Buchanan-Banks, J.M., 1983, Reconnaissance map showing thicknesses of volcanic ash deposits in the greater Hilo area, Hawaii: U.S. Geological Survey Miscellaneous Field Studies Map MF-1499, scale 1:24,000.

Introduction

This study was undertaken to determine the thickness and distribution of volcanic ash deposits in the greater Hilo area, Hawaii, as a step toward evaluating their susceptibility to failure during earthquake shaking. On several occasions their instability has resulted in serious damage. For example, the 1868 earthquake (m=7+), following a prolonged rainy period, caused a debris flow of hillside ash deposits that killed 31 people in Wood Valley (Brigham, 1869). The 1973 Honomu earthquake (m=6.2) resulted in more damage from shaking to areas underlain by ash deposits in the older part of Hilo than in other areas, and soil slips in ash, as well as rockfalls, were common along the roads north of town (Nielsen and others, 1977).

Three geologic units are represented on the accompanying map the ash deposits, a clay bed that locally underlies the ash, and the bedrock material.

Reconnaissance geologic mapping of volcanic ash deposits in the greater Hilo area suggests a repetitive history of eruption, deposition, and severe weathering. Ash deposits believed to be erupted mainly from Mauna Kea Volcano are interbedded with and overlain by Mauna Loa lava flows in the study area.

The thickest deposit of ash observed is 6 m and occurs south of the Wailuku River. North of the Wailuku River, the ash thickness undoubtedly has been decreased by sugarcane harvesting procedures that mechanically remove some ash while loosening the surface of the remaining ash. This results in accelerated erosion during rainy periods as well as an increase in downslope movement of the disturbed material.

The ash deposits in the study area are classified as medium to very sensitive. Although slopes with these sensitivities are more likely to fail during earthquake shaking than slopes with slight sensitivity, the ash deposits in the map area show no evidence of large-scale slope failures. However, ash deposits with a sensitivity and water content similar to those in the Hilo area failed at Wood Valley during the 1868 earthquake, which occurred during a prolonged rainy period. The combination of a large magnitude earthquake, prolonged shaking, and saturated ash deposits apparently has not occurred in the Hilo area since the deposition of the ash some 24,000 years ago. Thus, although the sensitivity of the ash indicates a high possibility of failure during earthquake shaking, the probability of large-scale failure in the greater Hilo area does not appear high. On the other hand, numerous small soil slips in ash and rock falls have been documented as a result of earthquake shaking and during heavy rains. These failures occur where the deposits are steepest, as well as along road embankments and stream banks where the material is unsupported. Whether such failures occur on a small or a large scale, they can be financially and personally devastating to an individual. Damage to property and danger to people can be minimized by careful site selection and appropriate earthquake-resistant design of structures.

The clay bed that locally underlies the ash may also fail during heavy rains as well as during earthquake shaking. Owing to its greater impermeability and finer particle size, it may cause water to accumulate at the base of the overlying ash, increasing pore pressure and thereby reducing stability.

Buchanan-Banks, J.M., 1993, Geologic map of Hilo 7 1/2' Quadrangle, island of Hawaii: U.S. Geological Survey Miscellaneous Investigations Series Map I-2274, text 17 p., scale 1:24,000.

The Island of Hawaii has felt the effects of several kinds of geologic hazards during the past 150 yr, among them volcanic eruptions, earthquakes, floods, and tsunami inundations (U.S. Geological Survey, 1977; Mullineaux and others, 1987). As the population increases, so does the impact of such natural disasters. To understand the causes and reduce the effects of some of these hazards, geologic mapping in the populous area In and near the city of Hilo, the main cultural and political center on the island, was undertaken. The evaluation of earthquake-related hazards and geologic causes of flooding in and near Hilo was presented in previous publications (Buchanan-Banks, 1983, 1987; Lockwood and Buchanan-Banks, 1981; Buchanan-Banks and Lockwood, 1982). Tsunami inundations, although infrequent, pose a great risk to life and property. Damaging tsunamis often result from distant earthquakes, but tsunamis have also been generated by local geologic events (U.S. Geological Survey, 1931; Macdonald and others, 1947; Eaton and others, 1961; Tilling and others, 1976; Moore and others, 1989). Few tsunamis, however, have been documented as resulting from eruptions (Cox and Morgan, 1977).

