 Weathering is the breakdown and alteration of earth-forming materials by low pressure, temperature, water, air, and biological organisms.

 Weathering happens quicker on newly exposed rock because the minerals have not met their equilibrium state with their environment.

 Weathering surface are changed in color, texture, composition, firmness or form, with little or no transportation of the altered material

 Weathering is responsible for soil formation, nutrients used by marine organisms, fossil fuels and sedimentary ore deposits.

 Erosion is the transportation and removal of material produced by weathering.

 Erosion is caused by wind, water, currents, glaciers, humans, and animals.

 This type of weathering involves breaking down rocks into progressively smaller pieces.  It increases the surface area exposed to the elements to increase the rate of chemical weathering.

1. Pressure or Stress Release (Unloading) ◦ The removal of surface material by water, glacial erosion or human activities that could cause the minerals in the rock to spread further apart to create large voids.

2. Frost Action ◦ The changes in pressure caused by the cycle of freezing and thawing of water in colder climates in joints and crevasses may cause the rocks to fracture.

3. Salt Weathering ◦ The salt penetrates the rock’s surface and embeds itself in the pores and small cavities in the rock. ◦ The salt change size by either absorbing water or when the temperature changes.

4. Heating and Cooling (Exfoliation) ◦ Rock is also a poor conductor of heat so the surface may be hot, but the interior might be cold. This difference in temperature may can the rock to break apart.

 Minerals in a rock undergo changes that make them more stable under their current environmental and biological conditions.

1. Water ◦ Water serves as a medium for any chemical reaction to occur between a rock’s environment and it’s minerals. Flowing water prevents the chemical reaction to reach a state of equilibrium, thus allows it to continue indefinitely.

2. Chemical Reactions ◦ the reaction between the ions in the water and the minerals. This decomposes igneous rock. Hydrolysis Ion Exchange

Oxidation Carbonation

 The type of weathering that is the result of biochemical or biophysical processes associated with living matter.

 Worms increase a surface’s exposure to air and water.

 Bacteria break down chemicals and minerals and produce harmful by-products.

 Algae, lichen and fungus colonize rock surfaces reducing their contact with water and air and create ions that react chemically with the surface.

 P. 161 #1-4  P. 166 #1-4