USGS Science⌕ Search

SEARCH · USGS Science

Results for “Geology of the Pacific Ocean”

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

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
USGS1981

The geology of Hess Rise, central north Pacific Ocean

The geology of Hess Rise is interpreted from studies of morphology and structure, igneous petrology, sediment lithofacies, seismic stratigraphy, and paleoenvironments. Hess Rise probably formed at a triple junction, between 116 and 95 m.y. ago, in the equatorial zone of the southern hemisphere. A large archipelago, formed by volcanism, subsequently moved northward as part of the Pacific Plate and subsided. A Late Cretaceous-early Tertiary tectonic and(or) volcanic event created oceanic islands and probably influenced the normal subsidence rate. The lithofacies reflect both the northward movement under various surface water masses of differing productivity and the subsidence history, which influenced calcareous-sediment accumulation and dissolution. Hess Rise is informally divided into three physiographic or morphologic provinces: northern Hess Rise, the central platform, and southern Hess Rise. Southern Hess Rise is further subdivided into the northwestern ridge, Mellish Bank, and the eastern ridge. The structure of Hess Rise is dominated by normal faults which bound grabens and horsts. The west and south boundaries of the rise are fault scarps. Most faults trend about 345 ° on northern Hess Rise, 039° to 060° on southern Hess Rise. Igneous rocks are tholeiitic basalt on northern Hess Rise at Site 464, and trachyte at Site 465 on southern Hess Rise. The tholeiite probably is not a mid-ocean-ridge basalt; more likely it is a transitional basalt erupted during off-ridge volcanism. The trachyte at Site 465 was erupted either in shallow water or subaerially; it represents a late-stage differentiate of alkali-basalt magma. Geochemically, the trachyte is similar to late-stage eruptives on many oceanic islands. The alkali basalt clasts in Upper Cretaceous calcareous ooze at Site 466 probably record a Late Cretaceous-early Tertiary tectonic event that brought old crust above sea level, where it was eroded; alternatively, volcanism may have built the islands. Cores recovered from Holes 464, 310, 310A, 465,465A, and 466 (north to south) show three major lithofacies: limestone of mid-Cretaceous (Albian-Cenomanian) age, calcareous ooze and chalk of Late Cretaceous to Quaternary age, and pelagic clay that is Late Cretaceous to Quaternary in age at Site 464 and Eocene in age at Site 310. Minor lithofacies in the carbonates and pelagic clay include siliceous microfossils and chert. The limestone contains as much as 8.6% by weight of organic carbon. The organic-carbon-rich sediments apparently were deposited along the sides of Hess Rise, above the CCD and within a mid-water oxygen minimum, as the rise crossed the highly productive equatorial divergence. Surface sediments are influenced by present-day near-surface water-mass productivity and the depth of deposition. Above about 3000 meters calcareous ooze is deposited, and below about 4000 meters pelagic clay is dominant. Between 3000 meters and 4000 meters, greater clay contents correlate with increased water depth. The seismic stratigraphy interpreted from single-channel seismic-reflection records can be correlated with the lithofacies. Three major acoustic units apparently vary in age, composition, thickness, and geographic distribution. The lowest acoustic unit generally is acoustically opaque; it corresponds to volcanic basement. In places, however, the top parts of this unit may be well-lithified limestone or chert. The middle acoustic unit, in general strongly layered acoustically, is Albian and Cenomanian limestone, chalk, and chert on southern Hess Rise and Albian and Cenomanian chert, chalk, limestone, and clay stone on northern Hess Rise. The middle unit probably is Albian to at least lower Tertiary chalk, chert, and nannofossil ooze on the central platform. The upper acoustic unit is weakly stratified to acoustically transparent and corresponds to Upper Cretaceous to Recent nannofossil ooze on southern Hess Rise and to pelagic clay of the same age on northern Hess Rise. On the central platform, it probably corresponds to Eocene to Recent nannofossil ooze, marl, and pelagic clay

Initial Reports of the D.S.D.P.↗
USGS2004

Twentieth century demographic changes in cirio and cardón in Baja California, Mexico

