Earth crust

1. Rocks, minerals and soil
GEOGRAPHY UNIT 1
GRADE 7
By Ma’am Laley Erum

2. After the Lesson we should be able to:
Describe the characteristics of different types
of rocks and soil.
Explain how rocks and soil are formed
Identify different rocks and soil in pictures.

3. Soil

4. Feature 1
Feature 2
Feature 3
Feature 1
Feature 2
Feature 3

19. Igneous Rocks
Magma- molten material
underground Lava-
magma that reaches the
surface
Igneous rocks are
formed from magma that
has cooled and hardened
either beneath the
surface or from a volcanic
eruption
Ways to Form Igneous Rock
Intrusive Igneous Rocks - form
when magma hardens beneath
Earth’s surface Magma intrudes
into existing rocks
Extrusive Igneous Rocks form
when lava hardens on the
surface of the Earth Extruded
onto the surface rhyolite granite
Classification of Igneous Rocks
Composition -refers to the
minerals that make up the rock
Texture -shape, size,
arrangement and distribution of
minerals that make up the rock

20. Sedimentary Rocks
• Made up of smaller rocks cemented together
• Sometimes have fossils
• Usually have layers
Form when loose sediment (rocks, sand) is
deposited by water, compacted, and cemented
together.
• Form as a chemical reaction in the water that
leaves a chemical deposit, usually on an ocean
bottom.
• Form along beaches, by rivers, or under the
water in lake or oceans.

21. How is a sedimentary rock formed?
Sediments get compacted and cemented together.
Particles carried by
water and wind
Particles deposited
as sediments
Densely packed
sediments
Loosely packed
sediments
Sedimentary
Particles
Cementing
Material

22. Metamorphic Rocks
• Form when igneous, sedimentary, or other
metamorphic rocks are heated and/or
squished, forming a new rock type.
• Usually has interlocking crystals and layers
(called foliation)
This can either happen underground or above
ground.
◦ – Underground: high pressure and heat
◦ – Above ground: volcano erupting
• When classifying metamorphic rocks, they
always come from a parent rock

23. Igneous
Sedimentary
Metamorphic
Magma pool
Lava
Sediments
Magma

24. The Rock Cycle
Igneous rocks
Sediments Sedimentary Rocks
Metamorphic rocks
Magma

25. What is a mineral?
A mineral is a naturally occurring
inorganic solid, with a definite
chemical composition, and an
ordered atomic arrangement.
This may seem a bit of a mouthful,
but if you break it down it becomes
simpler.
Minerals are naturally occurring.
They are not made by humans.
All rocks are composed of minerals
Minerals are naturally occurring,
inorganic, crystalline solid with a
definite chemical composition found on
Earth.
There are about 3500 known minerals
About 20 minerals make up more than
95% of all of the rocks in the Earth’s
crust

26. Composition of the Earth’s Crust
 Eight Elements that make up
over 98% of Earth’s Crust
Silicon (SI)
Aluminum (Al)
Iron (Fe)
Calcium (Ca)
Sodium (Na)
Potassium (K)
Magnesium (Mg)
%age present
silicon Aluminium Iron Calcium Sodium Potassium Magnesium

27. MINERAL PROPERTIES
Physical properties of minerals are dictated by the nature of the underlying atomic
structure, nature and arrangement of chemical bonds, and energy levels of valence
electrons.
Color:- Usually the first and most easily observed -Some minerals are always the
same color -Some minerals can have many colors ROSE QUARTZ SMOKY QUARTZ
Luster:- General appearance of a mineral surface in reflected light Glassy-
Obsidian
Hardness/Density :- MOH’S Hardness Scale (NOT absolute): Talc 1, Gypsum 2,
Calcite 3, Fluorite 4, Apatite 5, Orthoclase 6, Quartz 7, Topaz 8, Corundum 9,
Diamond 10
Crystal Shape