Calabrian Ridge, a newly discovered branch of the Mediterranean Ridge

Abstract

LONG range side-scan sonar surveys made from RRS Discovery during 1971 and 1973 have provided the first regional view of the structural grain of the Mediterranean Ridge, whose distinctive surface relief was known previously only from echo-soundings1–3. The sonar surveys clearly show that there is an important grain extending along much of the Ridge, but also there is considerable local variation and other trends are well developed in places. Individual ridges and troughs of about 1–2 km wavelength, and crest length of at least 5 km, have been followed for up to about 25 km and, although largely parallel, they also branch and are noticeably sinuous. Near to the western end of the Mediterranean Ridge the structural grain turns round to the north (Fig. 1) and seems to terminate against a fault zone, which is close to the northern end of the Hellenic Arc4 and to the northern limit of earthquakes in the Ionian Basin5. Extending south-westwards from this point a new branch, with a well developed grain in similar style topography, has been discovered. This dies out just before reaching the faulted, 3,000 m high Malta Escarpment. The inverted ‘Y’ shaped junction between these two Ridges encloses two sides of the triangular shaped Messina Abyssal Plain.