Aim&ensp; Our purpose was to discern long-term large-scale patterns of survivorship and recruitment of two dominant, charismatic and useful desert plants, cirio [Fouquieriaceae; Fouquieria columnaris (Kell.) Kell. ex Curran] and card&oacute;n [Cactaceae; Pachycereus pringlei (S.Watson) Britton & Rose], and to evaluate the effects of physical and human factors. Location&ensp; The study included 77 sites distributed over c. 13,200 km 2 in the northern Vizca&iacute;no Region of the Sonoran Desert, state of Baja California, M&eacute;xico. Method&ensp; Censuses used identified individuals ( n = 3780 cirio and 2246 card&oacute;n) and were based on repeat photography. Time intervals between censuses ranged from 29 to 96 years, ending in 1996&ndash;2002. Earlier repetition (1963) of old photographs at 14 sites allowed analysis of temporal variation. The effect of elapsed time was modelled with Weibull functions for survivorship and linear functions for recruitment. To explain the residual variations, we tested categorical and continuous variables related to substrate, geomorphology, climate and geography. Human impacts were weighed with historical and quantitative analysis. Results&ensp; Elapsed time accounted for 45% of the variation of survivorship in cirio but only 35% in card&oacute;n. The fitted Weibull curves were used to estimate longevity: all-size cohorts of 1000 individuals would die out in 388 (cirio) and 723 years (card&oacute;n). Recruitment in cirio was linearly related to time ( r 2 = 0.71) and averaged < 0.003 year &minus;1 but was less than mortality at 90% of the sites. For card&oacute;n, recruitment averaged > 0.005 year &minus;1 , was linearly related to time ( r 2 = 0.66) and was less than mortality at only 33% of the sites. Vital rates were not strongly correlated between mid- and late-century but were mostly similar to the long-term regional rates. Removing the factor of elapsed time, the residual variations showed that survivorship was greater on sites protected from winds for cirio and was less on very coarse soils for card&oacute;n. Recruitment increased with latitude in cirio and was greater on southern exposures for both species. The residual variations were not clearly affected, at a regional scale, by other factors thought to be important, including elevation, distance to the Pacific Ocean, geology, slope gradient, soil stability, older vs. young alluvial soils, and soil Ca : Mg and Na : K ratios. Human impacts have been sporadic and heterogeneous but locally strong; our quantitative indices of accessibility did not show regionally significant effects. Blowdown by hurricanes is a sporadic cause of major mortality for cirio but not necessarily for card&oacute;n. Main conclusions&ensp; At our scales, effects of time outweigh those of substrate, and human impact was scant. Large patterns were pronounced: cirio experienced a prolonged, widespread decline in the 1900s, while card&oacute;n fluctuated in different directions and degree among local populations. Cirio was found to be inherently much shorter-lived than card&oacute;n. We also suggest that recruitment in cirio was low due to long periods with relatively dry winters that affected the entire region, while spatial heterogeneity of card&oacute;n recruitment seemed more related to the variation in summer rains.

