Chapter 2: Formation of Soil from Parent Materials

Sapric and fibric are terms used to describe peat parent materials.

True

Residual parent materials have generally been subjected to weathering for a longer period of time than have lacustrine or alluvial parent materials.

True

The mixed angular gravel, rock, and soil found at the foot of a slope is typical of what type of parent material?

Colluvial

Glacial till is a term used to describe parent materials that:

Contain a heterogeneous mixture of mineral debris dropped by receding glaciers

Even if all the glaciers present today in the world were to melt, the melt water would have no measurable effect on the level of the world's oceans.

False

Glacial till can be recognized by the distinct layering of different kinds of particles.

False

Glacial till is laid down by melt waters gushing out from the front of glaciers.

False

Exfoliation is caused by changes in _________.

Temperature

Mechanical weathering processes results in

The disintegration of rocks due to differential expansion of minerals

Hydrolysis involves the splitting of water into its H+ and OH- components while hydration attaches intact.

True

Igneous rocks are formed when molten magma cools and solidifies.

True

Marine sediments are typical parent materials in coastal plain areas.

True

Organic deposits are most common in areas where water flow over the soil surface is restricted.

True

Residual parent materials have formed in place and have not been transported from one area to another

True

Secondary minerals are recrystallized products of the chemical breakdown and/or alteration of primary minerals.

True

Weathering of rocks usually is most intense in the center of a rock fragment, and gradually decreases toward the outside.

False

The element most often involved in oxidation reactions as minerals weather is ________.

Iron

Organic matter accumulation is most pronounced in the __________.

O horizon

If you wanted to find a soil where physical weathering dominated over chemical breakdown you would be most apt to find it in ________.

A desert region of Arizona

The presence of rocks such as shale and sandstone indicate the existence of ________.

Ancient seas

Silicate clay accumulation is most common in the ________.

B horizob

In which of the following horizons has the process of illuviation most likely occurred

B horizon

The transformation of gneiss into mica, quartz, and feldspar crystals is an example of:

Both A & C

The reaction: mica + H2O ---- K+ + OH- + acid clay is an example of _________.

Chemical weathering

The C horizons are generally more completely weathered than the other horizons.

False

Which of the following is not a secondary mineral?

Microcline

The A horizons are more apt to be cultivated that the E horizons.

True

The O horizons of a soil are dominantly organic horizons occurring above mineral horizons

True

Igneous, sedimentary, and metamorphic are three _________.

Types of rocks

Secondary minerals are most prominent in the _______ fraction of soils.

Clay

A soil developed in transported parent materials will likely have properties related to the properties of the rock below the C horizon.

False

Alluvial parent materials are those that have been laid down in former lake bottoms.

False

In most B horizons one of the dominant processes of soil formation has been eluviation.

False

Iron and aluminum oxides are major components of igneous rocks.

False

Living organism affect soil formation primarily by their constraining level of oxygen in the soil

False

Sandstones are good examples of metamorphic rocks.

False

Soils developed in wind-blown parent materials such as loess are generally of little agricultural value.

False

The parent materials for most coastal plain soils are residual in nature.

False

The presence of iron in a mineral generally increases its resistance to chemical breakdown.

False

The topmost horizon in most humid region forest soils is the A horizon.

False

Which mineral is the most resistant to weathering under humid temperate conditions?

Gibbsite

Granite is an example of a (n) ______.

Igneous rock

Which of the following statements is correct?

Lacustrine parent materials have been subject to weathering for shorter periods of time than residual parent materials nearby

Residual parent materials are best described as_________.

Materials formed by weathering of rocks and minerals in place.

Igneous rocks can best be characterized as

Rocks formed when molten solidifies

Alluvial fans are usually characterized by _______ soils.

Sandy & gravelly

Which of the following statements is not correct?

Tropical forests protect the soil from excessive weathering

A soil developed in residual parent materials will likely have properties related to the properties of the rock below the C horizon.

True

Chemical weathering is accelerated by water, oxygen, and organic and inorganic acids moving down through the regolith.

True

Climate influences not only the rate of weathering but the type of native vegetation dominant in an area.

True

Eluviation of clay, iron, and other materials is the principal process responsible for the formation of an E horizon.

True

Which of the following is not considered one of the five major factors influencing soil formation?

Valence state

"Biotite + clay + iron oxide" represents a _____.

Weathering sequence