Exam 3 Flashcards
Divergent Plate Boundary
Two plates, moving away from each other
Mostly located along the ridge systems in deep ocean basins
Represent sides of seafloor spreading
Convergent Plate Boundary
Two plates moving toward each other,
Associated w Volcanic Activity
Subduction
Subduction
One plate slides under the other
When only oceanic crust is involved, an island chain is formed (Ex. Aleutian Islands)
When only continental crust is involved, mountains are formed
Transform Plate Boundary
Two plates slip horizontally past one another
Seismic activity occurs, but little volcanic activity
Example: San Andreas fault system in California
Folding
Compression forces exerting pressure wherein the rock structure is bent and/or deformed
Is the result of a crustal movement (plate tectonics)
Anticline Folding
Upfolded rock layer
Ridge , arch
Syncline Folding
A down-folded rock layer
Valley or basin
Faulting
Rock layers are sustained and eventually fracture/break
One side of the rock layer is displaced relative to the other
Normal Fault
Vertical movement along an inclined plain
Overlying block is the hanging wall
Foundation block is the “Footwall”
Reverse Fault
Associated w/ converging plates
Produces hanging wall that moves upward
Thrust Fault
A type of reverse fault that is Much more significant vertical movement, More energy behind it, and a Higher risk for seismic activity
Strike Slip Fault
Transcurrent fault
Lateral movement along the transform boundary
San Andreas encompasses strike slip faults
Horst Landforms
Land between faults that is higher than the surrounding land. For example, the Sinai Peninsula.
Graben Landforms
Land between the faults that is lower than the surrounding land. For example, Death Valley.
Pacific Ring of Fire
Plate collisions in the PACIFIC RIM (which is comprised of North America and Asia) are responsible for a MAJORITY of seismic and volcanic activity on Earth
Cinder Cone Volcano
Cone shaped hill
Smallest type (these are not the famous giants of history)
Mostly pyroclastics (cinder, rock fragments, ash)
Not a lot of lava
Shield Volcano
Very gentle lava flows, Not a lot of ash, Very common in Hawaii, Lava flows form different kinds of cool rocks, Eruptions are not usually explosive unless water gets in vent, A lot of magma, Few pyroclastics
Composite Cone Volcano
Stratovolcano, Largest percentage of volcanoes fall into this category, Created by Subduction, High amounts of lava, ash, pyroclastics, Your classic scary apocalyptic volcano, “Giants of history”
Plug Lava Dome
Steep sides, Vent is repeatedly jammed, Immense pressure is created due to the blockage, Produce very cataclysmic eruptions, Kind of a subcategory of composite but differentiated by its steep sides and jammed vents!!!
Uniformitarianism
Earth has come to its present form through physical processes that have been constant and active in the environment throughout all of geologic time
Catastrophism
Earth has come to its present form as a result of large, sudden events
Plate Tectonics
Lithosphere is made up of a series of great and lesser plates that float over the asthenosphere, Continental drift is a consistent consequence of plate tectonics, Boundaries produce a majority of mountain ranges, volcanic eruptions, earthquake epicenters
Weathering
Weathering encompasses several processes involved in the disintegration and/or decomposition of rock material
Denudation (Weathering)
The process of reduction or rearrangement of landforms
Aggradation
Process of building up by accumulation of depositional material
Erosion
Wearing away or removal of a rock by an agent (e.g, running water, wind, ice)
Transport
Physical movement of rock debris
Deposition
The dropping/depositing of rock debris in a new location
Physical Weathering
Rock is broken and disintegrated w/o any chemical alteration or change
Frost Wedging (Physical Weathering)
Freeze-thaw action, Liquid water gets into cracks of rock and expands as it freezes, Rock cracks/fractures and breaks into pieces
Salt Crystal Growth (Physical Weathering)
Arid, semi-arid climates, Ground water is drawn to the surface of rock and evaporates , Mineral crystals that develop from dissolved minerals– Salt Crystals, Crystals grow into larger collections, Rock is cracked/fractured as crystals continue to grow
Chemical Weathering
Involves the actual decomposition and decay of the constituent minerals in the rock, Due to chemical change in minerals in the presence of water
Hydrolosis (Chemical Weathering)
Minerals (silicates, carbonates) chemically combine with water, One fragment of parent molecule combines with hydrogen and another with hydroxyl, Decomposition process: Chemical reactions produce different compounds/minerals
Acid/base salts combine w water
Acid Rain reacts w/ rock-forming minerals– produces clay and salts that are removed in solution
Oxidation
Gain of oxygen to a substance (particularly a metallic compound)
Oxides are physically weaker than original material, more susceptible to weathering
Iron and rusting
Accelerated by moisture and heat
Occurs above the water table
Reduction
Loss of oxygen from a substance (particularly a metallic compound)
Common where rock is totally submerged by still water
Occurs below the water table
Chemical reaction removes the oxygen but mineral may be altered again later if water circulation makes additional oxygen available
Solution
Minerals are actually dissolved in water
Minerals have low solubility in pure water. Rain contains carbonic acid limestone/marble
Large feature of glacial weathering. Colder water can hold more dissolved carbon dioxide.
