Chapter 8: Dynamic Earth Flashcards
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 currents
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
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.
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
Conservative plate boundaries
Solid crust is neither created nor destroyed at these boundaries. The San Andreas Fault is perhaps the best known example of a boundary between sliding plates.
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
regions in the crust where rocks in the upper mantle melt and magma surges upwards into the crust. Hotspots occur within plates. The active volcanoes in the Hawaiian Islands are caused by hotspots. The old volcanoes of Australia are also the result of hotspots.
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 break in a rock structure causing a sliding movement of the rocks along the break
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
Tremors
vibration on the Earth’s surface caused by an earthquake
Epicentre
the point on the Earth’s centre directly above the site where an earthquake originates
Focus
the point at which an earthquake begins
Triangulation
finding a location by using at least three different sources of detection
Seismograph
an instrument used to detect and measure the intensity of an earthquake
Richter scale
a scale that measures the amount of energy released during an earthquake
P-waves/Primary waves
compression waves that move through the Earth in the same way that sound waves move through air
S-waves/Secondary waves
the second set of waves to be detected after P-waves. During seismic activity, secondary waves or S-waves travel in the form of transverse waves.
Surface waves
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.
Body Waves
waves that travel through the interior of the Earth; P-waves and S-waves are said to be body waves
Tsunamis
a powerful ocean wave triggered by an undersea earth movement
Volcano
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
Active Volcanoes
describes a volcano that is erupting or has recently erupted
Extinct Volcanoes
describes a volcano that has not erupted for thousands of years and is effectively dead
Dormant Volcanoes
describes a volcano that has not erupted for more than 20 years but is not considered extinct
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
Pangea
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