Journal of Biogeography↗
USGS1983

Geologic evolution of Hess Rise, central North Pacific Ocean

Cores from four Deep Sea Drilling Project (DSDP) sites (310, 464, 465, and 466) and seismic-reflection profiles provide data that are used to interpret the geological evolution and paleoenvironments of Hess Rise, a prominent oceanic plateau in the central North Pacific Ocean. Hess Rise apparently formed in the Southern Hemisphere along the western flank of the Pacific-Farallon Ridge 110 to 100 m.y. B.P. Core stratigraphies and lithologies show the response of sedimentation to subsidence and northward movement of Hess Rise on the Pacific plate. Oceanic islands, which crowned Hess Rise during its early evolution, were eroded and subsequently subsided below sea level. Major structural trends include three northwest-trending (∼327°) arms, or ridges, and an east-northeast-trending southern Hess Rise that parallels the Mendocino Fracture Zone (060°). Normal faults offset basement as much as 3,000 m along the southern edge and 1,500 m on the western flank of Hess Rise. Many faults were active during sedimentation. Tholeiitic basalt from the base of Hole 464, trachyte from the base of Hole 465A, and alkalic basalt clasts within sediment of Hole 466 show the diversity of rock types that constitute the igneous basement. A major rock unit is middle Cretaceous limestone, chalk, and minor chert that form the basal sedimentary unit. Some limestone samples, rich in organic carbon, reflect accumulation above the carbonate compensation depth (CCD) within a mid-water oxygen minimum zone. The organic-carbon-rich sediments probably were deposited on the submarine slopes of islands and banks that were at upper bathyal depths as Hess Rise crossed the wide equatorial divergence where increased upwelling and biogenic productivity contributed to high accumulation rates. The source of organic matter was mostly lipid-rich, autochthonous, marine organic matter. Analyses of sediment samples from across the Cretaceous-Tertiary boundary at Site 465 show that there was a significant decrease in surface water temperature and biological productivity. An abrupt increase in transition metals and iridium suggests that an outside source, perhaps extraterrestrial, was the cause for many of the sudden oceanographic, geochemical, and biological changes at the boundary.

GSA Bulletin↗
USGS1963

Basalts dredged from the northeastern Pacific Ocean

Volcanic rocks dredged from seamounts, fault ridges, and other major geological features of the northeast Pacific Ocean include a wide variety of basalts. Most of these are vesicular, porphyritic types with near analogues in the Hawaiian and other oceanic islands. in addition, aluminous basalts and diabasic tholeiites impoverished in potassium also occur. There is no simple correlation of composition, degree of oxidation, vesiculation, or hydration of these basalts with texture, or depth of dredge site. Most samples appear to have been extruded at much shallower depths than those now pertaining at the dredge site. the distribution of these basalts suggests that the andesite line coincides with or lies on the continent side of the foot of the continental slope.

Science↗
USGS2005

Marine mineral resources of Pacific Islands— A review of the Exclusive Economic Zones of islands of U.S. affiliation, excluding the State of Hawaii

The United States Exclusive Economic Zone (EEZ) was established in 1983 and comprises all marine areas within 200 nautical miles (370 kilometers) of the nearest U.S. land. This vast area of 3.38 million square nautical miles (11.6 million square kilometers) is about 20 percent greater than the entire land area of the United States. The resource potential of the vast mineral deposits that occur within the U.S. EEZ is unknown, despite field studies that have taken place during the past 25 years. Since about 1975, information on marine mineral deposits has been obtained by numerous research cruises to the Pacific Ocean by the U.S. Geological Survey (USGS), the U.S. National Oceanic and Atmospheric Administration (NOAA), equivalent government agencies in Germany, Canada, France, Russia, Japan, China, South Korea, Australia, and New Zealand, and by academic researchers from all of these nations. Although most of the cruises by other nations explored areas outside the U.S. EEZ, information gained from those studies can aid in the evaluation of the mineral potential in the U.S. EEZ. However, the global effort remains inadequate to allow for the quantitative evaluation of mineral resources contained within the EEZ of nations or within international regions of the oceans.

Circular↗
USGS1981

The geologic history of the Mid-Pacific Mountains in the central North Pacific Ocean; A synthesis of deep-sea drilling studies

