TYPES OF WEATHERING

WEATHERING VERSUS EROSIONWeathering –rocks and minerals breaking down at or near the Earth’s surface

Mechanical weatheringChemical 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)

WEATHERINGPositiveBreaks down minerals to become part of soils and waterEnriches foods (plants, etc.) and water with essential nutrientsProduces soil, so we can grow crops, etc.NegativeCan weaken building, roads, etcCan destroy monuments, grave markers, etc.

READING ARTICLEWith your shoulder partner, read the article and as you read, think about how the two types of weathering are different or similar.

TYPES OF WEATHERINGMechanical 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

ICE WEDGING Water seeping into cracks in rocks. The water

freezes, expands and makes the crack bigger.

  Occurs in cold, moist mountain climates

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

ABRASION Rocks fall and collide into one another,

breaking off pieces and fragments of rock.

Occurs in cold, wet climates and near glaciers

TREE ROOTS As tree roots grow, they expand and push

apart the rock.   Occurs in warm, moist climates with dense

forests.

PLANT ROOTS CAUSE MECHANICAL WEATHERING

Plants (trees and grasses) are agents of weathering

THERMAL EXPANSION Over time, daily temperature changes cause rocks to break

apart.

Occurs in desert climates with wide ranges in morning and evening temperatures.