NASA image by Jesse Allen and Robert Simmon, using ALI data from the EO-1 Team. Caption by Mike Carlowicz.
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) 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. The EO-1 satellite passes directly over the volcano about once every 16 days, though images can occasionally be acquired more often if the sensor is turned toward the site and skies are mostly cloud-free.
