Weathering and Erosion

Question 1

Define weathering

Answer 1

The destructive process by which rocks are disintegrated into smaller particles and ions by exposure to atmospheric agents.

Question 2

What is the first stage of the sediment redistribution process

Answer 2

Weathering

Question 3

Define erosion

Answer 3

A mechanical process that loosens and transports soil and rock fragments downhill. Different rocks have variable resistance.

Question 4

Define physical weathering

Answer 4

Process of disintegration of a rock without chemical change

Ex. Zones of weakness, frost wedging, mineral crystallization

Question 5

Define Zone of weakness

Answer 5

Joints or cracks form along pre-existing planes of weakness.
No motion between two surfaces between cracks

Question 6

Define frost wedging

Answer 6

Process of water expansion as it freezes in joints. This pushes or wedges the rock apart.

Question 7

Define Mineral crystallization in weathering process

Answer 7

Minerals such as salt grow and usually form from evaporating solutions.

Question 8

Define sheeting and exfoliation

Answer 8

From igneous rocks, when brought to the surface a pressure release occurs during uplift which causes fracturing parallel to the rock surface

Question 9

Spheriodal weathering

Answer 9

The peeling of small rock bodies into onion like layers

Question 10

Define Weathering from biological activity

Answer 10

Process of displacement of minerals from roots, burrowing organisms, and human activity

Question 11

Surface area changes due to weathering

Answer 11

Physical weathering increases surface area
Chemical weathering rates are directly proportional to surface area
Therefore, physical weathering increases chemical weathering rates.

Question 12

Why does chemical weathering occur

Answer 12

Water plays a major role
Water is an oxygen atom that is covalently bonded with two hydrogens at an angle of 105 degrees.
This gives the molecular polarity which allows it to be more adhesive to other substances, and be cohesive to other droplets
Because water is a universal solvent, ions can pry ions away from crystals

Question 13

Define chemical weathering

Answer 13

A series of chemical reactions thereby altering the original composition of the rocks.

Question 14

Why is the fact that Carbon dioxide when combined with water creates carbonic acid, relevant for chemical weathering

Answer 14

Rainwater is naturally weakly acidic

Question 15

Chemical weathering in carbonate rocks

Answer 15

Rain can dissolve carbonate rocks completely over time.
This is due to layered properties of carbonate rocks.
Dissolved constituents run off into surface and subsurface over time.
Ex. Travertine

Question 16

Chemical weathering of silicate rocks

Answer 16

Silicate rocks have less resistant minerals such as feldspar which partially dissolves in water.
What doesn’t dissolve is changed into clay minerals
Minerals with low solubility, such as quartz are not changed.

Question 17

Chemical weathering in iron Rich rocks

Answer 17

Iron reacts with oxygen in water and atmosphere to form hematite or rust.

Question 18

Bowen’s reaction series and chemical weathering rate

Answer 18

High temp. + pressure = rapid weathering

Low temp. + pressure + slower weathering, whatever doesn’t dissolve forms clay.

Question 19

Inmature sandstones, test question on this

Answer 19

Contain a mix of clay Martix’s and sand grains that are angular and poorly sorted.

Question 20

What is the weathering product of quartz

Answer 20

Quartz

Question 21

What do most minerals produce

Answer 21

Clay minerals

Question 22

Factors controlling weathering rates

Answer 22

Parent rock:
Climate: chemical weathering is favoured by humid tropical climates. Physical weathering favours cold climates
Soil: traps water and acidifies it further, which enhances weathering
Time

Question 23

Define soil

Answer 23

Transition between biosphere and geosphere

Question 24

Factors of soil formation.

Answer 24

Climate
Parent material
Topography 
Organisms
Time

Question 25

How is Nitrogen bacteria relevant to weathering**test question on this

Answer 25

Bacteria converts N2 into compounds such as Ammonia, nitrates which allows plants to make DNA and amino acids.

Question 26

Human factors that cause erosion

Answer 26

Loss of rainforest exposes soil, which increases topsoil erosion,

Question 27

Wind erosion and the human element

Answer 27

Unprotected farmland can lead to massive dust storms

Question 28

What are the special properties of water

Answer 28

Polarity 
Cohesion 
Adhesion 
Hydrogen Bonds
Universal solvent

Question 29

Why are nitrogen fixing bacteria so important in soils.

Answer 29

The bacteria absorb nitrogen from the atmosphere then converted into nitrogen compounds. These compounds are absorbed by plants and used to make DNA amino acids and enzymes. That nitrogen is an essential component of production of proteins and DNA in biological life

Question 30

What is the relationship between Bowens Reaction Series and Weathering*** test question

Answer 30

Minerals at the top of the Bowen series crystallize under high temperatures and pressures, and chemically weather at a faster rate than minerals ranked at the bottom.