Chapter 11

Question 1

What makes the soil system?

Answer 1

weathering and detrital system

Question 2

pedogenesis

Answer 2

soil formation; the process of evolution of soil under the influence of various physical, biological, climatic, and geological factors

Question 3

What are the two primary mechanisms of rock breakdown?

Answer 3

1-brittle fracture (physical: at the scale of the rock mass)
2-crystal lattice (chemical: at molecular scale)

Question 4

What is brittle fracture?

Answer 4

-temperature (thermoclasty)
-water freezing (when water freezes it expands and break apart the rock): gelifraction
-salt weathering: haloclasty; abrasion of the salt is what breaks it apart
-growth and activity of living organisms: biomechanical forces (ex-grass getting into sidewalks; slow pressure plants can place on rock can break them up)

-gravity and solar energy are continually pushing their way into rock breakdown

Question 5

What is thermoclasty?

Answer 5

Process of physical weathering whereby the stresses set up when a rock is alternately heated and cooled become sufficient to cause failure.

Question 6

Primary mechanisms of crystal lattice breakdown

Answer 6

-water presence is important
-hydration: adorption of water
-dissolution: passing into solution
-hydrolysis: substitution of H+ and OH- ions: this is the change
-oxidation: reaction with oxygen
-acid (carbonic acid, etc)

Question 7

How do crystal lattices break down?

Answer 7

Through activating agencies:
-more surface area= faster breakdown
-leaching and plant root uptake can remove the products of lattice breakdown
-replenishment of reactants creates new material to weather

Question 8

What is the result of lattice breakdown?

Answer 8

stable but highly mobile cations in
aqueous solution
* Iron and Aluminum oxides (hydroxides)
* Silicates – clay minerals
* Salt crystal growth

Question 9

What is the final state?

Answer 9

regolith
1-minerals remain that are resistant to brittle fracture and crystal lattice breakdown
-quartz dominates the residual category (due to bond energy)
2-resynthesized minerals also contain materials in transition (some still undergoing the transition)
-zones closer to the surface will be in more advanced state of adjustment (due to temperature changes etc)
-impossible to separate weathering from pedogenesis (weathering plus carbon material/ conbiotic idea: can’t separate biotic and abiotic factors) except in environment devoid of life
-Figure 11.16