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
