15 terms

6th grade earth science ch. 7: weathering and soil

chemical weathering
occurs when chemical reactions dissolve the minerals in rocks or change them into different minerals
the average weather pattern in an area over a long period of time; can be classified by temperature, humidity, precipitation, and vegetation
contour farming
Planting along the natural contours of the land to reduce soil erosion.
each layer in a soil profile--horizon A (top layer of soil), horizon B (middle layer), and horizon C (bottom layer)
dark-colored, decayed organic matter that supplies nutrients to plants and is found mainly in topsoil
ice wedging
Mechanical weathering process that occurs when water freezes in the cracks of rocks and expands, causing the rock to break apart
the removal of minerals that have been dissolved in water
twigs, leaves, and other organic material that help prevent erosion and hold water and may eventually be changed into humus by decomposing organisms
mechanical weathering
physical process by which rock is split or broken into smaller pieces without changing its chemical composition, disintegration; can be caused by animals, ice wedging, and plant roots
no-till farming
Method for reducing soil erosion; plant stalks are left in the field after harvesting and the next year's crop is planted within the stalks without plowing.
chemical weathering process that occurs when some minerals are exposed to oxygen and water over time
mixture of weathered rock and mineral fragments, decayed organic material, water, and air that can take thousands of years to develop
soil profile
vertical section of soil layers, each of which is a horizon
farming method used to reduce erosion on steep slopes
mechanical or chemical surface process that break rock into smaller and smaller pieces