USGS Science⌕ Search

SEARCH · USGS Science

Results for “The Sedimentary Record”

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.

762 records · Page 43Linked to original sources
USGS1993

Map showing depth to basement in the deep-sea basins of the Pacific continental margin, Strait of Juan de Fuca to Cape Mendocino

The U.S. Geological Survey conducted a series of cruises, EEZSCAN 84 (EEZ-SCAN 84 Scientific Staff, 1986), to collect reconnaissance data on the newly proclaimed Exclusive Economic Zone (EEZ), the area out to 200 nautical miles from the coastline of the United States. The cruises systematically surveyed the entire conterminous United States west coast EEZ using the Geological Long-Range Inclined Asdic (GLORIA) side-scan sonar, a 160-in 3 airgun seismic-reflection profiler, a 3.5-kHz high-resolution seismic-reflection profiler, a 10-kHz echo sounder, and a proton-precession magnetometer. The nominal trackline spacing throughout the survey was 30 km. Derivative maps of sediment thickness (I-2089-A, I-2090-A, I-2091-A) and depth to basement (I-2089-B, I-2090-B, I-2091-B) in the basins of the west coast EEZ were compiled from both the sonar-image dala and the deep-penetration seismic data obtained on these cruises. Only EEZ-SCAN 84 data were used for the map compilations because available data from other cruises in this region are sparsely located, have poor navigational control, or were obtained with seismic systems that were not powerful enough to resolve oceanic basement. For this map series, sediment thickness and depth to basement were determined only in the deep-ocean basin regions because the seismic system used on the EEZ-SCAN 84 cruises could not resolve oceanic basement beneath the thick sediments of the continental slope. All the data used to compile the maps are presented in the "Atlas of the Exclusive Economic Zone, Western Conterminous United States" (EEZ-SCAN 84 Scientific Staff, 1986). Basement Outcrops GLORIA imagery was used to locate areas of basement outcrop throughout the region. Where possible, sediment thickness on and immediately adjacent to basement outcrops was measured from seismic data. Where there was no bathymetric or seismic control, a seamount peak was assumed to have no sediment cover. A pattern is used on the map to indicate all basement outcrops. Data Reduction Acoustic basement in the basins, invariably oceanic Layer 2, was observed on all of the seismic records. One-way traveltime was measured from the sea floor to acoustic basement. Because the trackline spacing of about 30 km is relatively large compared to the data density along track, we chose to measure the sediment thickness every 0.5 hour or at an interval of approximately 7.5 km. Water depth was measured with a 10-kHz profiler. Depth to basement was calculated using the sea surface as the zero datum and adding the corrected water depth (Carter, 1980) to the sediment thickness. Acoustic travel times were converted to depths by first calculating a regression equation from the interval velocity versus depth data of Connard and others (1984). Their data base comprises a compilation of all available Deep Sea Drilling Project data plus wide-angle refraction data, which were collected in Cascadia Basin west of Oregon and represents the best data set available for the United States west coast EEZ. The regression equation was integrated to determine sediment thickness as a function of one-way traveltime . The resulting equation is z = 1400t + 0 .5t 2 where z is sediment thickness in meters, and t is one-way traveltime in seconds. Sediment thicknesses calculated using this equation were compared to values calculated from the general equation of Carlson and others (1986). Values for sediment thickness calculated by the two equations differed by no greater than 10 percent throughout the range of travel times. Bathymetry The bathymetry is from Chase and others (1981). The bathymetric data were compiled from a variety of sources, and data quality is inconsistent. Because of differences in navigational precision and density of coverage, the bathymetric contours of a feature may be at a different location than the corresponding isopleths derived from the EEZ-SCAN 84 data, or a feature may not be indicated on the bathymetry at all. These situations occur because either the feature is poorly located in the bathymetric data set or, especially in the outer EEZ, the bathymetric data are too sparse to have defined the existence of a feature. Acknowledgments Topographic digital data bases were corrected and verified by Christina Lief. Gerald Evenden developed the computer software system MAPGEN, used to compose this map. Reviews, suggestions, and technical contributions from Edward C. Escowitz and Florence Wong and advice about cartographic design from Will Stettner substantially improved the quality of this map. References Cited Carlson, R.L., Gangi, A.F., and Snow, K.R., 1986, Empirical reflection-traveltime/ depth and velocity/depth functions for the deep-sea sediment column: Journal of Geophysical Research, v. 91, no. B8, p. 8249-8266. Carter, D.J.T., 1980, Echo-sounding correction tables: Taunton, United Kingdom, Hydrographic Department, Ministry of Defence, 150 p. Chase, T.E., Wilde, Pat, Normark, W.R, Miller, C.P., Seekins, B.A., and Young, J.D., 1981, Offshore topography of the Western United States between 32° and 49° North latitudes: U.S. Geological Survey Open-File Report 81-443, scale 1:864,518 at 38° latitude, 2 sheets. Connard, G., Couch, R., Keeling , K., Roy, J., and Troseth, S., 1984, Abyssal plain and continental net-objective sedimentary thicknesses, in Kulm, L.D., and others, eds., Western North America continental margin and adjacent ocean floor off Oregon and Washington, Atlas 1 of Regional Atlas Series, Ocean Margin Drilling Program: Woods Hole, Mass., Marine Science International, sheet 7. EEZ-SCAN 84 Scientific Staff, 1986, Atlas of the Exclusive Economic Zone, Western Conterminous United States: U.S. Geological Survey Miscellaneous Investigations Series I-1792, scale 1:500,000, 152 p. See Also "U.S. Pacific West Coast Field Activities" (Paskevich and others, 2011; http://pubs.usgs.gov/of/2010/1332/htmldocs/pc/pc_overview.html). Paskevich, V.F., Wong, F.L., O?Malley, J.J., Stevenson, A.J., and Gutmacher, C.E., 2011, GLORIA sidescan-sonar imagery for parts of the U.S. Exclusive Economic Zone and adjacent areas: U.S. Geological Survey Open-File Report 2010?1332, available at http://pubs.usgs.gov/of/2010/1332/.

