16 Nov 2015

The Big Picture

El Hierro, the youngest, the westernmost of the archipelago, is, like all the Canary Islands, of volcanic origin. It is the tip of a gigantic pyramid that rises above the floor of the ocean more than fifteen thousand feet, of which only one third is above sea level. Over the last million years, time after time our island has tried to recreate itself, time after time enormous volcanoes have grown out of the remains of those before them and time after time they have collapsed under their own weight. Now, old and tired, splattered with hundreds of cones and minor craters, the island is no more than a pile of volcanic rubble. But what rubble! Black sands, lapilli, pumice gravels and clays, basalt, clinkstone dikes … and lava.

The Trade Winds blow thousands of miles from the northeast most of the year at this latitude. When this damp sea wind hits the island, part of it rises up the northern slopes and over the mountain ridge, cooling and forming clouds as it does so. The rest goes round the horns of the island, filling in the void to the lee without rising so much. But luckily the island isn’t nice and smooth. There are nooks and crannies all over the place, bits sticking out and hollows and holes, cliffs and ravines. A hiker's heaven and a meteorologist's nightmare. Nevertheless, it’s safe to say the north is wetter and cooler, the south is sunnier, warmer and drier. If it's a cloudy day in the north it's likely to be sunny in the south, and vice-versa.

That is the big picture. The rest of the blog is about the little picture. Without the big picture, anything I can write about (including the people) might not make sense.



In this NASA photo, the northeast Trade Winds leave tails of turbulence to the lee of the islands that affect the wave patterns.

A dense blanket of clouds -"el Mar de Nubes" ("the Sea of Clouds") - is formed as the Trade Winds hit the heights of the island. Sometimes the clouds creep a short way over the ridge, as they are doing in the northeast in this photo by NASA.


No comments:

Post a Comment