Erosion and Deposition

Erosion… when parts of the land are moved by gravity, water, wind, and/or glaciers.

Elements of Erosion Wind Water Glaciers/ice Gravity

Wind At the Grand Canyon On beaches Wind erosion is dirt and other particles that are blown around eventually reshaping the earth’s features. This process usually happens over time.

Water is a powerful earth shaper!

Water causes more erosion than just about anything else. Need a canyon Water causes more erosion than just about anything else. Need a canyon? No problem! Give it some time, and water can wear away mountains!

Gravity + Glaciers Dragging materials in its path… Glaciers steadily creep downward, slowly scraping the earth, carrying tons of it downhill.

A fast change ~ an avalanche! While a glacier is a slow change... Whoosh! The roar of a mountainside of ice and snow crashing down in an avalanche, ripping everything up in its path, rapidly changes the face of the earth. A fast change ~ an avalanche!

Humans cause erosion too!

Deposition… Where erosion ends up

Where wind drops its load Wind picks up and transports grains of sand. Sand grains bounce along the ground. If you stand on a windy beach, you can feel them stinging your ankles! When the wind speed drops a little, sand stops being moved and is deposited, often building up dunes like the ones shown below. Sometimes, sand dunes gradually move as sand is blown up the dune and over the crest. It is then deposited where there is shelter from the wind. ( Shown below and below right.) Sand dunes, near Borth, Wales

Deposition by ice This ridge along the edge of a field is evidence that this area was covered by ice about 10,000 years ago. It was not man made, but was left at the front of a melting glacier. As glaciers move they scrape along the valley floor eroding large amounts of rock material. They also transport frost-shattered boulders that fall from the valley sides and land on the glacier. When the glacier melts, this mixture of finely-ground rock, pebbles and large boulders, is left as ridges.

Evidence of glaciers U-shaped valleys are formed by the scraping of glaciers. Imagine how much erosion had to occur to form these glacial valleys. Is there deposition in the valleys? What do you see here? How do you think these rocks ended up here?

Deposition by water The light colored material on the left side of the landform was deposited by a mudflow, and represents the most recent addition of sediment to this landform.

More deposition by water Fast-flowing streams move rock grains, pebbles, and even large boulders for short distances, after heavy rain. During their long journey down river, the rock fragments may settle, only to get picked up again many times, and become gradually more worn-down and smaller in size each time they are bounced along their journey. When rivers meet the sea, they often form estuaries like this one. As the current slows, sand and gravel is deposited to form sandbanks. (See photo.) The finest material, mostly mud, may settle, forming mudflats or be carried further out to sea where it finally settles to the bottom in calmer water

Compare… What causes deposition? wind water ice gravity