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7th science 8
weathering and soil erosion
definition | term |
---|---|
is the process that breaks down rock and other substances at Earth’s surface. | weathering |
is the removal of rock particles by wind, water, ice, or gravity. | erosion |
work together continuously to wear down and carry away the rocks at Earth’s surface. | weathering and erosion |
This principle states that the same processes that operate today operated in the past. | uniformitarianism |
The type of weathering in which rock is physically broken into smaller pieces is called. | mechanical weathering |
include freezing and thawing, release of pressure, plant growth, actions of animals, and abrasion. | the causes of mechanical weathering |
refers to the grinding away of rock by rock particles carried by water, ice, wind, or gravity. | abrasion |
When water seeps into cracks in rocks and then freezes when the temperature drops. Water expands when it freezes. Ice therefore acts like a wedge that forces things apart. Wedges of ice in rocks widen and deepen cracks. | ice wedging |
is the process that breaks down rock through chemical changes. | Chemical weathering |
include the action of water, oxygen, carbon dioxide, living organisms, and acid rain. | the causes of chemical weathering |
is the most important cause of chemical weathering. | water |
Iron combines with oxygen in the presence of water in a process. | oxidation |
also causes chemical weathering. | carbon dioxide |
The most important factors that determine the rate at which weathering occurs | type of rock and climate |
means that a material is full of tiny, connected air spaces that allow water to seep through it. | Permeable |
refers to the average weather conditions in an area. | climate |
the loose, weathered material on Earth’s surface in which plants can grow. | soil |
the solid layer of rock beneath the soil. | bedrock |
a mixture of rock particles, minerals, decayed organic material, water, and air. | soil |
a dark-colored substance that forms as plant and animal remains decay. | Humus |
The __________ of soil is a measure of how well the soil supports plant growth. | fertility |
Soil that is made up of about equal parts of clay, sand, and silt. | loam |
forms as rock is broken down by weathering and mixes with other materials on the surface. Soil is constantly being formed wherever bedrock is exposed. | soil |
A ______ __________ is a layer of soil that differs in color and texture from the layers above or below it. | soil horizon |
The A horizon is made up of ________, a crumbly, dark brown soil that is a mixture of humus, clay, and other minerals. | topsoil |
The B horizon, often called ________, usually consists of clay and other particles washed down from the A horizon, but little humus. | subsoil |
Scientists classify the different types of _______ into major groups based on climate, plants, and soil composition. | soil |
As plants shed leaves, they form a loose layer. | litter |
are the organisms that break the remains of dead organisms into smaller pieces and digest them with chemicals. | Decomposers |
the thick mass of tough roots at the surface of the soil—kept the soil in place and held onto moisture. | sod |
anything in the environment that humans use. | natural resource |
one of Earth’s most valuable natural resources because everything that lives on land, including humans, depends directly or indirectly on it. | soil |
The value of soil is reduced when soil loses its fertility and when topsoil is lost due to _______. | erosion |
can be damaged when it loses its fertility. | soil |
Whenever soil is exposed, _____ ___ ____ can quickly erode it. | water and wind |
The area of the Great Plains where wind erosion caused soil loss during the 1930s. | Dust bowl |
the management of soil to prevent its destruction. | soil conservation |
can be conserved through contour plowing, conservation plowing, and crop rotation. | soil |
farmers plow their fields along the curves of a slope. | contour plowing |
farmers disturb the soil and its plant cover as little as possible. | conservation plowing |
a farmer plants different crops in a field each year. | crop rotation |