Types of Weathering © Copyright 2004 - 2005.  M. J. Krech. All rights reserved.

Mechanical Weathering

Disintegration – breaks down into smaller pieces, no new substance

Frost Action or Ice Wedging

Frost Action Ice expands when frozen and cracks rocks Causes pot holes in winter Happens where the temperature goes both above and below the freezing point of water Called Ice Wedging

Abrasion

Wind blows sand which wears away cliffs Wind Abrasion Wind blows sand which wears away cliffs

Water Abrasion Water carries rocks along in streams & rivers which collide and become smoothed into rounded river rocks

Gravity

Landslides Gravity pulls rocks loose They break apart as they fall downhill

Organic Activity: Root Pry

Root Pry Roots expand as they grow and crack rocks. Other organic activity Ants, woodchucks, and worms dig holes that let in water that causes weathering.

Wetting and Drying

Rocks that contain CLAY swell and shrink as they absorb water then dry out, thus cracking the rocks

Joint Sheeting

As top soil erodes, rock layers below expand and crack into layers Called EXFOLIATION when large sheets of rock break away at the surface

Chemical Weathering

Decomposition – breakdown into new substances

Hydrolysis

The chemical action of water with other substances Example: Feldspar turns into clay

Feldspar +Water = Clay Feldspar A Clay Cliff

Plant Acids

Acids given off by lichens and mosses eat at rocks

Sulfuric Acid

ACID RAIN: Sulfuric acid causes blurred words on gravestones and monuments

Photo taken 100 years ago Photo taken recently

Both of these are Civil War headstones. Why has one weathered more? 1865 1862

Oxidation

RUST caused by oxygen combining with iron-bearing minerals in rocks causes red bands on limestone cliffs

Carbonation

Carbon dioxide combines with water to form carbonic acid which eats away layers of limestone rock Forms CAVES; KARST TOPOGRAPHY

Karst Topography A type of landscape in rainy regions where there is limestone near the surface, characterized by caves, sinkholes, and disappearing streams. Created by chemical weathering of limestone

Features of Karst: Sinkholes

Features of Karst: Caves

Features of Karst: Disappearing Streams

The end. © Copyright 2004 - 2005.  M. J. Krech. All rights reserved.