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Shaping the Landscape of North America (Weathering (Factors Affecting…
Shaping the Landscape of North America
Weathering
Definition of Weathering
Weathering is the break-up and decomposition of
rocks in-situ (in their place of origin).
Types of Weathering
Chemical Weathering
Carbonation or Solution
the mixing of water with carbon dioxide to make carbonic acid
often form limestone caves; ex. Luray Caverns, Virginia
Hydrolysis
breaking down rocks by acidic water to from clay and soluble salts
forms concave formations in flared slopes ex. The Wave, Arizona
Hydration
rock minerals absorb water and form new substances
ex. adding water to hematite to form limonite
Oxidation
breaking down rocks by oxygen and water, giving iron-rich rocs a rusty colored weathered surface
ex. rust formation: oxygen reacts with iron to form iron oxide; iron oxide is much more fragile than iron
Leaching
the process of water carrying soluble substances or small particles through soil or rock
ex. dissolving limestone through acid rain and ground water
Carlsbad Caverns, New Mexico
Definition
the erosion or disintegration of rocks, building materials, etc., caused by chemical reactions (chiefly with water and substances dissolved in it) rather than by mechanical processes.
Physical Weathering
Thermal Weathering
weathering from the expansion and contraction of rock, caused by temperature changes
ex. creation of bornhardts and inselbergs; ex. Namib Desert, Africa
Freeze-thaw/frost shattering/frost wedging
freezing water expands as it turns into ice, causing the rocks to crack
water within cracks freeze and expand; ex. road in Washington
Exfoliation
cracks develop parallel to the land surface a consequence of the reduction in pressure during uplift and erosion
ex. surfaces cracking and allowing water to flow through
Abrasion
Rocks and sediment grinding against each other wear away surfaces
Pressure release
overlying materials (not necessarily rocks) are removed (by erosion, or other processes), which causes underlying rocks to expand and fracture parallel to the surface
Salt crystallization
disintegration of rocks when saline solutions seep into cracks and joints in the rocks and evaporate, leaving salt crystals behind
ex. an be seen in the honeycombed stones in sea wall
Biological Weathering
Definition
Biological weathering is when flora and fauna break down the rock.
ex. roots cracking into the road all over North America
Factors Affecting Weathering
Geology
the science which deals with the physical structure and substance of the earth, their history, and the processes which act on them
Vegetation
plants considered collectively, especially those found in a particular area or habitat.
Climate
the weather conditions prevailing in an area in general or over a long period
Relief
difference in elevation between any two points
Aspect
he compass direction that a slope faces
Humans
construction, made made structures, man-made systems (water, electronics, buildings etc.) that speed up or slow down weathering
Physical Features Associated With Weathering
Limestone Pavement
limestone pavement is a flat expanse of exposed limestone formed by a combination of chemical weathering and erosion
ex. Malham Limestone Pavement, Malham, North Yorkshire
Karsts
geological feature created o by the drainage of water into the ground (include sinkholes, caves, natural bridges and sinking streams)
ex. Mammoth Cave, Kentucky
Stalactites
type of formation that hangs from the ceiling of caves, hot springs, or manmade structures such as bridges and mines
ex. Carlsbad Caverns, New Mexico
Stalagmites
type of rock formation that rises from the floor of a cave due to the accumulation of material deposited on the floor from ceiling drippings
ex. Lehman Caves, Great Basin National Park, Nevada
Erosion
Definition of Erosion
The geological process in which earthen materials are worn away and transported by natural forces such as wind or water
Physical Processes of Erosion
Rainfall and surface runoff
the flow of water that occurs when excess stormwater, meltwater, or other sources flows over the Earth's surface
ex. area near Washington State University
Rivers and streams
Flowing streams pick up and transport weathered materials by eroding sediments from their banks
ex. erosion of the Grand Canyon by the Colorado River
Coastal erosion
the loss of coastal lands due to the net removal of sediments or bedrock from the shoreline
ex. Drew Point, Alaska
Chemical erosion
the breakdown and decay or rocks or other geological features through a chemical process
ex. Mammoth Cavern, Kentucky, USA
Glaciers
Meltwater freezes in cracks, and pieces of bedrock are pried loose and incorporated into the ice
ex. Saskatchewan Glacier, Columbia Icefields, Jasper National Park, Alberta, Canada
Floods
Large floods can cause erosion to happen very quickly acting like powerful rivers
ex. flooding in Houston from Allison (2001)
Wind erosion
The physical forces of wind act on the loose rocks, leaving them sculptured and denudate
ex. Monzogranite rock formation, California, USA
Mass movement
is the transfer or movement of rock or soil down slope primarily by gravity
ex. Oso Mudslide, Washigton, USA, 2014
Factors Affecting the Rate of Erosion
Climate
the weather conditions prevailing in an area in general or over a long period
Vegetative Cover
trees, perennial bunch grasses and grasslands, legumes, and shrubs with an expected life span of at least 5 years
Topography
the arrangement of the natural and artificial physical features of an area.
Tectonics
relating to the structure of the earth's crust and the large-scale processes which take place within it.
Erosion of Earth Systems
Mountain Ranges
Plate Tectonics creates most mountains and plateaus; erosion shapes them
ex. Arches National Park on top of Colorado Plateau
Soils
Weathering away of the topsoil by wind, water, or tillage
Transportation
Definition of Transportation
the movement of material across the Earth's surface by water, wind, ice or gravity
Forces of Transportation
Gravity
Sediments and other materials are pulled downward, causing them to be transported to lower areas
ex. Landslides (Big Sur, California)
Water
Water current of lakes, rivers, and other bodies of water transport sediment from one area to another
ex. Copper Rive Delta, Alaska
Wind
Rock particles and other sediments are transported by wind patterns
ex. Sand dunes
Glaciers
Glaciers move accumulated sediments and rock particles (melt)
Moraine Lake, Canada
Deposition
Definition of Deposition
Deposition is the geological process in which sediments, soil and rocks are added to a landform or land mass
Types of Deposition
Floodplains and levees
type of geological feature that results when a river periodically overflows its banks due to rainfall, snow melt or other factors
ex. Paraná Delta is a floodplain in succession to the Paraná River, Brazil
Sand bars
a natural submerged ridge, bank, or bar that consists of, or is covered by, sand or other unconsolidated material, and rises from the bed of a body of water to near the surface
ex. Miami Beach, Florida, USA
Alluvial fans
It is a fan-shaped structure formed when water flows through hills or mountains
ex. The alluvial fan formation found near Lake Louise, Alberta, Canada
Terraces
The step like area formed by lateral erosion of stream or river
ex. Kanab Creek, Kane County, Utah.
Sand dunes
The sand blown by wind deposits in the form of a hill or ridge
ex. Guadalupe-Nipomo Dunes located in San Francisco, United States.
Moraines
Moraines are formed from debris previously carried along by a glacier and normally consisting of somewhat rounded particles ranging in size from large boulders to minute glacial flour
ex. Timpanogos Glacier located at Wasatch range of Utah, United States