This report details the sources of the eruptive deposits and the history of flow chronology within the Hilo 7 1/2' quadrangle and discusses the associated volcanic hazards. Mapping was done on vertical aerial photographs taken in 1965 and 1977. Artificial cover, dense vegetation, and (or) steep or hazardous topography hampered mapping in many areas. Artificial cover was a significant problem in the Keaau area where young flows are made arable by covering them with a rock and mud slurry. North of the Wailuku River, dense vegetation and precipitous banks interfered with data collection along many drainage channels. Similarly, bulldozed surfaces, lack of roads, and hazards posed by collapsed roofs of lava tubes concealed by dense vegetation hampered data collection in the eastern part of the quadrangle. Geologic contents in parts of the Piihonua and Mountain View quadrangles are added to the detailed geologic mapping of the Hilo quadrangle to permit plotting of sample localities that are pertinent to the geologic history of the Hilo quadrangle (see map note for specific information).

Chadwick, W.W., Jr., Smith, J.R., Jr., Moore, J.G., Clague, D.A., Garcia, M.O., and Fox, C.G., 1993, Bathymetry of south flank of Kilauea Volcano, Hawaii: U.S. Geological Survey Miscellaneous Field Studies Map MF-2231, scale 1:150,000.

"The great bulk of the Hawaiian volcanoes lies beneath the sea, and until recently only the most general picture of the surface configuration of this submarine realm has been available. Within the last two decades, with the advent of multibeam sonar and improved satellite navigation systems, it has been possible to greatly improve the capability for detailed bathymetric mapping. This is the first of a series of maps drawing together the most modem bathymetric data from the submarine flanks of the active volcanoes of Hawaii. The region depicted in this map is among the most volcanically and seismically active on earth (Stearns and Macdonald, 1946). The island's two largest earthquakes (1868, estimated mag. 8, and 1975, mag. 7.2) have occurred within this map area. The entire south coast of Kilauea volcano east of the southwest rift zone for a distance of 40 km subsided as much as 3.5 m at the time of the 1975 earthquake (Lipman and others, 1985).

Kilauea volcano has undergone about 50 volcanic eruptions since 1823 with the locus of eruptive vents occurring at the summit as well as along the east and southwest rift zones. Lava has repeatedly crossed the south shoreline of the volcano and flowed into the sea. In recent years volcanic activity in the middle reaches of the east rift zone has fed lava flows that crossed the shoreline. Large volumes of lava and its fragmented products have moved downslope, across the submarine terrain depicted in this map, to abyssal depths. This map was prepared with the expectation that an improved knowledge of the morphology of this important region should help in our understanding of the volcanic and tectonic processes that have shaped it in the past, and will modify it in the future."

Chadwick, W.W., Jr., Moore, J.G., Garcia, M.O., and Fox, C.G., 1993, Bathymetry of southern Mauna Loa Volcano, Hawaii: U. S. Geological Survey Miscellaneous Field Studies Map MF-2233, scale 1:150,000. [Prepared in cooperation with the National Oceanic and Atmospheric Administration Joint Office for Mapping and Research]

Mauna Loa, the largest volcano on Earth, lies largely beneath the sea, and until recently only generalized bathymetry of this giant volcano was available. However, within the last two decades, the development of multibeam sonar and the improvement of satellite navigation systems (Global Positioning System) have increased the availability of precise bathymetric mapping. This map combines topography of the subaerial southern part of the volcano with modern multibeam bathymetric data from the south submarine flank. The map includes the summit caldera of Mauna Loa Volcano and the entire length of the 100-km-long southwest rift zone that is marked by a much more pronounced ridge below sea level than above. The 60-km-long subaerial segment of the rift zone abruptly changes trend from southwest to south 30 km from the summit. It extends from this bend out to sea at the south cape of the island (Kalae) to 4 to 4.5 km depth where it impinges on the elongate west ridge of Apuupuu Seamount. The west submarine flank of the rift-zone ridge connects with the Kahuku fault on land and both are part of the amphitheater head of a major submarine landslide (Lipman and others, 1990; Moore and Clague, 1992). Two pre-Hawaiian volcanic seamounts in the map area, Apuupuu and Dana Seamounts, are apparently Cretaceous in age and are somewhat younger than the Cretaceous oceanic crust on which they are built.

