NAME:MISS IQRACLASS:8th A-B

NATURE OF ROCKS:Rocks are made up of soft minerals(e.g, gypsum and

calcite) that take a shorter time to break down.

Rocks made up of granite takes longer time to be weathered down because it is made up of quartz material.

Erosion:Erosion refers to the removal of the weathered

materials from the area where weathering of rock had taken place.

AGENTS OF EROSION:Flowing water:where streams and rivers flow across the earth’s

surface ,flowing water causes erosion to take place.

Winds:Wind erosion is dominant by dry areas:

NATURAL AGENTS OF WEATHERING:RUNNING WATER

RAINFALL:

TEMPERATURE:HOT TEMPERATURE:

COLD TEMPERATURE:

THERE ARE THREE TYPES OF WEATHERING:PHYSICAL WEATHERINGCHEMICAL WEATHERINGBIOLOGICAL WEATHERING

PHYSICAL WEATHERING:Physical weathering refers to the process whereby

rocks are break down.

It is also known as mechanical weathering.

TYPES OF PHYSICAL WEATHERING:There are three types of physical weathering.Alternate expansion and contraction of rocks.Freeze-thaw action of ice or frost shatteringRelease of pressure within rocks

Alternate Expansion and Contraction of Rocks:Exfoliation:Alternate expansion and contraction of rocks causes

the outer surface of rocks to break down into different layers this kind of peeling away of rock's layer is known as EXFOLIATION.

Reasons of Exfoliation:In arid regions like deserts during the day timing

rock become heated due to high temperature and expanded with rays of sun.

While in night timing rock becomes cool due decrease in temperature and contracted with the decrease in temperature.

Freeze-thaw action of ice or frost shattering:In mountainous areas, the temperature in the

atmosphere may drop below freezing point. This causes water in the cracks to freeze.

When water changes into ice, its volume increase by 10%.

PRESSURE RELEASE OF ROCKS:Disintegration of rock in parallel sheets as it expands

in response to the removal of confining stress.The most common mechanisms of pressure release is

removal of overlying rock by erosion.

BIOLOGICAL WEATHERING:Biological weathering refers the process whereby

rocks are breakdown through the action of plants and animals in situ.

The rocks slowly break down either by disintegration or by decomposition.

CHEMICAL WEATHERING:Chemical weathering is responsible for change in

chemical structure.When rainwater mixes with carbon dioxide in the air

it makes carbonic acid(carbonation)When calcium carbonate in limestone combines with

weak carbonic acid in rain water, the limestone's chemical composition changes to become calcium bicarbonate.

AGENTS OF CHEMICAL WEATHERING:Agents of chemical weathering are:Acid rainOxygenCarbon dioxideLiving organisms

Types of chemical weathering:Oxidation:Minerals in rocks react chemically with rainwater or

oxygen in the atmosphere.Minerals expand in volume and change their

chemical composition.Rocks weaken and decomposed.

References:Google imagesText bookUregina.ca