Hazardous Earth key terms Flashcards
Aftershocks
Follow an earthquake as the fault ‘settles’ into its new position.
Andesitic Lava
A thick and sticky lava erupted from composite volcanoes.
Asthenosphere
Part of the Earth’s mantle. It is a hot, semi-molten layer that lies beneath the tectonic plates.
Atmosphere
The layer of gases above the Earth’s surface.
Basalt
A dark-coloured volcanic rock, Molten basalt spreads rapidly and is widespread.
Collision zone
Where two tectonic plates collide - forming mountains like the Himalayas.
Composite Volcano
A steep-side volcano that is made up of a variety of materials, such as lava and ash.
Conservative boundary
Where two tectonic plates slide past each other.
Continental crust
The part of the Earth that makes up land, on average 30-50km thick
Convection currents
Transfer heat from one part of a liquid or gas to another. In the Earth’s mantle, the currents which rise from the Earth’s core are strong enough to move the tectonic plates on Earth’s surface.
Convergent boundary
Where two tectonic plates come together.
Core
The central part of the Earth’s structure, made up of a solid inner and liquid outer core.
Coriolis force
A strong force created by the Earth’s rotation. It can cause storms, including hurricanes.
Distribution
The way something is spread out or arranged over a geographic area.
Divergent boundary
Where two tectonic plates move away from each other.
Effusive
A type of eruption where runny lava flows steadily out of a fissure or
vent.
Epicentre
The point on the ground directly above the focus (centre) of an
earthquake.
Eye
The centre of a tropical cyclone; an area of clear conditions created by
air converging at the centre of the storm and then sinking.
Fault
Large cracks caused by past tectonic movement.
Focus
The point of origin of an earthquake.
Friction
The force which resists the movement of one surface over another.
Glacial
A cold period of time during which the Earth’s glaciers expanded widely.
Global atmospheric circulation model
A theory that explains how the atmosphere operates in a series of three
cells each side of the equator.
Greenhouse effect
The way that gases in the atmosphere trap heat from the sun. Like the
glass in a greenhouse – they let heat in, but prevent most of it from
escaping.
Greenhouse gases
Gases like carbon dioxide and methane that trap heat around the Earth,
leading to global warming.
Hot spot
Columns of heat in Earth’s mantle found in the middle of a tectonic
plate.
Interglacial
A long period of warmer conditions between glacials.
Inter-Tropical Convergence Zone (ITCZ)
A narrow zone of low pressure near the Equator where northern and
southern air masses converge.
Landslide
A rapid mass movement of rock fragments and soil under the influence
of gravity.
Latitude
How far north or south a location is from the Equator, measured in degrees.
Lava
Melted rock that erupts from a volcano.
Lava flows
Lava flows at different speeds, depending on what it is made of. Lava
flows are normally very slow and not hazardous but, when mixed with
water, can flow very fast and be dangerous.
Lithosphere
The uppermost layer of the Earth. It is cool and brittle. It includes the very top of the mantle and, above this, the crust.
Magma
Melted rock below the Earth’s surface. When it reaches the surface it is called lava.
Magnitude
Of an Earthquake (how much the ground shakes), an expression of the total energy released.
Mantle
The middle layer of the Earth. It lies between the crust and the core and
is about 2900km thick. Its outer layer is the asthenosphere. Below the
asthenosphere it consists mainly of solid rock.
Milankovitch Cycles (orbital change)
The three long-term cycles in the Earth’s orbit around the sun.
Ocean currents
Permanent or semi-permanent large-scale horizontal movements of the
ocean waters.
Oceanic crust
The part of the Earth’ crust which is under the oceans, usually 6-8km thick.
Plate boundaries
Where tectonic plates meet. There are 3 kinds: divergent, convergent and conservative.
Plumes
Upwelling of molten rock through the asthenosphere to the lithosphere.
Primary effects
The immediate effects of a natural hazard, caused directly by it.
Pyroclastic flow
A lethal hot mixture of broken rocks and gases that races down the side of a volcano.
Quaternary
Most recent period of geological time: The last 2.6 million years, during
which there have been many glacials.
Radioactive decay
The process where natural radioactive materials in the Earth’s rocks break down, giving out energy and heat as they do.
Richter scale
A scale for measuring the magnitude of earthquakes.
Remote sensing
Using satellites or aerial photography to provide information on land use over large areas.
Saffir-Simpson Hurricane Scale
A scale that classifies hurricanes into five different categories according
to their wind strength.
Secondary effects
The indirect impacts of an event , usually occurring in the hours, weeks, months or even years after the event.
Seismometer
A machine for recording and measuring an earthquake using the Richter scale.
Storm surge
A rapid rise in the level of the sea caused by low pressure and strong
winds.
Subduction
Describes oceanic crust sinking into the mantle at a convergent plate
boundary. As the crust subducts, it melts back into the mantle.
Tectonic hazards
Natural events caused by movement of the Earth’s plates that affect
people and property. Earthquakes, volcanoes and tsunamis (tropical
storms are NOT tectonic hazards)
Tectonic plates
The Earth’s surface is broken into large pieces, like a cracked eggshell.
The pieces are called tectonic plates, or just plates.
Thermal expansion
As a result of heating, expansion occurs. When sea water waters up, it
expands.
Track
The path followed by a tropical cyclone.
Tree rings
Marks on the inside of trees trunks that show individual growing seasons. The thickness of the rings varies depending on climatic
conditions during the seasons.
Tropical cyclone
A weather system that forms over the ocean in tropical areas and can
produce high winds and heavy rain.
Tsunami
Earthquakes beneath the sea bed generate huge waves that travel up
to 900km/h.
Volcanic Explosivity Index (VEI)
Measures the explosiveness of volcanic eruptions on a scale of 1 to 8.
