Ascension : Met Office Ascension Island Base - The Met Office Weather Report
Submitted by The Islander (Met Office) 11.08.2011 (Article Archived on 25.08.2011)

UK: Very warm and quite sunny for central and southeast England early in the week, though the weather more mixed further north and west.

 UK: Very warm and quite sunny for central and southeast England early in the week, though the weather more mixed further north and west. All parts of the UK became cooler and more unsettled from mid-week with many parts having some thundery showers. These gave some local flash floods in eastern England. Over the weekend it was the turn of Northeast England and Northeast Scotland to see some more persistent, quite heavy rain, with 30 to 40mm recorded in some spots with local flooding.

Falklands: The weather was rather mixed this last week. Though relatively mild at times, in general there was a good deal of quite cold weather with some snow showers.

Ascension: Rather cloudy for much of the week with just a few light rain showers, though Tuesday, Wednesday and again this last Sunday were quite sunny.

St Helena: A rather cloudy week, and partly because of this the daytime temperatures perhaps just a little cooler than one would expect, though the cloud also kept it relatively mild overnight. During Friday and this last weekend the cloud broke a little to give some sunny intervals, though also a few relatively light rain showers.

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Volcanoes in Chile.

The Cordon Caulle volcano is still active and producing ash clouds that are at times threatening to affect the airbridge to the Falkland Islands, - so why not have another short article on volcanoes.

The earths crust is made up of a series of plates and one of the most volcanically active belts on Earth is known as the “Ring of Fire”, a region of subduction zones all around the Pacific Ocean. This is where the Pacific plate moves under the continental plates surrounding it. In Chile the Pacific plate of oceanic rock descends beneath the continent of South America and this lifts the edge of the continent to form the Andes Mountains. Under the sea, just to the west of the Andes, this process causes the sea floor to be depressed giving rise to an oceanic trench. These trenches are the deepest topographic features on the earth's surface.

The subducting oceanic rock actually contains a significant amount of surface water, as well as water contained within minerals in the basaltic rock. As the subducting slab descends below the continental margin to depths of between 60 and 170km, over time it begins to encounter high temperatures and pressures. The water content of the rock has the effect of lowering the melting point, thus causing it to melt and produce magma.

The magma produced by this mechanism varies from basalt to andesite in composition. It is more buoyant than the surrounding rock and rises up to produce a line of volcanoes thrusting through the continental crust.

The Andes are not particularly old mountains, having started to develop from between 10 and 25 million years ago.

Compiled by  Chill       

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