Weathering and Mass movements quiz


Weathering- the chemical and physical breakdown of rocks on or at the Earth’s surface into smaller fragments.

  • Weathering is the preparation for erosion


Erosion- the movement of weathered material from one place to another. 

  • Response to the effect of the environment on Earth’s crust


Weathering agents- Change the physical and/or chemical characteristics of the rocks.

  • Climate is the most important factor in the weathering process


Weathering Types

The two types of weathering are physical and chemical


Physical weathering


Physical weathering- occurs when a rock is cracked, split, or broken into smaller pieces called sediments.

  • No change in rock composition


Sediments- Classified by size as boulders, cobbles, pebbles, sand, silt, clays, and dissolved particles.


Frost action- The breakup of rocks caused by alternate freezing and thawing of water.

  • Water condenses or seeps into the smaller cracks or spaces in rock as well as larger openings is more porous than before

  • Repeated freezing and expanding of water in these spaces will cause the rock to crumble


Abrasion- Physical wearing down of rocks as they trub or bounce against each other. Water or wind or gravity pick up other rocks

  • Mostly in dry windy areas, ex; under glaciers, stream channels


Exfoliation- Peeling away large sheets of loosened material at the surface of a rock. 


Root wedging- Large shrubs grow through cracks in boulders may break the rock apart.


Chemical weathering


Chemical weathering- occurs when a rock is broken down by chemical action resulting in a change in the composition of the rock.

  • Agents Oxygen, rainwater, carbon dioxide, and acids produced by decaying plants and animals.


Oxidation- Occurs when oxygen unites chemically with minerals

  • Ex; When oxygen combines with iron, rust (iron oxide) is formed

  • Looks different in different types of rocks.


Hydration- when waters unite chemically with minerals.

  • Certain minerals such as hornblende and feldspar unite with water, they crumble into small particles of clay


Carbonation- when carbon dioxide unites chemically with minerals. 

  • When carbon dioxide is dissolved in water, it forms weak carbonic acid

  • Carbon acid readily dissolves large masses of limestone, creating caves, caverns, and other structures in the bedrock


Acid Precipitation- Comes from acids mixed with rain or snow

  • Ex: Burning fossils fuels


Groundwater- Contains weak acids which dissolve some kinds of rocks


Sinkholes- Saucer shaped holes in the surface of the land are left when carbonic acid dissolves limestone in the ground.


Karst topography- A limestone area pitted with sinkholes


Stalactites- Limestone deposits on the ceiling and floor.

  • Icicle shaped

  • “C” Ceiling


Stalagmites- Deposits which “grow up” from the ground

  • “G” ground


Organic decay- occurs when acids, which are formed when plants and animals decay, dissolves in water


Soil-  the part of the weathered regolith in which rooted plants will grow. It is composed primarily of particles of rocks, minerals, and organic matter, and consists of all three states of matter. Solid, sand and clay make up the bulk of the soil while minerals and decayed organic matter supply it with nutrients. Liquid water allows the chemical actions necessary to produce a mature soil. Air and the gases, oxygen and nitrogen, present mainly in solution, provide the soil with nutrients and increase the weathering processes in the soil.

Particle size- The weathering rate of rock material varies inversely with particle size.

  • The smaller the particles the greater the weathering rate

  • Larger solid pieces of rock weather more slowly than smaller and loose pieces of the same rock


Mineral Composition- Rock particles weather at different rates depending on their mineral composition. 

  • Hard rocks= slower weathering

  • Soft rocks= faster weathering


Abrasion- the grinding and bumping of one rock against another.


Transported sediment- Rock material that has been transported from its place of origin to another location.


Residual sediment- Rock material that has weathered and remained in its place of origin.


Transporting agents- Forces which move sediments from one place to another.


Mass movement- When the Earth moves downslope under the influence of gravity.


Gravity- Primary Driving force behind all transporting (erosional) systems.


Soil Profile- As soils mature they grow richer, developing a series of layers called soil profile. Each layer has a different texture, colors, and composition


Topsoil- The top layer of the soil

  • Most organic matter

  • Best for growing plants


Subsoil- Under the topsoil

  • Rich in clay sized particles