Eruption continues off the coast of El Hierro

November 8, 2011 – EL HIERRO – 

The submarine volcanic eruption that began in mid-October in the Canary Islands continued in early November 2011. The volcanic island of El Hierro sits on a tectonic hot spot in the Atlantic Ocean off of North Africa and Spain. The Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite acquired this natural-color image of El Hierro and a plume of volcanic material in the surrounding waters on November 2, 2011. The waters south of the island have been bubbling and fizzing with heat, sediment, bits of volcanic rock, and minerals for weeks, with the plume stretching tens of kilometers. The eruption is believed to be venting about 50 to 100 meters below the water surface, and it is warming the waters by as much as 10 degrees Celsius, according to geologist and blogger Erik Klimetti. 

The temperature of erupting basalt can be as hot as 1100 to 1200 degrees C, he notes. “Flank eruptions are one way that volcanoes build up and out of the seafloor—and sometimes above the water surface,” notes marine geologist Dan Fornari of the Woods Hole Oceanographic Institution. “If the magmatism is maintained, platforms can develop between the islands, a la Galapagos. This is also an example of how the ocean acquires its chemical makeup. It’s not just run off from the continents, but also injection and chemical exchange caused by submarine volcanoes.” From October 26 to November 1, the Instituto Geográfico Nacional reported, 540 seismic events (quakes and tremors) were recorded by sensors on the island. Most of the activity was north of the island, at depths of 16 to 23 kilometers, and on the opposite side from where the plume of volcanic material was discoloring the water. More than 10,000 seismic events have been recorded near El Hierro since July 17. -NASA  

 In the Atlantic Ocean, off the Canary Island of El Hierro, 20-meter high jets of water are being spat into the air as the sea boils amid the stench of sulfur. The undersea volcano, which is set to create new land, is growing ever-nearer to the surface — but is the existing island at risk from the explosive eruptions? “The monster rises out of the water,” screamed the Spanish newspaper La Provincia. Scientists, meanwhile, are being a bit more level-headed about the undersea volcano south of El Hierro in the Canary Islands; they now believe it is in the third phase of its eruption — fountains of water have been shooting out of the Atlantic up to 20 meters in the air over the last few days. On Tuesday, some local residents even saw stones being catapulted out of the sea. 

A seething maelstrom, dozens of meters across, is bubbling away in the ocean. 

Measurements show that the vortices are significantly warmer than the surrounding water. So far, the volcano has only shown its explosive power beneath the water. But now the outbursts to the south of El Hierro are frothing up the surface, as if the ocean had hiccups. The lava is piling up on an underwater mountain. That the eruption is capable of firing jets of water into the air shows that this mountain is growing — the center of the eruption is approaching the surface. Geologists believe that new land could soon emerge from the sea, and islanders are already looking for a name for the new territory. 

There are only 70 meters to go until the mountain reaches the surface, experts from Spain’s National Geographic Institute (IGN) have reported. But how big is the risk to nearby residents? Last weekend, hundreds of people had to leave their homes in the southern part of El Hierro as streets were closed. And locals can quite literally smell the danger — stinking sulfur fumes are drifting across the ocean. The Volcanology Institute of the Canaries, Involcan, has reported a three-fold increase in carbon dioxide levels — a warning signal that further volcanic activity can be expected. –De Spiegel

Source : The extinction protocol

Aquatic Species Decline at Dams and Weirs

Dams and weirs have a stronger impact on the ecosystem of watercourses than was previously realized. Species diversity in the dammed area upstream of weirs shows a significant decline: the diversity of fish species is one-quarter lower on average, and species diversity among invertebrates is up to 50 percent lower.


The interruption of a river course thus has greater effects on the biodiversity than the geological origin of the river itself. Scientists from the Technische Universitaet Muenchen have demonstrated this on the basis of a survey of five rivers in the catchment areas of the Elbe, Rhine/Main, and Danube.


Their analysis records, for the first time, both abiotic factors, for example chemical composition, current, and river bed substrate, and biotic factors, such as the number, size, and diversity of all important animal and plant groups on the two sides of weirs. The TUM researchers will present their findings, which have already been published online in the Journal of Applied Ecology, at the annual conference of the German Limnological Society, which takes place from September 12 to 16, 2011.


Whether it is done for the generation of electricity, for flood protection, or collection of drinking water, the damming of a river represents a drastic intervention in its ecosystem. Weirs and dams alter the chemical and physical characteristics of the water and the riverbed. Their construction is accompanied by a clear decline in upstream species diversity, and this is exacerbated by successive damming.
This phenomenon, which is known as "serial discontinuity," has now been measured for all important animal and plant groups by system biologists from the TUM for the first time; the information available up to now concerned only individual taxonomic groups or species.


The scientists carried out a systematic survey of the aquatic organisms on both sides of the weirs in five rivers of different geological origins. Their survey revealed a significant reduction in the number, biomass and variety of periphyton, invertebrates, and fish species upstream of the weirs. Compared with downstream areas, the diversity of fish species measured upstream of weirs was 25 percent lower on average; a threefold decline in biomass was also observed.


Current-loving fish species, many of which are on the "Red List" of endangered species, are particularly severely affected. "Brown trout, grayling and Danube salmon are demanding fish species that require oxygen-rich water and spawn in coarse gravel areas.


As typical residents of the upper reaches of rivers, they are unable to find suitable habitats in dammed areas," explains Juergen Geist, Professor of Aquatic Systems Biology at TUM.


"These river sections are often dominated instead by bream, chub, and even carp - generalist species that are actually adapted to stagnant waters. The ecological impoverishment of rivers is particularly dramatic when series of dams prevent the sufficient interlinking of different habitat types," says Geist. According to the Bayerische Landesamt fur Umwelt (Bavarian Environmental Agency) there are more than 10,000 weirs in Bavaria's rivers alone.


According to the researchers, the main reason for the species decline is not the impermeability of the barrier to migrating fish species. Instead, the deciding factor is the chemical and physical alteration of the river itself which leads to a reduction of biodiversity.


If the current is decelerated or interrupted, the flow rate upstream of the weir declines, and this is accompanied by increased water depth. In all of the surveyed dammed areas, the TUM scientists also recorded major differences in the oxygen content and temperature of the water and the sediment in the river bed, which hinders reproduction in current-loving fish species.


The situation is compounded by differences in the structure of the sediments. The particles in the sediment found downstream of weirs are twice as large on average as those upstream, providing more and better quality spawning grounds.


River sections in the direct proximity of weirs should, therefore, be given greater consideration in ecological quality assessments, notes Prof. Geist: "During the evaluation of new weirs or modernization of hydroelectric power plants, attention should no longer be focused exclusively on the migration of fish species, but on the consequences of the structure and function for the river ecosystem as a whole."
To ensure this, affected river sections must be covered by the relevant laws or regulations, such as the European Union Water Framework Directive. "A set of instruments for the quantification of the effects of weirs is now available, which records both the quality of the habitat and its biodiversity," says the TUM scientist.



Publication: M. Mueller, J. Pander, J. Geist: The effects of weirs on structural stream habitat and biological communities, Journal of Applied Ecology and Innovative small-scale hydroelectric power plant: Shaft power plant designed by the Department of Hydraulic and Water Resources Engineering TUM.