IMAP↗
USGS1973

Erosional and Depositional Aspects of Hurricane Camille in Virginia, 1969

Probably the worst natural disaster in central Virginia's recorded history was the flood resuiting from an 8-hour deluge of about 28 inches (710 mm) of rain on the night of August 19-20, 1969. This study examines some of the intensive sediment erosion and deposition that resulted from the storm and flood. Most of the 150 people whom the flood killed in this mountainous area died from broken bones and other blunt-force injuries, rather than by drowning. The transport of sediment and other debris by the water therefore was very significant in loss of life and in property damage. Erosion resulted mainly from debris avalanches down the mountain-sides and channel scour along streams and head-water tributaries. Total amounts of sediment yield from certain mountainous areas in Nelson County were about 3.2-4.6 million cubic feet per square mile, probably the equivalent of several thousand years of normal denudation. Characteristics of the debris avalanches were that (1) they usually followed pre-existing depressions on hillsides and occurred on slopes greater than 35 percent, (2) the upslope tip of the avalanche scar tended to be located at the steepest part of the hillside, where the convex slope merged with the concave or planar zone immediately below, (3) hillsides facing north, northeast and east were more susceptible to avalanching than slopes facing other directions, and (4) debris-avalanches caused rapid and devastating surges of water and sediment in the mountain-stream channels. Such surges in some instances temporarily blocked the channel flow upstream. Slightly more than half of the total sediment contributed to the stream system was from erosion of stream channels. Channel erosion was very irregularly distributed; some ravines 10-20 feet wide and 5-10 feet deep were scoured in places which formerly had only a very small channel, whereas other channels only a few hundred yards away experienced little or no channel erosion. By the use of figures for the total amount of sediment removed from a drainage basin and the duration of the storm, estimates were made of the storm-average sediment-transport rate at the mouth of various basins. For drainage basins ranging up to about 1.5 square miles, the estimated storm-average sediment-transport rates varied from practically nothing to as much as 172,000 pounds per second (7.4 million tons per day). The types of sediment deposits were (1) debris-avalanche deposits, rather rare, at the base of hillslopes, (2) mountain-stream channel deposits, usually in scattered sediment patches but locally occurring as large wedge-shaped deposits behind debris dams, (3) alluvial fans, (4) delta-like deposits at the junction of a stream and major highway, where water backed up during the flood due to plugging of a culvert, and (5) accretion deposits on flood plains. The highway deltas and some downstream flood-plain sediments consisted mostly of sand-sized grains, but the other types of deposits usually contained particles ranging from silt or clay to boulders 5-10 feet in diameter. Changes in grain size and in volume of deposition with distance downstream were measured, and sedimentary features of the various types of deposits are described.