Chase, T.E., Miller, C.P., Seekins, B.A., Normark, W.R., Gutmacher, C.E., Wilde, P., and Young, J.D., 1981, Topography of the southern Hawaiian Islands: U.S. Geological Survey Open-File Map 81-120, 3 map sheets, scale 1:250,000.

The purpose of this series is to give the user a working set of maps for planning purposes, plotting of additional data, or aid in locating geologic features.

Crandell, D.R., 1983, Potential hazards from future volcanic eruptions on the island of Maui, Hawaii: U.S. Geological Survey Miscellaneous Investigations Map I-1442, scale 1:100,000.

Haleakala volcano, which forms the eastern part of the island of Maui, has erupted many times during the last thousand years, and as recently as 1790. The volcano thus is believed to be only dormant and still capable of erupting again in the future. The geologic history of Haleakala began more than 840,000 years ago, and has been described by Stearns and Macdonald (1942) and summarized by Macdonald and Abbott (1970) and Macdonald (1978). This report considers only the eruptive history of the last few tens of thousands of years. Most eruptions during this period were of basalt lava flows from vents situated along or adjacent to a narrow zone that extends east-northeastward from La Perouse Bay through the crater of Haleakala, and thence eastward to Hana. Such a linear concentration of volcanic vents is referred to as a rift zone. For the purpose of this report, the rift zone on Maui is subdivided into the southwest rift zone, the crater, and the east rift zone. In addition, some flows were erupted outside the rift zone at vents now marked by cinder cones such as Pimoe and Puu Olai on the southwest side of the volcano.

West Maui also is a volcano, but one so old--1.15-1.32 million years (McDougall, 1964)--that, for purposes of land-use planning, it probably can safely be regarded as extinct. A few small lava flows on West Maui are substantially younger than the rest of the volcano (Stearns and Macdonald, 1942), but even these bear soils that suggest ages of more than 25,000 years.

Eakins, B.W., Robinson, J.E., Kanamatsu, T., Naka, J., Smith, J.R., Takahashi, E., and Clague, D.A., 2003, Hawaii's Volcanoes Revealed: U.S. Geological Survey Geologic Investigations Series I-2809 (available online).

The Japan Marine Science and Technology Center (JAMSTEC) funded and led a four-year collaborative survey of the underwater flanks of Hawaii's shield volcanoes. This exploration, involving scientists from the U.S. Geological Survey (USGS) and other Japanese and U.S. academic and research institutions, utilized manned and unmanned submersibles, rock dredges, and sediment piston cores to directly sample and visually observe the sea floor at specific sites. Ship-based sonar systems were used to more widely map the bathymetry from the sea surface.

The state-of-the-art multibeam sonar systems, mounted on the hull of GPS-navigated research vessels, convert the two-way travel times of individual sonar pings and their echoes into a line of bathymetry values across the ship track. The resulting swaths across the ocean bottom, obtained along numerous overlapping ship tracks, reveal the sea floor in stunning detail. The survey data collected by JAMSTEC form the basis for the bathymetry shown on the map, augmented with bathymetric data from other sources. Bathymetry that is predicted from variations in sea-surface height, observable from satellites, provides the low-resolution (fuzzy) bathymetry in between ship tracks. Subaerial topography is from a USGS 30-m digital elevation model of Hawaii. Historical lava flows are shown in red.

Flanigan, V.J., Long, C., Rohret, D., and Mohr, P., 1986, Aeromagnetic map of the rift systems of Kilauea and Mauna Loa Volcanoes, island of Hawaii, Hawaii: U.S. Geological Survey Miscellaneous Field Studies Map MF-1845-A, scale 1:100,000.

Total-field aeromagnetic data presented on this map were acquired in a low-level, VLF magnetic survey of the rift systems associated with Kilauea and Mauna Loa volcanoes on the island of Hawaii. The aeromagnetic map is characterized by normally polarized, linear dipole magnetic anomalies associated with presumed dikes emplaced along major rifts. The dikes are thought to comprise a composite of volcanic basalt rocks, particularly in the east rift of Kilauea, that have displaced the south flank of Kilauea Volcano. Circular dipole anomalies are associated with the major craters of Halemaumau, Kilauea, and Mokuaweoweo. These dipole anomalies are apparently reversely polarized and are thought to be related in part to topography. The reversely polarized magnetic dipole anomaly associated with Kapoho cone and crater has not been seriously affected by terrain-caused magnetic anomalies and is thought to be the magnetic expression of a non-magnetic magma body within a magnetic terrain.

