Tectonic Processes and Hazards - Key Term Glossary Flashcards
Ash
The very fine particles of rock ejected during a volcanic eruption. These volcanic particles form part of tephra, which is a term for all sizes of ejected volcanic material
Asthenosphere
The part of the mantle, below the lithosphere, where rock is semi-molten
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. e.g. the Himalayas
Community adaptation/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 shallow earthquake foci
*Also known as a transform plate boundary
Divergent 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 known as a constructive 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 known as a 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 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 four-stage 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
Hot spot
Points within the middle of a tectonic plate where plumes of hot magma rise and erupt
Hydrometerological 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
Land-use zoning
A process by which local government regulates how land in a community may be used
Landslide
A mass movement of rock and soil down a steep slope under the influence of gravity, perhaps triggered by an earthquake loosening material
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 lava flow flows faster than andesitic lavas, for example, because of the different velocities