Permanent Stream Flow
Lasts all year long
Valley floor is lower than the lowest groundwater level
Intermittent Stream Flow
Seasonal stream
Valley floor is lower than the lowest groundwater level for part of the year
Ephemeral Stream Flow
Exists only after precipitation falls
No relationship with the groundwater level
Exotic Stream Flow
Crosses a desert
Examples: The Nile and Colorado Rivers
Dioric Stream Flow (Pluse 2 Types)
Crosses a mountain
Antecedent Dioric
-Stream is there first, mountain arises around it
Superimposed
-Streamflow works away/carves itself into mountain
Denditic Stream Type
Root-like shape
Evenly resistant rock
Gentle slopes
Parallel Stream Type
Steep slopes
Trellis Stream Type
Folded
Rectangular Stream Type
Faulted
Radial Stream Type
Domed surface
Centripetal Stream Type
Converges at basin
Derranged Stream Type
No geometric pattern associated
Tributary
A stream that feeds a larger stream or lake
A supplemental water source
How do Stream Orders Work?
First Order: No tributaries
Second Order Stream: Receives at least two first order streams
Third Order Stream: Receives at least two second order streams
Glacial Geography
Glaciers act as an agent of erosion
Glaciers create a U-Shaped valley
Rivers create V Shaped Valley
Alpine Glacier
Mountain source, Rugged scenery, Jagged rock, Stone and ice, Rockies, Alps, Andes, Himalayas
Continental Glacier
Ice Sheets, Thick mass of ice covering large portion of continent, Greenland, Antarctica
When Ice Carries Debris it…?
Deposits the debris somewhere else
Glacial Snow at higher elevations is…?
White in color
Glacial Snow at lower elevations is…?
Gray in color due to containing debris
Terminus
End of glacier.
Gray snow.
Crevasses
Vertical cracks in glaciers
Result of friction or tension from extension/compression
Transverse Crevasse
Most common, forms across the glacier
Splashing Crevasses
Form on the sides of glaciers
Longitudinal Crevassses
Form parallel to flow where expanding, Snow-covered, Fairly common in Antarctica
Dangerous
Lateral Moraines
Formed from accumulation of material on either side of the valley
Deposited on top of glacier. Does not experience post-glacial erosion
Freeze-thaw
Usually preserved as ridges along the valley side
Medial Moraines
Junction of lateral moraines where glaciers meet
Ridge is along center of the valley
End Moraines
Formed when glacier pauses after reaching equilibrium
Size and shape determined by whether or not glacier is advancing or receding
Recessional Moraines
Deposits are formed while glacier is stationary during retreat phase, Higher elevations, Terminal, Debris is dropped at glaciers farthest extent, Represents the farthest advance of the glacier, Conveyer belt
Lowest elevation
Ground Moraines
Till (collection of rock/dirt/mud/debris) spreads across the land surface
Hides the former landscape
Between lateral moraines
Unsorted debris
May be modified into other landforms by overriding ice
Drumlin (Glacial landform)
Glacial debris that is streamlined/smoothed by the passage of ice
Streamlining reflects the erosional and depositional processes
One end of the hill is steeper than the other, tapers down to ground level
Tear drop shaped
Common in great lakes region
Aligned, parallel, clustered together
Alternative Drumlin Form Theory
Catastrophic flooding of high pressure water flowing beneath ice sheet
Erratic (Glacial Landform)
Very large rock boulders carried to its present location by a glacier
Rock type is different than the rock type of the local area
Marks the path of glacial movement
Ice rafting
Esker (Glacial Landform)
Forming through meltwater deposits flowing beneath the surface of the glacier
Gravel ridge
Parallel to overall ice flow
Kame (Glacial Landform)
Stagnant ice topography
Deposits from glacial meltwater when glacier is stagnant and not moving
Irregular shape accumulates in depression within the glacier
More sediment deposited on top of other debris
What is the difference between a Kame and a Drumlin
A kame is deposited by meltwater and a Drumlin is deposited by ice.
