Option D - Geophysical Hazards Flashcards
What is the theory of plate tectonics?
- the Earth is made up of many layers
What is subduction?
- the plunging of one plate beneath another
Where do subduction zones form?
- where an oceanic lithospheric plate collides with another plate
Where does rifting occur?
- at constructive plate boundaries
What is the global internal heat flow?
- large-scale convection currents
What is a shield volcano?
- gently sloping sides, a shallow crater and large circumstances
- formed from very hot, runny lava that flows great distances
What is a composite (/strato) volcano?
- slopes of near 30° near the summit and 5° near the base
- formed by alternating eruptions of fragmental material followed by lava outputs
What is a cinder volcano?
- usually concave with a steep of angle at 30°-40°
- formed by fragments of solid material
What is a lava eruption?
- runny basaltic lava which flows down the sides of the volcano and gases escape easily
What is a pyroclastic eruption?
- explosive eruptions that produce pyroclastic rock
What is a vulcanian eruption?
- violent and occur when the pressure of trapped gases in viscous magma becomes sufficient to blow off the overlying crust of solidified lava
What are the primary hazards of a volcano?
- direct impacts of the eruption
- lava flows, ash fallout, pyroclastic flows, gas emissions, …
What are the secondary hazards of a volcano?
- may be due to the way that the ejected material reacts or changes form
- lahars, debris avalanches, avalanches, …
What is an earthquake?
- a series of seismic vibrations or shock waves which originate from the focus
What is the focus?
- the point at which the pates release their tension or compression suddenly
What is the epicentre?
- the point on the surface of the Earth immediately above the focus of the earthquake
What are primary waves?
- the fastest wave type and can move through solids and liquids - they shake the Earth forward and backward
What are secondary waves?
- move with a sideways motion and are unable to move through liquids - they make the ground move horizontally, causing a lot of damage
What are love waves (a wave that is transformed when a primary wave or secondary wave reaches the surface)?
- cause the ground to move sideways
- travels slowly through the crust, but causes the most damage
What are rayleigh waves (a wave that is transformed when a primary wave or secondary wave reaches the surface)?
- cause the ground to move up and down
- travels slowly through the crust, but causes the most damage
What is the primary hazard of an earthquake?
- ground shaking
What are some secondary hazards of an earthquake?
- ground failure and soil liquefaction
- landslides and rockfalls
- debris flow and mudflow
- tsunami
What are some impacts of an earthquake?
- loss of life
- loss of livelihood
- total or partial destruction of buildings
- interruption of water supplies
- breakage of sewage disposal systems
- loss of public utilities such as electricity and gas
- floods due to collapsed dams
- release of hazardous material
- fires
- spread of chronic illness due to lack of sanitary conditions
What are mass movements?
- any large-scale movement of the Earth’s surface that are not accompanied by a moving agent such as a river, glacier or ocean wave
What are some different types of mass movement?
- soil creep (slow)
- landslide (medium speed)
- debris avalanche (fast)
- …
What are some causes of mass movement?
- loading of slope
- weathering effects
- transient stress
- changes of structure
- organic effects
- …
Where do most earthquakes occur?
- near plate boundaries
What human activities could cause earthquakes?
- large dams
- mining
- testing of weapons
Where do most volcanoes occur?
- many near plate boundaries
- over hotspots
- about 3/4 of volcanoes lie along the Pacific Ring of Fire
What is a hotspot?
- a plume of hot material rising from the deep within the mantle (- which is responsible for volcanoes)
Where do landslides occur?
- all around the world
more common in areas that have: active tectonic processes, high rainfall, high population density
What is the recurrence interval (/return period)?
- the expected frequency of occurrence measured in years for an event of a particular size
What is the Richter Scale?
- measures the magnitude of earthquakes
- logarithmic scale
What is the Moment Magnitude Scale?
- measures the amount of energy released
- produces figures that are similar to the Richter Scale
What is the Volcanic Explosive Index?
- based on the amount of material ejected in the explosion, the height of the cloud it produces and the amount of damaged caused
What is the relationship between magnitude and frequency?
- the higher the magnitude, the lower the frequency
What is vulnerability?
- the geographic conditions that increase the susceptibility of a community to a hazard
What are the economic factors which increase vulnerability?
- levels of wealth and development
- building styles and building codes
- access to technology
- insurance cover
What are the social factors which increase vulnerability?
- education
- public education
- awareness of hazards
- gender
What are the demographic factors which increase vulnerability?
- population density
- age
- disability
What are the political factors which increase vulnerability?
- the nature of society
- effectiveness of lines of communication
What are some factors that affect the impacts of geophysical events?
- the magnitude and frequency of events
- population density
- type of buildings
- distance from the event
- types of rocks and sediment
What is risk?
- the likelihood of loss of life, injury, or destruction and damage from a disaster in a given period of time
What is disaster risk?
- the consequence of the interaction between a hazard and the characteristics that make people and places vulnerable and exposed
What are the factors affecting perception of risk?
- experience
- material well-being
- personality
What is a hazard profile?
- a description and analysis of a specific type of local hazard
What is magnitude?
- the size of the event
What is frequency (recurrence interval)?
- how often an event of a certain size occurs
What is duration?
- the length of time that the environmental hazard exists
What is areal extent?
- the size of the area covered by the hazard
What is spatial concentration?
- the distribution of hazards over space
What is speed of onset?
- the time difference between the start of the event and the peak of the event
What is regularity?
- how regular the hazard is
What are scientific predictions of hazards used for?
- used to provide precise statements on the time, place and size of the future event
How can earthquakes be predicted?
- seismometers (to record micro-earthquakes)
- magnetometer (to measure changes in the Earth’s magnetic field)
- strain meters (to monitor surface deformation)
How can volcanoes be predicted?
- chemical sensors (to measure increased sulphur levels)
- lasers/GPS (to detect the physical swelling of the volcano/crater)
- ultrasound (to monitor low-frequency waves in the magma resulting from the surge of gas and molten rank)
How can one prepare for a hazard event by geophysical hazard adaptation?
- land-use zoning
- insurance
- new technology
How can one manage landslides?
- terracing steep slopes
- drainage of water from slopes
- building restraining structures
- erosion control at the base of cliffs
- diversion of roads away from active areas
How can one manage the risk of earthquakes?
- building can be designed to withstand earthquakes (small windows, deep foundations, shock absorbers, light roofs, …)
- land-use planning
How can one control volcanoes?
- generally little that can be done
- diverting lava flows using dry channels or explosives or by pumping water onto the lava front to cool it
- GPS to monitor swelling of volcano, which could indicate an imminent eruption
What can one do to manage tsunamis?
- very costly
- sea walls
- early warning systems
What is rehabilitation?
- people being able to make their homes safe and live in them again
What are the post-event management strategies?
- rescue
- rehabilitation
- reconstruction
How are phones being used after hazard event occured?
- UNICEF training people in Brazil to map social and environmental risk
- RapidFTR (app) reunites children with their families after a disaster by registering information about the children