The Mid-Pacific Mountains constitute one of the largest aseismic rises in the central North Pacific Ocean. They have been generated by mid-plate volcanic events prior to Barremian time, but their volcanic activity continued through the remainder of the Cretaceous. Evidence of the latest stages of this volcanism are the trachytic ashes included in mid- and Late Cretaceous sediments and the presence of guyots atop the main volcanic pedestal. The thermal and volcanic history of the oldest part of the Pacific Plate and its plate tectonic movements since Cretaceous time have led to considerable horizontal and vertical movements of the Mid-Pacific Mountains. Reconstruction of their subsidence and evidence from the sediments from Site 463 suggest that they once, in Cretaceous time, constituted large, tropical volcanic islands which were covered by vegetation and which shed their erosional debris over the adjacent island slopes. Neritic fossils in Maastrichtian sediments document the presence of shoal areas until the end of the Mesozoic. Since then they have subsided to their present water depth. The horizontal movements of the Pacific Plate have carried the Mid-Pacific Mountains from a position well south of the Cretaceous equator to their present position under the unproductive surface waters of the subtropical central North Pacific Ocean. Site 463, on the western Mid-Pacific Mountains, probably crossed the equator in Maastrichtian time. Shallow-water-derived calcareous fossils are incorporated into the pelagic sediments covering the Mid-Pacific Mountains. They have been displaced from their source areas along the flanks of seamounts over the adjacent regions during times of low sea-level stands. Debris of land plants in Aptian sediments documents the presence of emergent volcanoes during that time. The pelagic sediments penetrated at Site 463 consist largely of a sequence of Cretaceous chalks, limestones, and cherts which accumulated fast and which document the presence of highly productive surface water masses around the former volcanic islands and above the shoals. The development of oxygen-deficient depositional environments and the lack of evidence for intensive reworking suggest at the same time very sluggish water movements in the meso- and bathypelagic environment during Early and mid-Cretaceous times. The Cenozoic calcareous oozes, on the other hand, are very condensed. They are interrupted in several places by hiatuses, and despite their position well above the CCD they show effects of dissolution and poor preservation of the calcareous faunas and floras. The frequency of reworked pelagic material together with the hiatuses indicate episodes of intensive renewal of the meso- and bathypelagic water masses which generated intensive sea-floor erosion and which were probably triggered by the climatic deterioration in the polar regions

Initial Reports of the D.S.D.P.↗
USGS2009

Database of the geologic map of North America— Adapted from the map by J.C. Reed, Jr. and others (2005)

Introduction The Geological Society of America's (GSA) Geologic Map of North America (Reed and others, 2005a; 1:5,000,000) shows the geology of a significantly large area of the Earth, centered on North and Central America and including the submarine geology of parts of the Atlantic and Pacific Oceans. This map is now converted to a Geographic Information System (GIS) database that contains all geologic and base-map information shown on the two printed map sheets and the accompanying explanation sheet. We anticipate this map database will be revised at some unspecified time in the future, likely through the actions of a steering committee managed by the GSA and staffed by scientists from agencies including those responsible for the original map compilation. Regarding the use of this product, as noted by the map's compilers: “The Geologic Map of North America is an essential educational tool for teaching the geology of North America to university students and for the continuing education of professional geologists in North America and elsewhere. In addition, simplified maps derived from the Geologic Map of North America are useful for enlightening younger students and the general public about the geology of the continent.” With publication of this database, the preparation of any type of simplified map is made significantly easier. More important perhaps, the database provides a more accessible means to explore the map information and to compare and analyze it in conjunction with other types of information (for example, land use, soils, biology) to better understand the complex interrelations among factors that affect Earth resources, hazards, ecosystems, and climate.

Data Series↗
USGS1996

The origin of the Bering Sea basalt province, western Alaska

Bering Sea basalt province consists of at least 15 late Cenozoic (less than 6 Ma) volcanic fields that occur on islands in the Bering Sea and along the adjacent west coast of Alaska. The fields are composed of widespread flows of tholeiitic and alkali olivine basalt and small cones, flows, and maar craters of more alkalic basalt, basanite, and rare nephelinite. Although the volcanic fields do not lie along a hot-spot trace, the rocks are compositionally similar to ocean island basalts. Although the rocks show some evidence for fractionation, the dominant control on composition is by varying degrees of partial melting of a mantle source. Trace-element and isotopic data further constrain the mantle source.

Geology of the Pacific Ocean↗
USGS2000

Compilation principles and the main units of the legend of the geodynamic map of North and Central Asia, Russian Southern Far East, Korea and Japan

A map at 1:5,000,000, covering the territories of Eastern and Southern Siberia, Mongolia, Northeast China and the southern part of the Russian Far East, Korea and Japan, is being compiled within the scope of the International Scientific Project on Tectonics, Geodynamics and Metallogeny. The principles and content of terrane analysis serving as a basis for the map are discussed in the article and definitions are given for key concepts: craton, terrane, accretion, amalgamation, dispersion, etc. The content of the terranes of different types shown on the map, overlapping and "suturing" together their formations, which are classified on the basis of the actualism principle, is set forth. The possibility of discriminating terranes in the Early Precambrian basement of cratons is discussed.