Professional Paper↗
USGS1964

Ground-water conditions in the Green Bay area, Wisconsin, 1950-60

The Green Bay area, which includes parts of Brown, Outagamie, and Shawano Counties, has an area of about 525 square miles in eastern Wisconsin at the south end of Green Bay. In 1960, it had a population estimated at 124,000; Green Bay, the largest city in the area, had a population of 62,888. The Green Bay area is underlain by a basement complex of crystalline rocks of Precambrian age. Sedimentary rocks of Cambrian, Ordovician, and Silurian ages overlie the crystalline rocks. These rocks are divided, in ascending order, as follows: The Dresbach Group, Franconia Sandstone, and Trempealeau Formation of Cambrian age; the Prairie du Chien Group, St. Peter Sandstone, Platteville Formation, and Maquoketa Shale of Ordovician age; and the Niagara Dolomite of Silurian age. The Maquoketa Shale and Niagara Dolomite are present only in the eastern part of the area. Unconsolidated deposits, largely of Pleistocene age and glacial origin, overlie the older rocks in most of the area. The rocks of the Dresbach Group, Franconia Sandstone, Trempealeau Formation, Prairie du Chien Group, and St. Peter Sandstone are connected hydraulically and can be considered to form one aquifer, called the sandstone aquifer. The sandstone aquifer is the principal source of ground-water supply in the Green Bay area and is one of the most productive water-bearing units in Wisconsin. All the public water supplies in the area, except the supply for the city of Green Bay, and many of the industrial water supplies are obtained from wells tapping the sandstone aquifer. Rates of discharge of individual wells range from about 200 to 1,000 gallous per minute. The city of Green Bay also obtained its water supply from wells tapping the sandstone aquifer until August 1957, when it began using Lake Michigan as a source of water supply. Several industries also use large quantities of surface water. The Niagara Dolomite, although largely undeveloped, is potentially an important aquifer, in the eastern part of the area. Small amounts of water are obtained from dolomite of the Platteville Formation and from sand and gravel deposits of Pleistocene age. Recharge to the sandstone aquifer in the Green Bay area is derived chiefly from precipitation that infiltrates at or near the outcrop area of the aquifer in northwestern Brown County, eastern Outagamie and Shawano Counties, and southern Oconto County. The amount of recharge is estimated to be at least 30 mgd (million gallons per day). Withdrawals of water from wells tapping the sandstone aquifer in the area began when the first well was drilled in 1886. The withdrawals gradually increased to an average of about 6 mgd in 1940, about 10 mgd in 1950, and about 13 mgd in January-July of 1957, after which time the city of Green Bay discontinued pumping from wells. From August 1957 through 1960, average annual withdrawals of water remained relatively constant at about 5 mgd. Water levels in wells tapping the sandstone aquifer persistently declined until August 1957 as a result of the gradually increasing withdrawals of water. In the area of concentrated ground-water withdrawals in downtown Green Bay, the piezometric surface, which had been about 100 feet above land surface in 1886, was about 340 feet below land surface in 1957. The cessation of pumping by the city of Green Bay in August 1957 resulted in a decrease in withdrawals of ground water from about 13.1 mgd in the first half of 1957 to about 5.3 mgd in the last half and a rapid recovery in water levels. ]n the area of concentrated withdrawals, the piezometric surface had recovered about 300 feet by September 1960. Rises in water levels were recorded throughout the Green Bay area, with the amount of the rise depending on the distance from the Green Bay city wells. In September 1960, water levels appeared to be affected more by local variations in the rates of pumping than by the recovery resulting from 1957 reduction in pumping. Much additional ground water could

Wisconsin↗
USGS2006

Hydrogeologic framework refinement, ground-water flow and storage, water-chemistry analyses, and water-budget components of the Yuma area, southwestern Arizona and southeastern California