Dike rocks associated with the east rift of Kilauea are inferred to be shallow compared to similar magnetic source rocks associated with the east rift of Mauna Loa. Northeast-southwest-trending geologic features are not expressed as clearly in the magnetic data as are the east-west-trending features; this difference in expression is thought to be a geometry problem, that is, the northeast-southwest-trending features are nearly parallel to the Earth's present magnetic field.

Flanigan, V.J., Long, C., Rohret, D., and Moir, P., 1986, Apparent resistivity map of the rift systems of Kilauea and Mauna Loa Volcanoes, island of Hawaii, Hawaii: U.S. Geological Survey Miscellaneous Field Studies Map MF1845-B, scale 1:100,000.

Apparent-resistivity maps presented here were computed from wave-tilt measurements of the horizontal electric-field quadrature component associated with the transmitted VLF radio wave operating at 18.6 kHz. Local perturbations of the electric field are chiefly related to the resistivity of the Earth at the observation site.

Apparent-resistivity lows are associated with the active part of the east rift of Kilauea Volcano and with areas of hydrothermal convection cells thought to be present, such as at Puulena Crater. An apparent-resistivity low extending southward from Puulena Crater indicates alteration of lavas by hot meteoric waters moving downslope, which are thought to be controlled by a fault transverse to the strike of the eruptive and non-eruptive features associated with the east rift of Kilauea Volcano. Two other apparent-resistivity lows are transverse to the east rift of Kilauea Volcano; the most notable is just east of Napau Crater and is thought to offset the active part of the rift zone to the north.

VLF magnetic anomalies are also associated with the active part of the rift zones and are generally caused by abrupt resistivity changes related to shallow or surficial volcanic features such as craters, cones, and cracks. This association is evident along the east rift of Kilauea Volcano and the southwest rift of Mauna Loa and to a lesser degree along the northeastern section of the east rift of Mauna Loa and the northeastern part of the southwest rift of Kilauea Volcano.

Apparent-resistivity lows and VLF magnetic anomalies are associated with the craters of Mauna Loa and Kilauea Volcanoes. Conductive rocks (less than 100 W•m) are thought to be due to the presence of a hydrothermal convection cell overlying the magma reservoir just southeast of Halemaumau Crater, within the Kilauea Crater area. Several conclusions are postulated from these data that require further study and additional evidence from other data sources: (1) Several northwest-trending faults intersect the east rift of Kilauea; one in the Puulena Crater area suggested by Zablocki (1977) is generally confirmed by conductive lavas thought to be associated with downslope movement of water heated by a deep heat source. A second possible transverse fault is inferred east of Napau Crater as evidenced by the apparent offset of the active part of the east rift from the interpreted south edge of the intrusive rift-zone dikes and by the presence of a conductive zone extending southeast. (2) If these northwest-trending conductive zones are indeed related to transverse faulting, then they might suggest differential south movement of the south flank of Kilauea Volcano, the greatest displacement occurring south of the summit. (3) Conductive lava flows and associated VLF magnetic anomalies over the summit craters of Kilauea and Mauna Loa Volcanoes suggest the presence of magmatic sources of volcanic activity although these sources were not detected directly.

Godson, R.H., Zablocki, C.J., Pierce, H.A., Frayser, J.B., Mitchell, C.M., and Sneddon, R.A., 1981, Aeromagnetic map of the island of Hawaii: U.S. Geological Survey Geophysical Investigations Map GP-946, scale 1:250,000.

Holcomb, R.T., 1976, Preliminary map showing products of eruptions, l962-l974 from the upper east rift zone of Kilauea Volcano, Hawaii: U.S. Geological Survey Miscellaneous Field Studies Map MF-811, scale 1:24,000.