Siberia↗
USGS2023

A characterization of the deep-sea coral and sponge community along the Oregon Coast using a remotely operated vehicle on the EXPRESS 2022 expedition

Deep-sea coral and sponge (DSCS) communities serve as essential fish habitat (EFH) by providing shelter and nursery habitat, increasing diversity, and increasing prey availability (Freese and Wing, 2003; Bright, 2007; Baillon et al., 2012; Henderson et al., 2020). Off the U.S. West Coast, threats to these long-lived, fragile organisms from bottom contact fishing gear, potential offshore renewable energy development, and ocean warming and acidification have been the subject of recent research (Gomez et al., 2018; Salgado et al., 2018; Yoklavich, et al., 2018; Gugliotti et al., 2019). Other DSCS studies have reported new species (Yoklavich and Love, 2005), analyzed species distribution and abundance (Tissot et al., 2006, Watters et al., 2022), developed predictive distribution models (Huff et al., 2013; Rooper et al., 2017; Kreidler, 2020), and discovered medicinal uses for corals and sponges (Essack et al., 2011; Shrestha et al., 2018). Due to the vast area of unexplored seafloor within the territorial waters and the U.S. exclusive economic zone (EEZ; 12-200 nautical miles off the coast) and the technological requirements and expense of deep-sea research, there is still much to learn about the distributions and biology of DSCS. This information is critical to resource managers for effective conservation and management of DSCS habitats. In order to minimize the adverse impacts of fishing on EFH, the Pacific Fishery Management Council (PFMC) and National Marine Fisheries Service (NMFS) designated several seafloor habitat areas as EFH conservation areas (EFHCA), first in 2006 (as part of Amendment 19 to the Pacific coast groundfish fishery management plan) and then again in 2020 (as part of Amendment 28). These areas are closed to bottom trawl fishing at a minimum, and in some cases to all bottom contact fishing gears. In addition to protections afforded by EFH-related regulations, the National Marine Sanctuary Program prohibits certain non-fishing activities within areas designated as national marine sanctuaries, such as oil and gas exploration or extraction, cable laying, and other forms of seabed alteration or construction that disturb benthic communities. NOAA’s Deep-Sea Coral and Research Technology Program (DSCRTP) began a 4-yr funding initiative for the U.S. West Coast in 2017. The goals of the West Coast Deep-Sea Coral Initiative (WCDSCI) were to: 1) gather baseline information on areas subject to fishing regulation changes prior to the implementation of Amendment 28; 2) improve our understanding of known DSCS bycatch “hot spots”; and 3) explore and assess DSCS resources within NOAA National Marine Sanctuaries with emphasis on areas of sanctuary resource protection and management concerns. As part of the WCDSCU, an 11-day expedition (3 Sep – 13 Sep 2022) was launched from the NOAA Ship Bell M. Shimada, beginning and ending in Newport, OR. The science team assembled for this cruise were members of the EXpanding Pacific Research and Exploration of Submerged Systems (EXPRESS) campaign, which brings together researchers from federal and nonfederal institutions to collaborate on scientific expeditions targeting the deepwater areas off California, Oregon, and Washington. EXPRESS supports researchers leveraging funding, resources, personnel, and expertise to accomplish more science than would have been possible by a single entity alone. The 2022 expedition included research partners from National Marine Fisheries Service (NMFS) Southwest Fisheries Science Center (SWFSC) and Northwest Fisheries Science Center (NWFSC), Bureau of Ocean Energy Management (BOEM), U.S. Geological Survey (USGS), Pacific Fisheries Management Council Habitat Committee, and Woods Hole Oceanographic Institution.

