2. Today, I should be able
to:
a. define weathering and
distinguish between the two
main types of weathering
b. identify the factors that affect
the rate of weathering
8. Terms to encounter…
a. Weathering
b. Mechanical weathering
c. Abrasion
d. Chemical weathering
e. Hydrolysis
f. Carbonation
g. Oxidation
h. Frost wedging
9. 2 types of
weathering
Physical weathering (or mechanical
weathering) disintegrates rocks,
breaking them into smaller pieces.
Chemical weathering decomposes
rocks through chemical reactions that
change the original rock-forming
11. a. Frost wedging- when water gets inside
the joints, alternate freezing and thawing
episodes pry the rock apart.
12. b. Salt crystal growth- force exerted by salt
crystal that formed as water evaporates from pore
spaces or cracks in rocks can cause the rock to fall
apart
13. c. Abrasion – wearing away of rocks by constant
collision of loose particles
Weathering occurs as a response to the low pressure, low temperature, and water and oxygen-rich nature of the Earth’s surface. Point out that physical weathering and chemical weathering almost always occur together in nature and reinforce each other
– areas that are cold and dry tend to have slow rates of chemical weathering and weathering is mostly physical; chemical weathering is most active in areas with high temperature and rainfal
– the minerals that constitute rocks have different susceptibilities to weathering. Those that are most stable to surface conditions will be the most resistant to weathering. Thus, olivine for example which crystallizes at high temperature conditions will weather first than quartz which crystallizes at lower temperature conditions.
rate of weathering is affected by the presence of joints, folds, faults, bedding planes through which agents of weathering enter a rock mass. Highly-jointed/fractured rocks disintegrate faster than a solid mass of rock of the same dimension
weathering occurs more quickly on a steep slope than on a gentle one
length of exposure to agents of weather determines the degree of weathering of a rock
