Controlled on deck, ROV fleet explores seabed at great depths
The research begins with a sophisticated scanning system which measures the depths and records a detailed, three-dimensional bas-relief of the seabed. Based on the reflectiveness of the signal, scientists can tell if the seabed is hard, soft or craggy and can choose what areas from which to take samples. While this recording is taking place, scientists use an instrument called an «air gun» for further measurements. According to a US government website, the air gun, like a water gun, is also a pneumatic sound source. The air gun system consists of an onboard air compressor and storage tanks, a shipboard electrical firing circuit controlled by a seismic recorder, and one or more air guns towed astern of the survey vehicle. The recorder commands the air gun to release a specific amount of air into the water at high pressure. The explosive release of air produces a shock wave followed by several oscillations. Such measurements could lead to many conclusions. Initially it will add to data provided by the scanning system so a proper location for sampling can be selected. As research continues, scientists will be able to analyze the information and interpret which belongs to the Minoan eruption and which to the Columbo explosion, and their magnitudes. On first analysis, the research indicates that a volcanic explosion larger than the one during the Minoan era may have taken place thousands of years before and about which scientists know virtually nothing. «The main advantage of this system is that it allows us read the developments of the geological past and possibly map out when a recurrence [of such eruptions] may take place in future,» says Dimitris Sakellariou, a geologist and researcher at Greece’s oceanography institute. In the next stage, samples are taken from the seabed and stored for detailed analysis in laboratories. After lab study, scientists can determine which ash belongs to which volcano, what kind of rock was projected in each explosion, the temperature of the rock and useful information about paleo-oceanography. Until now, all the information has come from sonic instruments and a few samples taken from submarine dives. To complete the picture, the scientists must go to the depths of the caldera. This will happen either through a deeper and more extensive submarine visit or with the help of remotely operated underwater vehicles, or ROVs. Underwater vehicles Last year, scientists went down in a submarine to get their first recordings and samples. This year, the team will send a ROV. ROVs are helpful because they can stay underwater for many hours and examine the morphology of the lava rocks and the direction in which the lava flowed. The ROV’s robotic arms can get samples from the seafloor. After the trip, we will analyze all the details. This could take months but will result in a physical model of the eruption. In the second stage of the research, the 185-foot research vessel Endeavor, from the University of Rhode Island’s Graduate School of Oceanography, will be used to get detailed recording, mapping and sampling of selected regions around the caldera and the greater Santorini area. The ROVs Hercules and Little Hercules will wrap up the research. Little Hercules allows a pilot and observers on the shipboard to observe conditions at the bottom of the ocean. Hercules is equipped with a high-definition color video camera, temperature sensors and manipulator arms controlled by scientists on the ship. The results of the work will eventually go online or be broadcast in the US and Greece. – This article first appeared in the June 25 edition of K, Kathimerini’s color supplement. Photographs by Vassilis Mentoyiannis.
