http://www.swfwmd.state.fl.us/hydrology/sinkholes/brochure.pdf
What is a sinkhole?Sinkholes are depressions or holes in the land surface that occur throughout west central Florida. They can be shallow or deep, small or large, but all are a result of the dissolving of the underlying limestone.
http://www.classzone.com/books/earth_science/terc/
content/visualizations/es1103/es1103page01.cfm?
chapter_no=visualization
Erosion
• Erosion is the process by which the surface of the Earth gets worn down.
• http://www.classzone.com/books/earth_science/terc/content/visualizations/es1205/es1205page01.cfm?chapter_no=visualization
Weathering
Mechanical and Chemical
Factors that influence weathering
• 1. Composition • Some materials are harder than others (quartz)• Some materials are more resistant to weathering (calcite)
• 2. Structure• Fractured and fine grained rock weathers faster
• 3. Topography• Severe temperatures expose fresh material
• 4. Climate• Moisture and heat accelerates weathering
Why is weathering important?
• It produces sedimentary rocks and soil
• Mineral resources – ore deposits
MechanicalMechanical WeatheringWeathering
Mechanical Weathering
• Physical forces break rock into smaller and smaller pieces without changing mineral composition.
Six types of Mechanical weathering
• 1. Frost Wedging
• 2. Unloading or exfoliation
• 3. Thermal Expansion or exfoliation
• 4. Salt formation
• 5. Biological Activity
• 6. Abrasion
1. Frost Wedging
• Freezing and thawing of water in cracks
• Ice expands by 9%
• This occurs in mountainous regions and colder areas
• Talus: material produced by frost wedging at the base of a mountains forming a talus slope
• http://academic.brooklyn.cuny.edu/geology/leveson/core/topics/weathering/processes/frost/frost_rollover.html
Talus slope from mechanical weathering
2. Unloading or exfoliation
• Pressure of overlying rock is removed by weathering
• Like the peeling of an onion
• This occurs because there is a reduction in pressure
• There is usually slab-like layers or loose sheets of rock
• Can be removed by erosion or ice sheets
3. Thermal Expansion
• Rock is a poor conductor of heat so the outside expands more than the inside
• This occurs in the desert – temperatures can vary by 30 degrees.
• This can causes exfoliation
Called: Exfoliation domes
4. Salt-crystal growth
• Salt crystal growth called haloclasty• Water in rock openings is saline, the water
evaporates and it leaves behind salt crystals which when heated expand and exert pressure on the rock.
• Causes granular disintigration• This is common along the coast or the
sides of the road in places where they salt the road
honeycomb weathering
5. Biological Activity
• Roots growing into the cracks and joints in rocks
• Earthworms and termites making tunnels
• People building roads, cultivating the land, exposing rocks to other types of weathering
6. Abrasion
• Abrasion refers to the breaking and grinding away of solid rock by collisions with moving particles.
• Abrasion takes place in many environments: fast-moving streams, beaches subject to storm waves, desert environments with high winds and beneath glaciers that are loaded with fragments of rock.
Just plain old gravity can be a factor of mechanical weathering like seen in these pictures…
http://www.uky.edu/AS/Geology/howell/goodies/
elearning/module07swf.swf
• http://www.classzone.com/books/earth_science/terc/content/visualizations/es1201/es1201page01.cfm?chapter_no=visualization