Date Vocabulary Weathering: The breakdown of rocks or minerals into smaller pieces by mechanical or chemical means. Announcements:

Weathering

SC Standards 7.EC25A.2 Construct explanations of how soil quality (including composition, texture, particle size, permeability) affects the characteristics of an ecosystem using evidence from soil profiles. 7.4.3 Describe natural processes that change Earth’s surface Interactions among changes in the environment due to natural hazards (including landslides, earthquakes, mountain building, new land being formed, weathering, erosion, sedimentation, soil formation).

What is Weathering? Weathering is simply the breakdown of rock into smaller pieces. Weathering can occur by chemical or mechanical (physical) means.

Weathering vs. Erosion (Know the difference!) The simple breakdown of rock in to smaller pieces. The result of weathering is soil. The MOVEMENT of rocks and weathered materials from one place and dropped off someplace else (deposition).

Chemical Weathering The breakdown of rocks by chemicals such as water or acid rain. A lot of chemical weathering is water dissolving minerals in rocks.

Acid Rain

Mechanical Weathering The physical breakdown of rocks into smaller pieces. Organic, temperature, frost, gravity, and “sandblasting.”

Root Wedging Roots of trees and other plants are very strong. Roots can burrow through rocks, pick rocks up, and push rocks downhill Where do you encounter root wedging?

Other Organic Weathering The activity of burrowing animals like worms, moles, and bees (right) further breaks down rocks. Worms even EAT soil which is weathered rock.

Temperature Changes When rock is heated it expands. When rock is cooled it contracts. The constant expansion and contraction of rock makes it brittle and causes it to easily break apart.

Frost Action When water freezes it expands. Water from rain and the groundwater gets into small cracks. When the water freezes, it wedges the sides opposite the crack apart. This process continues over and over, eventually breaking a rock down.

Gravity Weathering by gravity usually works in conjunction with something like frost action or temperature changes. When gravity pulls a loosened piece of broken rock, well that makes the rock smaller!

Abrasion Otherwise known as sandblasting. Happens when wind or water smash small rock particles into other rocks.

Weathering Conditions

Video

Recap 1. What are the two main types of weathering? 2. What is the difference between weathering and erosion? 3. Name 3 organisms that can weather rock.