VOLCANIC GROWTH FAULTS AND THE ORIGIN OF PACIFIC ABYSSAL HILLS

The topographic features known as abyssal hills characterize >30% of t he ocean floor, and yet their origin has been the subject of vigorous debate for over 40 years. Submersible-based investigations show that P acific abyssal hills are created on the flanks of the East Pacific Ris e as horsts and grabens which lengthen with time; Hills are bounded on one side by ridge-facing scarps produced by normal faulting, and on t he other by more gentle slopes produced by volcanic growth faulting.