Weathering PowerPoint Presentation for Science Students

This PowerPoint presentation is designed to introduce science students to the fundamental concepts of weathering, a key geological process that shapes the Earth's surface. The presentation provides a comprehensive overview of weathering, including its definition, causes, and different types—physical (mechanical), chemical, and biological. Each type of weathering is explored in detail, with explanations of the processes involved and real-world examples illustrating how they break down rocks and minerals. The presentation also discusses the critical role weathering plays in soil formation, explaining how weathered rock particles combine with organic material to create fertile soil layers essential for supporting ecosystems.

1. WeatheringWeathering
http://amazingworld.5u.com/photo.htmlhttp://amazingworld.5u.com/photo.html

2. ObjectivesObjectives
• Define weathering
• Identify causes of weathering
–Physical or Mechanical Weathering
–Chemical Weathering
–Biological Weathering
•Discuss soil formation

3. WeatheringWeathering
Weathering is a set of
physical, chemical, and
biological processes
that alter the physical
and chemical state of
rocks and soil at or near
the earth's surface.
http://www.uh.edu/~jbutler/physical/chapter6.htmlhttp://www.uh.edu/~jbutler/physical/chapter6.html

4. Effects of WeatheringEffects of Weathering
•Loss of atoms and molecules from
weathered surfaces.
•Addition of specific atoms to the
weathered surface.
•Breakdown of one mass into two or more
masses.

5. Chemical WeatheringChemical Weathering
•Involves the alteration of the chemical
composition of weathered material.
There are different process that result in
chemical weathering including:
–Hydrolysis
–Oxidation
–Carbonation

6. HydrolysisHydrolysis
Chemical weathering is a process that involves the reaction
between mineral ions and the ions of water (OH- and H+),
and results in the decomposition of the rock surface
by forming new compounds, and by increasing the pH of the
solution through the release of the hydroxide ions.
- Silicate minerals weather by hydrolysis to form clay.

7. OxidationOxidation
Chemical attachment of free oxygen to other
elements and compounds.
Iron-bearing silicate minerals that
undergo oxidation include the
following:
–pyroxene
–amphibole
–biotite
–olivine
Rocks that contain these elements weather by oxidation into
an orange color.
http://wwwrses.anu.edu.au/research/annrep/ar2006/ee/index.php?p=pillanshttp://wwwrses.anu.edu.au/research/annrep/ar2006/ee/index.php?p=pillans

8. CarbonationCarbonation
Dissolving of calcium
carbonate (limestone) in
acidic groundwater
- similar to hydrolysis but all the
products are ionic and there is
no residue
- produces bicarbonate (HCO3),
a major part of the dissolved
load of most rivers
- the carbonation of limestone
results in karst topography:
caves, sinkholes, etc.
http://www.khaolaklanddiscovery.com/_images/tours/http://www.khaolaklanddiscovery.com/_images/tours/
khao_sok/old_coral_big.jpgkhao_sok/old_coral_big.jpg

9. Physical WeatheringPhysical Weathering
•Breakdown of mineral or rock material by entirely
mechanical methods brought about a variety of reasons.
–Frost Wedging
–Exfoliation or Unloading
–Thermal Expansion
–Plant Wedging
http://members.aol.com/rhaberlin/mwstyg.htmhttp://members.aol.com/rhaberlin/mwstyg.htm

10. Frost WedgingFrost Wedging
•Mechanical disintegration, splitting
or break up of rock by the
pressure of water freezing in
cracks, crevices, pores, etc.
•Caused by repeated freeze-thaw
cycle of water in extreme
climates. http://regentsprep.org/Regents/earthsci/units/weathering/frostwedging.gifhttp://regentsprep.org/Regents/earthsci/units/weathering/frostwedging.gif

11. Exfoliation or UnloadingExfoliation or Unloading
•Expansion of rock
caused by lifting and
erosion
•Rock breaks off into
sheets along joints
that parallel surface.
http://facstaff.gpc.edu/~pgore/Earth&Space/condestr.htmlhttp://facstaff.gpc.edu/~pgore/Earth&Space/condestr.html

12. Thermal ExpansionThermal Expansion
•Repeated cooling and
heating of rock.
•Heat caused rock to
expand and cooling
causes rock to contract
•Looks very similar to frost
wedging and salt crystal
growth, but typically
occurs in climates of
extreme weather
changes.
Thermal shattering of sandstone by forest fire.
http://w3.salemstate.edu/~lhanson/gls210/gls210_weath1.htm

13. Plant WedgingPlant Wedging
•Plant roots can wedge into
cracks in rocks and produce
enough pressure to split them
• Chemicals produced by the
roots of plants help in the
chemical weathering, as
enzymatic activity digest the
rock as the plant searches for
nutrients in the rock.
http://facstaff.gpc.edu/~pgore/Earth&Space/condestr.htmlhttp://facstaff.gpc.edu/~pgore/Earth&Space/condestr.html

14. Biological WeatheringBiological Weathering
•Animals and Plants can
assist in breaking down
rocks into sediment and soil.
Biological Weathering can be
caused by:
•Roots of trees and other
plants
•Lichens, fungi, and other
microorganisms.
•animals http://w3.salemstate.edu/~lhanson/gls210/gls210_weath1.htm

15. Soil FormationSoil Formation
•Soil is formed from the
weathering of rocks and
minerals.
•Surface rock breaks down
by weathering and is mixed
with organic material. Over
time it creates a thin layer of
soil.
lh3.google.com/.../s800/IMG_1466-1.jpg

16. Five Soil Forming FactorsFive Soil Forming Factors
1.Parent Material- The primary material from which rock
is formed.
2.Climate- Weathering forces including heat, rain, ice
snow, wind, etc.
3.Organism- all animals living in or on the soil. Ex:
Animals living in the soil will affect how soil is moved
around and decomposition of waste materials.
4.Topography- the location of the soil on a landscape.
Ex: Soil at the bottom of a hill will get more water than
that on the slope.
5.Time- The formation of soil takes years.