GeomorphologyGrade 10
The Structure of the Earth
• The internal structure of the Earth• How does the Earth look beneath us?
• What does the crust of the Earth look like?
• Types of rocks• Rock Cycle
• How are rocks formed and classified
• Intrusive igneous activity• Landforms associated
• How are they formed? (Batholiths / Pipes / dykes/ sills / laccolith / lopolith)
Structure of the Earth
Laye
rs o
f th
e Ea
rth
Atmosphere640km
Crust6-70km - solid
Sial & Sima
Mantle 2900km Periodite
Semi-molten
Outer core 2000kmLiquid iron, nickel & oxygen
Inner core 2740kmSolid iron nickel - High pressureTemperature above 4500ºC
Layers in the Crust of the Earth
Seafloor
Continent
Mantle Sediments
Oceans
Earth structure
Layers of the crust of the Earth
• Continental crust• Sial – silica & aluminium
• Granite
• Less dense
• ‘Floats’ on Sima
• Not continuous
• Older rock
• Continents
• Seafloor• Sima – Silica & Magnesium
• Basalt
• Denser & heavy
• Covers mantle
• Continuous layer around the Earth
• New rock
• Seafloor
Moho Plane
ContinentSea floor
Sediments
Rock types
• Igneous rock• Lava or magma that solidifies to form rock
• Sedimentary rock• Weathered material deposited in layers that solidify under the
pressure of accumulative layers
• Metamorphic rock• Rock that changes form under high pressure and or temperature
Rock classification• UPPER CRUST: Sedimentary rock
• Sediments (dust/ rocks/ silt/ weather material / organic material) deposited by wind, water and ice build up in layers, weight from above compresses it into solid rock.
• CRUST: Igneous rock• Magma rises, cools down, solidifies
• Deeper Crust : Metamorphic rock• Igneous and sedimentary rock moves downward due to
plate movement, heat and pressure changes it into metamorphic rock
Igneous rock Lava or magma that solidifies to form rock
• When magma cools down and solidifies under the surface it forms intrusive igneous rocks.
• The rocks are later exposed by erosion.
• Examples: granite, dolerite
Characteristics of Igneous rock
• Igneous rocks do not have layers, but are made up of crystals (crystalline)
• It is extremely hard and weathers slowly
• It contains no fossils
• When weathered, it forms fertile soil
Uses of igneous rock
• Often used for building work e.g. road construction, kitchen tops, tomb stones etc.
• Granite is used for stone walls, facing blocks for buildings, stone chips on roads
• Dolerite weathers down to fertile soil
• Contains minerals and ores
Distribution of Igneous rocks in SA
• Granites are common around Nelspruit (Mbombela), Kruger Park, The Bushveld Igneous complex in the Polokwane- Mokopane area
• Paarl rock in Western Cape
• Namaqualand
Igneous rock
Sedimentary rockWeathered material deposited in layers and that solidify under the pressure of accumulative
layers
• Weathered rock is eroded by wind, rivers and glaciers
• This material is deposited in lakes and near to the coastline
• The layers of material that is deposited becomes more and heavier and the lower layers becomes solidified under the accumulative weight.
• The layers become stratified (strata)
• Can be of mechanical, chemical or biological origin, depending on the main type of weathering that broke down the original rock
Characteristics of sedimentary rocks
• They are deposited in layers/ strata
• They contain many fossils
• The erode easily
• Often forms fertile soil.
• The rocks are able to fold and bend and form fold mountains
• Layers are porous and allow water to penetrate
• Layers differ in respect of grain size, colour and composition.
Uses of sedimentary rocks
• Coal: a valuable source of heat and power.
• Sandstone: used for building purposes
• Shale: used in making paths, roadways of old time roof tiles
• Salt: used for domestic purposes and in the chemical industry.
• Limestone: used in making of cement and fertilisers and in the iron and steel industry
• Crude oil: make fuel
Distribution of sedimentary rocks in SA
• They constitute some 75% of the actual surface rocks of the Earth.
• The greatest part of South Africa consists of sedimentary rock.
• Golden Gate in Eastern Free State
• Cape Fold Mountains
RAINBOW MOUNTAINS-CHINA
RAINBOW MOUNTAINS-CHINA
RAINBOW MOUNTAINS-CHINA
RAINBOW MOUNTAINS-CHINA(photo shopped)
Metamorphic rockRocks that changed under high pressure and or temperature
• CHARACTERISTICS:
• Rock is harder than original rock but can be brittle.
