Geography - Folding and faulting Flashcards
Folding
Bending of rocks into folds due to strong compressional forces.
When tectonic plates converge, the sedimentary rock along the plate boundaries becomes compressed and folding occurs.
The buckling of a rock layer that was once horizontal.
What are the main types of folds?
- Anticlines
- Synclines
Faulting
It is the result of the movement of the Earth’s plates. Faults occurs where there is stress along a weak point in the Earth’s crust.
In unstable parts of the earth the crust is subjected to tension, compression and lateral forces.
Fold Mountain
The resultant landforms associated with converging plates.
What are some examples of plate mountains?
Himalayas
Alps
Rockies
Andes
Cape Fold Mountains
How are fold mountains formed?
- A thick layer of sedimentary rock strata builds up on the ocean floor.
- Plate movements (convergent) slowly compress the rock strata causing the strata to form folds.
- Further plate movement closes the ocean basin and pushes the strata onto the land to form a range of mountains (fold mountains)
What landforms are associated with folding?
When rocks are first folded, the anticlines stand out as hills and the synclines form valleys.
What are the different kinds of folds?
- Symmetrical folds
- Asymmetrical folds
- Overtured folds
- Overthrust folds
Describe a symmetrical fold
They have equal limbs and usually indicate an equal amount of pressure from either side.
Describe an asymmetrical fold
They appear to lean to one side. Pressure may have been greater from one side.
Describe an overturned fold
The pressure is even greater on one side.
One limb is very steep.
Describe an overthrust fold
Occur when pressure causes the strata to fracture.
One side of the fold slides along the line of fracture called a fault.
Fault
One side of the fold slides along the line of fracture.
Cracks or fracture in rocks.
Fault line
The line along the surface where the break has occured.
What are the different kinds of faults?
- Normal faults
- Reverse faults
- Lateral faults
Normal fault
Tension forces (apart) / rocks are thrown down.
Reverse fault
Compression forces (together) / rocks are pushed up.
Lateral fault
Tearing forces cause rocks to move past one another laterally.
What landforms are associated with faulting
Rift Valley
What are the stages in the formation of a rift valley.
Tension stresses set up convection currents in the mantle causing the crust to crack.
A plume of magma may rise within magma and increase tension on the rocks of the crust, causing faulting.
The rift valley widens as the crust continues to move apart.
Block mountain
A block of land that has moved upwards along fault lines due to compression
What is another name for a block mountain?
Horst
Rift Valley
An area of land that have moved downwards long fault lines caused by tension.
What is another name for a rift valley?
Graben
How do people make use of rift valleys?
Provides water from lakes formed in valleys
- Water availability for domestic, agricultural, and commercial use
- Contain fertile soil deposits for agricultural activities
- Large areas of grazing land for livestock farming
- Contain mineral deposits which encourages mining
- Lakes/rivers on valley floor supports fishing industry
- Lakes/rivers on valley floor supports recreational activities
- Water from lakes/ rivers can produce hydro-electricity
- Provide tourist attractions because of natural beauty
How does an Earthquake occur?
A sudden and violent movement of the Earth’s crust as a result of a sudden release of energy.
Focus
Exact point beneath the Earth’s surface when the plates shift.
Epicentre
Point directly above the focus of the Earth’s surface.
Fault scarp
The steep exposed rock face.
Fault
Crack in the Earth’s crust resulting from the movement of rock.
Wave front
Seismic waves releasing energy through the crust.
Seismic waves
A wave of energy generated by an earthquake.
What are the two types of seismic waves that are produced by all earthquakes?
- S waves
- P waves
P waves
Primary waves because they arrive at seismic reporting stations first.
S waves
Secondary waves because they travel at slightly slower speeds and are the second set of seismic waves recoded on seismographs.
Primary waves
Only occur underground / less damaging / waves that travel quickly through solids and liquids.
Secondary waves
They are more damaging / destructive / Travel slowly and cause the ground to shake / wobble.
What causes earthquakes?
- Divergent plate boundaries cause tension to build up in crust.
- Volcanoes: The sudden release of molten minerals through a crack in the Earth’s crust.
How do you measure an Earthquake?
- Richter scale
- Seismograph
- Seismogram
Richter scale
Method to allocate a magnitude number to qualify the energy released by an Earthquake.
Seismograph
Instrument used to measure and recode an Earthquake
Seismogram
A graph output from a seismograph
What is the impact of an earthquake on people and society?
- Injuries and/or death of people and animals.
- Destruction of infrastructure e.g. roads, houses.
- Transport and communication disrupted.
- Landslides flatten and destroy buildings.
- Burst water pipes reduce availability of fresh water.
- Contaminated water cause health issues e.g. cholera.
- Gas pipe leaks cause fires.
What is the impact of an Earthquake on the environment?
- Disruption of habitat.
- Destruction of vegetation.
- Landslides, mudslides.
- Soil liquefaction.
- Contamination of natural resources e.g. water, soil.
What is the impact of an Earthquake on the Economy?
- Businesses destroyed.
- Reduce employment.
- Expenses to rebuild/fix damages to infrastructure.
- Developing countries are more affected because of lower economic growth.
What are some features of Earthquake resistant buildings?
- Cross bracing
- Shock absorbers (base isolators)
- Shear walls
How does having cross-bracing make a building Earthquake resistant?
Reinforce walls using two steel beams.
How does having shock absorbers (base isolators) make a building Earthquake resistant?
It will absorb tremors of earthquakes.
How does having shear walls make a building Earthquake resistant?
(Concrete walls with steel bars in them) to reduce rocking movements
Tsunami
A tsunami can develop. A large wave produced by an Earthquake under the ocean.
Peak/ crest
The top of the fold on the anticline.
Trough
A trough is a bottom part of the syncline.
limb
Each side of the fold.