The ground-water and surface-water system in the Yuma area in southwestern Arizona and southeastern California is managed intensely to meet water-delivery requirements of customers in the United States, to manage high ground-water levels in the valleys, and to maintain treaty-mandated water-quality and quantity requirements of Mexico. The following components in this report, which were identified to be useful in the development of a ground-water management model, are: (1) refinement of the hydrogeologic framework; (2) updated water-level maps, general ground-water flow patterns, and an estimate of the amount of ground water stored in the mound under Yuma Mesa; (3) review and documentation of the ground-water budget calculated by the Bureau of Reclamation, U.S. Department of the Interior (Reclamation); and (4) water-chemistry characterization to identify the spatial distribution of water quality, information on sources and ages of ground water, and information about the productive-interval depths of the aquifer. A refined three-dimensional digital hydrogeologic framework model includes the following hydrogeologic units from bottom to top: (1) the effective hydrologic basement of the basin aquifer, which includes the Pliocene Bouse Formation, Tertiary volcanic and sedimentary rocks, and pre-Tertiary metamorphic and plutonic rocks; (2) undifferentiated lower units to represent the Pliocene transition zone and wedge zone; (3) coarse-gravel unit; (4) lower, middle, and upper basin fill to represent the upper, fine-grained zone between the top of the coarse-gravel unit and the land surface; and (5) clay A and clay B. Data for the refined model includes digital elevation models, borehole lithology data, geophysical data, and structural data to represent the geometry of the hydrogeologic units. The top surface of the coarse-gravel unit, defined by using borehole and geophysical data, varies similarly to terraces resulting from the down cutting of the Colorado River. Clay A is nearly the same as the previous conceptual hydrogeologic model definition (Olmsted and others, 1973), except for a minor westward extension from the city of Yuma. Clay B is extended to the southerly international boundary and increased in areal extent by about two-thirds of the original extent (Olmsted and others, 1973). The other hydrogeologic units generally are the same as in the previous conceptual hydrogeologic model. Before development, the Colorado and Gila Rivers were the sources of nearly all the ground water in the Yuma area through direct infiltration of water from river channels and annual overbank flooding. After construction of upstream reservoirs and clearing and irrigation of the floodplains, the rivers now act as drains for the ground water. Ground-water levels in most of the Yuma area are higher now than they were in predevelopment time. A general gradient of ground-water flow toward the natural discharge area south of the Yuma area still exists, but many other changes in flow are evident. Ground water in Yuma Valley once flowed away from the Colorado River, but now has a component of flow towards the river and Mexicali Valley. A ground-water mound has formed under Yuma Mesa from long-term surface-water irrigation; about 600,000 to 800,000 acre-ft of water are stored in the mound. Ground-water withdrawals adjacent to the southerly international boundary have resulted in water-level declines in that area. The reviewed and documented water budget includes the following components: (1) recharge in irrigated areas, (2) evapotranspiration by irrigated crops and phreatophytes, (3) ground-water return flow to the Colorado River, and (4) ground-water withdrawals (including those in Mexicali Valley). Recharge components were calculated by subtracting the amount of water used by crops from the amount of water delivered. Evapotranspiration rates were calculated on the basis of established methods, thus were appropriate for input to the ground-water flow model developed by the Bureau of Reclamation (William Greer, hydrologist, Bureau of Reclamation, written commun., 2005). Evapotranspiration by crops and phreatophytes were calculated by using crop coefficient methods and meteorological data. Other methods of calculating evapotranspiration rates by using combinations of satellite imagery and ground-based data could be used for higher spatial and temporal resolution. Ground-water return flow during years of low flow on the Colorado River (1972–82, 1987–92, and 1994–96) averaged 79,000 acre-ft per year. Ground-water withdrawal data for 1970–99 were similar to other estimates made by the U.S. Geological Survey for the Yuma area. New water-chemistry data were collected in 12 wells and 8 canals/drains to characterize spatial patterns in chemical constituents, determine isotopic ages of water, infer possible sources of ground water, and locate the vertical intervals of the aquifer that contribute most water to wells. Depth-dependent samples were collected at one of the wells (YM-10). A large quantity of water-quality data were compiled from Bureau of Reclamation and U.S. Geological Survey records and merged into the U.S. Geological Survey National Water Information System database. New samples were analyzed for major ions, nutrients, stable isotopes of oxygen and hydrogen, tritium ( 3 H), and carbon-14 ( 14 C) (along with C 13 /C 12 ratios). Light values of oxygen-18 ( 18 O) and deuterium ( 2 H, D) in well 242-2 indicate recharge from the Colorado River. Heavy water samples from wells 242-22, CADC, and Mesa del Sol indicate local recharge sources. Tritium data indicate there is young water in wells in the valleys and near the edge of Yuma Mesa, while older water is found far from the Colorado River. 14 C data indicate that water from wells near the southerly international boundary is at least several thousand years old.

