JOURNAL #1

• List two things you know about any of the following topics:– Weathering and erosion– Glaciers– Dunes– soil

• List two things you want to know about these topics.

WEATHERING & EROSION

Chapter 7

What is Weathering?

• Process by which rocks on or near Earth’s surface break down and change.

MECHANICAL WEATHERING

• Also called physical weathering.

• Changes rocks size and shape but NOT composition.

• EX:– Frost Wedging: freezing

water expands in rock causing cracks

– Pressure: • from tree roots • removal of rock layers

above. When rock layers are removed, rock can expand causing cracking.

CHEMICAL WEATHERING

• Changes rocks composition

• New minerals are formed

• Determined by– Composition of rock

• Calcite dissolves in acidic water

– Temperature• As temperature increases

so does rate of weathering

Water

• Hydrolysis- reaction of water with other substances.

Oxygen

• Oxidation- reaction of oxygen with water.

• Iron reacts with oxygen & creates rust

• Magnetite + oxgyen = hematite

Acids• Carbon dioxide,

nitrogen oxides, and sulfur dioxides from fossil fuels create acids in atmosphere.

• Cause acid rain.• These acids dissolve

minerals in rocks.• Can also tarnish

metals

WHAT AFFECTS THE RATE OF WEATHERING?

• Climate– Temperature &

precipitation in an area

– Chemical weathering more common where temperatures & precip are higher

– Physical weathering more common where dry, and cold (freezing & thawing occur more common)

• Rock type & composition– Hardness

– Sedimentary rocks more easily weathered than hard igneous or metamorphic

• Surface area– Mechanical weathering

breaks rock up into smaller pieces… creating more surface area for chemical weathering to occur

• Topography & other variables– Sloped areas expose

fresh rock after erosion. Fresh rock can then be weathered.

– Decaying organic matter releases CO2 which creates acid which weathers rock faster.

WHAT IS EROSION?

• Transporting weathered materials from one place to another.

WATER

• Steeper slopes, faster water flows

• Faster water flows, more erosion occurs

• Rill erosion- creates small channels

• Gully erosion- creates deep, wide channels

COASTAL EROSION

• Ocean waves & tides also cause erosion

• Constant erosion of beaches leads to creation of sand bars which eventually become barrier islands.

ICE

• Glaciers– Scrape out large

sections of earth’s landscape

– Carry large rocks & debris over many miles

WIND

• Occur in areas with limited rainfall and high temperatures

• Most of these areas have very little plant-life to hold soil in place

• Creates dunes

PLANTS, ANIMALS, HUMANS

• Minor impact compared to water, wind, glaciers

• When humans excavate land, cause erosion, leads to water pollution

• When animals burrow, shovel dirt somewhere else.