NASA image acquired June 24, 2011
Since it began erupting on June 12, 2011, emissions from Eritreaâs Nabro Volcano have drifted over much of East Africa and the Middle East. Ash has displaced residents living near the volcano and disrupted flights in the region. Despite the volcanoâs widespread effects, little is known about the eruption. Nabro is located in an isolated region along the border between Eritrea and Ethiopia, and few English-language reports have been published. Satellite remote sensing is currently the only reliable way to monitor the ongoing eruption.
This pair of satellite images are among the first detailed pictures of the erupting vent and lava flows. They were acquired by the Advanced Land Imager (ALI) aboard the Earth Observing-1 (EO-1) satellite on June 24, 2011.
The bright red portions of the false-color image (top) indicate hot surfaces. Hot volcanic ash glows above the vent, located in the center of Nabroâs caldera. To the west of the vent, portions of an active lava flow (particularly the front of the flow) are also hot. The speckled pattern on upstream portions of the flow are likely due to the cool, hardened crust splitting and exposing fluid lava as the flow advances. The bulbous blue-white cloud near the vent is likely composed largely of escaping water vapor that condensed as the plume rose and cooled. The whispy, cyan clouds above the lava flow are evidence of degassing from the lava.
The natural-color image (lower) shows a close-up view of the volcanic plume and eruption site. A dark ash plume rises directly above the vent, and a short, inactive (cool) lava flow partially fills the crater to the north. A gas plume, rich in water and sulfur dioxide (which contributes a blue tint to the edges of the plume) obscures the upper reaches of the active lava flow. Black ash covers the landscape south and west of Nabro.
NASA Earth Observatory image by Robert Simmon, using EO-1 ALI data. Caption by Robert Simmon.
EO-1 - ALI
To download the high res go here: http://earthobservatory.nasa.gov/IOTD/view.php?id=51216
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When a volcano erupts it sends thousands of tons of gases into the atmosphere – all of which can weaken the ozone layer. A team of German meteorologists studying giant eruptions in Nicaragua recently reported that due to the amount of ozone-depleting halogen gases already in the stratosphere (through man-made actions), if the world suffered a substantial eruption it could devastate the ozone layer.
Kirstin Krueger, a meteorologist with GEOMAR in Kiel, Germany noted that bromine and chlorine (two gases that are frequently erupted) “love to react — especially with ozone. If they reach the upper levels of the atmosphere, they have a high potential of depleting the ozone layer.” The team conducted field work and a series of geochemistry and existing atmospheric models to study previous Nicaraguan eruptions and found that they were explosive enough to reach the stratosphere and have an effect on the protective ozone layer.
Team member Steffen Kutterolf, a chemical volcanologist with GEOMAR, studied the gases that were released and used high-energy radiation from the German Electron Synchrotron in Hamburg to detect trace elements, including bromine. By studying the amount of gas within magma before the eruptions, he was able to calculate how much bromine and chlorine are released in a typical eruption.
The facts are unsettling: the typical eruption sends mushroom clouds of ash kilometers high, with 25% of halogens making it into the stratosphere. However the team only estimated 10% of the gases reaching the ozone layer for their study. Even worse, the gases that do reach the stratosphere can be carried across the globe leading to ozone depletion over a large area.
Krueger and her team are currently presenting their findings at the American Geophysical Union’s Chapman Conference on Volcanism and the Atmosphere in Selfoss, Iceland where they hope to predict future ozone destruction from the lessons of the past.
Images: NASA Goddard Photo and Video, Dyntr