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What on earth

Archive: November 2005

Record-breaking Hurricane Season

With Delta racing over the Canary Islands the Atlantic tropical storm season from 1 June to 30 November 2005 has broken several records.

The earliest ever F-hurricane (Franklin) occurred on 22 July.

A central pressure of 882 hPa was measured in Wilma – the lowest pressure ever.

For the first time (with more than 21, namely 25 named storms) it was necessary to use Greek alphabet names – Alpha, Beta, Gamma and Delta were born. Names are given to Atlantic depressions with average wind speeds above 17.5 m/s or 63 km/h.

Katrina killed more than 1200 people.

Vince was the first ever to return to Europe (West Africa -> North America -> Portugal/Spain). Vince was by the way also exceptional because it was created above seawater of only 23°C. It was normally thought that you need water of at least 26.5°C.

14 (or was it only 13 – I may have lost the count) true hurricanes (i.e. average speeds of above 32.7 m/s) was also a record.

Although the six-month Atlantic hurricane season officially ends today on 30 November forecasters warn that tropical storms and hurricanes can develop in December.

More on hurricanes at http://whatonearth.olehnielsen.dk/hurricanes.asp

Ole

PS

On Friday 2 December the Tropical Storm Epsilon became the unprecedented 14th Atlantic hurricane of the year two days after the six-month season officially.

Mount St. Helens

No plumes of steam and ash have risen above Mount St. Helens for nine months, but nevertheless it is still erupting. Not lava but a tube of still hot rock is coming out of the ground. It is certainly nothing like the cataclysmic eruption that blew off the top 1,300 feet of the mountain on 18 May 1980.

Mount St. Helens is full of mysteries and surprises.

Read the latest news at The New York Times: http://www.nytimes.com/2005/11/29/science/29volc.html?ei=5065&en=743d52e4fb8ab484&ex=1133845200&partner=MYWAY&pagewanted=print

List of my other blogs about volcanoes.

Ole

Iran earthquake

As I stated yesterday earthquakes are most frequent along plate boundaries. The earthquakes in Iran yesterday 27 November 2005 also occurred near a plate boundary. The epicentres were near the boundary where the Arabian plate is colliding with the Iranian plate.

The Bam earthquake in December 2003 also occurred near this boundary.



More of my scribbling on earthquakes.

Ole

Forgotten Earthquakes

Earthquakes are most frequent along plate boundaries. Mid Oceanic Ridges are also plate boundaries. Oceanic ridges are characterized by shallow earthquakes. These earthquakes practically never reach the news, probably because they usually occur on the ocean floor, Iceland being the exception. On land shallow earthquakes (0-33 km depth) are known to be the most devastating.

Yesterday, Saturday 26 2005, a magnitude 5.7 earthquake occurred in east China and it hit the front pages.
See Yahoo News at http://news.yahoo.com/s/afp/20051126/sc_afp/chinaquake_051126145359

It was a shallow earthquake - the US Geological Survey said it occurred about 10 kilometres below the surface of the earth.

On Tuesday November 22 2005 a magnitude 5.7 earthquake occurred near the Mid Indian Ridge.

See http://earthquake.usgs.gov/recenteqsww/Quakes/usftaj.htm

It was a shallow earthquake - the US Geological Survey said it occurred at a depth of about 10 kilometres.
Did you hear (or read) about it?
Here we have two earthquakes of the same magnitude within a week’s time. One was noticed, the other completely “forgotten”.

At http://www.seismo.ethz.ch/GSHAP/ there is a Global Seismic Hazard map. Lower on the page on the world map of earthquake frequencies the Mid Oceanic Ridges are clearly recognizable as red “lines” in the blue oceans.

Ole

Sea Level Rise

From 5,000 years ago until about 200 years ago the rate of ocean rise was 1 mm per year. Sea-level measurements since 1850 from tidal gauges and more recently from satellite images, when corrected for land settling along the shoreline, reveal that the current annual rise is 2 mm. The widespread increase in fossil fuel use and more greenhouse gases since the 19th century and the beginning of modern observation (global warming) is thought to be behind this doubling of the rate of ocean rise.

These finding are published in an article in the Nov. 25 issue of the journal Science (Science 25 November 2005: Vol. 310. no. 5752, pp. 1293 – 1298). Abstract at http://www.sciencemag.org/cgi/content/abstract/310/5752/1293?

News brought by EurekaAlert at http://www.eurekalert.org/pub_releases/2005-11/rtsu-gwd112105.php

See also my blog of Saturday, 1. October 2005, 09:42:08: Sea Level Rise

Ole

Carbon Dioxide and Methane

Analysis of Antarctic ice cores from the EPICA project shows that current levels of the greenhouse gases carbon dioxide and methane in the atmosphere are higher now than at any time in the last 650,000 years. 27 % more CO2 now than at the highest peak in all those years (380 ppm against 278 ppm).

BBC News at http://news.bbc.co.uk/1/hi/sci/tech/4467420.stm

More on greenhouse gases.

Ole

Quake and Tsunami 2 (Japan)

The earthquake I reported yesterday was after all not quite normal.

The earthquake occurred where the Pacific plate, which is moving west, dives beneath Japan at a rate of about 8 centimetres a year. Usually, the Pacific plate tends to make the Japanese plate jump up vertically during earthquakes, which tend to be centred on the Japan side of the subduction fault where the two plates meet. Now, however, the earthquake was caused by the Japanese plate dropping down relative to the Pacific plate, making the current earthquake "unusual."

The location of its epicentre was farther east (and farther seaward) of the trench than usual for this area. Its position relative to the majority of earthquakes on this subduction fault is "not totally abnormal," but not expected either.

Geotimes: http://www.geotimes.org/nov05/WebExtra111505.html (with location map)

Ole

Earthquake and Tsunami - Japan

A strong earthquake (magnitude around 7) shook northern Japan early Tuesday 15 November, triggering a small tsunami that struck coastal towns about 200 miles from the epicentre.

This event is in the Pacific plate in the bending zone before subduction, a normal-faulting event related to flexure of the lithosphere rather than the more dangerous thrust faulting typical of subduction zones. (See my log of Monday, 7. November 2005)




Ole

Krakatau tsunami

One of the greatest natural disasters in modern history was the eruption of the Krakatau (or Kakatoa) volcano in 1883. The following tsunami killed 36,000 people. If a similar explosion of the same power happened today, the tsunami might kill about one million people.

Anak Krakatau, Krakatau's child, was born about 70 years ago and now grows six meters a year. If its growth rate doesn't decrease, the world will face another great tragedy, says Indonesian volcanologist Supriyatman Sutavijaya from the Indonesian University of Volcanology and Geology. If the processes in the magma chamber maintains the current speed, another explosion will happen in 140 years.

Pravda at http://english.pravda.ru/science/19/94/377/16448_Krakatau.html

SFGate.com: http://www.sfgate.com/cgi-bin/article.cgi?f=/news/archive/2005/01/24/financial1017EST0041.DTL

Ole

Water vapour as greenhouse gas

Sometimes one tends to forget that water vapour is not only one of the greenhouse gases, but indeed the most important one. The major natural greenhouse gases are water vapour, which causes about 36-70% of the greenhouse effect on Earth (not including clouds); carbon dioxide, which causes between 9-26%; and ozone, which causes between 3-7%.

Actually water vapour rather than carbon dioxide in the atmosphere is the main reason why Europe's climate is warming, according to a new study.

The research is published in the journal Geophysical Research Letters.

Read the abstract at


News reported by


Ole

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