Weathering and Soil

Weathering

Involves the physical breakdown (disintegra- tion) and chemical alteration (decomposition) of rock at or near Earth's surface.

Mechanical Weathering

Physical forces that break rock into smaller and smaller pieces without changing the rock's mineral composition

Chemical Weathering

Involves a chemical transformation of rock into one or more new compounds

Chemical Weathering

Involves the complex processes that alter the internal structures of minerals by removing and/or adding elements. During this transformation, the original rock decomposes into substances that are stable in the surface environment

Why does rock weather?

Simply, weathering
is the response of Earth materials to a changing environment.

Mechanical weathering increases the surface area.

Erosion

The removal and transport of weathered rock material by water, wind, or ice.

Sugar Cube

Because the cube has
less surface area available for dissolution.

Between an equal volume of sugar grains and sugar cube, which is easier to dissolve in a liquid?

Frost Wedging

The mechanical breakup of rock caused by the expansion of freezing water in cracks.

9%

Liquid water has the unique property of expanding about how many percent upon freezing?

Salt Crystal Growth

As water evaporates, crystals grow in cracks and expand the cracks, breaking the rock mechanically

Rocky Shorelines and Arid Regions

In what environments does Salt Crystal Growth usually occur?

Arid Environment
Rocky Shorelines and Arid Regions
Alluvial Environment
Tropical Environment

Unloading

When the overlying rock is eroded away

Shitting

As erosion removes
the overlying bedrock, the outer parts of the igneous mass expand. Joints form parallel to the surface. Continued weathering causes thin slabs to separate and fall off. This process leads to the formation of an exfoliation dome.

Joints

A brittle-fracture surface in rocks along which little or no displacement has occurred.

Water

The most important agent of Chemical Weathering


Water
Soil
Wind

Oxidation

A chemical reaction in whic the "loss of electrons" from one element occurs.

Quartz

A mineral that is very resistant to chemical weathering and remains substantially unaltered when attacked by weak acidic solutions.

Spheroidal Weathering

A type of weathering that attacks the edges from two sides and corners from three sides, these areas wear down faster than a single flat surface. Gradually, sharp edges and corners become smooth and rounded. Eventually an angular block may evolve into a nearly spherical boulder.

Climate and Rock types influences the Rate of Weathering

Differential Weathering

The difference in degree of discoloration, disintegration, etc., of rocks of different kinds exposed to the same environment.

Soil

Is considered an interface—a common boundary where different parts of a system interact.

Regolith

The layer of rock and mineral fragments produced by weathering that covers Earth's surface.

Soil

A mixture of the following
45% Mineral Matter
5% Organic Matter
25% water and
25% air.

Parent Material

the rock material from which the inorganic components of a soil are derived.

Residual Soils

When the parent material is bedrock

Transported Soil

When the parent material is developed on unconsolidated sediment

Climate

Among the following factors that influences the control of soil formation, which of the following is the most influential?


Parent Material
Climate
Time
Topography

Leaching

Removal of dissolved materials from soil by water moving downwards

Plants

The primary source of organic matter is __________.

Plants
Animals

South-facing slope

This slope orientation receives more sunlight.

North-facing slope
South-facing slope

Horizons

Vertical differences, which usually become more pronounced as time passes, divide the soil into zones or layers known as _________

Soil Profile

A vertical section through a soil showing its succession of horizons and the underlying parent material.

Horizon O
Horizon A
Horizon E
Horizon B

Based on the Soil Profile, which are considered as "True Soil"

Horizon O
Horizon A

What are the top soils in the soil profile?

Horizon B

Known as the Subsoil in the Soil Profile

Horizon O

A soil horizon where loose and partly decayed organic material is found.

Horizon O

_________ horizon is teeming with microscopic life, including bacteria, fungi, algae, and insects.

Horizon A

A soil horizon where mineral matter is mixed with humus.

Horizon A

A soil horizon in a soil profile where biological activity is high.

Horizon E

Refers to the zone of Eluviation and Leaching


Horizon O
Horizon A
Horizon E
Horizon B
Horizon C

Horizon E

A light-colored layer that contains little organic material. As water percolates downward through this zone, finer particles are carried away.

Eluviation

The washing out of fine soil components

Leaching

Depletion of soluble materials from the upper soil is termed

Horizon B

A soil horizon where accumulation of clay that are transported from above is found.

Horizon B

Refers to the zone of accumulation.

Horizon O
Horizon A
Horizon E
Horizon B
Horizon C

Horizon C

A soil horizon characterized by partially altered parent material.

Mature

If a soil profile is well developed which indicates that environmental conditions have been relatively stable over an extended time span.

Immature

If some soils lack horizons altogether because soil building has been going on for only a short time

Nonrenewable

Soil is considered as __________ resource.

Renewable
Nonrenewable

Gullies

When reels are enlarged after a heavy rain they can transformed into still deeper cuts in the soil termed as _________.

Rills

During erosion, runoff travels and forms tiny grooves in the soil called ________.

1930s Dust Bowl

Large dust storms like this one stripped topsoil from large parts of the Great Plains during the dry 1930s.

Although it is a recognized fact that soil erosion can never
be completely eliminated, soil conservation programs can substantially reduce the loss of this basic resource.

Terraces

These nearly flat, steplike surfaces slow runoff and thus decrease soil loss while allowing more water to soak into the ground.

Grassed Waterways

A common practice in soil erosion prevention where natural drainage ways are shaped to form smooth, shallow channels and then planted with grass. The grass prevents the formation of gullies and traps soil washed from cropland

Soil erosion by water also occurs on gentle slopes. One conservation method in which crops are planted parallel to the contours of the slope. This pattern reduces soil loss by slowing runoff. Strips of grass or cover crops such as hay slow runoff even more and act to promote water infiltration and trap sediment.

Secondary Enrichment

Refers to the concentration of minor amounts of metals that are scattered through unweathered rock into economically valuable concentrations by weathering processes.

Bauxite

Principal ore of Aluminum

Bauxite

This ore of aluminum forms as a result of weathering processes under tropical conditions.

Tropical Environment

Where is Bauxite usually formed?

Arid Environments
Alluvial Environments
Tropical Environments
Fluvial environments

Bauxite

Name an important ore that is associated with weathering processes.