lesson 13: rocks

Lesson 13 ROCKS

ROCKS

are found everywhere on Earth.

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ROCKS• come in many colors.• come in different sizes.

BOULDERS• Rocks that are gigantic in size.

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Earth’s crustis made up of different kinds of rocks. They differ in appearance because of their different physical properties.

Physical properties depend on:

1. The kind of mineral present in the rock;

2. The amount of different minerals contained in the rock;

3. How the grains of these minerals are arranged and held together.

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TYPES OF ROCKS

• IGNEOUSROCKS

• SEDIMENTARYROCKS

• METAMORPHICROCKS

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The Rock Cycle

The different

processes

involved in the

formation of the

three types of

rocks, namely

igneous,

sedimentary and

metamorphic.

It also shows how

rocks change

from one form to another.

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IGNEOUSROCKS

Covers about

65%of the Earth’s crust

Igneous means “fire”Formed from the

hardening

of molten rocks.

Magma –

molten rock

Lava –

extruded rock

Intrusive igneous rocks – rocks that

are formed from magma but are not

extruded into the Earth’s surface.

Extrusive igneous rocks –

rocks that have been spewed

out into the surface of the

Earth.

GRANITE

BASALT

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Are the oldest

types of rocks.

Considered the

mother of all

rocks.

Also called

primary rocks.

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SEDIMENTARYROCKS

Covers about

8%of the Earth’s crust

Sedimentary means “settling”

Composed of layers of sand, gravel, mud and other

sediments that have settled at the bottom of the oceans.

These materials are cemented and hardened into rocks by mean of great

pressure exerted on them below the Earth’s surface.

Mudstone – formed from clay and mud.

They are basically hardened mud.

Sandstone – cemented sand formed

through accumulation of sand deposits or silica

or calcium carbonate.

Conglomerate – made up of coarse-

grained material like round pebbles or gravel

which are tightly packed or cemented together.

Shales – that are fine-grained are almost

waterproof and are good underground basins for

water or oil because they are less permeable.

Mechanical means…

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Rock salt or halite – composed of

sodium chloride when a chloride solution is

deposited when water evaporates.

Rocks that are formed from the remains of

plants and animal that have been cemented

together. Examples:

Limestone, Chalk and Corals

Chemical means…

Organic means…

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METAMORPHICROCKS

Covers about

27%of the Earth’s crust

Metamorphic means “has been changed”

Once an igneous or sedimentary rock.

Metamorphism –The process by which a rock is changed

into metamorphic form.

Metamorphism of Limestone into Marble

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Metamorphism of Quartzite

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Thank you