12: Hazards Flashcards
What are the two main things used to measure and event’s extremity?
Magnitude and frequency
What differentiates tsunamis from normal waves?
They are impulsively generated not tidally generated
What wavelengths can tsunamis reach?
> 500km
What can intervals between tsunamis reach?
10 minutes to 2 hours
What is the potential speed of tsunamis?
700-900km/h
What are 6 causes of tsunamis?
Earthquakes, landslides, submarine slides, turbidity currents, volcanic eruptions, nuclear tests and asteroids
What are near and far field causes of tsunamis?
Far field means they are generated further away from the point of impact whereas near field is more local
What differentiates far and near field causes of tsunamis in terms of detection?
Far field tsunamis are more likely to be detected before they strike as they will pass lots of monitoring stations before. Near field however are less detectable prior to impact and so are more likely to have more damaging impacts as well as they will retain more of their initial energy
What happens to tsunamis in shallow water?
Speed decreases and height increases
Where are tsunamis barely detectable and why?
Middle of the ocean - because their wavelengths are so long that they can be spread out over such a broad area
What might happen at the coast/beach just before a tsunami strikes
It may seem like the tide is rapidly falling then rising again as the wave approaches
What may the runup of tsunamis exceed as they approach the coastline?
30m
What % of tsunamis are classed as ‘catastrophic’?
10%
How many tsunamis occur on average in the Pacific?
5
What is the classed risk of Australia to cyclone?
‘moderate’
What are the two things that can be do towards preparing for tsunamis and mitigating their potential impact?
Monitoring and warning centres
Give an example of a warning centre
Pacific Tsunami Warning Centre or Australian Tsunami Warning System
Give an example of a tsunami monitoring body?
Deep Ocean Assessment and Reporting of Tsunamis (DART)
What potential evidence is there of past tsunamis occurring in NSW?
Boulders collected on top of a 25m platform in Jervis Bay
Who claimed the boulders on top of a platform in Jervis Bay was a product of a tsunami and who disagreed and why?
Ted Bryant and Bob Young proposed the boulders were carried by tsunami. However Switzer and Burston (2010) stated that thsi is unjustified and currently there is no adequate evidence to truly supportt this claim
When was the Sulawesi Tsunami?
2018
What was the magnitude of the Sulawesi Tsunami?
7.5
What was the wave height of the Sulawesi Tsunami?
4-7m
Where did the Sulawesi Tsunami impact massively?
Palau and surrounding islands
What does Colin believe in terms of distinguishing storm surge and tsunami-derived deposits?
Deposits located on islands in the middle of the ocean are more likely to be a storm surge because tsunamis do not usually break in waters as deep as those around oceanic islands
What are two places that have deposits that are debated over in terms of whether they are a product of a storm surge or a tsunami?
Suwarrow and Aran Islands
What is a good place to study the difference between storm surge and tsunami deposits and why?
Japan - because it experiences a significant amount of both
What is the main difference between storm and tsunami deposits proposed by Goto et al., 2010?
Tsunami deposits usually reach further inland as the energy within Tsunamis can support transport of these larger pieces of material for a longer time period and therefore over a greater distance in direction of wave
What are the main causes of storm surges
Low pressure systems - strong onshore winds and low atmospheric pressure
What way do low pressure system rotate in the southern hemisphere?
clockwise
What are two major things that can enhance the impact of storm surges on the coast?
- Continental shelf and local topography - if the journey of the surge to the coast is over a smooth sea floor then the energy is conserved better and then if when it reaches the coast it is funnelled through a bathymetric groove then this energy is concentrated just before it hits the coast
- Flooding (extreme rainfall) can cause the local SLR and therefore the associated impacts of this storm become more extreme
What is important to remember even if the storm surge does not reach the land?
The peak can still occur in the ocean and the impacts deriving from within the ocean can be transported to the coast
What was the maximum storm surge height recorded in Australia and where?
13m in Cape York
Where will storm surge levels be highest when a storm surge crosses the coastline?
Higher on the left (in the direction of cyclone movement)
When was Hurricane Katrina?
2005
Describe the strength of Katrina as it passed over North America?
It was a C4 when it reaches south Florida, it then went to a C3 but then once it went over Gulf of Mexico it went up to a C5. It then reached its second landward movement and travelled up to Quebec but it was significantly weaker by this point
What island group was particularly devastated by Hurricane Katrina?
Chandeleur Islands
What is the name of the US cyclone scale and how is it different from the Australian one?
Saffir-Simpson. It’s measurements for the same category of storm severity is slightly higher
What are the 3 main challenges for the Mississippi Delta that might cause future cyclones/hurricanes to be more damaging?
SLR
Subsidence (more rapid than rate of SLR so relative SLR is a lot higher)
Decreased sediment influx (sediment marhses are deprived of sediment due to damming
What is being done to try and restore the sediment influx to the Mississippi Delta?
Efforts to try and divert the river towards the delta so it can recover
When is the Cyclone season in Australia?
November to April
How many cyclone pass through Australia during the cyclone season?
13
What % of the global total of cyclones pass through Australia?
16%
Where do 1/2 the cyclone in Australia affect?
Western Australia
What % of cyclones in Australia actually become severe?
50%
What is an example devastating cyclone in Darwin and a period where cyclones were very frequent?
Cyclone Tracy in Darwin and the 1970s was a major problem which massively affected Brisbane
Where is knowledge of cyclones really important and why?
Queensland because there is a lot of agriculture in this state
Outline the future state of cyclones under climate change as a general course
Number of storms increasing
Hurricanes are getting stronger and lasting longer
Ocean energy is rapidly increasing
What was an example cyclone of the potential effects that climate change is having on their cyclone occurrence?
Hurricane Sandy
What was a really devastating cyclone that occurred recently and where did it affect?
Hurricane Michael in 2018 that affected Mexico Beach, Florida
