Bubble curtain. Incredible amounts of carbon dioxide (CO2) gas seen streaming out from the lava rubble pile and especially at the toe of an advancing lava flow. Image is ~ 1 meter across. [lower right inset: Close-up of some of the CO2 bubbles which wobble and spin as they rise through the water column.] Click image for larger view and image credit.
Hades Breath
April 25, 2006
Cornel E.J. de Ronde
Geologist
Institute of Geological & Nuclear Sciences (GNS)
Lower Hutt, New Zealand
The beauty of a twisting, curling plume as it exits the crater.
(Quicktime, 2.1 Mb.)
A
surprise every 5 mintues! (Quicktime,
2.1 Mb.)
De-gassing
of the toe of an andesite lava flow (Quicktime, 1.8 Mb.)
Hades
breath: Most definitely poisonous! (Quicktime,
2 Mb.)
One
last hurrah! (Quicktime, 2 Mb.)
What an incredible smorgasbord of events our eyes have been feasting on here at NW Rota-1, one of many submarine volcanoes along the Mariana arc. Only 9 hours after we surfaced from our 3rd dive on this volcano we were back down there again, 560 meters (1840 feet) below the sea surface, drawn by the excitement of witnessing new lava forming at the summit of the volcano. Yes, right before our eyes! Here's how the events of the past 24 hours unfolded.
A zoomed-out view looking down on an advancing andesite lava flow (obscured by the plumes). The yellow parts of the plume contain molten droplets of sulfur; the white parts possibly other mineral particles (like alunite, an aluminum-bearing sulfate). Image is about 2 meters across. Click image for larger view and image credit.
After the excitement of the previous dive to Brimstone Pit, we quietly
wondered if that could be surpassed by anything we might see next. How
wrong we were! Our initial approach to Brimstone revealed a line of
bubbles (mainly the gas carbon dioxide) being expelled from a fracture
in the underlying rock, which was similar to the previous dive. Check.
But as we got closer to the pit, something was a little odd with the
layout of the area. That was it, in place of the previously flat ground
that described Brimstone Pit yesterday, some sort of mound had formed.
In fact, it was a small cinder cone about 6 meters (20 feet) in diameter
with walls about 1 meter (3.3 feet) high, and was made up entirely of
fine-grained ash. As we approached, we saw a plume building out of the
center of the cone and on closer inspection we
noticed ash was 'raining' out of the bottom of the plume (Quicktime,
2.1 Mb.) and being dumped on the flanks of the small cone. And
so it was built. Incredible.
Piece of andesite lava (~4 inches across) newly formed near Brimstone Pit that shows elemental sulfur infilling the vesicles in the lava. [inset: Close-up of the sulfur which would have been liquid as it fills the cavities and has an origin in the magmatic gases sulfur dioxide (SO2) and/or hydrogen sulfide (H2S). Click image for larger view and image credit.
Again we saw the bubbles of gas coming out of Brimstone Pit. Things
had calmed down. But what's that happening over to the right? A
plume forming from the de-gassing of newly created lava on the seafloor (Quicktime,
2.1 Mb.).
Wow, it's spectacular! It totally captivates us as it swirls and dances
before our eyes, hugging the seafloor as it moves forwards. Mesmerizing.
But wait a minute, its coming straight for us. Let's get out of here!
We then ventured off and did a sonar survey a small distance away. As
soon as we could, we returned to Brimstone Pit, drawn to the drama unfolding
below us. Looking around a bit more carefully, we
witnessed the de-gassing of a blocky lava flow (Quicktime, 1.8
Mb.). The
rock type is andesite and it does not flow particularly well, but rather
it advances like some slow moving robot, bit by bit, chunk by chunk.
As the lava advances, the toe of the flow vigorously de-gases. The
gases are mainly sulfur-rich like sulfur dioxide and hydrogen sulfide
which, upon mixing with the surrounding seawater, can form strong acid(!)
and precipitate elemental sulfur. The
elemental sulfur adds a beautiful yellow hue to the plume (Quicktime, 2 Mb.). We
often see sulfur raining on the seafloor as small droplets (the sulfur
was liquid inside the plume) and forming the matrix of the highly vesiculated
lava. That is, the sulfur in-fills the numerous holes in the lava where
the gases escaped. Locally, carbon dioxide forms waterfalls of bubbles in front of the advancing
lava. It is these different gases that are the force behind the vigorous
'mini-explosions' within the lava flow. Quite the drama...the forceful
main character lava, an accompanying crescendo of blocks of lava and
ash being ejected, the brooding clouds of poisonous gases, the dancing
bubbles of carbon dioxide...
Close up of the front edge of the andesite lava flow. Note the large pieces of sulfur in the foreground, which have enveloped pieces of lava. Click image for larger view and image credit.
Scientist return to visit the Brimstone Pit on dive J2-189 and experience what seems like a burp from Hades.
Click
image to view a slide show.
An
incredible eruption of rock, ash and gases (Quicktime, 2 Mb.).
One last burp from Hades (Flash,
200 Kb.) to remind us that there is altogether a completely different world
under the sea.
