Chapter 4: Weathering, Erosion, & Mass Wasting Flashcards
What is Mass Wasting?
Transfer of sediment down slope under the influence of gravity
What is the definition to weathering?
Disintegration and decomposition of material at or near surface; happens in place
What is Erosion?
transportation of material by a mobile agent (wind, water, or ice)
What is a Landslide Scar?
evidence of previous mass wasting at the same site
Important triggering factors of mass wasting include?
1) Saturated material w/ water
2) Removal of anchoring vegetation (EX: wildfires)
3) Ground shaking from earthquakes, ect.
4) Removal of supporting material @ base of slope (undercutting)
5) Over steeping of slopes
Mass wasting process are defined by what?
1) material involved- sediment, soil, or rock
2) The type of movement of material: fall, slide, flow
3) the rate of movement: fast slow
The types of movement in the mass wasting materiel?
Fall: vertical free-fall of rock/ sediment
Slide: material moves downslope along well-defined surface
Flow: material moves as a viscous fluid
The rate of movement within mass wasting?
Fast: seconds or minuets
Slow: months, years, or decades
The four forms to mass wasting?
A) Slump B) Rockslide C) Debris flow (or mudflow) D) Earthflow E) Creep F) Slolifluction
What is a slump?
Rapid movement along a curved surface
Occurs along over- steepened slopes
Also known as a rotational landslide
What is a rockslide?
Rapid movement
Blacks of bedrock slide down a slope
What is a Debris flow (or mudflow)?
Rapid flow of debris with water
Often confined to channels
Lahars= debris flows composed mostly of volcanic materials
What are Engineered structures?
Safety structures can be built to improve slope stability or to reduce movement hazards.
Five Examples of Engineered structures
1) Retaining walls: barriers that pin base and trap rock
2) Covers: fencing or coating that drapes over the
outcrop
3) Rock Staples: Rods drifted into rock to hide loose
fencing
4) Avalanche sheds: structures that shunt avalanche
snow
5) Controlled blasting: intentional removal of dangerous
rock
What is earthflow?
Rapid movement
Occurs when water saturates the soil
Typically occurs on hillsides in humid regions during
heavy rain or snow melt
What is Creep in terms of the mass wasting process?
Slow downslope movement of soil and regrowth
What is Solifuluction in terms of mass wasting process?
Slow movement in area underlain by permafrost (permanently frozen ground)
Upper solid layer becomes saturated and slowly flows over the frozen surface below
What is permafrost?
Permanently frozen ground
Two types of weathering?
Mechanical weathering- physical breakdown of rocks into smaller pieces
Chemical weathering- alters internal structure of minerals by removing or adding elements
What is the process of Mechanical weathering?
A) Frost wedging- “freeze-thaw” effect
B) Unloading and exfoliating- removal of overlying sediment and rock
C) Biological activity- plants and aniamals help to mechanically weather rocks
Angular rock debris fragments on slope, is called what?
Talus
What is the most important agent to Chemical weathering?
Water!
Oxygen dissolves and oxidizes materials (speeds up chem. weath.)
CO2 dissolved formed carbolic acid and alters rocks/minerals
The two weathering rate factors?
1) Rock characteristics- mineral composition/ solubility of rock. Physical features speed up breakdown process.
2) Climate- temp and moisture are crucial factors.
What type of weathering is the slowest in cold areas and most effective in warm moist areas?
Chemical weathering
What is differential weathering?
Caused by variations in rock composition.
Creates unusual/ spectacular rock formations and landforms
Soil is the combination of what?
1) Organic matter
2) Mineral matter
3) Water
4) Air
What are the controls of Soil Formation?
CL. O. R. P. T
1) Climate
2) Organisms
3) Slope (relief)
4) Parent material
5) Time
What is the most influential in Soil Formation?
Climate because it determines nature and intensity of weathering that occurs over geographic areas
Organisms act to churn up the soil is called what?
Bioturbation
Residual soil and Transported soil are what type of parent material?
RS- parental material is the bedrock
TS- parent material has been carried elsewhere and deposited
Two factors of the Soil formation: Slope?
Angle of slope:
steep slopes often have poorly developed soil and optimum relief for soil to form on flat upland surface
Orientation (direction of slope:
influences soil temp and moisture
Another word for relief
Topography
The Natural Rates of Soil Erosion depends on?
Soil characteristics- climate, slope
Type/ amount of vegetation- more vegg in an area, less erosion will occur
Soil Erosion and Sediment can cause what?
Water reservoirs to fill with sediment
Contamination of water by pesticides and fertilizers
When was the Dust Bowl?
known as the ‘dirty thirties’
1937 near Elkhart, Kansas
