Showing posts with label Hazard. Show all posts
Showing posts with label Hazard. Show all posts

Monday, 5 May 2008

Cyclone Nagris devastates Myanmar

Myanmar, formerly known as Burma was hit by Cyclone Nargis on Saturday 3rd May as it ripped through the Irrawaddy Delta and the commercial capital Yangon. Five regions have been declared disaster zone and tens of thousands have been left homeless with over 350 deaths already reported.


With many communication networks down including roads and bridges and many remote villages having been affected it is difficult to get a full overview of the damage caused. UN International agencies are working to co-ordinate their response, however the movement of foreign aid workers is restricted in military ruled Myanmar. Travel permits and official escorts are required and the transport of supplies and materials has restrictions on it.
Current aid priorities include water purfication tables and mosquito nets and with many thousands now left homeless in the current rainy season, waterproof sheeting is required to provide some shelter.

For more details on the cyclone, follow up some of the news links below.

Images
Videos:
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Sunday, 4 May 2008

Chaiten Volcano Erupts ending long period of dormancy

Over a 1000 people have already been evacuated from the area around Chaiten in Southern Chile as Chaiten volcano contains to spew ash and other volcanic materials since it began erupting in the early hours of May 2nd.

The video clip below gives a brief overview of the status of the eruption so far:

Find out more about the eruption and the rescue / evacuation attempts which are under way by following some of the links below. Also think about the nature of the volcanic hazards involved.

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Saturday, 5 May 2007

Tornado Terror

A tornado in the US has claimed 9 lives as it ripped through Greensburg, Kansas on Friday (4th May 2007). Around 90% of the small rural town of Greensburg has been destroyed. Greensburg, is in Tornado Alley, the central part of the US which is frequently hit by tornadoes. Stunning video footage of the tornado (courtesey of Sky News http://news.sky.com) can be seen here.

The BBC News article can be found here.

9 people were killed just under two weeks ago when a strong tornado struck a small Texan community on the US border before passing into Mexico.

Find out more about these deadly natural phenomenum in this Tornadoes special from CNN with quizzes, photos and tornado facts and figures.

Stunning images of tornadoes can be found in the NOAA Tornadoes Photo library.

Tornado Formation

So how do Tornadoes form? This excellent animation from CNN shows the processes involved in the formation of a Tornado. The movement of air within a tornado is visualized by scientists in this animation.

The most severe "supercell" thunderstorms which often produce tornadoes from in unstable atmospheric conditions where cold dry polar air meets warm moist tropical air (ref). Tornado Alley in Central America is where some of the most devastating tornadoes occur in the US. The area includes parts of Texas, Oklahoma, Kansas and Nebraska. The area, broadly speaking is between the Rocky and Appalachian Mountains; the flat nature of the Great Plains of Tornado alley results in cold dry polar funnelled south from Canada meeting warm moist tropical air which is travelling north from the Gulf of Mexico (ref).

Tornadoes mostly form in the northern hemisphere between March to June when the conditions for the development of severe thunderstorms are optimum (ref). "A tornado is a violently rotating column of air in contact with and extending between a cloud (often a thunderstorm cloud) and the surface of the earth" (ref). The exact process of tornado formation is debated but the deadliest tornadoes results from supercell tornadoes (long-lived rotating thunderstorms which last several hours) and begin with air rising from the ground into the bottom of the thunder cloud. Changing wind speeds and wind directions result in the formation of a spinning vortex. This spinning updraft of warm air stabalises and feeds the thunderstorm (hence the long-lived characteristics of the supercell). Next a strong downdraft of cooler dense air forms with increasing speed bringing the rotating vortex downwards. As it reaches the ground, some of the downdraft spreads, as it does so a visible condensation funnel forms, when the downdraft reaches the ground, the funnel cloud becomes a tornado. As the updraft of warm moist air continues it feeds the tornado and it grows until it reaches the mature stage at which point it lasts from between a few mins to over an hour. Gradually the tornado weakens as it's air supply is reduced by the cold downdraft which wraps around the funnel (ref).

Find out what it is like inside a tornado through this amazing footage on the National Geographic site - a probe fitted with 7 video cameras captures footage from inside the tornado! Find out more about how this is done through an interview with the storm chaser.

See also this excellent flash from National Geographic looking at characteristics, formation and effects of Tornadoes.

Finally there are more stunning Tornado visualizations here.

The Effects of Tornados: A Case Study

Oklahoma Tornado - May 3rd 1999

A particularly severe Tornado (an F5 on the fajita scale) hit Oklahoma on May 3 1999 with winds of 318mph. It was the first stage of a severe weather system which latest 3 days. 36 people were killed in the tornado and it became the fourth most costliest single tornado in US history with $1.1 billion damages. A total of 10,500 buildings and 47 businesses were destroyed (ref).

The following links provide more details on the case study:

Footage of the May 1999 Oklahoma F5 tornado can be seen in this YouTube video.



Tornado Preparedness

Here is an excellent pdf file on Tornado Preparedness including information on Torndao formation as well as safety advice and disaster plans - helps to give a sense of how people living in tornado prone areas plan for the possible even of a tornado.

Other links:

Tornado Footage

This YouTube video contains footage of a collection of violent tornadoes and their aftermath.


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Saturday, 28 April 2007

Earthquakes in the UK


An earthquake measuring 4.7 on the richter scale struck Southern England at 8.18am this morning (Saturday 28th April 2007). The map to the left shows the location of the quake (source credit: U.S. Geological Survey, Department of the Interior) - further maps of the quake (including seismicity) can be found here. It is also worth looking at the location on the Worldwide Earthquake locator (try altering the map to add on fault lines, plate names etc.)




News Articles:
Earthquake shakes part of Kent (BBC News)
Eyewitness accounts of the earthquake (BBC News)
Homes evacuated after earthquake hits Kent (Times Online)
Photographs of the earthquake damage (Sky News)
Earthquake shakes Southern England (SKy News)
The House shook "Its chaos down here" (Sky News)
Homes crumble as earthquake rocks Kent (This London.co.uk)
In pictures: Kent Earthquake (BBC News)
Q&A - Kent Earthquake (BBC News)

Video Links:
Interview with BGS on initial thoughts on Earthquake (Sky News Video link)
The View from above (Sky News video link)
Chimneys and Roofs damaged by quake (Sky News Video link)
Eyewitness Interview (Sky News video link)

It is also worth looking at the location of the quake in the Worldwide Earthquake locator (you can alter the map to display fault lines, plate boundaries etc.)

The latest earthquakes from around the world are mapped here.

Earthquakes in the UK

Between 200-300 earthquakes in the UK are recorded by the BGS (British Geological Survey) every year. Despite not being on a major plate boundary (the closest is the Mid-Atlantic Ridge), we do experience earthquakes due to the release of tensions in the crust built up by movements along pre-existing faults in the crust. The largest recorded earthquake to hit the UK was a magnitude 6.1. The quake hit in 1931, with its epicenter in the North Sea, 120km offshore NE of Great Yarmouth.

Further details on UK earthquakes and their cause and impacts can be found on the here. As can be seen from this list of earthquakes in the UK over the last 30 days, most of the earthquakes we experience are low i magnitude; those that are below 3.5 on the richter scale are rarely felt - hence why they are often not reported in the news. These quakes are however picked up by recording instruments. The BGS undertakes careful seismic monitoring with 145 seismic stations around the UK. By monitoring background seismic information, the BGS are able to better define the seismic risk in the UK.

Further information on earthquakes in the UK can be found here:

Pictures Source: Credit U.S. Geological Survey, Department for Interior
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