1. What is Weathering?
Weathering is the process that produces change in the surface of rocks exposed to the atmosphere and/or hydrosphere.
The end result of weathering produces sediment.
I took the picture at Niagara Falls (Canada)

2. Physical / Mechanical Weathering
Breaking rock by force into smaller pieces
There is NO change in the rock’s composition
Total exposed surface area increases
Bottom – I took at Grand Canyon (Colorado River)

3. Frost Action / Ice Wedging
Breakup of rock caused by the freezing and thawing (expansion and contraction) of water – Ex. Pot holes
Water seeps into small cracks in rocks.
When the water freezes it expands creating great pressure.
The crack widens and allows water to seep deeper into the rock.
I took the one on the right - Yellowstone

4. Exfoliation
Peeling away of large sheets of loosened materials at the surface of a rock
Rocks formed deep in the Earth are made under high pressure – when pressure is released, rocks expand and crack
Thermal expansion – repeated heating and cooling causes stress
Common in granite, shale, slate, and mica
Left – I took in Colorado (Dinosaur Ridge)

5. Plant Action Tiny roots seek out small cracks in rock
Once the root hairs find a place they grow and expand
Expansion causes great pressure and cracks the rock
Top – I took on lava field of Big Island, Hawaii; Bottom – I took at Shenandoah National Park (Virginia)

6. Abrasion Wearing down rocks as they rub or bounce against each other
Most common in windy areas, under glaciers, or in stream channels
“Sand blasting" – wind abrasion shapes exposed bedrock (up to about 1-2 meters above the surface because sand grains are lifted a short distance)
Top – I took at Garden of the Gods (Colorado)

7. Name that physical weathering mechanism!
Wind Abrasion!
Plant Action!
I took bottom left - Yellowstone
Water Abrasion!
Ice Wedging!

8. SHALE SHALE SHALE WATER DOLOSTONE WHICH ROCK IS THE MOST RESISTANT TO
WEATHERING?
SHALE
LIMESTONE
SANDSTONE
SHALE
SANDSTONE
SHALE

9. SHALE SHALE SHALE DOLOSTONE WHICH ROCK IS THE LEAST RESISTANT TO
WEATHERING?
SHALE
LIMESTONE
SANDSTONE
SHALE
SANDSTONE
SHALE

10. Chemical Weathering
Unlike physical weathering because rock composition is changed after reacting with a chemical
Like physical weathering because it breaks down rock

11. Oxidation
Oxygen in water or the atmosphere combines with iron-bearing minerals = rust
Rocks become red, orange, or brown in color

12. Hydrolysis
Water is the universal solvent – minerals commonly break apart in water
Common in silicate based rocks = increase porosity and decrease stability
Silicate minerals weather by hydrolysis to form CLAY
Feldspar alters to clay (kaolinite) plus dissolved materials (ions)

13. Acid Rain
Rain is naturally slightly acidic, but dissolved materials can increase acidity
Sulfur Dioxide in the atmosphere dissolves in rain water forming a strong acid = sulfuric acid
Corrosive forces result in loss of polished finish on buildings/structures and impacts wildlife

14. Carbonation
CO2 dissolves in rain water as it falls through the atmosphere
Forms a weak carbonic acid – reacts with minerals in rock
Commonly reacts with halite, calcite, limestone, and marble
Cave formation
Carbonic Acid?
I took this in Indian Echo Caverns (PA)
Alternate video:

15. Karst Topography Layers of soluble bedrock dissolves in carbonic acid
Characterized by sinkholes and caves
A three-story building in northern Guatemala City fell into a sinkhole in May It measured 66 feet across and 100 feet deep.