Hazards Flashcards
What are body waves? List 2 types of body wave too.
Waves that travel through the earth. They are either the primary or secondary type.
How do primary/pressure waves work?
Like a slinky, they alternatively compress and expand. Particle motion is parallel to wave movement here. They can travel through ALL substances, and are the fastest type of wave.
In context with some land, explain how primary waves would impact this?
Primary waves cause rocks to move back and forth making the ground break up.
How do secondary (AKA sheer or shaking) waves work?
A transverse movement of particles that is 90 degrees (perpendicular) from the movement of the wave. However it cannot travel through air or water, they are slower but cause more damage than primary waves. It’s like shaking a rope, or the sound waves you get which are transverse (oscillating in right angles to wave movement).
In context with some land, explain how secondary waves would impact this?
Secondary waves cause the ground to shake up and down.
What are surface waves? List 2 types of these waves too.
Travel along the earth’s surface, cause the most damage, as they cause more ground movement and travel more slowly so take longer to pass. 2 Types of surface waves are the Raleigh and love wave.
How do Raleigh waves work?
Rock moves in an elliptical motion to as the wave moves horizontally and this clock-like movement breaks up the ground. It’s like a ground roll. Similar to surface water waves.
How do love waves work?
Horizontal sheer waves, move the ground from side to side at right angles to the direction of the movement. This damages infrastructure and buildings.
List primary effects of seismic events [2]
Ground ruptures and ground shaking.
What is the level of ground shaking (primary effect of seismic activity) dependent on?
Magnitude, depth of focus, distance from epicenter and local geological conditions
What’s a ground rupture?
Displacement of the earth’s surface along a fault line
Give an example of a secondary effect of a seismic event that occurs in the hydrosphere?
Tsunamis
How does a tsunami form due to seismic activity
Formation:
Earthquake vertically moves the seabed up by several meters. Displacing (moving) the water above.
Large waves radiate outwards across the ocean away from the epicentre of the earthquake.
When it reaches shallow water near the coast, the base is slowed down by friction and becomes taller. This is called shoaling.
A large wave hits the coast, a tsunami.
Factors that affect tsunami strength? List [4]
- Distance wave has travelled.
- Coastal geography: relief of the coastline.
- Coastal land use and population density.
- Lack of warning systems and evacuation plans.
Why does the distance the wave has travelled affect tsunami strength?
This is because as waves travel, they lose energy - this means that the further away from the coast an earthquake occurs, the less powerful it is when it reaches the coast.
Hazards can be classified as a mixture of these geographic processes (geophysical, hydrological and atmospheric). Give an example
A tropical storm. Hydrological / Atmospheric, as both of these processes contribute to the hazard. The heavy rainfall is a result of atmospheric and hydrological interactions, and interaction of low and high pressure is atmospheric.
Give 4 factors that can affect hazard perception
- Wealth
- Past experiences
- Education
- Religion
How can wealth affect hazard perception?
Wealthier people may percieve a hazard to be smaller, as they are less vulnerable. As a result, they may not partake in preparation and evacuation - heightening their risk.
However, wealthier people may view hazards as a greater risk, due to heightened costs of property damage and financial loss than someone less wealthy. This is dependent on the person.
How can experience affect hazard perception?
Someone who’s experienced more hazards may be more likely to understand the full effects of a hazard.
Studies also suggest that people who have experienced
hazards are likely to have an optimistic and unrealistic outlook on future hazards, almost like a
‘lightning never strikes twice”.
How can education affect hazard perception?
A person who is more educated about hazards may understand their full effects on
people and how devastating they can be and have been in the past.
Those who are less educated
may not understand the full extent of a hazard and may not evacuate etc.
How can religion affect hazard perception?
Some may view hazards as put there by God for a reason, or being part of the natural cycle of life. So may not percieve them to be negative.
How can mobility (highly reliant on age) affect hazard perception?
Those who have limited access to escape a hazard may perceive hazards to be
greater threats than they are.
Whether they are in a secluded location, or if they are impaired with
a disability or illness, those who cannot easily leave an area quickly may feel more at risk, so may take extra effort to evacuate quickly
What’s a passive response to a hazard?
fatalist attitude - doing nothing, and letting the hazard impact you.
What viewpoint does fatalism adopt?
hazards are uncontrollable natural events. Any losses should be accepted as nothing can be done to stop them.
Give examples of active responses to a hazard. There are 5.
Prediction, Adaption, Mitigation, Management, Risk Sharing
What viewpoint does Prediction adopt? Also what does it sometimes manage to do to natural hazards?
Using scientific research and past events to know when a hazard will take place, therefore warnings can be delivered > impacts reduced.
In some cases, prediction helps stop hazards altogether before they start. (i.e. wildfires as a result of a long drought).
What viewpoint does adaption adopt?
Attempting to live with hazards by adjusting lifestyles and settings of people, so that vulnerability to the hazard is lessened (i.e. earthquake proof houses).
What viewpoint does mitigation adopt?
Strategies carried out to lessen hazard severity. sandbags to offset flood impacts
What viewpoint does management adopt?
Coordinated strategies to reduce a hazard’s effects. Including prediction, adaption, mitigation.
What viewpoint does risk sharing adopt? And what does it consist of as a process?
A form of community prepardness,
where the risk posed by a natural hazard is shared by the community, they all invest collectively to lessen (mitigate) the impacts of future hazards.
What’s the case study for risk sharing?
New Zealand
What types of hazards do New Zealand have?
earthquakes, volcanoes, tsunamis, weather related hazards - making it a multi hazard environment.
