Land and Water, Hillslopes, Weathering, and Soils Flashcards
What are the two types of hillslopes?
- Limited (bedrock) hillsopes
- Transport-limited (soil mantled) hillslopes
What are the four features of limited (bedrock) hillslopes?
- Soil production < erosion
- Steep slopes
- Thin to absent soil mantle due to slow rates of soil production
- Common in arid cimates
What are the four features of transport-limited (soil mantled) hillslopes?
- Soil production ≥ erosion
- Gentle slopes
- Thick surface mantle. Surficial layer of soil covers bedrock
- Common in humid climates
How do humid hillslope profiles evolve?
In humid climates, the slope declines, forming a profile that is not parallel with the oldest profile
How do arid hillslope profiles evolve?
In arid climates, the slope retreats parallel to the oldest profile
What are the three hillslope-forming mechanisms?
- Flow (wet)
- Slide (dry)
- Heave (moist)
What are three example of flow in regards to hillslope forming mechanisms?
- River
- Mud flow
- Earthflow
What are two example of slide in regards to hillslope forming mechanisms?
- Rockslide
- Landslide
What are two example of heave in regards to hillslope forming mechanisms?
- Seasonal soil creep
- Soilflucation
Soil creep
The slow movement of soil on a slope due to gravity
What is the difference between weathering and erosion?
Weathering: The alterantion or breakdown of material at or near the Earth’s surface
Erosion: The displacement and/or further breakdown of material away from its original location. Always occurs after weathering
What are the three types of weathering?
- Physical
- Chemical
- Biological/biochemical
What are the three types of physical weathering?
- Exfoliation
- Freeze/thaw
- Salt and hydration/dessication
Exfoliation
As rock is uncovered/rises to the surface, pressure decreases, causing the rock to expand and peel off as sheets
Freeze/thaw
Water seeps into cracks within rocks which, once frozen, expands to further fracture the rock
Salt and hydration/dessication
Similar to freeze/thaw, salt precipitates in voids expand through wetting and drying, further fracturing rock.
This process creates characteristics pits on the surface
What are the two types of chemical weathering?
- Dissolution
- Acid reactions
Dissolution
The removal of soluble materials by dissolving in water. This includes many organic compounds which slowly break down rocks
Acid reactions
The combination of water and carbon dioxide which creates carbonic acid. This increases water acidiity which further aids in the weathering of rocks and subsequently the production of acids
What are the three types of biological/biochemical weathering?
- Physical stress (root growth expanding and weakening zones)
- The manufacturing of litter and humic acids
- Bioturbation (the biogenic transport or breakdown of rock)
Where are chemical and mechanical weathering most effective?
Chemical weathering: Humid climates
Mechanical weathering: Cold climates where there are frequent freeze/thaw cycles
What four other factors control weathering?
- Vegetation
- Topography
- Parent material
- Time
Soil
Solid earth material that has been physically, chemically, and biologically altered in ways that enhance its life-supporting properties
How do connectivty relationships differ between New Zealand and Australia?
New Zealand: Experiences rapid convergence of sediment and is hillslope dominated
Australia: Experiences limited/slow convergence of sediment. It is valley floor dominated so tributaries are disconnected from the trunk stream