"Between 1962 and 1974 lava erupted many times from various places on Kilauea's upper east rift zone. The eruptive episodes varied considerably in behavior, duration, and products and are the subjects of ongoing studies. included among them was the first well-observed long-duration flank eruption (1969-1974) in historic time, an eruption that seems particularly significant in understanding the history of Kilauea."

"This map is intended to serve as a guide to the area of recent eruptions, as a base map for current work, and as a possible model for further mapping of the prehistoric lava flows of Kilauea and volcanic regions elsewhere."

Jackson, E.D., and Clague, D.A., 1982, Distribution of the nodule beds of the 1800-1801 Kaupulehu flow on Hualalai Volcano, island of Hawaii: U.S. Geological Survey Miscellaneous Field Studies Map MF-1355, scale 1:1,200.

Hualalai Volcano on the Island of Hawaii last erupted in 1800-1801, at which time the voluminous Kaupulehu and smaller Huehue alkalic basalt flows issued from the northwest rift zone (fig. 1). The Kaupulehu flow is well known for the abundant xenoliths it contains. Richter and Murata (1961) described a locality at about 3100 ft on the northwest side of the volcano where the xenoliths were deposited in beds like lag gravel. A plane-table map of this locality, made by E. D. Jackson in 1965, was intended to supplement detailed data on the site, structure, mineral modes, and rock chemistry of the xenoliths (published only recently in Jackson and others, 1981) and on the chemistry of the 1800-1801 flow (Clague and others, 1981). Richter and Murata (1961) proposed that the rapidly flowing, extremely fluid lava lost velocity when it reached an area of reduced gradient, and the xenoliths were deposited in extensive beds. On the basis of the detailed map presented here, we suggest that the xenoliths were erupted from three discrete local vents (identified as N, North; C, Central; and S, South). Eruption at these vents brought the xenoliths to the surface, where they were quickly deposited near the vents.

Klein, F.W., and Koyanagi, R.Y., 1985, Earthquake map of south Hawaii, 1968-1981: U.S. Geological Survey Miscellaneous Investigations Series Map I-1611, scale 1:100,000.

Lindwall, D.A., 1988, A free-air gravity map of the Hawaiian Islands and adjacent areas of the Pacific Ocean: Geological Society of America Map and Chart Series Map MCH065, 4 map sheets, scale 2 inches per degree of longitude.

Lipman, P.W., and Swenson, A., 1984, Generalized geologic map of the southwest rift zone of Mauna Loa Volcano, Hawaii: U.S. Geological Survey Miscellaneous Investigations Series Map I-1323, scale 1:100,000.

Lockwood, J.P., Lipman, P.W., Petersen, and Warshauer, F.R., 1988, Generalized ages of surface lava flows of Mauna Loa Volcano, Hawaii: U.S. Geological Survey Miscellaneous Investigations Series Map I-1908, scale 1:250,000.

Mauna Loa, the largest active volcano on Earth, is a classic shield volcano, which rises to 13,680 ft above sea level on the island of Hawaii. The volcano is composed of numerous, relatively thin basalt lava flows, overlain in places by ash deposits derived from adjoining volcanoes. These flows were erupted from Mauna Loa's summit and from rift zones extending to the northeast and southwest, as well as from isolated radial fissures on the north and west flanks. Mauna Loa basalts are entirely of tholeiitic composition; olivine and plagioclase are the only common megascopically visible minerals. The highly generalized ages of these flows are shown on this 1:250,000-scale map, as well as the approximate distribution of aa and pahoehoe lavas.

This map is derived from a larger scale reconnaissance geologic map that was prepared for the quantitative evaluation of the Holocene eruptive history of Mauna Loa (Lockwood and Lipman, 1987). That map was compiled at a scale of 1:24,000 from unpublished geologic maps of the 47 U.S. Geological Survey 7 1/2-minute quadrangles that comprise the subaerial part of Mauna Loa. The mapping quality varied from relatively detailed along Mauna Loa's rift zones (see Lipman and Swenson, 1984, Lockwood, 1984) to aerial photographic interpretation with only limited field control, especially on the north and west flanks. In generalizing the 1:24,000 mapping at 1:250,000 scale, the flow patterns were greatly simplified, and contacts between individual lava flows of the same age group were eliminated.

