Week 1, A Global and Canadian Outlook on Natural Disasters Flashcards
Internal heat is primarily generated from
ongoing decay of naturally occurring radioactive elements that have been present in the earth since the beginning.
The frequency of weather related disasters is
increasing world wide.
The frequency of geologic disasters is
stable.
Why is the economic cost of natural disasters increasing rapidly?
Increasing population
Vulnerable infrastructure
Why do developed countries have fewer casualties but higher economic costs?
More money for mitigation
Extensive and expensive infrastructure
Rheology
How a material strains under stress.
Stress
Force per area
Compression
Pressure perpendicular to surface
Tension
Perpendicular to surface
Extension
Shear
Parallel to surface
Distortion
Strain
Relative deformation under stress.
When you apply stress to an area it will strain.
What do liquids do under stress?
They flow
Elastic Strain
Deformation is recoverable
Ductile Strain
Deformation is permanent
Brittle Strain
Rigid object fractures
Like a Kit Kat
Plastic Strain
Flows like high viscosity fluid
Like a Mars Bar
The Earth’s crust is ____ while the mantle undergoes _____ ______.
The Earth’s crust is brittle while the mantle undergoes plastic flow.
What does rheology depend on?
Temperature and pressure
Why does oceanic crust tend to sink and subduct below continental crust?
Because it is heavier.
Solid/melted state depends on…?
Pressure: Increases approximately linearly inward due to overburden weight
Temperature: Increases non-linearly inward due to heat from radioactive decay
Composition: Different materials melt at different pressure/temperature combinations
Isostacy
Buoyancy
Gravitational equilibrium whereby lithosphere “floats” on denser, deformable, asthenosphere at an elevation dependant on its thickness and density.
Topography
Like icebergs, the higher they extend above water, the higher they extend below water.
We can observe this in mountain ranges.
Isostatic Adjustment
Post Glacial Rebound
Glacier weight causes subsidence
Crust rebounds when ice is removed
Seismology
Using earthquakes to study the earth’s interior
Causes of earthquakes
Volcanic Activity Oil and Gas Production Meteorite Impacts Mining Landslides Caldera Collapses Explosions Glaciers
Faults
A fracture in the earth across which two sides move relative to each other.
Complex, irregular surfaces where interlocking rock is held together by friction.
Fault Rupture
Elastic Rebound Theory
- Fault is locked by friction
- Relative motion across fault accommodated as elastic strain
- Stress exceeds friction, causes rupture, releases energy as seismic waves
Hypocentre
Focus
Point where rupture initiated
Epicentre
Point directly above hypocentre on Earth’s surface
Strike-slip
Transform
Horizontal Motion
Dip-slip
Vertical Motion
Normal and reverse faults
