weathering and erosion,soil, and mass movements.

Rock Fall

Rocks that typically fall *straight* down from a *cliff* after being broken up by weathering processes. Only one that doesn't use a slope.

Wind

Wind is a major agent of erosion in areas of *limited* precipitation and *high* temperatures. Such areas typically have little *vegetation* to hold soil in place, and the wind is easily able to pick up and move the fine, dry particles found there.

Running water

With the exception of extremely strong winds (*tornades* and *hurricane*), water has more power to move large particles of weathered material than wind does. Running water moves along Earth's surface from *higher* elevations to *lower* elevations. Rivers carry *eroded* *sediments* to the ocean where they are *deposited*, forming a *delta*. In the ocean, *currents*, *waves* and *tides* continue the erosion process by carving out cliffs, arches and other features along the continents' edges. Erosion also wears away the *shorelines* of islands

3 major soil horizons

Zone A Contains *high* of organic matter and humus Top soil Zone B Contains subsoils that are enriched with *clay* Zone C Contains weathered *parent* material

Plants, Animals and Humans

As plants and animals carry on their *life* *processes*, they move material from one place to another (ex: animals burrowing). Human *construction* projects and *farming* also contribute to the movement of materials. These total effects are minimal compared to the effects of wind, water & glaciers.

weathering and erosion

As we learned when discussing sedimentary rock formation, the processes of *weathering* and *erosion* change Earth's landforms and form soil, an important natural *resource*. Soil is needed mostly for food Both weathering and erosion have been going on since the crust of Earth formed, *billions* of years ago.

Soil formation

As we learned when discussing weathering and erosion, soil is a valuable *natural* *resource*. Without soil we would have difficulty growing *food*, growing feed for *livestock*, growing wood for construction, as well as a serious reduction in the amount of *oxygen* produced by plants.

polar soils

Forms at *high* latitudes & *high* elevations. These soils have good drainage, but no distinct horizons because they are quite shallow—sometimes only a few inches deep. Not very much soil, low plant growth

Slide

A *sudden* downslope movement of Earth materials that occurs when a relatively *thin*block of loose soil rock & debris separates from the underlying bedrock (ex: landslide and avalanche). Loose liquid on top sliding down

Soil Horizon(e)

A distinct layer, or *zone*, within a soil profile.

Flow

A mass movement where the materials move as if they were a thick *liquid* (ex: mudflow) loose,wet, and moves as a liquid

Soil Types

A soil's appearance, rate of formation, and productivity are determined to a great extent by *climate*. Because soils form from different bedrock, and experience different climatic conditions, soils vary greatly from one *location* to the next. The four major soil types are: *polar*, *temperate*, *desert* & *tropical*

Desert soils

Due to very low *precipitation*, desert soils often have high levels of accumulated salts, and can support only limited amounts of *vegetation*. These soils have very little organic matter, and a thin A-horizon, but they do have abundant nutrients

Soil composition

During its formation, soil forms in *layers*. The smallest pieces, along with living and dead organisms form the uppermost layer. It can take hundreds of years for a single *inch* of soil to form.

Glaciers

Glaciers, now only covering 10_% of Earth's surface, scrape and gouge out large sections of the landscape. Glaciers can move enormous amounts of materials, depositing them as they *melt* and *retreat*.

Tropical Soils

High temperatures & heavy precipitation lead to intensely *weathered*, and often infertile, soil. These soils have very little humus and few nutrients. Few nutrients because the plants have already taken up all of the nutrients.

Erosion and deposition

Many agents can *transport* weathered materials from one place on Earth to another.

Topography

Materials on *level* surfaces are likely to remain in place as they undergo changes, whereas materials on *slopes* have a greater tendency to move as a result of *gravity*. As material moves down a slope, it uncovers more material, exposing it to weathering.

Surface area

Mechanical weathering breaks up rock into smaller pieces. As the pieces become *smaller*, their *surface* *area* increases, allowing more surface for chemical weathering to occur

Slump

Occurs when the mass of material in a landslide *rotates* and slides along a *curved* surface.

