Chapter 12 Vocabulary
Weathering, Soil, and Erosion
Abrasion – The wearing away of rock by grinding material
Acid Rain – Rainwater that contains unusually high amounts of acids that can be traced back to
pollutants, including sulfur dioxide, nitrogen compounds, and carbon dioxide.
Chemical weathering – The breakdown or decomposition of rock that takes place when
minerals are changed into different substances.
Erosion – The removal and transport of materials by natural agents such as wind and running
water.
Exfoliation – The peeling of surface layers from exposed bedrock.
Frost wedging – A mechanical weathering process in which water freezes in the cracks of a rock
and wedges it apart.
Hydrolysis – The chemical reaction of water with other substances.
Landslide – The rabid movement of a mass of bedrock or loose soil and rock down the slope of
a hill, mountain, or cliff.
Mass movement – The downslope transportation of large masses of earth materials by gravity.
Mechanical weathering – The breakdown of rock that takes place when a rock is broken into
smaller pieces of the same material without changing its composition.
Oxidation – The chemical reaction of oxygen with other substances.
Parent material – The rock material from which a soil is formed.
Residual soil – Soil whose parent material is the local bedrock beneath it.
Salinization – A soil condition caused by the evaporation of irrigation water, which leaves too
much mineral matter on the soil’s surface for crops to grow.
Soil – Loose, weathered rock and organic material in which plants with roots can grow.
Soil depletion – The process by which soil gradually becomes so lacking or depleted in nutrients
that it can no longer grow a crop.
Soil fertility – The ability of soil to grow plants.
Soil horizon – A soil layer with physical and chemical properties that differ from those of
adjacent soil layers.
Soil profile – A cross section of soil layers that displays all soil horizons.
Subsoil – The B-horizon of soil; contains clay and iron oxides washed from the topsoil.
Talus – Cliff rock fragments that have been weathered loose and pulled down by gravity.
Topsoil – The A-horizon of soil; contains organic material, or humus, that forms from decayed
plant and animal materials.
Transported soil – Soil that formed from parent material left by winds, rivers, or glaciers or soil
that itself was moved from its original location.
Weathering - The breakup of rock due to exposure to processes that occur at or near Earth’s
surface.