Unit 4.4: External Forces weathering Flashcards
what are denudation processes?
external forces that weaken, strip away and tera down Earth’s crust, creating new landforms.
what are some denudation agents?
gravity, running water, glaciers, wind, coastal waves, etc…
what is weathering?
breakdown of rock by physical disintegrating and/or chemical decomposition.
What are the types of weathering?
physical, chemical, and differential
what is physical weathering?
breakdown of rocks without chemical changes occurring to the minerals; caused by external disruptive forces
where is physical weathering greatest? what is it influenced by?
greatest at high elevations and latitudes where difference in seasonal temperatures is greatest. influenced by climate and rock jointing (more jointing means more weathering)
What are the different types of physical weathering?
- exfoliation: caused by stress release or removal by erosion of rock material that has pressed down on rock. when stress is released, cracks form parallel to the surface.
- frost wedging: repeated growth and melting of water/ice in pore spaces with a rock. the freezing causes the rock to wedge apart.
- salt wedging: similar to frost wedging, salt crystals grow in pore spaces and dislodge individual mineral grains within the rock.
- root wedging: plant roots penetrate cracks and pry rocks apart as the root grows. AKA biophysical weathering.
what is chemical weathering?
a chemical reaction that changes the minerals in the rocks.
what are the types of chemical weathering?
- Hydrolysis: chemical reaction of rock with water where minerals are transformed into other mineral compounds.
- Oxidation: reaction of rock with oxygen in air. produces reddish-brown hues on top layers of rock
- Carbonation: reaction of rock with carbon dioxide or carbonic acid.
- Biochemical weathering: chemical weathering caused by activities of organisms which produce acids.
what is differential weathering? what does it lead to?
weathering at different rates across a rock surface. leads to formation of rounded of spherical boulders.
define “mass movement”.
movement of rock, snow, ice, or soil downslope by gravity.
what is the difference between a stable and unstable slope?
stable slope is unlikely to fail or material will not move downslope whereas unstable slope has failed in the past and likely to do so again.
what determines slope stability?
- friction and electric charges that hold soil particles together
- soil moisture
- vegetation
what is the angle of repose?
steepest slope angle that can be maintained without slipping downward. typically between 15&50o
what are the 7 types of mass movement? define them.
- soil creep: slower, imperceptible downslope movement of individual soil particles due to melting and freezing of soil. you’ll see leaning stuff.
- solifluction: downslope flow of supersaturated soil that has reached its liquid limit. it is slower and occurs in permafrost environments.
- Landslide: rapid downslope movement.
- slumps: regolith detaches and slides downslope along a spoon shaped plane. top is called the head scarp and the base is called the toe. it kind of makes a cliff
- flows: mix of rock and water; faster than a landslide.
- Avalanche: turbulent cloud of rock or snow mixed with air and moves very fast
- rockfall: rapid falling, leaping, bouncing, and rolling decent of material. results from tilting or rotating of well-jointing rocks and triggered by tectonic activity.