Residual Soil

Soil located *above* the parent rock. Soil touching the parent rock

Transported Soil

Soil that has been moved to a location *away* *from* its parent bedrock. How can this transported soil wind up away from its parent rock? Erosion can move soil from one place to another now is considered transported when it is away from its parent material

Erosion

The *removal* and *transport* of weathered material from one *location* to another.

Creep

The *slow*, steady downhill flow of loose, weathered Earth materials, especially soil.

Soil Profile

The *vertical* *sequence* of soil layers.

Rock type and composition

The characteristics of the rock, including how hard they are, depend on their type and composition. In general, *sedimentary* rocks are more easily weathered than harder igneous or metamorphic rocks.

Humus

The dark-colored, partially *decomposed* plant or animal material that forms the *organic* portion of soil. Soil-forming begins when *weathering* breaks rock into smaller and smaller particles. Soon organisms, such as *bacteria*, *fungi* and insects begin to live in the material. Over time, these organisms die, decay and add nutrients to the weathered material to form soil.

Gravity

The force of gravity tends to pull materials *downslope*. Also, without gravity, glaciers would not *move* and rivers and streams would not *flow*.

Soil

The loose covering of broken rock particles and *decaying* organic matter overlying the *bedrock* of Earth's surface. Soil is the result of chemical & mechanical weathering and biological activity over long periods of *time*. Soil is made of two parts, weathered rock and the organic matter

Soil fertility

The measure of how well soil can support the growth of *plants*.

mass movements

The movement downslope of *loose* sediments and *weathered* rock resulting from the force of *gravity*. Need slope and need gravity in order for a mass movement to occur. Usually, after an area of Earth's surface is weathered, erosion soon follows. However, after the weathering process has weakened and *broken* rocks into smaller pieces, mass movement may occur and carry the debris *downslope*. All mass movements occur on *slopes*. Because very few places on Earth are completely *level*, mass movements occur almost everywhere. Mass movements range from extremely *slow* motions, to sudden (and often violent) slides, falls & flows. The material that is moved can range from *fine* mud to *large* boulders. Four variables that influence mass movement: 1) The material's *weight* 2) The material's *resistance* to sliding or flowing 3) A trigger, such as an *earthquake* 4) *water*

Mechanical weathering

The process by which rocks & minerals *break* *down* into smaller pieces. Also known as *physical* weathering. This does not result in any change in the rock's *composition*. Some agents of mechanical weathering include *temperature* (ex: frost wedging) and *pressure* (ex: exfoliation & root wedging).

Chemical weathering

The process by which rocks & minerals undergo changes in their *composition* as a result of *chemical* reactions. Some agents of chemical weathering include *water*, oxygen, carbon dioxide and *acids*. Water dissolves everything/ certain rocks

Weathering

The process by which rocks on or near Earth's surface *break* *down* and change. Weathering is the process of breaking down rock

Soil texture

The relative proportions of *sand*, *silt* and *clay* in a mixture of soil. The texture affects its capacity to retain moisture & therefore support growth.

Parent Rock

The solid *bedrock* from which weathered pieces of rock first break off.

Temperate soils

These soils vary greatly and can support diverse environments, such as *forests*, *grasslands* & *praires*. Grasslands have an abundance of humus providing for a rich, fertile soil. Forests are characterized by less deep & less fertile soils that contain clays and iron oxides.

mass movement

Weathering and erosion is the *breaking down* and *transporting* of rock through the actions of *wind*, *water*, *ice* and *gravity*. Weathering and erosion of a large mass.

What affects the rate of weathering?

climate, rock type and composition, topography, surface area.

Climate

includes: *temperature*, *precipitation* & evaporation Chemical weathering is most abundant in *tropical* zones (i.e. warm temperatures, abundant rainfall and lush vegetation) Physical weathering is most abundant in *temperate* zones (i.e. cool, dry climates where water undergoes freezing & thawing)