Kettle (Glacial Landform)
Depression resulting from melting of buried ice
“Kame and Kettle Topography”
Can fill with water and become KETTLE LAKES!!
When were Ice Sheet Land Forms formed
During the last ice age
Cirque (Alpine Landform)
Hollowed out amphitheater-like
Cliffs shelter it from heat, encouraging accumulation of snow and ice
Frost wedging can affect/increase the size
Arete (Alpine Landform)
Thin ridge separating two valleys parallel erosion from the two glaciers
Can also form from two cirques eroding headward toward each other
Col (Alpine Landform)
Two opposing glaciers meeting at Arete
Carves a gap or a pass
Horn
Pyramidal peak
Created by erosion of multiple glaciers converging on a central point
Human Causes of Desertification
Firewood Collection
Overgrazing
Intensive Agriculture or Cultivation
Erg Desert
Classic sea of sand
Not very Common
Desert Pavement
Rocky and stony landscape
Common
Hamad
Barren/exposed surface, bedrock
West Coast Deserts
A rain-shadow forms on the leeward side of a mountain range…the normal rain-shadow grows and turns into a desert.
Examples of West Coast Deserts
Mojave Desert in North America: 34° North
Atacam in South America: 23° South
Great Sandy in Australia: 20° South
Fluvial Erosion
running water
Aeolian Erosion
wind
Glacial Erosion
moving ice
Solution Erosion
ground water
Diastrophism
The folding and faulting of earth’s crust
Volcanism
Surface discharge of molten rock
Extrusive Volcanism
Volcanic Eruption
Intrusive Volcanism
only a small fraction of magma reaches the surface. Creates
Batholiths
Dykes
Sills
External Geomorphic Processes
Weathering
Erosion
Mass Wasting
Internal Geomorphic Processes
Crustal rearrangements (plate tectonics)
Volcanism
Diastrophism
Mass Wasting
the geomorphic process by which soil, sand, regolith, and rock move downslope typically as a mass, largely under the force of gravity, but frequently affected by water and water content as in submarine environments and mudflows
Plate Tectonics
Lithosphere is made up of a series of great and lesser plates that float over the asthenosphere
Continental drift is a consistent consequence of plate tectonics
Boundaries produce a majority of mountain ranges, volcanic eruptions, earthquake epicenters
Snider-Pelligrini 1958
Produces a map of South Africa’s eastern coastline fitted against Africa’s coastline, Cited close similarity in fossil plant types in coal bearing rocks in Europe and North America
Wegener 1912
Pangea- Supercontinent theory
Less dense layer of continental rock moving like a raft through a sea of more dense ocean rock
American Geologists rebuke
Violation of laws of physics because two strong rigid rock layers could not behave in this manner (one embedded in the other)
50s-60s in Plate Tectonics
Polar wandering- Helped explain continental drift
Plate tectonics develops for continental drift (theory)
Aeolian Deflation
Removing and lifting of individual loose particles
Aeolian Abrasian
The grinding of rock surfaces w/ a sandblasting action by the captured particles in air
Base Level
Lowest elevation of surrounding area that a river valley can be eroded down to
The Seven Categories of River Valley Assesment
Stream Gradient: Slope, degree of inclination of channel?
Tributaries: How prevalent they are?
Dominant Surface: Elevation of Surrounding land?
Draining Quality: How well the surrounding land drains away excess water?
Lakes/Swamps: How prevalent are they?
Waterfalls: How prevalent are they?
Profile: Just a cross section of the channel
Carbonation
limestone/marble
Large feature of glacial weathering. Colder water can hold more dissolved carbon dioxide.
Ferromagnesian Silicate
Green or dark, sometimes crystals
Nonferromagnesian Silicate
Colorless or white, translucent, cleavage
Oxide
Red, silver or black or blue
Sulfide
Brassy
Carbonate
White or colorless
Halide
Table salt or flouridic
Native Elements
Gold, Silver
