T YPES OF W EATHERING

W EATHERING VERSUS E ROSION 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)

W EATHERING 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.

R EADING A RTICLE With your shoulder partner, read the article and as you read, think about how the two types of weathering are different or similar.

T YPES OF W EATHERING 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

I CE W EDGING Water seeping into cracks in rocks. The water freezes, expands and makes the crack bigger. Occurs in cold, moist mountain climates

W ATER EXPANDS ~9% WHEN IT FREEZES, WEDGING OPEN WATER - FILLED CRACKS IN ROCKS & ROADS !

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

T REE R OOTS As tree roots grow, they expand and push apart the rock. Occurs in warm, moist climates with dense forests.

P LANT ROOTS CAUSE MECHANICAL WEATHERING Plants (trees and grasses) are agents of weathering

T HERMAL E XPANSION Over time, daily temperature changes cause rocks to break apart. Occurs in desert climates with wide ranges in morning and evening temperatures.