Types of Weathering

1. Types of Weathering

2. Weathering versus Erosion Weathering –rocks and minerals breaking down at or near the Earth’s surface Mechanical weathering Chemical weathering Erosion –moving water, wind, or ice carrying away pieces of rock and soil Streams, rivers, glaciers, wind and/or waves carry sediment (loose, fragmented surface material that makes up many sedimentary rocks)

3. Weathering Positive Breaks down minerals to become part of soils and water Enriches foods (plants, etc.) and water with essential nutrients Produces soil, so we can grow crops, etc. Negative Can weaken building, roads, etc Can destroy monuments, grave markers, etc.

4. Reading Article • With your shoulder partner, read the article and as you read, think about how the two types of weathering are different or similar.

5. Types of Weathering • Mechanical Weathering –rocks are broken into smaller pieces without changing the chemical makeup of the individual pieces • Examples: Frost wedging, thermal expansion, abrasion, tree root • Chemical Weathering –rocks and minerals that are decompose and are chemically changed • Examples: oxidization, dissolving

6. Ice Wedging • Water seeping into cracks in rocks. The water freezes, expands and makes the crack bigger. • Occurs in cold, moist mountain climates

7. Water expands ~9% when it freezes, wedging open water-filled cracks in rocks & roads!

8. Abrasion • Rocks fall and collide into one another, breaking off pieces and fragments of rock. • Occurs in cold, wet climates and near glaciers

9. Tree Roots • As tree roots grow, they expand and push apart the rock. • Occurs in warm, moist climates with dense forests.

10. Plant roots cause mechanical weathering Plants (trees and grasses) are agents of weathering

11. Thermal Expansion • Over time, daily temperature changes cause rocks to break apart. • Occurs in desert climates with wide ranges in morning and evening temperatures.