Geography Exams Semester 1 Flashcards
Geomorphic hazards:
Hazards concerned with the movement of the earths surface, these can include landslides, earthquakes, tsunamis, volcanoes etc
Earthquakes:
They are associated with tectonic plate boundaries, they also occur where fault lines lie. At the heart of an earthquake is an epicentre from which seismic waves radiate.
What is a seismic wave?
The source of energy required for the earths movement.
Tsunami:
A series of waves usually triggered by an earthquake, volcanic eruption or another cause eg meteorite that causes a rapid displacement of water body.
Volcanoes:
A vent on the earths surface that allows magma to escape the interior, explosiveness is determined by how easily the magma can escape and the gas trapped within it.
What are the 3 types of volcanoes?
- Shield volcanoes: the magma is very hot and runny, eruptions are gentle
- composite volcanoes (strato): the magma is cooler and sticky, explosive eruption
- caldera volcano: no build up of materials, vent unsupported and collapses.
Landslides:
Movement of mass rock, soils and debris down a slope
Lithosphere:
Includes the crust and upper mantle (800km thick)
Continental crust:
25-100 km thick, made up of granite rocks
Oceanic crust:
11-16 km thick, dense basalt rocks
Core:
Outer core: 2900km thick, liquid
Inner core: 5100km thick, solid
Tectonic plate theory:
- Suggests that tectonic forces are produced by slow movement of 12 large tectonic plates of rock within the lithosphere (2-5cm per year)
- rock in mantle moves slowly in series of giant convection currents produced from the core
- currents rise and spread beneath the crust before cooling and sinking.
How do plates move?
Force created by friction isn’t enough to move plates.
Slab pull- the weight of the leading edge of a plate that is being subducted into the mantle due to a collision.
How does the sea floor spread?
- The earths magnetic field reverses polarity from time to time (paleomagnetism- a record of these changes) is preserved in the basalt rock, when material rises through the mid-oceans ridges and cools.
- symmetrical pattern of paleomagnetic stripes in rocks on either sides of the ridges and rocks at a similar distance away from the ridge lines were found to be the same age
Convection currents in the mantle:
Mechanism of how tectonic plates move
Convection currents in the mantle are the force moving tectonic plates and making new hotspots
Divergence:
As plates seperate, magma is forced into the gap creating an oceanic ridge. Earthquakes can occur
Convergent:
Plates move towards each other, forces of compression
When an oceanic plate meets continental plate, the oceanic subducts into the mantle forming an ocean trench in subduction zone.
When two continental plates collide, the surface is force upwards forming mountain ranges
Transform plate boundaries:
Movement of plates past each other, creates tension
Results in horizontal displacement of the surface along the fault line
These result in earthquakes as the built up pressure along the fault lines is released.
Spatial distribution:
Refers to how features or objects are arranged on the earths surface.
How to measure earthquakes?
The Richter scale (not so much anymore)
- How intense was the earthquake (amount of movement and sheer energy released) determined on the moment magnitude scale
- What effects did the earthquake have? (Looks at damage caused) mercalli scale.
Moment magnitude scale:
Measures the amount of energy released. Calculated using a formula that includes the rigidity of the rock affected, the distance moved and fhe size of the area involved
Each magnitude releases approx 32 times more energy than the magnitude before it.
What is temporal distribution?
Concerned with examining the distribution of natural hazards over time
What are the 5 key points of the severity of a hazard?
Magnitude Duration Frequency Probability Scale of special impact
Three basic patterns in examining spatial distribution?
Clustered
Random
Uniform