Radiocarbon dating of charcoal recovered from beneath Mauna Loa lava flows was used for quantitative age assignments for prehistoric flows. More than 170 radiocarbon ages for Mauna Loa flows (Rubin and others, 1987) have been determined from samples recovered using the methods described by Lockwood and Lipman (1980). Flows which do not yet have absolute 14C ages were assigned to age categories based on weathering characteristics (Lipman, 1980, table 1) or stratigraphic position relative to dated flows.

Lockwood, M., Elms, J.D., Lockridge, P.A., Moore, G.W., Nishenko, S.P., Simkin, T., and Newhall, C., 1990, Natural hazards map of the circum-Pacific region: Pacific Basin sheet: U.S. Geological Survey Circum-Pacific Map Series Map CP-35, text 31 p., scale 1:17,000,000.

Luedke, R.G., and Smith, R.L., 1988, Map showing distribution, composition, and age of late cenozoic volcanic centers in Hawaii: U.S. Geological Survey Miscellaneous Investigations Series Map I-1901-G, scale l:100,000.

This map, inclusive of data through 1984, is the seventh and last of a series of maps showing the distribution, composition, and age of late Cenozoic volcanoes and volcanic rocks of the United States. Designed primarily as a guide for exploration and evaluation of igneous-related geothermal resources, this map series also should be useful as a base for evaluation of volcanic hazards, for studies of volcanology and volcano tectonics, and for studies of the general geology of volcanic rocks. Because few or no reliable data were available for many areas, this series of maps is, to a considerable degree, our interpretation of the general age and composition of the volcanic rocks. Thus, current gaps in the data may be located by the combined use of the data source and reliability diagrams (figs. I and 2).

In the earlier maps of this series (Luedke and Smith, 1978a, 1978b, 1981, 1982, 1983, 1986), the late Cenozoic was designated to extend from 16+/-1 Ma to the present. This time cutoff was chosen because, in the western conterminous United States, a widespread change in the state of volcanism (and tectonism) occurred at about that time. The same time interval on the earlier maps of the series has been retained for this map. We recognize that, geodynamically, this time frame has less meaning for Hawaii and Alaska than for the western conterminous United States. The principal islands of Hawaii were constructed mostly within the last five million years.

Within this late Cenozoic time interval, the ages of the volcanic rocks are arbitrarily divided into three periods: 0-5 Ma, 5-10 Ma, and 10-16+/-1 Ma. The time increment from the present to 1 Ma is further subdivided by use of colored vent symbols; vents older than 1 Ma are shown in black. All older K-Ar ages have been recalculated using the conversion tables of Dalrymple (1979) to conform with the recommended new set of decay and abundance constants.

Macdonald, G.A., 1971, Geologic map of the Mauna Loa Quadrangle, Hawaii: U.S. Geological Survey Geologic Quadrangle Map GQ-897, scale 1:24,000.

"The Mauna Loa quadrangle contains the summit of Mauna Loa Volcano (13,677 feet altitude) and its caldera, Mokuaweoweo. extending south-southwestward from the caldera is the upper end of the southwest rift zone of the volcano, along which lie three pit craters: South Pit, Lua Hohonu, and Lua Hou. At its northern end the caldera coalesces with another pit crater, North Pit, and just beyond is the upper end of the northeast rift zone Lua Poholo, east of the junction between North Pit and the caldera proper, is a pit crater formed by collapse, probably sometime in the period 1874-1885. East Bay, an indentation in the eastern side of the caldera 1.5 miles south of the northern edge of the quadrangle, also is a pit crater, probably formed since 1885. The cliffs bounding the caldera are slightly eroded fault scarps; the one on the western wide is 600 feet high at the highest point, but that on the east is only about 200 feet high. A line of fault scarps from less than a foot to 15 feet high extends southward from the eastern edge of North Pit and marks the eastern limit of slight subsidence of the mountain top. Macdonald, G.A., 1971, Kipuka Pakekake Quadrangle, Hawaii: U.S. Geological Survey Geologic Quadrangle Map GQ-957, scale 1:24,000.

