Geography Chapter 2.4 external forces

Wind, heat, cold, glaciers, rivers, and floods alter the surface of the earth.

The results of weathering and erosion change the way humans interact with the environment.

Weathering is the physical and chemical processes that change the characteristics of rock on or near the earth’s surface

Can change landscapes over time and create soil for plant life - Occurs slowly over MANY years, even

centuries

The image shows weathering of sandstone and shale. The steep cliffs are made up of weathering resistant sandstone, while the slope at the base of the cliff is composed of rock units containing a larger abundance of shale.

The surface pattern on this pedestal rock is honeycomb weathering, caused by salt crystallization. This example is at Yehliu,

Taiwan.

• A maze of hoodoos in Bryce Canyon National Park in southern Utah in the early morning. This photo was taken on a sunny day in May 2002.

Weathering creates smaller and smaller pieces of rock called sediment.

-Sediment can be identified as fine particles of rock such as mud, sand, silt, etc.

Processes that break rock into smaller pieces - Does not change the

composition of the rock – ONLY ITS SIZE!

- Many factors can contribute to mechanical weathering including; water, ice, wind, plants, animals and even humans!

Occurs when rock is actually changed into a new substance due to the interactions of the elements in the air, water or minerals. - Climates that are warm and moist will produce

more chemical weathering than cool dry areas.

Sea caves form from carbonation, a type of chemical weathering.

Occurs when weathered material is moved by the action of wind, water, ice, or gravity.

Ex. Water carrying topsoil from a hill into a river will cause the river to narrow.

1) when water flows in a stream or river, picks up loose material and moves it downstream

2) abrasion, grinding away of rock by transported particles

3) water dissolves chemical elements in the rock (changes composition of rock)

When a river enters an ocean, the sediment is deposited in a fan-like landform

Mississippi River Delta

Waves on a coastline may also change the land

Waves can reduce or increase beaches

Sediment from waves may build up sand bars or islands

Double trouble Dana Goegelman looks over the damage and erosion to the beach beside her parents hotel in Indiatlantic, on Tuesday, Sept. 28, 2004. The Casablanca Inn was damaged by Hurricane Frances and then later lost much of its beach and walkway to erosion when Hurricane Jeanne pounded the Florida coast on Sunday. (AP/ Dave Martin / September 28, 2004)

loess (LOH•uhs)

windblown silt and clay sediment that produce very fertile soil

silt – fine sand carried by moving water

A typical loess exposure in southern Illinois

The Mississippi River Valley in the U.S. and grasslands of Argentina have extensive amounts of loess.

May produce new landforms (sand dunes)

Similar to water erosion, the wind transports and deposits sediments in other locations

glaciers

large, long-lasting mass of ice move because of gravity form in mountainous areas form in heavy snowfall regions

the changing of landforms by slowly moving glaciers

Erosion occurs when glaciers move

When glaciers move, they carry rocks with them

Rocks left behind by a glacier may form a hill or ridge called a moraine

Who you callin’ a moraine!?

Different kinds of moraines on and near Gornergletscher, Valais, Switzerland: 1 - lateral moraines, 2 - middle moraines, 3 - terminal moraine (this moraine was deposited during the Little Ice age by the small cirque glacier of which two remnants remain, above and above left of the letter "3".

hyoo-muhs the organic material in soil

humus

1) parent material 2) relief 3) organisms 4) climate 5) time

The variety of soils – and the climates in which they’re found – determine what can grow there.