Science Starter Pick up a post-it note at the front desk and answer the following questions… What is weathering? What is erosion? Place your post-it note on the white board.

Mechanical Weathering Mechanical Weathering physically breaks down rock into smaller pieces Mechanical weathering is a slow process and breaks down through natural agents – Freezing and thawing, release of pressure, plant growth, actions of animals, and abrasion

Mechanical Weathering Agents Abrasion – grinding of rock by rock particles carried away by ice, wind, gravity, or human activity. Frost wedging – wedges of ice in rocks expands in cracks – Repeated freezing and thawing, the cracks expand until pieces of rock break off

Chemical Weathering Chemical Weathering breaks down rock through chemical changes Agents of chemical weathering include the following: – Water, oxygen, carbon dioxide, living organisms, and acid rain

Chemical Weathering Agents Oxygen – Oxidation: iron combines with oxygen in the presence of water -Rusting occurs during this process Carbon Dioxide - gas that dissolves in water creates carbonic acid and easily wears away rocks (limestone) Living Organisms – plant’s produce weak acids Acid Rain – Acid mix combines with raindrops