Arizona, California↗
USGS2004

Holocene reef accretion: southwest Molokai, Hawaii, U.S.A.

Two reef systems off south Molokai, Hale O Lono and Hikauhi (separated by only 10 km), show strong and fundamental differences in modern ecosystem structure and Holocene accretion history that reflect the influence of wave-induced near-bed shear stresses on reef development in Hawaii. Both sites are exposed to similar impacts from south, Kona, and trade-wind swell. However, the Hale O Lono site is exposed to north swell and the Hikuahi site is not. As a result, the reef at Hale O Lono records no late Holocene net accretion while the reef at Hikauhi records consistent and robust accretion over late Holocene time. Analysis and dating of 24 cores from Hale O Lono and Hikauhi reveal the presence of five major lithofacies that reflect paleo-environmental conditions. In order of decreasing depositional energy they are: (1) coral-algal bindstone; (2) mixed skeletal rudstone; (3) massive coral framestone; (4) unconsolidated floatstone; and (5) branching coral framestone-bafflestone. At Hale O Lono, 10 cores document a backstepping reef ranging from ∼ 8,100 cal yr BP (offshore) to ∼ 4,800 cal yr BP (nearshore). A depauperate community of modern coral diminishes shoreward and seaward of ∼ 15 m depth due to wave energy, disrupted recruitment activities, and physical abrasion. Evidence suggests a change from conditions conducive to accretion during the early Holocene to conditions detrimental to accretion in the late Holocene. Reef structure at Hikauhi, reconstructed from 14 cores, reveals a thick, rapidly accreting and young reef (maximum age ∼ 900 cal yr BP). Living coral cover on this reef increases seaward with distance from the reef crest but terminates at a depth of ∼ 20 m where the reef ends in a large sand field. The primary limitation on vertical reef growth is accommodation space under wave base, not recruitment activities or energy conditions. Interpretations of cored lithofacies suggest that modern reef growth on the southwest corner of Molokai, and by extension across Hawaii in general, is controlled by wave-induced near-bed shear stress related to refracted North Pacific swell. Holocene accretion patterns here also reflect the long-term influence of wave-induced near-bed shear stress from north swell during late Holocene time. This finding is consistent with other studies (e.g., Grigg 1998; Cabioch et al. 1999) that reflect the dominance of swell energy and sea level in controlling modern and late Holocene accretion elsewhere in Hawaii and across the Pacific and Indian oceans. Notably, however, this result is refined and clarified for Hawaii in the hypothesis of Rooney et al. (2003) stating that enhancement of the El Niño Southern Oscillation beginning approximately 5000 years ago led to increased north swell energy and signaled the end to net accretion along exposed coastlines in Hawaii. The exposure of Hale O Lono to north swell and the age of sea floor there (ca. 4,800 cal yr BP), coupled with the lack of north swell incidence at Hikauhi and the continuous accretion that has occurred there over the last millennium, strongly supports the ENSO reef hypothesis as outlined by Rooney et al. (2003). Other factors controlling Holocene reef accretion at the study site are relative sea-level position and rate of rise, and wave sheltering by Laau Point. Habitat suitable for reef accretion on the southwest shore of Molokai has shrunk throughout the Holocene.

