Abstract

A prominent system of submarine canyons has been discovered in the Ionian Sea south of the Strait of Messina. The canyons are from 2 to 5 miles wide and more than 100 fathoms deep. Below the base of the continental slope, the canyons widen and develop flat floors as they extend southward 150 miles across a large cone to the Messina Abyssal Plain.

On December 28, 1908, the Strait of Messina was affected by a severe earthquake which devastated the city of Messina and nearby communities. Only two of the eight submarine cables which linked Italy and Sicily within the area of maximum intensity were damaged. Ten hours after the quake, a cable from Malta to Zante parted 120 miles to the south in 1800 fathoms depth at a point where the cable crossed the submarine canyon leading from the Strait to the abyssal plain. The earthquake apparently generated a slump which initiated a turbidity current which broke the two successive cables as it traveled downslope through the canyon at an average speed of 12 knots. The tsunami which swept repeatedly against the surrounding coasts appears to have been produced by the slump and the turbidity current. The cables lying in shallower parts of the Strait, although directly within the epicentral area, did not break because the strong currents through the Strait had removed essentially all the unconsolidated sediments.

Multiple sub-bottom echoes, observed beneath the canyon floors and beneath the abyssal plain but absent from the cone, are reflections from coarse-grained layers of sediment deposited by turbidity currents. Cores from within the canyons contain graded beds of sands and silts. Cores from isolated topographic locations show a pelagic record of stagnations and tephra falls which may be correlated.

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