• How are weathering and soil formation related?

• How do weathering, erosion, and deposition change Earth’s surface?

• How are erosion and deposition related?

Weathering, Erosion, and Deposition

• weathering• erosion• physical weathering• chemical weathering

Weathering, Erosion, and Deposition

• soil• sediment• deposition

• Weathering refers to the processes that break down rocks, changing Earth’s surface over time.

• Erosion is the moving of weathered material, or sediment, from one location to another.

Weathering

Slowly but surely, weathering and erosion wear down mountains.

Weathering (cont.)

Photo by Tim McCabe, USDA Natural Resources Conservation Service Dr. Parvinder Sethi

• The process of breaking rock into small pieces without changing the composition of the rock is physical weathering.

• Frost wedging is what occurs when water in rocks freezes and melts repeatedly, breaking the rocks apart.

Weathering (cont.)

The roots of plants can grow into cracks in rock and eventually break the rock.

Weathering (cont.)

• The process of changing the composition of rock and minerals by exposure to water and the atmosphere is called chemical weathering.

• Gases in the atmosphere can cause chemical weathering.

Weathering (cont.)

• Physical weathering exposes more surface area of rocks, allowing more water and atmospheric gases to enter rocks.

• Chemical weathering weakens rocks by changing the composition of some minerals and dissolving others.

Weathering (cont.)

• Soil consists of weathered rock, mineral material, water, air, and organic matter from the remains of organisms.

• Soil forms directly on top of the rock layers from which it is made and is the result of hundreds to thousands of years of weathering.

Weathering (cont.)

Soil formation begins when physical and chemical weathering break down rocks.

Soil formation begins when physical and chemical weathering break down rocks.

• Warm, wet climates produce soil fastest. • Large amounts of rain can speed

weathering of rocks, and chemical reactions are faster in warmer temperatures.

Weathering (cont.)

• The minerals and small pieces of rock produced by weathering are called sediment.

• Moving water causes erosion by picking up rock pieces and sediment, which scrape along the ground picking up more material.

Erosion

• Large masses of ice, called glaciers, cause erosion by flowing down a mountain and removing rock and sediment.

• Erosion by glaciers makes deep valleys and steep peaks.

• Strong winds also can erode and move sediment.

• Soil and rock that are not protected by plants can be eroded by wind.

U.S. Department of Agriculture

• Deposition is the process of laying down eroded material in a new location.

• If the speed of flowing water decreases, the water can no longer carry sediment and the sediment settles at the bottom of the water.

• Floodplains form when sediment settles out of rivers that flood the areas next to them.

Deposition

• When glaciers melt, the water produced by the melting ice does not flow fast enough to carry sediment.

• Glacial deposits of sediment are called moraines.

• Wind also can deposit sediment. • Sand dunes are landforms made as wind

continually moves and deposits sand grains.

Tim McCabe/NRCS

• The locations where sediment accumulates are called sedimentary basins.

• Sediment continues to be deposited in low areas and then forced upward as tectonic activity forms mountains.

Deposition (cont.)

• Physical and chemical weathering work together and change Earth’s surface. They break down rock and form sediment.

• Erosion occurs when sediment is removed and transported from where it formed.

• Deposition occurs when sediment is laid down in new locations.

Which process breaks rock into small pieces without changing the composition of the rock?

A. depositionB. erosion C. chemical weathering D. physical weathering

A. glaciersB. sand dunes C. sediment D. soil

Which are the minerals and small pieces of rock produced by weathering?

A. soilB. glacier C. sand dune D. sedimentary basin

Which location accumulates sediment?

5. Rocks cannot change.6. Sediment can be transported by water,

wind, and ice.

Do you agree or disagree?