Lecture 13 - Weathering and Erosion

Question 1

What is the Definition of Weathering?

Answer 1

-Series of processes that happen to rock as it is exposed to Earth’s surface; this may be physical, chemical or biological

Question 2

What is the Definition of Erosion?

Answer 2

-The transportation of rock away from its exposure to another location

Question 3

What is the Definition of Denudation?

Answer 3

-The removal of rock either by chemical decomposition or physical removal that wears down the Earth’s surface
-Erosion + chemical dissolution

Question 4

What is Chemical Weathering?

Answer 4

-Involves chemical reactions with minerals, new minerals are formed and they may be soluble in water and easily transported

Question 5

What is Physical Weathering?

Answer 5

-Rocks broken up into smaller pieces by mechanical force

Question 6

What is Biological Weathering?

Answer 6

-Rocks altered chemically and or physically by the presence of plants, animals and bacteria

Question 7

Factors Affecting Weathering: What is Lithology?

Answer 7

-Mineralogical composition and structure of rock

Question 8

Factors Affecting Weathering: What is Climate?

Answer 8

-Rainfall and temperature are both important
-The same rock changes its weathering resistance depending on climate (tropical rainforests tend to have higher rates of weathering due to higher temperatures and rainfall)

Question 9

Factors Affecting Weathering: What is Length of Exposure?

Answer 9

-The longer a rock is exposed at surface, the more weathered it will be
-Weathering is strong when erosion is low (material stays in place for longer)

Question 10

Chemical Weathering: What is Solution?

Answer 10

-Simplest form of chemical weathering
-Minerals are decomposed with water acting as a solvent

Question 11

Chemical Weathering: What is Carbonation?

Answer 11

-CO2 reacts directly with a mineral to from new minerals and releases bicarbonate ions (HCO3-)
-E.g. weathering of feldspars to form clay is a carbonation process (works quicker with higher temperatures)

Question 12

Chemical Weathering: What is Oxidation?

Answer 12

-Process whereby an atom or ion loses an electron, increasing its positive charge
-Main oxidising agent is oxygen dispersed in water

-E.g. the Banded Iron Formation:
-formed when oxygen appeared
in oceans produced as waste by
cyanobacteria
-Oxygen entered contact with Fe-
rich waters (possibly from the
deep ocean)
-Fe was rusted and deposited
forming the BIF

Question 13

What is Regolith and Soil?

Answer 13

-As rock reaches the Earth’s surface, it undergoes physical and chemical weathering
-Weathering can penetrate at depth, creating a weathered profile; a continuum from fresh rock to fractured and weathered rock, with soil at the top
-Regolith constitutes this entire layer of unconsolidated material