Processes of Weathering and Erosion (L15) Flashcards
How are weathering and erosion different?
weathering is the breakdown of material and erosion is the physical removal of material from the site of weathering by mobile agents
how does weathering continue while erosion is taking place?
because material can continue to break down while it is in transit
What is mechanical weathering?
the physical breakup or disintegration of material
material broken down into smaller bits
the 3 important ways mechanical weathering can occur?
frost wedging, root wedging, and unloading
how does frost wedging work?
this occurs when water flows into existing cracks within a rock and freezes, and then the water expands into ice, so widens the cracks and ultimately results in the breakup of the material
what is another name for the frost wedging process?
freeze-thaw weathering
How does root wedging occur?
occurs when roots of plants penetrate into small cracks
as roots increase in size, they increase the size of the crack until pieces of the rock break apart
how does unloading occur?
when an igneous rock body expands as overlying rock is removed by erosion
outer layers of the intrusion expand more than the rock below and seperate like layers of an onion (process called exfoliation)
sheets of igneous rock “pop” off the surface as the body continues to expand
what is Chemical Weathering?
the breakdown or decomposition of minerals due to chemical reactions of minerals with water or gases in the air
3 main processes of Chemical Weathering?
Dissolution, Oxidation, and Hydrolysis
what is Dissolution?
dissolution is the process in which a material is dissolved in a liquid (e.g., salt in water)
How does the corrosive action of water occur?
the presence of acids in the natural environment
rainwater is important for erosion, b/c all rainwater is naturally acidic
what is an acidic solution?
a solution containing a lot of hydrogen ions
what is a mineral that is prone to acid dissolution?
Calcite
How does Oxidation occur?
it occurs when oxygen combines with another element to form an oxide that can be removed by erosion
in nature, what is something that is prone to oxidation and forms hematite (rust)
Iron
what is oxidation an important process for?
the decomposition of mafic minerals
How does Hydrolysis occur?
occurs when minerals react with water to form other products
what type of rocks are most easily weathered and broken down by simple dissolution?
rocks containing simple salts (e.g., halite)
what do all rock classes include?
some rocks with silicate minerals
How does mechanical and chemical weathering work together?
mechanical weathering increases the amount of exposed surface that can be acted upon by chemical weathering
in which areas are weatherings tend to be concentrated at?
intersections of fractures such as joints or fault
what are the 4 main erosional agents?
Liquid water
Wind
Ice
Gravity
What are the 3 main things that make liquid water one of Earth’s most potent agents of erosion?
- it can transport dissolved substances released by chemical weathering
- water can flow, so flowing water can loosen and pluck particles from rock surfaces
- the particles plucked from surfaces can impact underlying rock and abrade it
the erosive action of water is enhanced by ____
the impact of suspended sediment particles with rock
what happens in stream erosion?
grains are plucked from the riverbank, when suspended in water, these particles can then abrade the riverbank as well
what is the plucking of sediment grains by wind called?
deflation
why are not all deserts sandy?
because of deflation and selective removal of light/fine sediment grains, pavement of pebbles and boulders are found in desert areas
how does ice work as an erosional agent?
flowing glacial ice can pluck loose sediment grains from the ground and these plucked fragments of rocks can abrade rock beneath the ice
How does gravity work as an erosional agent?
material weakened by even gentle weathering can fail and be transported
what is mass-wasting?
the rapid downslope movement of materials due to gravity
