Aim: What is weathering?

I. Weathering – the breakup of rock due to exposure to the atmosphere.

A. Erosion – is the removal and transport of earth materials by agents (streams, rivers, glaciers, wind, waves and currents, and gravity)

B. Two types of weathering:

1. Mechanical (physical) weathering – occurs when rock is broken or split into smaller pieces of the same material without changing its composition.

a. Ice wedging (frost action) – when freezing water causes rocks to crack

b. Ice heaving – when water in ground freezes and lifts the pavement above it.c. Wetting and drying – especially effective at breaking up rocks that contain clay.

d. organic activity (Plants and animals)

i. plants’ roots may grow through rocks

ii. Ants, earthworms, woodchucks dig holes and expose bedrock to atmosphere.

2. Chemical Weathering (Decomposition) – occurs when the minerals are changed into different substances due to rainwater, oxygen, carbon dioxide, and acids of plant decay.

a. Hydrolysis – reaction of water with other substances.

b. Oxidation – the chemical reaction of oxygen with other substances (iron bearing materials are most easily affected – rust or iron oxide).

c. Carbonic acid – weak acid formed from carbon dioxide dissolving into water.

•Carbonation – when some minerals react with carbonic acid to form a new product. (underground caverns).

http://www.classzone.com/books/earth_science/terc/content/visualizations/es1201/es1201page01.cfm?chapter_no=visualization

http://www.classzone.com/books/earth_science/terc/content/visualizations/es1202/es1202page01.cfm?chapter_no=visualization

Examples of Physical weathering

Example of Chemical weathering