80 Weathering and Erosion Notes 10/27/14 79 10/27/14 Starter: Warm Up: Application/Connection/:...
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Transcript of 80 Weathering and Erosion Notes 10/27/14 79 10/27/14 Starter: Warm Up: Application/Connection/:...
80 Weathering and Erosion Notes
10/27/14
79
10/27/14
Starter: Warm Up: Application/Connection/: Notes
Practice:Architects change the landscape around us all the time, what are natures 4 architects?
Exit: Explain how the landscape is changed by the 4 architects.
Paste Notes here when done.
Weathering and Erosion Notes
October 27, 2014
AGENDA 1 Starter2. Notes 3. Exit
Objective 7.8B Review and Analyze the effects of
weathering, erosion, and
deposition on the environment in ecoregions of
Texas by analyzing and completing
notes.
Table of Contents
Date Lecture/ Activity/ Lab Page10/17 Disaster Writing 67-6810/20 Disaster Mobile 69-7010/21 Texas Ecoregions Poster 71-7210/22 Texas Ecoregions Poster and presentation 73-7410/23 Unit 5 vocabulary 75-7610/24 Quiz/Writing 77-7810/27 Weathering and Erosion Notes 79-80
She can plant trees and other vegetation.
She could reduce the slope of the land;
The deposit of sediment where a river flows into an ocean or lake
What is Weathering?
• First step to forming soil and sedimentary rock
– Breakdown of rock into smaller pieces
– The smaller pieces do not move to a new location until erosion carries them away
– Many types of weathering
What is Mechanical Weathering?
• Breakdown of rock into smaller pieces without any change in the chemical composition of its minerals– Sometimes called “physical” weathering– Rock is torn apart by physical force, rather
than by chemical breakdown– Smaller pieces do not move to a new
location until erosion carries them away
Mechanical - Ice Wedging Ice Wedging
– Water fills joints of rocks and freezes– Water expands 10% when it freezes, pushes
rock apart– Repeated freeze and thaw cycles over the
years causes rock to break along joint
Mechanical - Exfoliation• Exfoliation or unloading
– Rock breaks off into sheets along joints which are parallel to the surface
– Caused by expansion of rock due to uplift and removal of surface material that originally buried the rock
Mechanical - Thermal • Thermal expansion
– Repeated daily heating and cooling of rock which causes rock to expand and contract then break
– Different minerals expand and contract at different rates causing the rock to split
Mechanical - Biotic• Biotic – means life
– Weathering caused by living organisms – Plant roots act as a wedge and widen cracks– Other causes of biotic weathering are digging
animals, microscopic plants and animals, algae and fungi.
What is Chemical Weathering?• Breakdown of rock into smaller pieces because
of change in the chemical composition of its minerals– Chemical reactions break down the bonds holding
the rocks together, causing them to fall apart
– Chemical weathering occurs in all types of rock
– Rock reacts with water, gases and solutions
Chemical - Oxidation• Oxidation - oxygen combines with other
elements in rocks to form new types of rock– New substances are usually much softer than
original, easier for other forces to break rock apart
– Causes a “rusting” of the rock, often causes a color change in the rock
Chemical - Carbonation• Carbonation – Carbon dioxide (CO2) is
dissolved in water making carbonic acid– Weak acid is formed when CO2 in the air
mixes with rain. This is the same acid found in soft drinks.
– Acid is too weak to harm plants and animals but slowly causes feldspars and limestone to decompose
What is Erosion?• Erosion - moving of rock material from
one place to a new location– For erosion to occur three processes must
take place: detachment of particles, lifting them, and transporting them
– Many agents of erosion - flowing water, moving ice, waves, gravity, or wind
– Sand consists of small pieces of rock that have been weathered from a parent rock, eroded, and deposited somewhere else
What Is Wind Erosion?• Wind - responsible for wearing away rocks and
creating great deserts like the Sahara Desert and Gobi– Most effective in moving loose material – Two main effects: (1) Wind causes small
particles to be lifted and moved away. (2) Suspended particles may impact on solid objects causing erosion by abrasion (rubbing).
– Occurs in areas where there is not enough rainfall to support vegetation
What Is Water Erosion?• Water - most influential force in erosion
– Ability to move materials from one location to another over long distances
– The faster water moves in streams the larger objects it can pick up and transport
– Responsible for wearing away of rocks in rivers, lakes, and the oceans
What Is Wave Erosion?• Waves - relentless pounding
– Erodes the softer, weaker parts of the rock first, leaving harder, more resistant rock behind
– Can take over 100 years to erode a rock to sand
– Energy of waves along with the chemical content of the water erodes the rock off the coastline
What Is Gravitational Erosion?• Mass movement - downward movement of
rock and sediments, mainly due to the force of gravity. – Moves material from higher elevations to
lower elevations where streams and glaciers can pick up the material and move it to lower elevations
– Process is occurring continuously on all slopes, some act very slowly while others occur very suddenly until equilibrium is reached
What Is Glacial Erosion?• Ice - moves and carries rocks, grinding the
rocks beneath the glacier– Glaciers pluck and abrade to cause erosion– Plucking occurs when water enters cracks
under the glacier, freezing, and breaking off pieces of rock that are then carried by the glacier.
– Abrasion cuts into the rock under the glacier, smoothing and polishing the rock surface
What is Deposition?• Deposition - laying down of sediment that has
been transported by a medium such as wind, water, or ice – Process of erosion stops when the moving
particles fall out of the transporting medium and settle on a surface. This settling is deposition.
– If the speed of the medium slows or the resistance of the particles increases, the balance changes and causes deposition.
– Speed can be reduced by large rocks, hills, vegetation, etc.
Deposition - Wind• Wind speed can be related to variations in
heating and cooling– Wind can transport fine particles in suspension
hundreds of km from its original source in the desert. – Heavier material may be blown along the ground.– Material is eventually deposited when the wind
changes direction or loses its strength.– Obstacles, whether natural of man-made, will often
decide where the deposition occurs and the nature of the feature formed.
Deposition - Water• Running water enters a large, fairly still body of
water and its speed decreases. – As speed decreases, water's ability to carry
sediments decreases– Sediments carried by running water are deposited
where the slowing water can no longer move them. Largest particles are deposited near the shore. Increasingly smaller particles settle out farther from the shore where the water is calmer
– Occurs in streams, rivers, oceans, etc.
Deposition - Ice• Glacial flows of ice - become slower when the ice
begins melting
– Deposits left by glaciers are called moraines and outwashes– Moraines are large chunks of broken rock left at the base and sides of the glacier as it melts and recedes– Finer material is carried in the rivers that form when the
glacial ice melts. The deposits of these rivers look similar to normal river deposits and are called outwashes
What’s the Difference?
• WEATHERING - think weather wearing rock down
• EROSION - think of a road and traveling
• DEPOSITION – think of depositing money in a bank
80 Weathering and Erosion Notes
10/27/14
79
10/27/14
Starter: Warm Up: Application/Connection/: Notes
Practice:Architects change the landscape around us all the time, what are natures 4 architects?
Exit: Explain how the landscape is changed by the 4 architects.
Paste Notes here when done.
Weathering and Erosion Notes