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Components of the Physical environment
Earth’s surface is a vast area of 500 million square
kilometres.
Four immense systems interact
Biotic Vs. abiotic systems (human-nature relationships)
Rocks and Landforms
Internal structure of the Earth
Rocks and Landforms
1. Crust: composed of sial (gigantic rocks forming
continents) which can be 70 km thick. This layer
together with the rigid top layer of the mantle
are collectively known as the lithosphere.
sima (basaltic rocks forming ocean beds) which
averages 6-10 km in thickness. At its deepest, it
has a temperature of 1200 degree Celsius.
Rocks and Landforms
2. Mantle: composed mainly of silicate rocks, rich in iron
and magnesium.
Apart from the rigid top layer, the rocks in the
remainder of the mantle, the asthenosphere, are
kept in a semi-molten state.
The mantle extends to a depth of 2900 km
where temperatures may reach 5000 degrees
Celsius. These high temperatures generate
convection currents.
Rocks and Landforms
3. Core: Consists of iron and nickel and is the size of Mars.
The outer core is kept in a semi-molten state, but
the inner core is solid.
Temperature at the centre of the earth is about
6200 degrees Celsius.
This is at 6371 km below the surface and it is
hotter than the surface of the Sun.
Rocks and Landforms
Rocks form the crust.
Rock: a solid material made up of one mineral or a number
of minerals such as quartz, feldspar and mica in
granite, calcium carbonate in limestone.
the minerals are solidified in the form of
interlocking crystals.
Rocks and Landforms
Types of rocks
Literally thousands of rocks have been identified, all the
result of three kinds of rock forming processes:
1.Igneous
2.Sedimentary
3.Metamorphic
The interrelationships of these three processes gives rise to
the rock cycle.
Rocks and Landforms
The Rock
Cycle
Rocks and Landforms
Types of rocks
1.Igneous Rocks
 Rocks that solidify and crystallize from a molten state.
 They form from magma, which is molten rock from
beneath the earth’s surface.
 It can either be intrusive or extrusive
Rocks and Landforms
Types of rocks
1a. Intrusive/plutonic igneous rocks
-formed by the cooling and solidification of magma
inside the earth’s crust.
- eg. Granite and Gabbro
1b. Extrusive/volcanic rocks
-formed by the cooling and solidification of lava on the
earth’s surface.
- eg. Basalt
Rocks and Landforms
Types of rocks
2. Sedimentary rocks
a. Mechanically formed rocks – formed by the
compression and cementation of sediments deposited
over long periods in the sea.
Eg. Shale, Sandstone, Conglomerate
Rocks and Landforms
Types of rocks
2. Sedimentary rocks
b. Organically-formed rocks: formed by the compression
and cementation of plant and animal remains.
Eg. Coal (from decayed plants)
Limestone and Chalk (from shells of sea animals)
Rocks and Landforms
Types of rocks
2. Sedimentary rocks
c. Chemically-formed rocks – formed when water has
evaporated from solutions which contain minerals.
Eg. Rock salt
Rocks and Landforms
Types of rocks
Metamorphic rocks
-formed when igneous or sedimentary rocks are changed
by extreme heating or compression
- two types: foliated and non-foliated.
Rocks and Landforms
Types of rocks
Metamorphic rocks
a. foliated: minerals are segregated in wavy bands
through metamorphism.
Eg. Slate (from shale)
Schist (from shale or basalt)
Gneiss (from granite)
Rocks and Landforms
Types of rocks
Metamorphic rocks
b. Non-foliated: Rocks originally composed of one
dominant material
Eg. marble (from limestone)
quartzite (from sandstone)
Rocks and Landforms
Characteristics of Rocks
Igneous rocks
1. Crystalline in nature.
2. Intrusive rocks cool slowly, thus the mineral crystals
have time to grow large.
3. Extrusive rocks cool quickly, thus they contain small
mineral crystals.
Rocks and Landforms
Characteristics of Rocks
Sedimentary rocks
1. May be stratified as sediments are laid down in
horizontal layers called strata.
2. May also contain fossils
Rocks and Landforms
Uses of rocks
1. Source of building and road making materials
2. Source of industrial raw materials
3. Source of power
4. Source of minerals
5. Source of soil
6. Source of gems and precious metals
How do we identify rocks?
Reference
Pellant, C. (1992) Rocks and Minerals, London: Dorling Kindersley.