Hawai'i↗
USGS1946

Geology and ground-water resources of the island of Hawaii

Hawaii, the largest island in the Hawaiian group, is 93 miles long, 76 miles wide, and covers 4,030 square miles. Mauna Loa Volcano is 13,680 feet high and Mauna Kea is 13,784 feet high. Plate 1 shows the geology, wells, springs, and water-development tunnels. Plate 2 is a map and description of points of geologic interest along the main highways. Plate 3 (same sheet as plate 2) shows highways and points of geologic interest in Hawaii National Park area. The volcanic terms used in the report are defined. Hawaii was built by five volcanoes. All the rocks are volcanic, except for minor amounts of sedimentary rock derived from them. Mauna Loa and Kilauea volcanoes erupt often; Hualalai Volcano last erupted in 1801; Mauna Kea has had Recent but no historic eruptions; Kohala Mountain has long been extinct. Kohala Mountain constitutes the northern end of the island. It is built largely of rocks of the Pololu volcanic series which are dominantly olivine basalt with a few thin intercalated beds of vitric basaltic ash. After the eruption of this series, Kohala Volcano was deeply eroded on the windward (northeastern) side, and a deep soil formed on its other slopes. Later, oligoclase andesite and trachyte lava flows, named the Hawi volcanic series, were erupted. They rest on soil at the top of the Pololu series, and lie in the valleys cut into the Pololu lavas on the windward slope. Both the Pololu and Hawi volcanics were erupted from three rift zones trending N. 35° W., S. 65° E., and S. 50° W. from the summit of the mountain. The rift zones are marked at the surface by rows or cinder cones, and beneath the surface by innumerable dikes. A caldera occupied the summit of the mountain at the beginning of the eruption of the Hawi lavas, and for a time confined the flows. It was gradually filled and the lava escaped northeastward into the large valleys. Some of the caldera faults can still be traced. A shallow graben indents the summit now. South of Kohala Mountain lies the much larger volcano of Mauna Kea. The early rocks of Mauna Kea constitute the Hamakua volcanic series. The lower member of this series consists chiefly of olivine basalt flows with intercalated thin beds of vitric basaltic ash. The olivine basalt of the lower member changes gradationally into the upper member, in which basalt and olivine basalt arc still abundant, but andesite also is present. Lavas of the upper member interfinger with Hawi lavas of Kohala Mountain. The Hamakua volcanic series is mantled with Pahala ash 5 to 20 feet thick, above which lie the rocks of the Laupahoehoe volcanic series. Locally the two series are separated by erosional unconformity, The Laupahoehoe lavas are dominantly andesite. The andesites erupted after the last glacial epoch are mapped separately on plate 1. The Laupahoehoe volcanic series, and probably also the Hamakua volcanic series, were erupted principally from three rift zones, trending west, northeast and south-southeast from the summit of the mountain. The upper slopes are studded with many large cinder cones, lying principally along the rift zones. Late in its geologic history, Mauna Kea was capped by a small glacier, presumably contemporaneous with the Wisconsin stage of glaciation in North America, which left conspicuous terminal, lateral, and ground moraines. Deposits exposed in canyons on the southern slope, formerly believed to be of glacial origin, are now believed to be volcanic explosion breccias. The main bulk of Hualalai Volcano is built of basalts of the Hualalai volcanic series. One flow of andesite has been found. The cinder and spatter cones lie principally along three rift zones which trend northwest, north, and southeast from the summit. On the northern slope of Hualalai Volcano lies the large trachyte pumice cone of Puu Waawaa, and its thick flow of trachyte. These are grouped together as the Waawaa volcanics. They are partly buried by later basalts from both Hualalai and Mauna Loa. The last eruption of Hualalai Volcano, in 1800–1801, produced olivine basalt. The earliest exposed rocks of Mauna Loa comprise the Ninole volcanic series. Several beds of altered vitric ash are intercalated with the lavas. Following eruption of the Ninole series, a long period or quiescence occurred, during which deep amphitheater-headed valleys were cut. This was followed by the eruption of the Kahuku volcanic series, consisting mostly of lavas with some thin beds of ash. The Rahuku series is overlain by the Pahala ash, which overlies also the Hilina volcanic series on Kilauea, the Hamakua volcanic series on Mauna Kea, and the Hawi volcanic series on Kohala, providing a rough datum for correlation of the lavas of the four mountains. Deposition of the Pahala ash was followed on Mauna Loa by eruption of the Kau volcanic series, which has continued until the present time. The historic and flaws of the Kau series are mapped separately on plate 1. The historic eruptions and volcanic activity of Mauna Loa are briefly described. The