A 13‐month flank eruption of Fayal volcano occurred in 1957 and 1958. Intermittent violent explosions (phreatomagmatic) and ejection of ash characterized the eruption during its first 8 months. Following a 2‐day intense seismic period, Capelinhos volcano entered an effusive phase which continued during the last 5 months of activity; Strombolian activity occurred in the crater vent, and a number of lava flows issued from the base of the cone. An outer, semicircular cinder cone, an inner spatter cone, and associated tephra deposits added 2.5 km2 of new land to Fayal Island. Total energy dissipated during the eruption was estimated to be 4×1021 ergs. Differential movements or warping of west Fayal occurred during the seismic crisis. Tephra and lava composition is olivine basalt. Lava viscosity was computed to be between 3×104 and 5×106 poises. Eruption sounds and flashing arcs were tape recorded and analyzed by an audio and subaudio spectrograph; Strombolian‐type eruptions produced essentially broadland sound, explosions had maximum energy below 50 cps, and the dominant recorded energy of flashing arcs was between 30 and 50 cps.

Shear strength, expressed as cohesion, was measured by compression and laboratory vane tests on short, usually continuous samples of 30 sediment cores collected by the Hydrographic Office from water depths of 400 to 5,120 m in 8 areas of the North Atlantic, West Mediterranean, and Central Pacific. Clayey silt-and silty clay-size sediments were predominantly of terrigenous origin. The least cohesion measured is about 4.2g/cm2 and the maximum 234g/cm2. Although cohesion usually increased with depth in the cores, fluctuations in the strength-depth profile are the rule rather than the exception.Validity of strength data, in light of disturbance caused by both piston and gravity core sampling and other forms of disturbance, was considered with the conclusion that the cohesions reported are sufficiently reliable for engineering use at the present time.Shear strength and laboratory-determined consolidation data are applied, with numerical examples, to the computation of sea-floor sediment ultimate bearing capacity and consolidation under structural loads.Dr. Richards.

Thirty-five gravity-and piston-type cores were collected by the Hydrographic Office in depths of 400 to 5120 m from 8 different areas in the North Atlantic, Central Pacific, and West Mediterranean Sea. Most cores were composed of terrigenous silt-and clay-size particles. Mass physical property laboratory measurements of more than 700 samples included: grain size, specific gravity of solids, wet unit weight, water content, void ratio, pore-water saturation, liquid and plastic limits, and compressive and/or vane shear strength. Also computed were porosity, liquidity index, plastic index, cohesion, sensitivity, activity, and modulus of elasticity.

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Volcanic sounds were tape‐recorded on ten occasions during the decade 1950–1960. Analyses of the recordings show that underwater sounds from Bárcena volcano in the north‐eastern Pacific, in November 1952, possessed frequencies in a strong harmonic progression with an apparent fundamental frequency of about 50 cps, little energy above 550 cps, and a pulse duration of 1 to 2 sec. Airborne sounds of explosions in Mihara Yama, O Shima volcano, Japan, in January 1954 had an apparent fundamental frequency of 16 to 17 cps, a strong harmonic progression, and a pulse duration of 0.5 to 1 sec. Less violent explosive activity of the same volcano in September 1950 produced essentially broad‐band acoustic energy, with sound durations of 1 to 2 sec. Recorded airborne sounds of Izalco volcano, El Salvador, in 1956, were similar to those from O Shima in 1950, but had longer pulses. Capelinhos volcano, Azores, in 1958 generated the following airborne sounds: crater explosions had maximum energy below 50 cps and little energy above several hundred cycles; eruptions of liquid lava from the crater produced broad‐band sonic energy; and almost all energy of pressure waves or flashing arcs was below 50 cps. It is suggested that the quality of recorded sounds is related to the types of volcanic activity defined by Lacroix and in this paper: Hawaiian eruptions tend to be acoustically quiet; strombolian activity is characterized by broad‐band sounds that may show a fundamental frequency and harmonics of small intensity; and vulcanian eruptions are denoted by a marked fundamental frequency and strong harmonics of relatively large intensity. Peléan activity has not been recorded. Recording instrumentation and analytical procedure in which sound pressure level‐frequency and frequency‐time methods were used are briefly discussed as an aid to those wishing to make similar investigations.