p5 Flashcards
A tsunami
a series of larger-than-normal waves.
Tsunami Formation
Most tsunamis are caused by underwater earthquakes, a small number are produced by underwater landslides, or by meteor/asteroid strikes.
* Energy released during the earthquake causes the sea floor to uplift – displacing the water column.
A water column
is the area of seawater from the surface to the sea floor
Tsunami Characteristics
- Tsunami waves can move fact – up to 500 mph!
- When the wave crest reaches the shore, it first produces a vacuum effect – it sucks the water back out to sea, exposing a large amount of the sea floor (a warning sign of a tsunami).
- Majority of tsunamis are linked to plate boundaries – particularly the Pacific Ring of Fire – why?
Predicting Tsunamis
- Since most tsunamis are caused by submarine earthquakes (and we can’t predict them), there is no way to predict tsunamis before they occur.
- However, it is possible to give people early warning before a tsunami reaches the coast and threatens lives.
Monitoring Tsunamis
Early warning systems are now in place in both the Pacific and Indian Oceans.
* These systems use seismic sensors to detect submarine earthquakes, however because not all submarine earthquakes causes tsunamis, additional equipment is used.
* DART – Deep-ocean Assessment and Reporting of Tsunami.
Monitoring Tsunamis - DART
The DART system uses seabed sensors and surface buoys to monitor changes in sea level and pressure.
* When waves are detected, the system sends the information via a satellite to tsunami warning stations.
* These stations then analyse the data to estimate the size and direction of the tsunami, before informing the areas at risk.
Consider the pros and cons of computer modelling for monitoring tsunamis.
Pros:
- Can save lives
- Information can be
reviewed regularly due to multiple sensors and sea surface buoys.
Consider the pros and cons of computer modelling for monitoring tsunamis.
Cons:
- If the equipment is
faulty then it will result in inaccurate data. - If there is a shallow earthquake,
equipment can become damaged.
Indian Ocean Tsunami - 2004
Cause
An earthquake of magnitude 9.1 due to the rupture of the Sunda Megathrust fault caused the seabed to rise by 15m for over 1500 km. This caused a 30m wave.
The Sunda Megathrust fault is a destructive plate boundary between the Burma plate and the subducting Indo- Australian Plate.
In many places affected, the natural defence of mangrove swamps on the coast had been removed for economic reasons or for tourism, therefore exemplifying the impact of the tsunami.
Indian Ocean Tsunami - 2004
Global effects
Earth’s orbit altered – Days are now 2.68 microseconds shorter. 12 countries in total were affected.
Indian Ocean Tsunami - 2004
Social impacts
Death toll: 228,000
Most coastal populations were taken by surprise due to a complete lack of Tsunami Warning systems. Many people ventured onto exposed beaches due to the drawback effect, causing many casualties by drowning.
High population and tropical climate meant that diseases spread fast – Cholera, Dysentery and Hepatitis epidemic feared.
Indian Ocean Tsunami - 2004
Economic impacts
Many communities affected were dependant on the fishing industry, so loss of income earners, fishing equipment and ships damaged local economy in some areas.
Infrastructure, such as fresh water supplies were damaged, making it difficult for farmers to irrigate. The saltwater made land infertile.
Indian Ocean Tsunami - 2004
Environmental impacts
Coastal ecosystems such as mangroves, coral reefs and forests destroyed by the wave surge. Many more ecosystems polluted by human and chemical waste in the floodwater.
Indian Ocean Tsunami - 2004
Responses
US$14 billion was provided in aid.
The US provided aircraft for Search and Rescue, surveying, and transport of aid cargo. Corruption hampered aid efforts. For example, Sri Lanka refused Israeli aid efforts. Tsunami warning system implemented in response.
