Dynamic Earth Flashcards
Seismic Waves
waves of energy that travel through the Earth’s crust, caused by earthquakes
Continental Drift
movement of the plates of the Earth’s crust in relation to each other
Pangaea
a super-continent that existed about 225 million years ago. All of the landmasses that existed at this time were joined together to form this super-continent.
Panthalassa
the vast sea surrounding the supercontinent of Pangaea
Plate tectonics
the theory concerning the movement of the continental plates
Mantle
thick layer inside the Earth, below the crust. Most of the mantle is solid rock, although the upper part is molten rock called magma.
Convection current
circular movement that occurs when warmer, less dense fluid particles rise and cooler, denser fluid particles sink
Continental crust
circular movement that occurs when warmer, less dense fluid particles rise and cooler, denser fluid particles sink
Oceanic crust
one of the types of crust that makes up the Earth’s outer layer. Oceanic crust is thinner than continental crust and made up of dense, heavy rocks such as basalt.
Subduction
process in which two tectonic plates push against each other, and oceanic crust sinks below the less dense continental crust
Destructive plate boundaries
a convergent boundary where two plates collide
Constructive plate boundaries
plate that creates new land from cooling magma
Ocean ridges
an area where the tectonic plates move apart, allowing magma from the mantle to rise, forming underwater volcanoes and creating new oceanic crust as it is cooled and solidified by sea water
Laurasia
one of the two smaller continents created when the supercontinent Pangaea broke apart about 200 million years ago
Gondwanaland
one of the two smaller continents created when the supercontinent Pangaea broke apart about 200 million years ago
Hotspots
a localised place where an activity occurs
Folding
buckling of rocks caused when rocks are under pressure from both sides
Anticlines
folds that bend upwards
Synclines
folds that bend downwards
Fault
a break in a rock structure causing a sliding movement of the rocks along the break
Rift Valleys
a sunken area where two blocks of crust have dropped down between faults
Horst
a block of the Earth’s crust, with faults on either side, that has been pushed upwards by the forces below
Slip Fault
a geological feature where movement along a fault is sideways—that is, where the blocks of crust slip horizontally past each other
Volcanoes
natural opening in the Earth’s crust connected to areas of molten rock deep inside the crust
Magma
a very hot mixture of molten rock and gases, just below the Earth’s surface, that has come from the mantle
Lava
mixture of molten rock and gases that has reached the Earth’s surface from a volcano
Volcanic bombs
large rock fragment that is blown out of erupting volcanoes; also known as a lava bomb
Active
describes a volcano that is erupting or has recently erupted
Extinct
describes a volcano that has not erupted for thousands of years and is effectively dead
Dormant
describes a volcano that has not erupted for more than 20 years but is not considered extinct
Conservative Plate Boundaries
when plates slide past each other in opposite directions, but without creating or destroying lithosphere. … those that link a destructive boundary with a constructive boundary.
Tremor
a slight earthquake.
Epicentre
the point on the earth’s surface vertically above the focus of an earthquake.
Focus
the point of origin of an earthquake.
Trilateration
the process of determining absolute or relative locations of points by measurement of distances, using the geometry of circles, spheres or triangles
Seismograph
an instrument that measures and records details of earthquakes, such as force and duration.
Richter Scale
a numerical scale for expressing the magnitude of an earthquake on the basis of seismograph oscillations. The more destructive earthquakes typically have magnitudes between about 5.5 and 8.9; it is a logarithmic scale and a difference of one represents an approximate thirtyfold difference in magnitude.
Body wave
a seismic wave that moves through the interior of the earth, as opposed to surface waves that travel near the earth’s surface. P and S waves are body waves.
Surface wave
A seismic wave that travels across the surface of the Earth as opposed to through it. Surface waves usually have larger amplitudes and longer wavelengths than body waves, and they travel more slowly than body waves do. Love waves and Rayleigh waves are kinds of surface waves.
Tsunami
a long, high sea wave caused by an earthquake or other disturbance.
Primary Wave
Primary waves are alternatingly compressional and extensional, and cause the rocks they pass through to change in volume. These waves are the fastest traveling seismic waves and can travel through solids, liquids, and gases.
Secondary Wave
An earthquake wave in which rock particles vibrate at right angles to the direction of wave travel. Secondary waves can travel through solids but not through liquids.
Love Wave
A type of seismic surface wave in which particles move with a side-to-side motion perpendicular to the main propagation of the earthquake. The amplitude of this motion decreases with depth. Love waves cause the rocks they pass through to change in shape.
