Weathering processes are classed into three types:  chemical, physical, and biological

Weathering processes are classed into three types:  chemical, physical, and biological

Weathering processes are classed into three types:  chemical, physical, and biological (which includes human-caused weathering like digging ditches to lay cables).  However, weathering is complex and each of these weathering processes operates in a dynamic feedback with the others to contribute to overall breakdown of rocks and minerals at and near the Earth’s surface.

Chemical weathering is the decomposition of rocks, minerals, and materials through a process of chemical change whereby those materials are transformed from one type of material to another.  For instance, the chemical weathering of iron through exposure to oxygen causes the transformation of that iron and oxygen into iron oxide, a new chemical compound.  The major chemical weathering processes are oxidation, reduction, hydrolysis, hydration, and dissolution.

Physical weathering (or mechanical weathering) is the physical disintegration of rocks, minerals, and materials into smaller particles without a change in chemical composition.  Water freezing and expanding as ice within the cracks of a wall causes those cracks to expand and enlarge, breaking small fragments of brick from the wall.  In this case, the brick remains brick, but breaks into smaller fragments through a physical weathering process known as frost heaving.  Other major physical weathering processes include thermal stress, pressure release, unloading, corrasion, abrasion, and salt crystallization.

Biological weathering involves a combination of chemical and physical weathering processes wherein the weathering agent is a biological organism (either macroscopic or microscopic).  Biological weathering occurs in a variety of forms, but some processes include: root acid etching, tree fall, root expansion, pedogenesis, stone line/zone formation, krotovinas/burrowing, and digging.

For this assignment, I want you to venture outdoors and identify an example of one of each of the three major weathering processes (chemical, physical, and biological).  The weathering can be affecting rocks, minerals, soils, or human structures or artifacts.  Take a photograph of each weathering process and upload it with your assignment.  Identify each weathering example by type and describe what is taking place.  Be as detailed as possible in your descriptions and do your best to figure out the specific kind of chemical, physical, or biological weathering you observe.  Each description should be 4 to 5 sentences long.

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