Hazards facts Flashcards
What happened in cameroon in 1986?
In 1986, escaped carbon emissions from the Lake in the crater of Nyos, killed 1,700 people.
What happened in the Roman city of Pompeii in 79AD
In 79AD the Roman city of Pompeii was destroyed by pyroclastic flows.
What happened in 1985 in the Colombian town of Armero?
In 1985, a lahar destroyed the Colombian town of Armero after an eruption of the volcano Nevada del Ruiz.
- Only 1/4 of the 28,700 population survived.
- The Colombian volcano Nevada del Ruiz came to life in 1984 with small scale activity but volcanologists although they know the danger of a major eruption would pose to the surrounding area, were unable to predict when the major event would take place.
Sea waves after the eruption of Krakatoa?
Sea waves generated by violent eruptions as those after the eruption of Krakatoa (Indonesia) in 1883.
- Tsunami from this eruption estimated to have killed 36,000.
Why is there a risk assessment for the area around Mt Rainier (part of the Cascade Range in the USA)?
A risk assessment is made for the area around Mt Rainier (part of the Cascade Range in the USA) as it is one of the most studied volcanoes in N America as 3.5 million people live and work in close proximity to it.
What was done in Mt Etna in Sicily and Haeimacy (Iceland) in attempt to control the erutptions.
In Mt Etna in Sicily, digging trenches, dropping block into the lava stream and using explosives has been successful in slowing down the flow of lava and in some cases diverting it.
In 1973, the inhabitants of Haeimacy (Iceland) were able to divert lava flow by pouring sea water on the front so it would solidify quickly.
In parts of the Hawaiian Islands, barriers have been built across valleys to protect settlements from lava flows and lahars.
What was the ‘boxing day’ tsunami?
In December 2004: East Indian Ocean off Sumatra:
- Generated by a powerful magnitude 9.0 EQ - some 25km below the Indian Ocean floor off NW Sumatra (one of the biggest EQs ever recorded).
- The tsunamis which spread across the Indian Ocean killed an estimated 300,000 people in bordering countries and devastated hundreds of communities.
- Extensive damage to coastal communities - particualrly bridges and railway lines and damage to local economies left people unable to feed themselves.
- After - a warning system was set up among the countries that border the Indian Ocean - Despite the enormous human disaster the insurance industry estimated that the disaster could cost less than $5bill.
Tsunami in March 2011 off the Pacific Coast of the Tohoku region of Japan:
EQ recorded 70km offshore and a magnitude of 9.0
- Most powerful EQ ever recorded in Japan.
- Estimated that it moved the main island Honshu 2.4metres east.
- Tsunami waves reached over 40m in height and some penetrated over 10km inland.
Tsunamis killed nearly 16,000
Over 300,000 people displaced from homes
127,000 buildings entirely destroyed
Fukushima nuclear plant affected - resulting in the evacuation of people living within 20km of the facility.
Economic cost to Japan - $235 billion.
Tsunami waves ran right across the Pacific to N and S Amrica - In Chile 2m waves.
What is paleomagnetism?
The alternating polarity of the rocks that form the oceanic crust.
Iron particles in lava erupted on the ocean floor are aligned with the Earth’s magnetic field.
As the lavas solidify, these particles provide a permanent record of the Earth’s polarity at the time of the eruption (paleomagnetism).
However, the Earth’s polarity reverses at regular intervals (approx every 400,000 years).
The result is a series of magnetic ‘stripes’ with rocks aligned alternately towards the north and south poles.
This striped pattern, which is mirrored exactly on either side of a mid-oceanic ridge, suggests that the oceanic crust is slowly spreading away from its boundary.