Report↗
USGS2010

Geologic structure of the northern New Caledonia ridge, as inferred from magnetic and gravity anomalies

Bathymetric, gravity, and magnetic data collected in the southwest Pacific Ocean over the northern New Caledonia ridge show that the main geological units known from the island of New Caledonia extend northward from this island, beneath the Grand Lagon Nord, the Grand Passage, and the d'Entrecasteaux reefs. These data support the model of tectonic evolution of the New Caledonia region proposed by Kroenke [1984]. We interpret a linear axial gravity low that extends from southern New Caledonia to the Grand Passage as evidence for the continuity of the thick pre-Permian to Jurassic core of the island. The Belep magnetic pattern, which covers the southwestern half of the Grand Lagon Nord, shows linear, high relief (1000–2000 nT) anomalies that are locally associated with a 120-mGal gravity high. These magnetic and gravity anomalies resemble anomalies measured over the west coast of New Caledonia, suggesting that the Cretaceous to Eocene basaltic complex of the coastal area is overlain by ophiolite remnants as far north as the western d'Entrecasteaux reefs. The similarity between the Belep magnetic pattern and a highly magnetic province evident 200 km southwest across the New Caledonia basin, along the Fairway ridge, indicates that volcanic rocks lie symmetrically on both sides of the New Caledonia basin. We suggest that part of these volcanic rocks were emplaced during the middle Cretaceous when the New Caledonia ridge rifted from the Australian margin. Simple gravity models of an elongated gravity high, having peak values in the range of +130 to +150 mGal, suggest that the ophiolite, which was thrust over New Caledonia during the Upper Eocene, extends along the east side of the Grand Lagon Nord and as far north as the d'Entrecasteaux reefs. Gravity and magnetic models suggest that in the area of the d'Entrecasteaux reefs, the ophiolite belt includes two subunits. The first subunit underlies the Huon-La Surprise platform and may include highly serpentinized ultramafic rocks without basaltic oceanic crust. The second subunit, which lies beneath the Guilbert ridge, may include ultramafic rocks as well as thin imbricate slices of oceanic crust. At the northern termination of the New Caledonia ridge, seismic and geopotential data evidence a major east-west trending tectonic zone that separates the basement of the New Caledonia ridge from the d'Entrecasteaux zone, an arcuate oceanic feature extending northward from the ridge. Differences in structure, geophysical signatures and morphology evident between areas north and those south of the Grand Passage, together with the nearness of the Le Noroit massif west of the Grand Passage, suggest that contemporaneously with Eocene to early Oligocene subduction along the western New Caledonia margin, an arc-ridge collision may have occurred near the northern termination of this subduction zone.

Tectonics↗
USGS2009

U.S. Geological Survey (USGS) Western Region; Santa Barbara Channel Coastal and Ocean Science

USGS coastal and ocean science in the Western United States and the Pacific integrates scientific expertise in geology, water resources, biology, and geography. Operating from 10 major science centers in the Western Region, the USGS is addressing a broad geographic and thematic range of important coastal and marine issues. In California, the Santa Barbara Channel represents one area of focus.

Fact Sheet↗
USGS1990

Geology and geochemistry of epithermal precious metal vein systems in the intra-oceanic arcs of Palau and Yap, western Pacific

The Palau and Yap arcs are part of an intra-oceanic island-arc-trench system which separates the Pacific and Philippine plates in the western Pacific Ocean. The 350-km-long Palau arc consists of over 200 islands while the 400-km-long Yap arc located to the north has only four major islands exposed. Four of the largest islands in Palau are composed primarily of early Eocene to mid-Miocene volcanic rocks and the four islands comprising Yap contain only Miocene volcanic rocks. Basalt and basaltic andesites of the Babelthuap Formation are the oldest volcanic rocks in Palau and are characterized by high MgO, Ni and Cr and low TiO 2 and have a boninitic affinity. They form the central and southeastern parts of Babelthuap Island. Oligocene arc tholeiite flows having an age of 34–35.5 Ma comprise most of the three smaller volcanic islands in Palau and the western part of Babelthuap. The youngest volcanic rocks are dacitic intrusions having an age of 22.7–23.2 Ma. The Yap arc is unusual in that metamorphic rocks up to amphibolite grade form most of the islands. These are underlain by a melange composed of igneous and volcanic clasts as well as clasts from a dismembered copper-gold skarn deposit. Miocene volcanic rocks consisting of flows and volcaniclastic deposits overlie the melange and metamorphic complex.

