Tectonics Key Terms Flashcards
What is an Aftershock?
A smaller earthquake following the main shock of a large earthquake.
What is Andesite Magma?
Magma with high silica + gas content, which is viscous, sticky and is likely to cause an explosive eruption featuring multiple hazards such as ash, gas, pyroclastic flows, lahars etc.
What is the Asthenosphere?
A semi-fluid layer of the Earth’s mantle located just below the lithosphere, extending from about 100 to 200 km beneath the Earth’s surface.
What is Basaltic Magma?
Magma with low silica + gas content, which is effusive, ‘runny’, flows easily and is likely to cause a gentle eruption featuring just lava flows.
What is the Benioff Zone?
A zone of seismic activity at a destructive plate boundary where oceanic crust is being subducted, characterized by numerous shallow and deep earthquakes.
What is a Collisional Plate Boundary?
A boundary where two continental plates collide and form mountain ranges.
What is a Conservative Plate Boundary?
A boundary where two plates slide past each other horizontally, resulting only in earthquakes.
What is a Constructive Plate Boundary?
A boundary where two plates are moving away from each other, creating new land (e.g. Mid-Atlantic Ridge).
What are Continental Tectonic Plates?
Plates that are primarily composed of granite and form the continents.
What are Convection Currents?
Circular currents in the mantle caused by the magma being heated by radioactive decay in the Earth’s core.
What is the Core?
The innermost layer of the Earth, consisting of the outer core (liquid) and inner core (solid), primarily composed of iron and nickel.
What is the Crust?
Earth’s outermost layer, ranging from about 5 to 70 km in thickness, composed of solid rock.
What is a Destructive Island Arc?
A chain of volcanic islands formed at a destructive plate boundary.
What is a Destructive Plate Boundary?
A boundary where two plates are moving towards each other, and one is forced to subduct beneath the other.
What is an Earthquake?
When accumulated stress along a fault line is suddenly released, resulting in seismic waves.
What is Elastic Rebound?
The concept explaining how earthquakes are generated and why they often occur repeatedly along the same faults.
What is an Epicentre?
The point on the Earth’s surface directly above the focus of an earthquake.
What is a Fault Line?
A fracture along which sections of crust on either side have moved relative to one another.
What is the Focus (Hypocentre)?
The location within the earth where an earthquake begins.
What is a Jökulhlaup?
A sudden glacial outburst flood caused by the abrupt release of large volumes of meltwater from a subglacial or glacier-dammed lake.
What is a Lahar?
A destructive mudflow on the slopes of a volcano, formed when ash combines with water or glacial meltwater.
What is Lava?
Magma that reaches the Earth’s surface.
What is the Lithosphere?
The rigid outer layer of the Earth, encompassing the crust and the uppermost part of the mantle.
What is Liquefaction?
The process by which water-saturated soils temporarily lose their strength and behave like a liquid during an earthquake.
What are L-Waves (Love Waves)?
Surface seismic waves that cause horizontal shearing of the ground, moving it side to side.
What is Magma?
Molten rock beneath the Earth’s surface.
What is a Mantle Hot Spot?
An area in the mantle from which heat rises as a thermal plume from deep in the Earth.
What is the Mantle?
The thick layer of the Earth located between the crust and the core, composed mainly of silicate rocks.
What is the Mercalli Scale?
A scale that measures the intensity of an earthquake based on its observed effects.
What is the Moment Magnitude Scale (MMS / Mw)?
A scale that measures the total energy released by an earthquake, logarithmically.
What are Oceanic Tectonic Plates?
Plates that are primarily composed of basalt and form the ocean floor.
What is Palaeomagnetism?
The study of the direction and intensity of Earth’s magnetic field at the time the rocks were formed.
What is Plate Tectonics?
The theory explaining the movement of the Earth’s plates.
What are P-Waves (Primary Waves)?
Seismic waves that compress and expand the ground in the direction they travel.
What is a Pyroclastic Flow?
A fast-moving flow of hot gas, ash, and volcanic rock that flows down the sides of a volcano during an explosive eruption.
What are R-Waves (Raleigh Waves)?
Surface seismic waves that cause the ground to move in an elliptical motion.
What is Rhyolite Magma?
Magma with high silica + gas content, which is viscous and likely to cause an explosive eruption.
What is the Richter Scale?
A scale that measures the magnitude of an earthquake recorded 100km from the epicentre.
What is Ridge Push?
The force exerted by rising magma at mid-ocean ridges that pushes tectonic plates apart.
What is a Rift Valley?
A lowland region formed by tectonic plates moving apart.
What is Seafloor Spreading?
The process by which new oceanic crust is formed at mid-ocean ridges.
What are Seismic Waves?
Waves of energy that travel through the Earth’s layers.
What is Slab Pull?
The force exerted by a sinking tectonic plate that pulls the rest of the plate along with it.
What is a Subduction Zone?
A region where one tectonic plate slides under another.
What are S-Waves (Secondary Waves)?
Seismic waves that move the ground up and down or side to side, perpendicular to the direction of wave travel.
What is a Tsunami?
A series of large ocean waves caused by sudden displacement on the sea floor.
What is a Volcano?
A rupture in the Earth’s crust where molten lava, ash, and gases are ejected.
