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Fred N. Spiess

Publications and source records attributed to Fred N. Spiess.

3 recordsLinked to original sources
USGS1999

No spreading across the southern Juan de Fuca ridge axial cleft during 1994-1996

Direct-path acoustic measurements between seafloor transponders observed no significant extension (−10±14 mm/yr) from August 1994 to September 1996 at the southern Juan de Fuca Ridge (44°40′ N and 130°20′ W). The acoustic path for the measurement is a 691-m baseline straddling the axial cleft, which bounds the Pacific and Juan de Fuca plates. Given an expected full-spreading rate of 56 mm/yr, these data suggest that extension across this plate boundary occurs episodically within the narrow (∼ 1 km) region of the axial valley floor, and that active deformation is occurring between the axial cleft and the plate interior. A cleft-parallel 714-m baseline located 300 m to the west of the cleft on the Pacific plate monitored system performance and, as expected, observed no motion (+5±7 mm/yr) between the 1994 and 1996 surveys.

Geophysical Research Letters↗
USGS1990

Origin of Florida Canyon and the role of spring sapping on the formation of submarine box canyons

Florida Canyon, one of a series of major submarine canyons on the southwestern edge of the Florida Platform, was surveyed using GLORIA, SeaBeam, and Deep-Tow technologies, and it was directly observed during three DSRV Alvin dives. Florida Canyon exhibits two distinct morphologies: a broad V-shaped upper canyon and a deeply entrenched, flat-floored, U-shaped lower canyon. The flat- floored lower canyon extends 20 km into the Florida Platform from the abyssal Gulf. The lower canyon ends abruptly at an ∼3 km in diameter semicircular headwall that rises 750 m with a >60° slope angle to the foot of the upper canyon. The sides of the lower canyon are less steep than its headwall and are characterized by straight faces that occur along preferred orientations and indicate a strong joint control. The upper canyon is characterized by a gently sloping, straight V-shaped central valley cut into a broad terrace. The flat floor of the upper canyon continues as terraces along the upper walls of the lower canyon. On the flanks of the upper canyon, there are five >50-m-deep, >0.5-km-wide, closed sink-hole-like depressions which indicate subsurface dissolution within the platform. The origin of the lower canyon is difficult to explain with traditional models of submarine canyon formation by external physical processes. The movement of ground water, probably with high salinities and reduced compounds along regional joints, may have focused the corrosive force of submarine spring sapping at the head of the lower canyon to produce the canyon's present shape.

Florida Canyon↗