BSES 34 - WEATHERING AND EROSION

Rock Cycle

A model of natural changes in rocks and rock material

Weathering

Process by which rocks are broken down due to exposure to processes occurring at the Earth's surface

Mechanical Weathering (Physical weathering)

Rock is broken down into smaller pieces of the same material (no change in composition)

Chemical Weathering

The breakdown or decomposition of rock that occurs when minerals are changed into different substances (change in composition)

Frost (Ice) Wedging

Process in which water freezes in the cracks of rock and wedges (pushes) it apart because water expands when it freezes

Abrasion

The wearing away of rock material by grinding action

Thermal expansion and contraction

Repeated heating and cooling of materials cause rigid substances to crack and separate

Plant Growth and Burrowing Animals

Plant roots can split rock, also known as "Root pry" or "Root action"

Exfoliation

Gradual peeling of layers due to uplift and frost action

Carbonation

Carbonic Acid in water dissolves Calcite

Oxidation

Oxidation of minerals with iron (magnetite, pyrite) results in the formation of rust or iron oxide

Hydrolysis

Minerals may chemically combine with water to form new minerals

Regolith

"Rock blanket" which is composed of small rock and mineral fragments

Soil

Regolith mixed with organic matter

Erosion

The removal and transport of weathered materials by natural agents

Glaciers

Mass of compacted ice and snow that moves under its own weight

Erratic

Large boulders that glaciers can leave behind

Striations

Grooves that glaciers can carve into rocks

Velocity

How fast the water moves

Gradient

The steepness, the slope that a river or stream travels

Discharge

The amount of water that moves past a certain point in a river in a given amount of time

Creep

Very slow movement of earth material caused by repeated freezing and thawing

Slump

Slow downward movement of a large mass of soil

Mudflow/Earthflow

Thick pastes of sediments that travel downhill at great speeds

Landslide/Rockslide

Fast movement of large blocks of rock

Scree

Loose sediments transported by gravity

Deposition

The process of dropping or depositing soil and sediments

Humus

The dark colored semi-soluble organic substance formed from decomposition of soil organic matter

Forest soil

A kind of soil that grows in humid weather, cool seasons and forest of hardwood and evergreen

Desert soils

Very dry, shallow soils that contain much calcium

Arctic soils

Soils found at the bottom layer that is permafrost and poorly drained

Tropical soil

Soil that thrives in high temperatures and heavy rain

Grassland soil

The kind of soil that must have enough rain for heavy grass

Sand

A granular form that can be seen by the naked eye

Loam

A kind of soil that is medium-textured

Silt

Smooth and slimy when wet and its particles are smaller than sand

Clay

Sticky and mud like projection of a soil

Residual soil

The parent rock is the bedrock beneath the soil (the soil has not moved)

Transported soil

Soil forms from parent material left by winds, rivers, glaciers, or soil that was moved from its original location

Soil Profile

Cross section of soil layers revealing all soil horizons

Soil Horizon

A soil layer with physical and chemical properties that are different from adjacent layers

O Horizon

Organic material (humus)

A Horizon

Topsoil

B Horizon

Subsoil

C Horizon

Partially weathered parent material

Leaching

The removal of nutrients or toxins in soil as water passes through the layers

Soil Texture

The size of soil particles