Chapter 6 1-Know and understand the following processes: weathering, mass wastin

Question

Chapter 6

1-Know and understand the following processes: weathering, mass wasting, erosion.

2-Understand the difference between mechanical and chemical weathering.

3-Understand the following terms and physical processes of mechanical weathering: frost wedging, talus slope, unloading, sheeting, exfoliation, thermal expansion/contraction, salt crystal growth, biological activity, and abrasion.

4-Understand the basics of the following chemical weathering processes: dissolution, oxidation, hydrolysis.

5-Which mineral is not broken down chemically?

6-Which minerals are most affected by dissolution?

7-Understand how feldspar is broken down by hydrolysis and the products that result.

8-Know how the following affect the rate of weathering: rock characteristics, climate, differential weathering.

9- What factors control the formation of soil?

Chapter 7

1-How are sedimentary rocks classified and what are the origins and characteristics of each type. Detrital (clastic) and chemical sedimentary rocks.

2-Know and understand the following terms: diagenesis, lithification, recrystallization, compaction, cementation (know 3 types of cement and where they come from), sorting, facies, strata, beds, bedding planes, cross-bedding, graded bedding, ripple marks, oolites.

3-Know the three detrital sediment sizes and their corresponding rock names (Figure 7.3).

4-What is the difference between breccia and conglomerate?

5-Know relative abundances of sedimentary rocks by percent crustal volume and percent covering the Earth

Explanation / Answer

1)

Weathering

generally restricted to material breakdown in place
The physical and chemical (mineralogical) changes that occur in rocks in response to conditions that obtain at the interface of the Earth's hydrosphere and atmosphere.
Mass Wasting

Refers to material that falls under influence of gravity with little or no transporting agent
Processes range considerably in rate
Erosion

Refers to processes that move material to another site under the influence of transporting agents such as, water, ice, or wind.

2)

WEATHERING PROCESSES
CHEMICAL and PHYSICAL (mechanical)
INORGANIC and ORGANIC elements
Physical and Chemical Processes

In nature PHYSICAL and CHEMICAL processes work in combination to produce WEATHERING
In different CLIMATES one or the other of the two processes may dominate over the other, but rarely does one act alone.

3)

Physical Processes

Gravity
Stress relief (fractures)
Frost heaving
Surface area effects
Heating and cooling (fire, ...)
Tree roots, soil organisms (worms, ....)
Salt growth in cracks and open spaces
FROST ACTION

Water -> Ice (10% expansion)
Grain Size Important

Weathering is a surface phenomenon
More surface area means more access by water and the atmospheric gases CO2 and O2
Permeability (connected pore space) allows water to move into the rock to promote weathering
SURFACE AREA

Weathering occurs at surfaces of minerals
Area of cube one cm on a side = ??

4)

CHEMICAL PROCESSES

Chemical weathering of mineral matter to other minerals and dissolved ions
Biochemical breakdown of rock, mineral, and organic matter by soil microorganisms (bacteria, lichen, plant roots....)
PROCESSES

Solution
Precipitation
Oxidation
Carbonation
Hydrolysis (Water splitting)
SOLUTION

Action of water on minerals to produce dissolved ions
Halite
NaCl + H2O -> Na+ + Cl-

Gypsum
CaSO4

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