western and southern slopes of Mauna Loa are cut by normal faults along which the lower flanks of the mountain have slipped seaward. The Kau volcanic series and presumably also the Kahuku and Ninole volcanic series were erupted principally from vents along two rift zones which extend northeast and southwest from the summit caldera. The lavas of all three series are preponderantly olivine basalt. Many of the lavas contain small amounts of hypersthene. The Pahala ash on the northeastern and eastern slopes of Mauna Loa was derived largely from Mauna Kea. West and south of Kilauea Caldera, however, it was derived principally from Kilauea. Minor amounts were contributed by eruptions of Mauna Loa. It is a vitric basaltic ash, now generally altered to palagonite. The earliest exposed lavas and thin intercalated ash beds of Kilauea Volcano comprise the Hilina volcanic series. These are capped by the Pahala ash, which in turn, is overlain by the lavas and thin ash beds of the Puna volcanic series. The volcanics of both series were erupted along two rift zones, one extending southwestward from Kilauea Caldera, and the other extending southeastward for 5 miles and then bending sharply east by north. The lavas of both series are very largely olivine basalt. A few flows contain hypersthene. Augite phenocrysts are common in Mauna Loa lavas, but rare in those of Kilauea, indicating that crystallization has not progressed as far in the magma chamber of Kilauea Volcano as in that of Mauna Loa. Eruption of the Puna volcanic series has continued until the present time, the historic flows being separated from the prehistoric ones on plate 1. The historic eruptions and volcanic activity of Kilauea are briefly described. Kilauea Volcano originated on the southern slope of Mauna Loa where faults intersected the Eastern Fundamental Fissure of the Hawaiian Archipelago. The southern flank of Kilauea is cut by normal faults, along which the southern part is sliding seaward. The volcanoes of the island of Hawaii are believed to have started their activity in the Tertiary period. The great erosional period which followed deposition of the Pololu and Ninole volcanic series is placed near the end of the Pliocene. The Hilina and Hamakua volcanic series were probably erupted in the late Pliocene and earlier Pleistocene. The Hawi volcanic series and the Waawaa volcanics are probably early or middle Pleistocene in age. The main period of deposition of the Pahala ash was probably late in the middle Pleistocene or early in the upper Pleistocene. The Laupahoehoe volcanic series is late Pleistocene and Recent in age, most of the flows antedating the Wisconsin glaciation. The Hualalai volcanic series probably extends from Tertiary to historic time, and the Kau and Puna volcanic series from late Pleistocene to the present. A chapter is devoted to the petrography of the rocks in which are listed all reliable chemical rock analyses. The rocks of the island are highly permeable. Most of the rainfall sinks quickly into the ground. Perennial streams are present only on the windward slopes of Kohala Mountain and Mauna Kea. Most of the water sinks rapidly to the basal water table, where it floats on salt water according to the Ghyben-Herzberg principle. Basal water escapes in springs at or near sea level all along the coast. Only a very small proportion of it is recovered in wells. Along the windward coasts the basal water is of good quality and large supplies await development. Along the leeward coasts most of the basal water is brackish. In Kohala Mountain, much water is perched on ash beds in the Pololu volcanic series and on ash and soil at the base of the Hawi volcanic series. It escapes in perched springs in the big valleys and along the windward sea cliff and is recovered in tunnels. Along the windward slope of Mauna Keu, small amounts of water are perched by ash beds and dense lava flows in the Hamakua volcanic series. Small perched springs issue from these structures and water is recovered by tunnels. In the Kau District ash beds perch considerable water, which is recovered by many tunnels. On the southern slope of Mauna Kea small springs are perched by beds of hill wash. Dikes in the rift zones are relatively impermeable, but enclose masses of permeable rock. Water is confined at high level in the interdike compartments in Kohala Mountain, and probably in the other volcanoes. It escapes in high-level springs in the deep valleys on Kohala Mountain; some of it is recovered by tunnels. It is estimated that an average of about 13,085 million gallons of water a day falls as rain over the whole island. Of this only about 2.5 percent is visibly discharged from wells, tunnels, and springs. Large supplies of basal groundwater await development. Projects for development of additional water for the city of Hilo and the Kona District are described. Chemical analyses of water, water supplies of towns and villages, descriptions of wells, springs, and tunnels, and discharge records of numerous springs and tunnels are given in tabulated form.

Hawaii↗