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