SEABED MORPHOLOGY AND GAS VENTING IN THE BLACK-SEA MUDVOLCANO AREA - OBSERVATIONS WITH THE MAK-1 DEEP-TOW SIDESCAN SONAR AND BOTTOM PROFILER

The central part of the Black Sea was investigated with the MAK-1 deep -tow acoustic system providing sidescan observations and acoustic prof iling. Subsequently underwater TV recordings and bottom sampling was d one in an area with extensive mudvolcanism. The mud volcanoes can be d ivided into three types according to their dimensions and morphology. The first type has a seabed diameter of more than 2 km, reaches a heig ht of 100-150 m, has a complex top with a crater-like structure and ge ntle slopes, and reflects massive mudflows in the crater and at its fl anks. The second type has smaller dimensions, is more conical in cross -section almost without relief on its relatively steep slopes, and is characterised by small, radial mudflows. The third type is made up by the only mud volcano with a partially collapsed rim and with massive a nd liquid mudflows. The first type expectedly is in a mature, relative ly passive stage, the latter two types seem to be younger and more act ive. Various types of low relief slides are found in the area and are related to the presence of shallow subbottom gas (40-100 m below the s eafloor) or mudvolcano activity. Evidence for the presence of gas in t he mudvolcano area is shown by gas venting, acoustic turbidity (acoust ic masking), numerous pockmarks, acoustic voids, and acoustic windows. Gashydrates do occur associated with some of the mudvolcanoes.