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.