40 terms

Unit 4 - Plate Tectonics

This unit covers the topics of plate tectonics, fault boundaries, crustal stresses and mechanisms of plate motion. This unit discusses causes of earthquake and volcanic actions, precautions and safety measures, as well as zones of occurrences, and types of seismic waves.
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Seafloor Spreading
The process in which the ocean floor is extended when two plates move apart, forming a crack where magma can rise to the surface, cooling and forming new crust.
Magnetic Reversal
A change in the Earth's magnetic field.
Mantle Convection
The driving mechanism of plate tectonics - caused when heated magma rises, cool, and then sinks.
Rift Valley
When continental crust begins to separate, the split crust forms a long narrow depression.
Intensity
The degree of damage from an earthquake. Can be measured by the Mercalli Scale.
Magnitude
Measure of the energy released during an earthquake, which can be measured/described using the Richter Scale.
Pyroclastic Flow
Swift moving, clouds of dust, gas, ash and other volcanic material produced by a violent eruption.
Epicenter
The point on Earth's surface directly above the focus of an earthquake.
Focus
The point where slippage first occurs under the Earth's surface where an earthquake originates.
Hot Spots
Volcanoes located far from plate boundaries - caused by unusually thin areas of crust where hot magma is able to push through the surface.
Seismic Waves
Vibrations of the ground during an earthquake.
Viscosity
The resistance of a substance to flow. (i.e. water has a lower viscosity than maple syrup)
Mantle
Is located beneath the earths crust. Part of the mantle consists of the molten material that circulates beneath the earths crust.
Lithosphere
A rigid layer made up of the uppermost part of the mantle and the crust.
Asthenosphere
The solid, plastic layer of the mantle beneath the lithosphere; made of mantle rock that flows very slowly, which allows tectonic plates to move on top of it
Mohorovicic Discontinuity
the zone between the crust and mantle that marks a boundary between the 2, discovered because it changes the speed of seismic waves
Seismograph
A device that measures the strength of an earthquake.
Richter Scale
A logarithmic scale of 1 to 10 used to express the energy released by an earthquake
Mercalli Scale
A scale that rates earthquakes according to their intensity and how much damage they cause at a particular place
P-Wave
primary earthquake waves travel fastest
S-Wave
secondary earthquake waves only goes through solids
Continental Drift
The hypothesis that states that the continents once formed a single landmass, broke up, and drifted to their present locations
Plate Tectonics
A theory stating that the earth's surface is broken into plates that move.
Pangaea
A supercontinent containing all of Earth's land that existed about 225 million years ago.
Ridge Push
the process in which new material at a ridge or rift pushes older material aside, moving the tectonic plates away from the ridge
Divergent Boundary
A boundary where the plates are moving AWAY from each other.
Convergent Boundary
A plate boundary where two plates move toward each other.
Subduction
One plate going under another plate
Transform Boundary
The boundary between tectonic plates that are sliding past each other horizontally
Anticline
A fold in rock that bends upward into an arch
Syncline
A downward fold in rock formed by compression in Earth's crust
Normal Fault
A type of fault where the hanging wall slides downward; caused by tension in the crust
Reverse Fault
A type of fault where the hanging wall slides upward; caused by compression in the crust
Thrust Fault
a reverse fault in which the hanging wall slides over to the foot wall.
Dome Mountains
Formed when magma collects and pushes the rock layers above it into a rounded-dome shape.
Eroded Mountains
Mountains created as a result of erosion.
Lava
Magma that reaches Earth's surface
Cinder Cone
A short, steep, cone-shaped hill or small mountain made of volcanic ash, cinders, and bombs piled up around a volcano's opening
Shield Volcano
A low, flat, gently sloping volcano built from many flows of fluid, low-viscosity basaltic lava
Composite Volcano
Tall explosive volcano (stratovolcano)
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