Erosion DEPOSITION Erosion Deposition Terms Erosion is the

Erosion & DEPOSITION

Erosion & Deposition Terms • Erosion is the process that moves weathered rock sediments from one location to another • Deposition is the dropping of sediments. • Weathering is the breaking down of rock into smaller pieces

The following slides show examples of weathering: Chemical & Mechanical

This rock is red because of the oxidation of iron in the sediment when the rock was being formed. (Chemical)

Root Pry The tree is growing in the rock and soon the rock will break apart because of the tree roots.

This is a picture of the Half Dome. The rock is peeling away from the mountain in layers just like an onion. This is exfoliation. (Mechanical)

Frost Action or ice wedging slowly breaks up this sedimentary rock into unusual shapes. (Mechanical)

Acid Rain 1908 to 1969 Acid rain has eaten away this limestone statue. (Chemical)

Erosion There are many kinds of Erosion. Here a few: • Wave Action • Avalanche • Creep • Running Water • Glaciers • Rock Fall • Landslides • Slump • Mud Flow

Wave action is when waves hit the rocks and pieces of rock break off. (Mechanical)

Agents of Erosion • • Gravity Running Water Wind Glaciers All agents of erosion carry sediments when they have energy of motion, and drop them when they lose their energy of motion.

Gravity Mass Movements Caused by Gravity: Slumps, Creeps, Rockslides, & Mudflows

This is a picture of a landslide. A landslide is a term used for all mass movements. Landslides leave unstratified deposits.

Slumps • A type of mass movement that takes place on steep slopes • loose materials slip down as one large mass • doesn’t travel fast or far • curved scar is left • material underneath slumped

In this picture the land has slumped into the road below.

Creep • leaning things such as telephone pole, fence posts, or trees • sediments slowly creep down the hill • common where freezing and thawing occur (ice wedging) • ground freezes, pushing up sediments, the ground thaws and the sediments fall downslope • less than a mm at a time

This is a diagram of creep. The hillside slowly slips over many years from temperature or water.

Rockslide • when large blocks or rock break loose from top of steep slopes and tumble to the bottom • happen in mountainous areas • happen frequently after earthquakes and heavy rains but can occur without warning • “beware of falling rocks” signs • pile of rocks at the bottom of a slope (talus slope)

Mudflows • thick mixture of sediments and water • happen in relatively dry areas where thick layers of dry sediments form • heavy rains mix with sediments and form a thick, pasty substance • lots of energy, can move anything in its path ( cars, houses, etc) • drops sediments and debris and forms coneshaped deposits

Mudflows

Mudflows

This is a picture of an avalanche. It is similar to a landslide with ice and snow instead of rock.

How All Mass Movements are Similar • • happen where there is a steep slope all depend on gravity occur frequently after heavy rains erosion of sediments from the top of a slope to further down • makes slopes less steep

Running Water Erosion Caused by Running Water

Running Water • Water erodes more sediments than any other agent of erosion. • Water moves downslope. • When water loses energy, it deposits sediments. • Sediments are picked up from the bottoms and sides of streams. • Large sediments roll along the bottom; small sediments are picked up and carried by the water. • Sediments that are being carried knock even more sediments loose, which causes channels to widen and get deeper

Types of Water Erosion Rill Erosion Gully Erosion Sheet Erosion

Rill Erosion • small stream forms during heavy rain • carries away plants and soil • leaves a scar • can lead to gully erosion

Gully Erosion. --carries away large amounts of soil - rill channel gets broader and deeper

Sheet Erosion • happens outside stream channel • water accumulates and eventually starts moving downslope, carrying soil with it • water soaks into soil or evaporates, leaving a sheet of soil

In this picture the running water eroded the sides of this canyon and created the V-shaped valleys.

Water Deposition

Water Deposition • Some stream sediments travel great distances before being deposited • The Coastal Plain region of Virginia was formed from the deposition of sediments eroded from the Appalachian Mountains • Water has a lot of energy when flowing downslope- but it loses it when the ground becomes level

Types of Water Deposition • Alluvial Fans -shaped like a triangle -located on land at the bottom of slopes • Delta -sediments are deposited when a channel runs into a gulf, ocean, or lake -triangle-shaped deposits -Mississippi River Delta- largest in United States

Alluvial Fans

Alluvial Fans

Deltas

WIND EROSION & Wind Deposition

Wind Erosion • Deflation- the moving of small sediments • Abrasion -compares to sandblasting -grains bump into one another as they roll along ground -grains pit and polish rocks

These rocks have been blasted by wind and sand causing them to become rounded. WIND ABRASION

Wind Deposition 2 Types: Dunes & Loess

Dunes • most common wind deposits • happen when sediments blow against an obstacle and pile up • form in deserts and beaches • dunes on Mars are evidence of wind

Dunes

Loess Deposits • large deposits in United States and China • mid-western area has good farming because of these deposits • loess deposits of China form from sediments from Gobi and Ordos Deserts • fine as talcum powder

This is a picture of a glacier which carves out a U-shaped valley where it flows dragging rocks and boulders along the way.