Physical Processes and Tectonic Hazards
- Created by: belle-madeleine
- Created on: 28-08-17 00:19
View mindmap
- Physical Processes and Tectonic Hazards
- Earthquakes, Crustal Fracturing and Ground Shaking
- Earthquakes
- Movements are caused by a gradual build-up of tectonic strain
- When the pressure exceeds the strength of the fault, the rock fractures
- Sudden release of energy, creating seismic waves
- Crust then rebounds either side of the fracture causing the ground to shake
- Hypocentre
- Point of rupture
- Can occur at any depth between the surface and 700km
- The most damaging events occur with a hypocentre of less than 40km
- Seismic Waves
- Seismometer measures the amount of ground shaking during an earthquake
- Severity of an earthquake is linked to the amplitude and frequency of wave types
- Primary waves
- Vibrations caused by compression
- They spread quickly at about 8 km/sec
- Secondary waves
- Move slowly at 4 km/sec
- Vibrate at right angles to the direction of travel
- Can't travel through liquids
- Love waves
- Surface waves with the vibration occurring in the horizontal plain
- High amplitude
- Earthquakes
- Liquefaction and Landslides
- Liquefaction
- Causes buildings to settle, tilt and collapse
- Water-saturated material can temporarily lose normal strength and behave like a liquid
- Landslides
- Slopes weaken and fall
- Occur when earthquake magnitude is bigger than 4
- Can travel miles
- Grow in size as they collect trees, boulders and cars
- Liquefaction
- Tsunamis
- Wavelength is longer
- Grow in height when they reach the coastline because it is shallow
- Series of waves caused by seabed displacement
- Generated by subduction zones
- Impact Factors
- Duration
- Wave amplitude
- Water column displacement
- Distance travelled
- Water depth
- Gradient at the shoreline
- Degree of coastal ecosystem buffer
- Timing
- Coastal development
- Volcanoes
- Primary Hazards
- Pyroclastic flows
- Responsible for most deaths
- Bubbles burst ejecting hot gases and pyroclastic materials
- Glass shards
- Pumice
- Crystals
- Ash
- Clouds can be 1000 degrees
- Tephra
- Ejected rock fragments into the atmosphere
- Can be bombs to dust
- Can cause building roofs to collapse and can cause fires
- Dust reduces visibility
- Affects air travel
- Lava flows
- Threat if they are fast moving
- Viscosity determined by silicon dioxide
- Volcanic gases
- Water vapour, sulphur dioxide, hydrogen and carbon monoxide
- Pyroclastic flows
- Secondary Impacts
- Mudflows
- Lahars
- Fine sand and silt material
- Hazards depends on steepness of slopes, the volume of material and particle size
- Associated with heavy rainful
- Floods
- Jokulhlaups
- Glacial outburst flood
- Cause landform modification through erosion and deposition
- Rapid discharge of large volumes of water, ice and debris
- Mudflows
- Primary Hazards
- Earthquakes, Crustal Fracturing and Ground Shaking
Comments
No comments have yet been made