journal #1 list two things you know about any of the following topics: –weathering and erosion...
TRANSCRIPT
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.