Chapter 8 - The 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 landmass that existed at this time were joined together to form this upper-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
The plates of the Earth’s crust that make up the land
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 tech tonic 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
Anticline
Folds that bend upwards
Syncline
Folds that bend downward
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
Slip fault
A geographical 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.
Primary waves (p-waves)
Compression waves that move through the Earth in the same way that sound waves move though air.
Secondary waves (s-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.
Body waves
Waves that travel through the interior of the Earth; P-waves and S-waves are said to be body waves.
Seismologists
A scientist who studies earthquakes
Tsunamis
A powerful ocean wave triggered by an undersea earth movement.
Meltdowns
The melting of a nuclear-reactor core as a result of a serious nuclear accident
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 when it has reached the Earth’s surface of a volcano.
Volcanic bombs
Large rock fragment that is blown out of erupting volcanoes.
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.