Journal of Geochemical Exploration↗
USGS1967

A photo-mosaic of western Peru from Gemini photography

The Geological Survey in cooperation with the National Aeronautics and Space Administration and with the Raytheon Company has prepared a mosaic from photographs taken during the Gemini IX mission. The 1:1,000,000-scale photo-mosaic extends from the Sechura Desert in northern Peru to northern Chile and from the Pacific Ocean to the headwaters of the Amazon. In addition to a wide variety of geological features, such things as landslides, roads, snow fields, irrigated lands, jungle agricultural sites, archeological sites, and smoke (brush burning) have been identified on the photo-mosaic. A lineation, interpreted here as a major fault, extends across several photographs and for several hundred miles. The magnitude of this lineation was not realized until the photographs were rectified and the mosaic constructed. For many purposes this mosaic is superior to the best existing 1:1,000,000-scale conventional maps of the area. This mosaic will supplement, not replace, existing conventional maps and aerial photographs. Mosaics of photographs taken from space should be of considerable interest to the scientific community and of immense practical use in the efficient management of natural resources.

Open-File Report↗
USGS2024

Developing version 2 of satellite-estimated precipitation monthly reports for selected locations in the Republic of the Marshall Islands

The Republic of the Marshall Islands (RMI; also known as the Marshall Islands) is a nation of more than 30 low-lying atolls and islands, most of which are inhabited, dispersed across an Exclusive Economic Zone over 770,000 square miles in the tropical central north Pacific Ocean. The study objectives and methods were originally presented in U.S. Geological Survey Data Report 1181 and are summarized herein. Monitoring environmental conditions for potential drought risk is challenging in such a dispersed island nation, and current drought hazard products provide generalities regarding conditions on a broad geographic scale. In 2022–23, a team of U.S. Geological Survey scientists, and managers of natural resources and natural hazards in the RMI, used Integrated Multi-satellitE Retrievals for Global Precipitation Measurement satellite estimates of precipitation to develop content and a template for timely monthly reporting of precipitation for 23 inhabited atolls and islands. After a year of report production and user feedback, the team incorporated lessons learned and revised user priorities to update the content and layout of the template. This data report describes the collaboration process and results of revising the report content and layout into version 2 of the monthly satellite-estimated precipitation report.

Data Report↗
USGS1948

Geology and ground-water resources of Iwo Jima

Iwo Jima, in the western Pacific Ocean, consists of Motoyama, a broad volcanic cone, at the north, and Mt. Suribachi at the south, with an undulating isthmus between. Motoyama is largely light-gray-buff tuff. A thick andesitic lava flow under Suribachi, exposed in several places, is overlain by a thick deposit of cinder and scoria. The isthmus (called Tidorigahara by the Japanese) is underlain by more than 200 feet of loose black volcanic ash and fine cinder derived from Suribachi. Several small coral reefs are located about 340 and 110 feet above present sea level. Iwo Jima first came into existence, probably early in Pleistocene time, with the building above sea level of the tuff cone of Motoyama. Quite late in the active life of Motoyama, volcanic activity on the southwestern flank resulted in the formation of Suribachi. This activity may have started with the welling up of the andesitic lava which underlies Suribachi. Following the major eruption of Suribachi, relative sea level changed, and the sea stood about 360 feet higher than at present. The broad cone of Motoyama was beveled; the relative sea level then dropped 240 feet, with minor halts to about 120 feet above present level. As the island rose, Suribachi burst forth in its last stage of explosive activity. Wave erosion cut deeply into the andesite flow of Suribachi, and a prominent bench level was formed 120 feet above present sea level. The Japanese on the island were often faced with serious water shortages. Americans drilled wells and obtained moderately large supplies of usable water. The temperature of the water ranges from 105° to 179° F., and the water is somewhat mineralized. The most favorable area for ground-water development is the isthmus.

Iwo Jima↗