Geo: rocks

What are the different types of rocks

Igneous

Metamorphic

Sedimentary

What are intrusive rocks

Magma that displaces rock inside the crust

What are extrusive rocks

Magma that flows onto the surface

How are extrusive rocks formed

Lava cools on the earths surface

How are intrusive rocks formed

Magma cools on the inside of the earth

Characteristics of igneous rocks

Massive, it forms one large mass with no layers

Crystalline

Consists of many elements

When magma cools elements combine to form crystals and minerals

Elements that igneous rocks may consist of

Silica

Iron

Magnesium

Relation of how quickly magma cools to the size of the crystals of igneous rocks

Quickly cooling magma forms small crystals (extrusive rocks)

Slowly cooling magma forms large crystals (intrusive rocks)

Uses of igneous rocks

Contains valuable metals

Mining companies mine the metals if its economical

Building materials

Stone chips extracted from quarries reinforce cement

Work surfaces and gravestones are made from granite

Types of igneous rocks

Granite

Basalt

Dolerite

Granite characteristics

Intrusive

Magma cools slowly forming large crystals

What are the different types of granite

Quartz-glassy appearance

Mica- black, flaky appearance

Feldspar-large white/pink crystals

Characteristics of basalt

Extrusive

Cools quickly forming small crystals

Hard, black rock forming on the earth surface

Lava flows over the surface to form a plateau

Characteristics of dolerite

Intrusive

Magma cools slowly forming small crystals

Forms closer to the surface

Greenish appearance

Forms at the top of most flat-topped hills

The different intrusive igneous rocks features

Batholith

Laccolith

Lopolith

Sill

Dyke

Volcanic pipe

Monolith

Batholith

Largest type, forms deep within earths surface by cooling slowly (granite)

Laccolith

Mushroom shaped structure, forms when magma forces overlying layers upwards, cools moderately and has medium sized crystals

Lopolith

Saucer shaped. Caused by the weight of the overlying rock strata causing it to sink

Sill

Magma intrudes horizontally between laters along the bedding plane

Dyke

Magma intrudes vertically across the layers of rock

Volcanic pipe

Deep carrot shaped pipe of solidified magma and often contains diamonds

Monolith

Similar to a batholith, when exposed at the surface it formed a doomed rock

Characteristics of a granite dome

Forms from batholiths which are exposed at the surface

Softer rock layers above the batholith are eroded away leaving granite dome

Extent of the batholith can extend thousands of km2

Found in western and northern cape. E.g. paarlbeg

Landforms associated with igneous rocks

Granite domes

Tors

Characteristics of a tor

Form when a granite dome below the surface undergoes chemical weathering

Chemical weathering forms core stones

Less resistant sedimentary layers above core stones erode at the surface leaving piles of core stones and creating a stacked appearance

What are sedimentary rocks formed from

Layers of compressed sediments

What are sedimentary layers formed through

Mechanical processes ad compression and consolidation

Process of forming sedimentary rocks

Layers of broken down material are deposited on top of one another in layers called sediments. The combined weight of it and water compresses the layers till it eventually consolidates to form rock layers called strata

What separates layers in sedimentary rocks

Bedding planes

Characteristics of sedimentary rocks

Sediments of different sizes form in different areas

Layers can be bent and shaped as earth’s crust moves

Plants and animals can be preserved in layers to form fossils

Where are larger pebbles deposited in

Shallow water

Where are medium sized pebbles deposited

In deeper water

Where are fine pebbles deposited

In very deep water

Uses of sedimentary rocks

Building material

Dolomites and shale can be heated and crushed into a dine powder to form cement

Clay is used to build houses, make bricks and tiles

Shale is used for floors and decorative purposes

The different types of sedimentary rocks

Conglomerate

Sandstone

Shale

Limestone

Coal

Sandstone characteristics

Medium sized sediments accumulate in layers on the ocean floor

Beige colour

Layers are evident

Shale characteristics

Fine grained sediments become consolidated

Distinctive layers of various shades

Limestone characteristics

Organically consolidated layers

Formed from shells of marine animals

Shells are made of calcium carbonate/lime

Layers of crushed shells are consolidated to form limestone

Coal characteristics

Organically consolidated layers

Formed from dead plants and trees

Other rocks compressed the organic layers to form it

Conglomerate characteristics

Pebbles cemented together by fine grained sediments

Mixed texture with air spaces

Description of a plateau

Extensive flat/gently undulating area of land elevated above the surrounding terrain

Main characteristics of a plateau

Large areas with relatively flat top and steep sides

Example of a plateau

Karoo plateau

High veld plateau

Description of a mesas

Flat-topped with steep sides, smaller than a plateau, larger than a butte

Main characteristics of a mesa

Flat top, steep cliff like sides, isolated

Examples of a mesa

Carina on area

Namaqualand

Description of a butte

Isolated hill with steep, often vertical sides and often a small flat top

Characteristics of a butte

Smaller than a mesa; flat top significantly eroded

Example of a butte

Karoo region

Description of a pointed butte

Further eroded butte where the top is pointed rather than flat

Characteristics of a pointed butte

Steep, narrow, pointed peak

Example of a pointed butte

Some formations in the eastern cape and Karoo

Description of a conical hill

Hill shaped like a cone, typically the final stage of erosion of a plateau type landform

Characteristics of a conical hill

Rounded/pointed peak steep slopes

Examples of a conical hill

Scattered conical hills in the Karoo

Regional metamorphism

A large amount of pressure changes rocks

Contact metamorphism

Heat causes crystals to melt and form new crystals

Characteristics of metamorphic rocks

Appear in layers/bands

Hardest type of rock

Contain valuable metals/minerals

Uses of metamorphic rocks

1. Metals and minerals within can be mined

2. Crushed gneiss is used to build roads

3. Thinly layer rocks such as slate are used for roof and floor tiles

4. Gem stones are polished for jewelry and decoration

5. Marble is used as a material for sculpting

Marble characteristics

Originally limestone

Made of recrystallized calcite

Can be polished

Relatively soft

Smooth

Often pink, white or grey

Crystalline

Shiny

Characteristics of quartzite

Originally sandstone

Usually light coloured: white, grey or pink

Very hard

Formed from quartz grains fused together under heat and pressure

How does metamorphic rocks change into igneous rock

It melts into magma and then cools

How does sedimentary rock change into metamorphic rock

It undergoes heat and pressure

How does igneous rock change into metamorphic rock

It undergoes heat and pressure

How does igneous rock change into sedimentary rock

It undergoes weathering and erosion to form sediments which are then compacted and cemented

How do sediments change into sedimentary rocks

It is compacted and cemented

How does metamorphic rocks change into sediments

It undergoes weathering and erosion

Slate characteristics

Fine grained

Splits easily into flat sheets

Formed under low grade metamorphism

Dull To slightly shiny

Layered in appearance

Originates from shale

How does igneous rock change into magma

It melts

Why is it called the rock cycle

Rocks are always changing from one type to another in a continuous never ending process

What is erosion

land, soil, and rocks are worn away and transported by natural forces like wind, water, and ice

What is weathering

the natural process of breaking down rocks and minerals on the Earth's surface, primarily by physical and chemical means. This process does not involve the movement of the broken-down material,

Characteristics of gneiss

Originates from granite

Coarse grained

Shows banding due to mineral segregation under high pressure

Alternating light and dark bands]looks striped

The different types of metamorphic rocks

Quartzite

Marble

Slate

Gneiss