The sun rises over the Aegean and bathes the sea in a warm light. A new day begins on the Maria S. Merian, the research vessel that navigates through this geologically active region. Researchers and crew are preparing for the next stage of an expedition that will provide insights into the dynamic processes beneath the water's surface. The mood is good, not least thanks to St. Nicholas Day, when the ship's „Nikolaus“ left surprises on the cabin doors - a welcome moment of pause in the intense everyday life on board.
Santorini and Kolumbo have a fascinating and eventful history. The Santorini archipelago, known for its spectacular caldera and white houses, was the scene of one of the largest volcanic eruptions in history around 3,600 years ago. This “Minoan eruption” left behind a huge caldera and is considered a possible trigger for the end of the Minoan culture on Crete. The Kolumbo volcano, located slightly northeast of Santorini under water, last erupted in 1650. At that time, it ejected rocks and gases from its crater and caused a tsunami that hit the coasts of the Aegean. This region is still one of the most earthquake-prone in southern Europe today - and a hotspot for volcanic activity.
The mission of the researchers on board the Maria S. Merian is to better understand these geological processes in order to minimize risks for coastal residents. Among other things, they are investigating how hydrothermal activity in Kolumbo affects the stability of the volcanic edifice and how earthquakes and volcanism are linked. The Amorgos fault, which triggered one of the strongest earthquakes in the region in 1956, is also being investigated.
Route of the Maria S. Merian to the research area (Animation: Andrea Geipel)
Everyday life on board follows a strict schedule. Breakfast is served at 7:30 a.m., lunch at 11:30 a.m. and dinner at 5:30 p.m. In between, the focus is on data collection, working on measurement systems, evaluations and documentation. Around half of the researchers also work in shifts to ensure 24-hour data collection. They continuously monitor the various systems, including a 2D seismic system, a sediment echo sounder and a multibeam echo sounder. The team meets daily at 10:20 a.m. to discuss progress and plan the next steps. There are alternating short presentations on the scientific issues or on the measuring equipment they use on board. In addition to the scientific work, there is also time for relaxation. Breaks on deck, where the sun glistens and the wind whistles around the ears, are refreshing and clear the heads.
This week, the researchers used a variety of devices to investigate the geological structures in the Aegean Sea. One of these systems is the Ocean Bottom Seismometer (OBS). These devices are specially designed to measure the smallest movements of the earth beneath the surface of the water. But how do they work? An OBS consists of several components: a seismometer that records ground movements, a hydrophone that measures sound waves in the water, a data recorder, sensors for measuring water temperature and water pressure and a robust housing that protects the sensitive technology. In addition, the device has a weight that allows it to sink to the seabed and buoyancy bodies made of syntactic foam. These ensure that the OBS rises to the surface again later.
The device is lowered from the ship onto the seabed at strategic points in the Kolumbo Crater and along the Amorgos Fault. There it registers even the smallest movements in the subsurface. After a few days, the OBS is released by another signal and rises to the surface again, where it is recovered and the collected data is analyzed.
The seismometer itself works according to a simple principle: a heavy weight is suspended from a spring and initially remains in position due to inertia, while the housing of the OBS - and therefore the earth - moves. This movement generates an electrical voltage through a coil, which is measured and recorded. In this way, the researchers can determine whether the movements were caused by an earthquake, volcanic activity or other geological processes.
One highlight of this expedition is the trip to the caldera of Santorini, one of the most impressive landscapes in the Aegean. Even if we can only see the island itself from a distance, the sight of the steep cliffs and the huge volcanic structure is breathtaking. But more of that next time.
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