7: Composition of the Solid Phase

Question 1

What can parent material be made out of?

Answer 1

Igneous, metamorphic, and sedimentary rocks

Question 2

Weathering

Answer 2

A process of transformation that involves the destruction of the parent material and synthesis of new minerals in the soil

Physical and chemical weathering

Question 3

Physical (mechanical) weathering

Answer 3

Breakdown of rock without changing chemical composition

Main agents are temperature, abrasion, and plants/animals

Question 4

Chemical weathering

Answer 4

Chemical transformation of the soil minerals through the action of geological agents and organisms.

Main agents are geological (oxygen, water) agents and organisms

Question 5

Igneous rocks

Answer 5

Granite and basalt

Question 6

What are the minerals in granite and how do they affect the soil once weathered?

Answer 6

Quartz: resistant to weathering and doesn’t contain minerals

Feldspars and muscovite: more easily-weathered but still contain few nutrients

Soils derived from granitic rock are coarse-textured and have low fertility

Question 7

What are the minerals in basalt and how do they affect the soil once weathered?

Answer 7

Dominated by small-grained, easily weathered, nutrient-rich minerals including hornblende, augite, biotite.

Parent materials and soils derived from basaltic rock are fine-textured and fertile

Question 8

Sedimentary rocks

Answer 8

Sandstone, limestone, and shale

Compacted or cemented particles weathered from any type of preexisting rocks. Resistance to weathering depends on dominant minerals and cementing agent.

Silica: high resistance
Calcite-containing rocks: least resistant

Question 9

Sandstone and how it affects soil

Answer 9

Sand-sized particles translocated and deposited by water. Cemented by pressure and CaCO3 or SiO2.

Coarse-textured soils with low fertility

Question 10

Shale and how it affects soil

Answer 10

Clay particles translocated and deposited by water and compacted. Shale rock susceptible to weathering.

Fine-textured, relatively fertile soils

Question 11

Limestone and how it affects soil

Answer 11

Mainly formed in shallow oceans where CaCO3 accumulates and is cemented.

Easily weathered, and soil formed is fine-textured, have a neutral to basic pH, and high fertility

Question 12

Metamorphic rocks

Answer 12

Formed when rocks are subjected to high heat, pressure, or hot mineral-rich fluids (or any combination of these factors)

Usually more resistant to physical weathering

Question 13

Soil organic matter (OM)

Answer 13

Mixture of all plant, animal, and microbial organic components of the soil at a given time.

Transitions from biomass to detritus to humus, which has the organic colloids