Pyroclastic clouds During eruptions, volcanoes can blast out clouds of incandescent rock particles and superheated gases. These fiery “pyroclastic clouds” are much more dangerous than lava flows. They are extremely hot (several hundred degrees Centigrade) and can travel at speeds of several hundred kilometres per hour. In 1902, 30,000 people perished in a few minutes when the town of St Pierre on the island of Martinique was struck by a pyroclastic cloud from Mt Pelee.
2:04 PM
23.5.03
Christchurch Cathedral The original stone spire of Christchurch Cathedral was damaged in three earthquakes. On 5 December 1881, a quake lasting 45 seconds brought down some ornamental moulding. In an earthquake on 1 September 1888, the top 7.8 metres of the spire collapsed. On 16 November 1901 the top 1.5 metres of stonework was shaken loose by an earthquake. The spire was finally remodelled in hardwood, sheathed in metal. 3:11 PM
16.5.03
Earthquakes and faultlines All but the deepest earthquakes (deeper than 600 kilometres) occur on faults. Earthquake waves are generated when the land on either side of a fault suddenly shifts and the blocks of land slide past each other. For most earthquakes, the fault breakage does not extend up to the surface. Scientists can, however, pinpoint the location of the fault by analysing the seismic waves. Some faults can extend for hundreds of kilometres.
1:30 PM
9.5.03
What is the difference between earthquake magnitude and intensity? Magnitude is a measure of the strength of an earthquake – the amount of energy released at the point where the earthquake occurs. Intensity is a measure of the effects of an earthquake on people, fittings (furniture, crockery, etc.), buildings and the environment. Intensity decreases with distance - the amount of damage diminishes the further you are from the earthquake epicentre.
2:04 PM
2.5.03
Natural disasters kill 25,000 worldwide in 2001 According to Munich Re, the world's largest reinsurer, natural disasters caused at least 25,000 deaths worldwide in 2001, more than double the previous year. The worst event in terms of the number of deaths was an earthquake in the densely-populated northwestern Gujarat region of India with 14,000 deaths confirmed and many more feared dead. Total economic losses were put at US$36 billion, with storms and floods causing 91 percent of all insured natural disaster losses.
12:59 PM
