Happy Monday! Please pick up the handouts and have a seat. You may also look at your test scores on the board Test corrections are to be done by Friday. Sign up is outside of my door If you did not finish your test, you will do so after our notes today Prepare to change seats once I start class (your choice, just can’t be at the same table)

Think About it If something is “weathered”, what do you think of? Do you know what the two types of weathering are?

Mechanical Weathering Physical Weathering- the process by which rocks break down into smaller pieces by physical means Frost Wedging- alternate freezing & thawing of water

Exfoliation- peeling away of large sheets of loosened material Root/plant wedging: the process in which plant roots cause rocks to break as the plant and roots grow

Abrasion- when rocks rub against each other

Chemical Weathering Chemical weathering: the process by which rock is broken down chemically due to chemical interactions with the environment Oxidation- when oxygen unites chemically with a mineral. Ex. Rust (iron oxide)

Hydration- when water unites chemically with minerals.

Mechanical Weathering Chemical weathering Pressure/stress release Organic acid (moss, lichen, or pine needles) Abrasion by wind, water, or human activity Hydrolysis (reacting with water) Gravity (mass wasting) Acid precipitation Exfoliation Hydration (dissolving in water) Ice wedging Oxidation (metal and oxygen) Biological (animal burrows, roots)

Rates of Weathering Surface area - If particle size goes down then, weathering rate goes up (more surface area exposed). Weathering eats away sharp edges first (makes things round)

Rates of Weathering Climate- the average weather of a location over time

Differential Weathering Different minerals weather at different rates. Hard rocks weather slowly Soft rocks weather quickly