Weathering is the process of decomposing, breaking up, or changing rocks without moving them from their original location. Erosion is the process of moving weathered rock and soil particles from their original location by forces like wind, water, or ice. Weathering can occur through chemical processes that alter the minerals in rocks or through mechanical processes that break rocks into smaller pieces without changing the minerals. Once weathered, smaller rock pieces can be eroded and transported elsewhere by natural forces.

1. What is the difference between weathering
and erosion?
Weathering is the process of decomposing, breaking up, or
changing the color of rocks. Weathering may be caused by the action of
water, air, chemicals, plants, or animals. Chemical weathering involves
chemical changes in the minerals of the rock, or on the surface of the rock,
that make the rock change its shape or color. Carbon dioxide, oxygen,
water, and acids may all cause chemical weathering. Mechanical
weathering is the process of breaking a large rock into smaller pieces
without changing the minerals in the rock. Mechanical weathering may be
caused by frost, ice, plant roots, running water, or heat from the sun.
Once the small pieces of rocks are changed or broken apart by
weathering, they may start to be moved by wind, water, or ice. When the
smaller rock pieces (now pebbles, sand or soil) are moved by these natural
forces, it is called erosion.
So, if a rock is changed or broken but stays where it is, it is called
weathering. If the pieces of weathered rock are moved away, it is called
erosion.
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2. Erosion caused by rain or irrigation, showing how
water can wash away the soil
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3. Shoreline erosion caused by the ocean
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Soil erosion caused by rain

4. Erosion at the edge of a road, caused by rain
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Erosion caused by flooding

5. The Grand Canyon, formed by erosion from water and wind
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6. Erosion by waves, forming a natural bridge
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7. Natural Bridge, Virginia, formed by erosion from river water
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8. Weathering and erosion caused by wind
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9. Erosion in fields caused by wind blowing loose soil
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10. Wind erosion of sand dunes
Dust storm caused by wind erosion of loose soil
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11. Extreme erosion caused by wind over long periods of time
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12. Chemical weathering caused by chemicals in the rocks reacting
with the groundwater
Chemical weathering of a statue, caused by acid rain
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13. Chemical and mechanical weathering, caused by rain
and wind
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14. Mechanical weathering caused by glacial ice
Mechanical weathering by frost and ice, causing the rocks to break apart
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15. 15
Mechanical weathering

16. Mechanical weathering called exfoliation,
causing the rocks to break into layers
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17. 17
Chemical weathering
causing minerals in the
rocks to dissolve, and
then form stalactites
and stalagmites in a
cave

18. Mechanical weathering showing how rocks can be broken by
ice or water
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19. 19
Mechanical weathering
caused by tree roots
Mechanical weathering
caused by plant roots,
lichens, and mosses on
the rock

20. Mechanical weathering and erosion caused by a landslide
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21. Natural Chimney, West Virginia
What do you think caused this rock formation?
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Compiled for Project PROMISE,
2007