Transcript rock

Unit G1- Environmental Chemistry
Rocks & Soils
Form Group 3G
27th November 2006
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 Rocks
Rock Types
Type
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
-Small crystals due to fast cooling. Hard
rocks.
-Large crystals due to slow cooling.
Hard rocks.
-Granite
Weathering?
Process of disintegration of rocks, soils and
their minerals through direct, or indirect
contact with the atmosphere.
Physical
Chemical
Biological
Physical Weathering
Effect of the sun
Effect of freezing water
• During the day the
rocks are warmed up
and expand while...
• ...at night they cool
down and contract.
• Any water which gets
into cracks in rocks will
expand when it freezes.
• Cracks will get bigger
and bigger...
Rocks cracking and
eventually breaking up.
The rock will break up into
smaller pieces
Chemical Weathering
Due to chemical reactions between
substances in the rock and
acidic rainwater.
e.g. Acid Rain
Biological Weathering
Due to the actions of plants and animals.
About Soils...
• Soils forms when the rocks are physically and
chemically weathered over the years.
6 different components:
1 – Rock Particles
2 – Mineral Salts
3 – Humus
4 – Water
5 – Air
6 – Living organisms
Soil Types
1. Sandy
2. Clay
3. Loam or Silt