Processes of Weathering and Erosion (L15)

Question 1

How are weathering and erosion different?

Answer 1

weathering is the breakdown of material and erosion is the physical removal of material from the site of weathering by mobile agents

Question 2

how does weathering continue while erosion is taking place?

Answer 2

because material can continue to break down while it is in transit

Question 3

What is mechanical weathering?

Answer 3

the physical breakup or disintegration of material

material broken down into smaller bits

Question 4

the 3 important ways mechanical weathering can occur?

Answer 4

frost wedging, root wedging, and unloading

Question 5

how does frost wedging work?

Answer 5

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

Question 6

what is another name for the frost wedging process?

Answer 6

freeze-thaw weathering

Question 7

How does root wedging occur?

Answer 7

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

Question 8

how does unloading occur?

Answer 8

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

Question 9

what is Chemical Weathering?

Answer 9

the breakdown or decomposition of minerals due to chemical reactions of minerals with water or gases in the air

Question 10

3 main processes of Chemical Weathering?

Answer 10

Dissolution, Oxidation, and Hydrolysis

Question 11

what is Dissolution?

Answer 11

dissolution is the process in which a material is dissolved in a liquid (e.g., salt in water)

Question 12

How does the corrosive action of water occur?

Answer 12

the presence of acids in the natural environment

rainwater is important for erosion, b/c all rainwater is naturally acidic

Question 13

what is an acidic solution?

Answer 13

a solution containing a lot of hydrogen ions

Question 14

what is a mineral that is prone to acid dissolution?

Answer 14

Calcite

Question 15

How does Oxidation occur?

Answer 15

it occurs when oxygen combines with another element to form an oxide that can be removed by erosion

Question 16

in nature, what is something that is prone to oxidation and forms hematite (rust)

Answer 16

Iron

Question 17

what is oxidation an important process for?

Answer 17

the decomposition of mafic minerals

Question 18

How does Hydrolysis occur?

Answer 18

occurs when minerals react with water to form other products

Question 19

what type of rocks are most easily weathered and broken down by simple dissolution?

Answer 19

rocks containing simple salts (e.g., halite)

Question 20

what do all rock classes include?

Answer 20

some rocks with silicate minerals

Question 21

How does mechanical and chemical weathering work together?

Answer 21

mechanical weathering increases the amount of exposed surface that can be acted upon by chemical weathering

Question 22

in which areas are weatherings tend to be concentrated at?

Answer 22

intersections of fractures such as joints or fault

Question 23

what are the 4 main erosional agents?

Answer 23

Liquid water
Wind
Ice
Gravity

Question 24

What are the 3 main things that make liquid water one of Earth’s most potent agents of erosion?

Answer 24

1. it can transport dissolved substances released by chemical weathering
2. water can flow, so flowing water can loosen and pluck particles from rock surfaces
3. the particles plucked from surfaces can impact underlying rock and abrade it

Question 25

the erosive action of water is enhanced by ____

Answer 25

the impact of suspended sediment particles with rock

Question 26

what happens in stream erosion?

Answer 26

grains are plucked from the riverbank, when suspended in water, these particles can then abrade the riverbank as well

Question 27

what is the plucking of sediment grains by wind called?

Answer 27

deflation

Question 28

why are not all deserts sandy?

Answer 28

because of deflation and selective removal of light/fine sediment grains, pavement of pebbles and boulders are found in desert areas

Question 29

how does ice work as an erosional agent?

Answer 29

flowing glacial ice can pluck loose sediment grains from the ground and these plucked fragments of rocks can abrade rock beneath the ice

Question 30

How does gravity work as an erosional agent?

Answer 30

material weakened by even gentle weathering can fail and be transported

Question 31

what is mass-wasting?

Answer 31

the rapid downslope movement of materials due to gravity