Tectonics Flashcards
Ash
The very fine particles of rock ejected during a volcanic eruption.
These particles form part of the tephra, which is a term for all sizes of
ejected volcanic material.
Asthenosphere
The part of the mantle, below the lithosphere, where the rock is semimolten
Benioff zone
The area where friction is created between colliding tectonic plates,
resulting in intermediate and deep earthquakes.
Collision plate
boundary
Where two plates move towards each other causing a very slow
collision which is likely to cause folding and faulting of crustal rocks
and the uplift of continental crust to form fold mountains.
Community
adaptation
People within communities, either whole or parts of settlements, work
together to change their way of life so that the impact of a tectonic
hazard event is not as hazardous.
Community
preparedness
People within communities, either whole or parts of settlements, work
together to change their way of life so that the impact of a tectonic
hazard event is not as hazardous
Conservative plate
movement
Where two plates meet and move alongside each other in a similar
direction or opposite direction, usually at different speeds. Friction
between the two plates is great and stresses and strains build up to
create shall earthquake foci.
Also transform plate boundary.
Constructive plate
boundary
Where two plates move in opposite directions, leaving a zone of
faulting and a gap into which magma from the asthenosphere rises.
Also divergent plate boundary.
Convection currents
Hot, liquid magma currents moving in the asthenosphere.
Convergent plate
boundary
Where two plates move towards each other and at the boundary the
denser oceanic plate (basaltic) is subducted beneath the less dense
continental plate (granitic), creating surface features such as a
trench, and deep features such as the Benioff zone.
Also destructive plate boundary.
Crustal fracturing
When energy released during an earthquake causes the Earth’s crust
to crack.
Epicentre
The point on the Earth’s surface directly above the focus of an
earthquake.
Focal depth
The depth at which an earthquake starts (focus). It is divided into
shallow, intermediate and deep. Shallow earthquakes have the
greatest impacts, as the seismic waves have not lost as much of their
energy by the time they reach the surface.
Focus
The point inside the Earth’s crust from which the pressure is released
when an earthquake occurs.
Geological structure
The arrangement of rock in layers, or folds and the joints and bedding
planes within them.
Hazard-management
cycle
A theoretical model of hazard management as a continuous fourstage cycle involving mitigation, preparation, response and recovery
Hazard profile
An analysis of different types of hazard, or actual events, based on a
range of criteria. This allows a useful comparison to be made.
Hazard-response
curve
*see Park model
Hot spot
Points within the middle of a tectonic plate where plumes of hot
magma rise and erupt.
Hydrometeorological
hazards
Natural hazards caused by climate processes (including droughts,
floods, hurricanes and storms).
Intra-plate
earthquakes
Earthquakes which occur far from plate margins.
L waves
The slowest seismic waves, which focus all their energy on the Earth’s
surface
Lahar
A mixture of meltwater from snow and ice on top of an active
volcano and tephra (volcanic material such as ash) from eruptions
that travels very quickly down existing river valleys, reaching some
distance away from the volcano.
Landslide
A mass movement of rock and soil down a steep slope under the
influence of gravity, perhaps triggered by an earthquake loosening
material
Land-use zoning
A process by which local government regulates how land in a
community may be used.
Lava flow
Molten magma that reaches the Earth’s surface is known as lava. It
will flow down the sides of a volcano until it cools and solidifies.
Basaltic lavas flow faster than andesitic lavas, for example, because
of the different velocities.
Liquefaction
When the violent shaking during an earthquake causes surface rocks
to lose strength and become more liquid than solid.
Lithosphere
The solid layer, made from the crust and upper mantle, from which
tectonic plates are formed.
Mega-disaster
When a major hazardous event becomes catastrophic and more
than a disaster. For example, the scale of the impacts are unusually
great or very sever with huge numbers of deaths, loss of buildings and
infrastructure, or long-lasting impacts on normal social and economic
systems.
Magnitude
The amount of energy releases by a tectonic event. For earthquakes
this is best measured on the Moment Magnitude Scale (MMS) and for
volcanoes the Volcanic Explosivity Index (VEI).
Mass movement
The downward movement of material under the influence of gravity.
It includes a wide range of processes such as rockfalls, landslides and
solifluction
Mercali scale
An earthquake intensity scale based on 12 levels of damage to
areas.
Modify loss
Reduce the impact of losses experienced from a tectonic hazard, for
example by insuring belongings and property.
Mitigation
Action to reduce the impacts of an event.
Modify the event
Alter the natural hazards itself in order to change its likely impacts.
Earthquakes cannot be changed, but some volcanic activity can be
modified, such as by diverting lava flows
Modify vulnerability
Vulnerability is a key factor in determining the impact of a hazard, so
making people less vulnerable will reduce the scale of a disaster.
Moment Magnitude
Scale (MMS)
The most accurate earthquake magnitude scale, it measures the
total energy released by an earthquake.
Multiple-hazard zone
e An area that is at risk from multiple natural hazards such as hurricanes
and earthquakes.
Natural hazard
A physical geographical event, tectonic, hydrological or
meteorological, which has a negative impact on people through
causing injury or deaths, loss of property, or disruption to the normal
way of life.
P waves
The fastest seismic waves which travel through both solids and liquids
Park model
Shows how a country or region might respond after a hazard event.
Pressure and release
(PAR) mode
A tool used to work out how vulnerable a country is to hazards.
Rapid onset
A hazard that happens very quickly with no or little warning e.g. an
earthquake
Resilience
The ability of a community to resist the impacts of a hazard by
adapting and recovering.
S waves
Seismic waves which only travel through solids and move with a
sideways motion.
Sea floor spreading
The movement of the oceanic crust away from a constructive plate
boundary, as recorded by the magnetic stripes in the basaltic rock
(palaeomagnetism)
Slab pull
When newly formed oceanic crust sinks into the mantle, pulling the
rest of the plate further down with it
Sub-aerial processes
The processes of weathering and mass movement.
Slow onset
A hazard that happens very slowly with plenty of evidence and
warning, such as a drought.
Subduction zone
The area in the mantle where a tectonic plate melts.
Transform fault
A fault created on a large scale when two plates slide past each
other.
Volcanic Explosivity
Index (VEI)
The scale used to measure the magnitude of a volcanic eruption.
Water column
displacement
The movement of a volume of seawater above the point at which
the seabed was moved up or down by an earthquake, such as a
thrust.
