Monday, 3 March 2014

Quest for the wild canary - part 1: Landscape and geography

Mt Teide, Teneriffe - inside the caldera
The canary is such a common cage bird that I expect hardly anyone ever thinks about where they come from, and I very much doubt that the word “canary” conjures up images of large explosions or the possible devastation of much of the seaboard of the east coast of the United States. However, I hope that by the time these posts are finished, you might have a better picture of the back story of one of the commonest cage birds in the world.
This series is inspired by thoughts and reflections on a trip I have just got back from with Ornitholidays to the Canary Islands. For those non-European readers, the Canaries are a group of volcanic islands controlled by Spain and situated in the Atlantic, more or less due west of Morocco, and out 100km from the African coast at the closest point. The islands, like the Hawaiian Islands, are situated over a volcanic hot spot, a plume of magma rising from deep under the earth’s crust and which have produced a series of shield volcanoes, which increase in age from west to east. The oldest of them, Fuerteventura, probably emerged above sea level around 20 million years ago, and the western islands are still growing, in fact the most recent eruption off the coast of El Hiero, started in 2011 and appears to be in the process of forming a new island. Several quakes under El Hiero have happened in the last few months, and further activity is also possible on other islands. Grand Canaria had eruptions in the 1960’s, and further back even larger eruptions have occurred – the Lanzarote eruption that started in 1730 lasted 5 years and covered 200 square kilometres with lava flows.

La Gomera - view from cloud forest to the sea
The holiday I was on visited three islands, Tenerife (with a day trip over to La Gomera), and Fuerteventura. The island of Tenerife has the tallest mountain in Spanish territory, with the central peak of Mt Teide reaching over 3700m. Even that is less than the mountain once stood – the current peak is inside a caldera 14km across and before it erupted the peak may have been over 4500m. Even 200 years after the last eruption the caldera is almost lifeless and the aa lava (so called from the Polynesian term, although it is also the sound you make if you try to walk on it) looks as fresh as the day it erupted. La Gomera is extinct and scarred by heavily eroded valleys, but is still high enough to trap rain bearing winds so it is still forested. Fuerteventura is so heavily eroded, and so close to the Sahara, that it is effectively desert. Only the highest parts of the island have any woods at all, and the population relies on desalination plants for water.

central Fuerteventura - eroded volcanic cone and surrounding plain
To get back to the devastation of the coast of the US – don’t worry, that is highly unlikely. It is not however totally impossible, as a result of the structure of the islands. Despite their size, volcanoes are basically large piles of rubble glued together with solidified lava, and movements of the magma or earthquakes during an eruption can cause large landslides. How big a splash results depends on whether the piece of volcano falls in one large mass or in a series of smaller pieces, but a tsunami probably originating in a collapse on the Canaries a few thousand years ago ripped blocks of coral the size of houses from the seabed off the Bahamas and left them well inland, so keep an eye on the news if you hear of a major eruption there in the news.

Next time – plants of the Canaries.

(images taken by me this year)

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