AIM: What is Weathering? Do Now – Choose one of the following pictures and describe what is/has happened. a b c f E D

I. Weathering It is the breaking down of a rock by natural processes. An Increase in the amount of Surface area, Increases the amount of Weathering

II. Mechanical Weathering - Breaking a rock into smaller pieces without changing it’s chemical composition. Abrasion: the act of rocks hitting and smashing against each other.

Expands III. Types of Mechanical Weathering Frost Wedging –The mechanical breakup of rock caused by the expansion of freezing water in cracks. This material is called talus What happens to water when it freezes? Do Not Copy Expands

breaking off in layers due to expansion of Igneous rock 2) Unloading – breaking off in layers due to expansion of Igneous rock Reduced pressure on igneous rock causes it to expand and allows slabs of outer rock to break off in layers in a process called exfoliation. Do Not Copy

3) Biological Activity - The activity of organisms, plants, burrowing animals, and humans.

IV. Chemical Weathering - Breaking a rock into smaller pieces by changing it’s chemical composition. - It forms a new material * Water is the most important agent.* Acid Rain Damage

V. Types of chemical weathering Acid Rain - water combines with different elements to make acids. - H2O + carbon dioxide = carbonic acid * - H2O + sulfur = sulfuric acid (acid rain) - H2O + nitrogen = nitric acid

Acid rain that seeps into the ground reacts with calcite and dolomite in the rocks (Limestone). This dissolves the rocks creating Karst Topography (caves).

b) Oxidation - Water and oxygen react with metal to create rust.

VI. Rate of Weathering 1) Rock Characteristics: A. Mineral composition and solubility of the rock (the minerals that make the rock) Granite Limestone

b. Physical features such as joints or cracks. - amount of surface area determines amount of chemical weathering

2) Climate: - Temperature and moisture are the most crucial factors. - Chemical weathering is most effective in areas with high temperatures and abundant moisture.

3) Differential Weathering - Different parts of a rock often weather at different rates due to variations in composition. Hoodoo

Closure: In your Notes Slate Headstone Marble Headstone What is the difference between these headstones, which both have been exposed to weathering for roughly the same amount of time?

Cleopatra’s Needle 2) Describe one factor that explains why Cleopatra’s needle changed after it was brought from Egypt to New York. 1900 - Egypt Present Day - Central Park