Unit G1- Environmental ChemistryUnit G1- Environmental Chemistry

Rocks & SoilsRocks & Soils

Form Group 3GForm Group 3G

27th November 200627th November 2006

What is a Rock?What is a Rock?

A rock is a naturally occurring aggregate of minerals. They are classified by mineral and chemical composition, by the texture of the constituent particles and by the processes that formed them.

Types of RocksTypes of Rocks

Rock TypesRock TypesType Examples Characteristics

Sedimentary

-Sandstone-Limestone

Grainy and Crubly. They may contain fossils.

Metamorphic

-Slate-Marble

-Small crystals in layers (or bands). Hard and smooth.

Igneous -Basalt

-Granite

-Small crystals due to fast cooling. Hard rocks.-Large crystals due to slow cooling. Hard rocks.

Weathering?Weathering?

Process of disintegration of rocks, soils and their minerals through direct, or indirect contact with the atmosphere.

PhysicalChemical Biologica

l

Physical WeatheringPhysical Weathering

Effect of the sun

• During the day the rocks are warmed up and expand while...

• ...at night they cool down and contract.

Rocks cracking and eventually breaking

up.

Effect of freezing water

• Any water which gets into cracks in rocks will expand when it freezes.

• Cracks will get bigger and bigger...

The rock will break up into smaller pieces

Chemical WeatheringChemical Weathering

Due to chemical reactions between substances in the rock and acidic rainwater.

e.g. Acid Rain

Biological WeatheringBiological Weathering

Due to the actions of plants and animals.

About Soils...About Soils...

• Soils forms when the rocks are physically and chemically weathered over the years.

6 different components:1 – Rock Particles2 – Mineral Salts3 – Humus4 – Water5 – Air6 – Living organisms

Soil TypesSoil Types

1. Sandy

2. Clay

3. Loam or Silt