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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 199 records · Page 11Linked to original sources
USGS2026

The USGS Rotating X-ray Computed Tomography (RXCT) Coral-Core Archive: Scope, access, and standardization

We announce the U.S. Geological Survey (USGS) Rotating X-ray Computed Tomography (RXCT) Coral-Core Archive, a digital resource derived from ~400 coral reef cores curated at the USGS Pacific and St. Petersburg Coastal and Marine Science Centers. The archive de-livers calibrated 3-D image volumes that enable reproducible values of skeletal density, linear extension, and calcification from decadal-to-centennials scale records of coral growth and bioerosion. Cross-study comparability within the archive is supported by a unified RXCT workflow that minimizes imaging artifacts. This includes rejecting im-age-intensity–density regressions with r² < 0.95, back-calculating standard densities to verify a ±10% target precision, and confirming that band-averaged density values fall within published species- and site-specific ranges. Given global coral-reef decline and the rarity of physical archives, we release data under FAIR (Findable, Accessible, Interopera-ble, Reusable) principles. Calibrated imagery and scan metadata are distributed through CoralCache/CoralCT for analysis (DeCarlo et al., 2025), while core locations and collection metadata are published through the USGS Geologic Core and Sample Database (DOI: 10.5066/F7319TR3) with links to CT slice imagery in a USGS ScienceBase repository (DOI: 10.5066/P139Y9H4). This archive provides a powerful dataset for evaluating environ-mental controls on coral growth, establishing restoration baselines, and improving coastal-hazard assessments in the face of global coral-reef declines.

American Somoa, Guam, Florida, Hawaii, U.S. Virgin↗
USGS1988

Maps showing the Seabeam bathymetry and sedimentologic and biologic sample locations on Horizon Guyot, Mid-Pacific Mountains and a summary of existing data

Horizon Guyot (Fig. 1) is a 300-km-long, 75-km-wide volcanic ridge with a relatively flat summit that is diagnostic of guyots (Hess, 1946). The U. S. Geological Survey (USGS) began a study of Horizon Guyot in 1983 as part of a program on the origin, distribution, and composition of ferromanganese-oxide precipitates that encrust the hard substrate of sea floor edifices, such as seamounts and volcanic ridges (Hein and others, 1985a). Mass movement and bedload transport of sediment appears to influence the thickness of these crusts on seamount flanks (Hein and others, 1985b). Because Horizon Guyot has been studied more extensively than any other volcanic edifice in the Mid-Pacific Mountains (Heezen, Fischer, and others, 1971; Lonsdale and others, 1972; Winterer, Ewing, and others, 1973), it was chosen as the principal site for a USGS study of sediment transport processes and the geotechnical behavior of sediment on seamounts (Cacchione and others, 1988; Schwab and others, 1988). In March, 1987, Horizon Guyot was again investigated using the R/V ATLANTIS II and the D.S.R.V. ALVIN (cruise 118-12); sponsored by the National Science Foundation. Although primarily a biologic investigation, observations from 10 submersible dives, bottom samples collected at depth using ALVIN and from the surface using the ATLANTIS II, and Seabeam swath-bathymetry (sponsored by the USGS and the Office of Naval Research) add to the overall Horizon Guyot data set. In this report, we summarize the existing data base, present a Seabeam bathymetric map of the study area, ALVIN dive tracklines, the sample locations, and a brief description of the samples collected or other station activities on the ATLANTIS II cruise 118-12. The detailed bathymetric map of the study area (Plate 1) was constructed by merging data obtained by a Deep-Tow study (Lonsdale and others, 1972) (Fig. 1) with data obtained from the swath-bathymetry mapping system onboard the ATLANTIS II. Detailed information on the Seabeam bathymetric system is given by Renard and Allenou (1979).

Open-File Report↗
USGS1981

East Pacific rise at 21°N: the volcanic, tectonic, and hydrothermal processes of the central axis

Photographs obtained by the ANGUS survey system at 21&deg;N reveal many similarities to the geological processes delineated at other spreading centers and in particular those observed in the Galapagos Rift at 86&deg;W. The region of recent volcanism is restricted to a narrow zone (Zone 1) approximately 1 km wide. This suggests that the width of the magma chamber feeding these flows is also narrow at the top. Variations in sediment cover are used to subdivide the flows within Zone 1 into three sheet-flow/pillow-flow pairs. The youngest pair appears to have erupted form a linear fissure 8 km long running parallel to the valley axis. This fissure is part of a larger en echelon pattern of eruptive fissures. Active hydrothermal vents associated with the youngest flows are situated directly above the apparent eruptive fissure. The high (350&deg;C) temperature for some of the fluids exiting from the vents suggests a highly restricted circulation system involving, at times, little to no mixing with cold seawater. The lava terrain in the remainder of Zone 1 and bordering regions is characterized by extensive fracturing, further suggesting a narrow upper dimension to the magma chamber and also that subsurface hydrothermal deposition of massive sulfides may lead to a reduction in the mixing processes.

Earth and Planetary Science Letters↗