ON THE LITHOSPHERE EARTH SCIENCE UNIT 11 Mechanical Weathering Weathering Mechanical weathering occurs when physical forces break rock into smaller and smaller pieces without changing the rocks mineral composition ID: 441859
Download Presentation The PPT/PDF document "EROSION, HUMAN IMPACT" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
EROSION, HUMAN IMPACT
ON THE
LITHOSPHERE
EARTH SCIENCE UNIT 11
◆Slide2
Mechanical Weathering
Weathering
◆
Mechanical weathering
occurs when physical forces break rock into smaller and smaller pieces without changing the rock’s mineral composition.
◆
In nature three physical process are especially important causes of weathering: frost wedging, unloading, and biological activity. Slide3
Mechanical Weathering
Weathering
1.
Frost wedging
The mechanical breakup of rock caused by the expansion of freezing water in cracks and crevices
Sections of rock that are wedged loose may tumble into large piles called
talus,
which typically form at the base of steep, rocky cliffs.Slide4
Frost WedgingSlide5
Mechanical Weathering
Weathering
2.
Unloading
3.
Biological activity
Reduced pressure on igneous rock causes it to expand and allows slabs of outer rock to break off in layers in a process called
exfoliation.
The activity of organisms, including plants, burrowing animals, and humans, can also
cause mechanical weathering.Slide6
Unloading and Exfoliation
of Igneous RocksSlide7
Weathering and
Biological ActivitySlide8
Chemical Weathering
Weathering
◆
Chemical weathering
is the transformation of rock into one or more new compounds.
◆
Chemical Weathering of Granite
• Weathering of potassium feldspar produces clay minerals, soluble salt (potassium bicarbonate), and silica in solution.Slide9
Chemical Weathering
Weathering
◆
Chemical weathering
is the transformation of rock into one or more new compounds.
◆
Chemical Weathering of Granite and silicates
• Weathering of potassium feldspar produces clay mineralsSlide10
Rate of Weathering
Weathering
◆
Two other factors affecting the rate of weathering are rock characteristics and climate.
1. Rock characteristics
Mineral composition and solubility
Physical features such as joints Slide11
Rate of Weathering
Weathering
2. Climate
• Temperature and moisture are the most crucial factors.
• Chemical weathering is most effective in areas with high temperatures and abundant moisture.Slide12
How do we get coal out of the ground?
Surface Mining:
Typically occurs at depths above 180 ft.
Most common form in Wyoming
Underground Mining
Typically occurs at depths below 300 ft.
Accounts for 60% of world coal production Slide13
Surface mining
4 Main Types of Surface Mining
Strip Mining
Removal of large strips of overlying rock and soil to reveal coal.
Open-Pit Mining
Removal of rock and soil creating a vast pit where coal can be extracted.
Mountaintop Removal Mining
Removal of mountain tops with explosives. Land made flat after reclamation.
Highwall Mining
A continuous miner cuts holes horizontally into the coal formation.Slide14
The paper aims to…
Emphasize “deforestation” as a
global environmental problem.
Deforestation is the conversion of forested areas to non-forest land for use such as arable land, pasture, urban use, logged area, or wasteland. Generally, the removal or destruction of significant areas of forest cover has resulted in a degraded environment with reduced biodiversity. Slide15
Deforestation…
Results from removal of trees without sufficient reforestation, and results in declines in habitat and biodiversity, wood for fuel and industrial use, and quality of life. Slide16
Causes of Deforestation
Population Growth
It is clear now that the role of population factors in deforestation varies considerably from one setting to another depending on the local patterns of human occupancy and economic activity.
Population (especially rapidly increasing or dense population) can increase demands for land and wood, eventually exceeding the carrying capacity of forests that are expected to supply wood fuels , food, and environmental protection for local people.Slide17
Causes of Deforestation
Climate
Forest disappear naturally as a result of broad climate changes or catastrophes such as fire and landslides.
Agriculture
Growing populations need expanding food supplies, so forests are cleared by shifting cultivators for annual or permanent crops. Rates of clearing are likely to be higher in countries where little or no progress has been made in agricultural productivity or where land productivity falls rapidly after the natural forest cover is removed.Slide18
Causes of Deforestation
Logging
Commercial logging operations deplete forest stocks. Regulated timber extraction should not permanently damage the forest, but when it is not controlled, mechanized logging or even selective timber harvesting may severely alter the character of the forest
Fuel
Forests in developing countries provide wood fuels for local populations. Fuelwood and charcoal are widely used for domestic cooking and heating.
Burning and Grazing
Deforestation may occur in ways other than outright clearing or wood removal. The practice of annual burning in many areas prevents forest regrowth , and grazing by sheep, goats and cattle has much the same effect.