• It weathers slowly.
• Can have attractive colours and a fine texture
• Streaky in appearance
Examples of metamorphic rock
• Granite changes to Gneiss
• Sandstone changes to Quartzite
• Limestone changes to Marble
• Coal changes to diamonds under very specific conditions
• Shale changes to slate
Uses of metamorphic rock
• Stone chips for road works.
• Slate is used on roofs and garden paths
• Marble is used in buildings and for sculpture
• Contains many minerals e.g. gold, silver, diamonds
Distribution on metamorphic rock in SA
• Magaliesberg mountains- quartzite
• Mable Hall- marble
• Phalaborwa area- different minerals
• Barberton area- different minerals
• Bushveld Igneous Basin- different minerals
Quartz
Serpentine
Asbestos a type of serpentine also called crocidolite
Tiger’s Eye
Buddstone
Agate
Jasper
Hardness of Rock types
Rock classification
• UPPER CRUST: Sedimentary rock• Sediments (dust/ rocks/ silt/ weather material / organic material) deposited
by wind, water and ice build up in layers, weight from above compresses it into solid rock.
• CRUST: Igneous rock• Magma rises, cools down, solidifies
• Deeper Crust : Metamorphic rock• Igneous and sedimentary rock moves downward due to plate movement,
heat and pressure changes it into metamorphic rock
THE ROCK CYCLE
Activity 2: Understanding the rock cycle, p97• 1) Rock Cycle: The ongoing process of making, destroying, changing and
remaking one type of rock into another type.
• 2) * Rocks change when they are heated and melted underground.
• * On the Earth’s surface weathering and erosion changes rocks.
• * IGNEOUS ROCKS from when lava or magma is cooled.
• * METAMORPHIC ROCK form when igneous or sedimentary rock change because of heat and pressure.
• * SEDIMENTARY ROCKS form when weathered rocks and organic material are deposited (put down) in layers.
• 3) IGNEOUS ROCKS: when magma rises to the earth’s surface and is cooled.
• METAMORPHIC ROCK form when igneous or sedimentary rock change because of heat and pressure.
• SEDIMENTARY ROCKS form when weathered rocks and organic material are deposited (put down) in layers by wind water and ice
• 4) Rock name Type
Shale Sedimentary
Basalt Igneous
Marble Metamorphic
Granite Igneous
Limestone Sedimentary
Intrusive landforms
• Batholith
• This is the largest type of igneous intrusion.
• They form deep in the crust .
• Large round shape.
Laccolith
• This is a mushroom shaped structure where magma forces the overlying strata upwards.
Laccolith
Lopolith
• This is similar intrusion to a laccolith
• The weight of the overlying strata causes the lopolith to sink into a saucer shaped structure .
Sill
• A sill forms where magma intrudes horizontally between layers of rock .
Dyke
• A dyke forms when magma intrudes vertically between layers of rock .
Dikes exposed to surfaces
Pipe
Batolith
Lopolith
Laccolith
Dyke
Sill
PipeMASSIVE
Batholith: Paarl Rock
Underground Igneous Features
Dikes exposed to surfaces
Laccolith
Activity 3: Mind map: Intrusive Igneous activity, p 99
INTRUSIVE IGNEOUS LANDFORMS
Batholiths* The largest of all the forms*Enormous mass of magma pushes up and solidify under the surface* Granite
SillsWhen magma spreads horizontally between sedimentary layers* Dolerite
DykesA Wall-like intrusion, solidified in a thin sheet• Cuts vertically across
horizontal layers• Dolerite• Forms narrow ridges
on top of surface
Lopoliths*Magma intrudes between sedimentary layers, but the layers below cannot support the weight and sinks in a saucer shape• Smaller than Batholith• * Connected to magma
source with pipe/dyke
Laccoliths*Magma intrudes between sedimentary layers and forces the layers upwards in mushroom shape• Smaller than batholith• Connected to magma source by
a pipe or dyke
PipesChimney-shaped intrusion• Magma can move upwards to
the surface (Volcano)• Solidifies as dolerite
Rock structure and landforms
• Resistance
• Permeability
• Sedimentary rocks LAYERS
• Igneous rocks TORS
Activity 4 Paragraph
•Figure 8.3 shows layering in rocks which is an indication of sedimentary rock. The photo shows that lots of erosion has taken place, therefore these rocks are softer.
•Figure 8.4 shows dikes and pipes which indicates that intrusive igneous activity took place therefore these rocks are harder in nature.