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

http://upload.wikimedia.org/wikipedia/commons/b/be/GeologicalExfoliationOfGraniteRock.jpg

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