During the Okeanos Explorer expedition in the Gulf of Mexico, sidesonar pinged something interesting 1,900 meters below on the ocean floor. Expecting a shipwreck, the team sent a remotely operated vehicle to explore. Instead, they found a pair of asphalt volcanoes!
The Deep Discoverer investigated a suspected shipwreck that wasn't. Image credit: NOAA
The remotely operated vehicle is the Deep Discoverer (D2), a submarine robot loaded with cameras. The research team sat their archaeologists down to watch the video feed to observe the hull shape and look for debris, but instead they found a distinctly un-ship-like stone flower. Pulling the scientists over, they realized this was no shipwreck, but an asphalt volcano.
When you think of volcano, you're probably thinking of conical structure gushing lava. But volcanoes can happen from the release of all sorts of material under pressure, like mud, shale, or salt. Or, in this case, asphalt.
This isn't the first discovery of an asphalt volcano — the German exploration ship F/V SONNE found some volcanoes 3,000 meters deep in the south of the Gulf, and a few others have been found off the coast of California and West Africa.
Spotting chemosynthetic tube worms made scientists suspect that this wasn't an ordinary shipwreck, but something different. Image credit: NOAA
Asphalt is naturally-occurring in the Gulf, formed by the same processes that produce the oil and gas that lure platforms into the region. Old oil that has been heated for millions of years causes volatiles to evaporate, leaving behind goopy, greasy residue. When that mixes with sand, gravel, and lighter oil, then heated, it produces asphalt. We do this purposefully as part of the petroleum refining process, but in the right conditions, nature can create it all on its own.
The asphalt volcanoes are also called tar lilies for their floral structure. Image credit: NOAA
The asphalt squeezes out in ductile masses, but are quickly cooled by cold seawater. The plug of asphalt split into ropey extensions, individual petals growing until finally cracking apart.
A single petal of the tar lily is colonized with corals and anemones. Image credit: NOAA
Corals take a long time to grow in relatively deep, dark water. The rate of growth helps establish an age for these lilies as decades to centuries old. Other critters also call the lilies home: barnacles, anemones, and fish. Bacteria even munch on the oil, who in turn are munched on by chemosynthetic tube worms.
Check out video from the Deep Discoverer dive 12 that explored the tar lilies here:
Read more on the NOAA Okeanos Explorer website. For more fun and games, have you ever considered using a volcano for garbage disposal? Someone did, and we've got the video! You might also be curious about other deep-sea ecosystems revealed by ROV exploration.