Ch 13: Tectonic Processes and Landforms

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Plate Tectonics
theory that the Earth's crust is divided into a number of plates that move because they float on the asthenosphere
Pangaea
hypothetical supercontinent, composed of all the present continents, that existed between 300 and 200 million years ago
Continental Drift
theory that the continents move relative to one another in association with plate tectonics
Passive Margin
place where the continental crust and the oceanic crust are on the same tectonic plate and thus do not move relative to one another
Transform Plate Margin
plate boundary where opposing plates move horizontally relative to each other
Rifting
spreading apart of the Earth's crust by magma rising between fractures in the Earth's plates
Mid-oceanic Ridge
ridge-like feature that develops along a rift zone in the ocean due to magma upwelling
Subduction
process by which one lithospheric plate is forced beneath another; this usually happens when oceanic crust descends beneath continental crust, but can happen where two plates of oceanic crust meet
Rock Structure
internal arrangement of rock layers
Monocline
geologic landform in which rock beds are inclined in a single direction over a large distance
Anticline
convex fold inrock in which rock layers are bent upward into an arch
Syncline
concave fold in rock in which rock layers are bent downward to forma trough
Overturned Fold
structural feature in which the fold limb is tilted beyond vertical, which results in both limbs inclined in the same direction, but not at the same angle
Overthrust Fold
structural feature where one part of the rock mass is shoved up and over the other
Geomorphology
branch of physical geography that investigates the form and evolution of the Earth's surface
Landform
a natural feature, such as a hill or valley, on the surface of Earth
Orogeny
a period of mountain building, such as the Allegheny Orogeny
Hogback Ridge
ridge underlain by gently tipped rock strata with a long, gradual slope on one side and a relatively steep scarp or cliff on the other
Anticlinal Valley
topographic valley that occurs along the axis of a structural anticline
Synclinal Valley
topographical valley that occurs along the axis of a structural syncline
Earthquake
shaking of the Earth's surface due to the instantaneous release of accumulated stress along a fault plane or from underground movements within a volcano
Fault
a crack in the Earth's crust that results in the displacement of one lithospheric plate or rock body relative to another
Epicenter
point on Earth's surface that lies directly over the focus of an earthquake
Richter Scale
logarithmic scale used to measure the strength of an earthquake
Normal Fault
steeply inclined fault in which the hanging rock block moves relatively downward
Horst
an upthrown block of rock that lies between two steeply inclined fault blocks
Graben
a downthrown block of rock that lies between two steeply inclined fault blocks
Fault Escarpment
step-like feature on Earth's surface created by fault slippage
Reverse Fault
steeply inclined fault in which the hanging rock block moves relatively upward
Strike-slip Fault
a structural fault along which two lithospheric plates or rock blocks move horizontally in opposite directions and parallel to the fault line
Natural Hazard
an actual or potentially occurring natural event, such as an earthquake or volcanic eruption, that has a negative effect on people or the environment
Tsunami
destructive sea wave caused by a disturbance within the ocean, such as an earthquake, volcanic eruption, or landslide
Volcano
a mountain or large hill containing a conduit that extends down into the upper mantle, through which magma, ash, and gases are periodically ejected onto the surface of Earth or into the atmosphere
Cinder-cone Volcano
a small, steep-sided volcano that consists of solidified magma fragments and rock debris that may form in only one eruption
Composite Volcano
a large, steep-sided volcano that grows through progressive volcanic eruptions which are usually explosive, and consists of layers of volcanic debris
Pyroclastic Material
fragmented rock materials resulting from a volcanic explosion or ejection from a volcanic vent
Lava Dome
steep-sided volcanic landform consisting of highly viscous lava that does not flow far from its point of origin before it solidifies
Volcanic Arc
a chain of volcanoes created by rising magma derived from a subducting tectonic plate
Pacific Ring of Fire
chain of volcanoes that occurs along the edge of the Pacific lithospheric plate
Shield Volcano
a very broad volcano with shallow slopes that forms in association with non viscous lava flows
Hotspot
stationary zone of magma upwelling that is associated with volcanism within the interior of a crustal plate
Geyser
a superheated fountain of water that suddenly sprays into the air on a periodic basis
Mudpot
bubbling mixture of gaseous mud and water at the Earth's surface that is associated with geothermal activity
Fumerole
steam vent that results because underlying groundwater is boiled away before reaching the surface
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