondary hazard - A series of larger than normal
waves, which are caused by a volcanic eruption or
underwater earthquakes.
The energy released during an earthquake causes the
seafloor to uplift – displacing the water column above.
This displaced water forms a tsunami wave.
The area of seawater from the surface to the sea floor.
Magma contains dissolved gases that are released into
the atmosphere during a volcanic eruption.
A mixture of dense hot rock, lava, ash and gas ejected
from a volcano.
Tephra and ash fall
Lahars
Jökulhlaups
Volcanic Explosivity
Index (VEI)
Resilience
Risk
Vulnerability
Development
Inequality
Governance
Mercalli
Tectonic Hazard
profile
Tephra are pieces of volcanic rock and ash that blast
into the air during volcanic eruptions.
Secondary hazard - Masses of rock, mud and water that
travel quickly down the sides of a volcano.
Secondary hazard - The heat of a volcanic eruption can
melt snow and ice in glaciers – causing heavy and sudden
floods caused jökulhlaups or glacial outburst floods.
This is used to describe and compare the size or
magnitude of volcanic eruptions. The VEI uses a scale
from 0 (non-explosive) to 8 (extremely large)
The ability to protect lives, livelihoods and
infrastructure from destruction, and to restore an area
after a natural hazard has occurred.
The exposure of people to a hazardous event. More
specifically, it is the probability of a hazard occurring
that leads to the loss of lives and/or livelihoods.
The ability to anticipate, cope with, resist and recover
from a natural hazard.
Linked to and improving society, enabling people to
achieve their aspirations. It includes the provisions of
social services, acquisition of economic assets, improved
productivity and reducing vulnerability to hazards. Loew
levels of development are closely associated with high
levels of risk and vulnerability to natural disasters.
An unfair situation or distribution of assets and
resources. It may be sued when people or nations and
non-state players have different levels of authority,
competence and outcomes.
The sum of many ways individual, institutions, public and
private manage their common affairs. It is a continuing
process through which conflicting or diverse interests
may be accommodated and co-operative action may be
taken.
A scale which measure earthquake intensity, which takes
observations from people who experienced the
earthquake and puts them on a scale of I (hardly
noticed) to XII (catastrophic).
A technique used to try to understand the physical
characteristics of different types of hazards.
Hazard Mitigation
Hazard adaptation
Multiple-hazard
zones
Land use zoning
Spearman’s Rank
correlation
Hydrometeorological
Precursors
Pressure and
Release (PAR)
model
Hazard
management cycle
The Park Model
Early Warning
systems
Hazard risk
equation
Strategies meant to avoid, delay or prevent hazard
events (e.g. land use zoning, diverting lava flow, GIS
mapping and hazard resistant design and engineering).
Strategies designed to reduce the impacts of hazard
events (e.g. high-tech monitoring, public education and
community preparedness).
An area at risk from multiple hazards, and is vulnerable.
Process by which local government regulates how land in
a community may be used.
A statistical method used to test the strengths of a
relationship between two variables. +1 indicates a
perfect correlation, -1 indicates a negative correlation
and 0 indicates no correlation.
Natural hazards caused by climate processes (including
droughts, floods, hurricanes and storms).
Warning signs that may suggest a hazard is about to
happen.
PAR model looks at the underlying causes of a disaster.
Looking at processes which create vulnerability (root
cause, dynamic pressures and unsafe conditions) and the
hazard itself.
A process in which governments and other organisations
work together to protect people from natural hazards
that threaten their communities. The different stages in
the hazard management cycle (response, recovery,
mitigation, preparedness).
The Park hazard-response curve is a model that shows
how a country might respond after a hazard event.
In place in both the Pacific and Indian Oceans. These
systems use seismic sensors to detect underwater
earthquakes.