Moore, J.G., and Peck, D.L., 1965, Bathymetric, topographic, and structural map of the south-central flank of Kilauea Volcano, Hawaii: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-456, scale 1:62,500. [(Land-based triangulation by S. Aramaki, S. Hiraga, W.T. Kinoshita, R.Y. Koyanagi, T. Miyazaki, R.T. Okamura, and D.L. Peck. Shipboard operations by Captain S. Ueda, H.L. Krivoy, and J.G. Moore. Position plotting by R.T. Okamura.)]

Land topography modified from U.S. Geological Survey Puna, Kilauea, and Paha quadrangles, 1:62,500 series. Ocean floor topography from echo-sounder traverses made in 1963 by Kagoshima Maru, whose position was fixed by transit readings from three land styations every 10 minutes. Water depths uncorrected for temp4erature, salinity, slope, or tide. Assumed sound velocity in water, 1,500 meters per second. (Land-based triangulation by S. Aramaki, S. Hiraga, W.T. Kinoshita, R.Y. Koyanagi, T. Miyazaki, R.T. Okamura, and D.L. Peck. Shipboard operations by Captain S. Ueda, H.L. Krivoy, and J.G. Moore. Position plotting by R.T. Okamura.)

Moore, J.G., 1971, Bathymetry and geology-east cape of the island of Hawaii: U.S. Geological Survey Miscellaneous Geologic Investigations Map MI-677, scale 1:62,500.

"The crest of the submerged part of the rift zone ridge is directly on line with the subaerial part of the east rift zone of Kilauea Volcano. Submarine hills on the crest of the ridge are believed to be constructional volcanic cones at vents, and deep-sea photography shows that they are mantled with coherent pillows and pillow fragments. The submarine cones, like the subaerial cones and fissures, occur in a zone about 2 km wide. This fact and the possible presence of grabens like that on the east cape probably account for the broad, rather flat top of the rift zone ridge.

The bathymetric map clearly shows a variation in roughness along the flanks of the rift zone ridge. The ocean bottom downslope from the subaerial part of the east cape is smooth compared with the flanks of the submarine part of the rift zone ridge farther east. Dredging and ocean-bottom photography have shown that the smooth, even slopes are mantled by angular glass sand and scoria produced by explosive disintegration of subaerial lava flows when the hot flows enter the sea. The irregular slopes of the summit and flanks of the submarine ridge to the east are mantled by pillow lavas, and both coherent and broken pillows are widely distributed. The origin of the many small lobes and benches on the flanks of the ridge is probably complex. Some could be the surfaces and toes or pillowed lava flows, others could be slump and slide lobes, and still others may be piles of pillows at vents fed by dikes extending outward from the core of the rift zone."

Moore, R.B., and Clague, D.A., 1991, Geologic map of Hualalai Volcano, Hawaii: U.S. Geological Survey Miscellaneous Investigations Series Map I-2213, 2 map sheets, scale 1:50,000.

Hualalai is a shield volcano that occupies the west-central part of the Island of Hawaii; it makes up most of the North Kona district. A cap of alkalic basaltic lava has completely buried the underlying shield of tholeiitic basalt. Hualalai rises to a height of 2,521 m (8,271 feet) above sea level, covers an area of about 751 km2 (about 290 mi2), and has a subaerial volume of about 600 km3 (about 144 mi3). Hualalai is bounded by Mauna Loa to the northeast, east, and south, and lavas of the two volcanoes are interbedded. Lavas of Hualalai are chiefly Holocene in age but include deposits that are latest Pleistocene.

Hualalai has three rift zones, recognized by prominent cinder and spatter cones, that strike northwest, north, and south-southeast from a point about 5 km east of its summit. The subaerial part of the clearly defined northwestern rift zone, 2 - 4 km wide, is 24 km long; bathymetry suggests that it may continue another 70 km offshore. The poorly defined northern rift zone, about 10 km long and 5 km wide, contains less than 5 percent of Hualalai's vents and has been inactive during the past 2,000 years. The south-southeast-trending rift zone, 3 - 5 km wide, is about 13 km long. In marked contrast to the dominant alkalic basalt of Hualalai, a trachyte cone, Puu Waawaa, and an associated trachyte flow at Puu Anahulu, crop out on its northern flank. On the basis of K-Ar dating, these are the oldest rocks exposed on the volcano.

Moore, R.B., and Trusdell, F.A., 1991, Geologic map of the lower east rift zone of Kilauea Volcano, Hawaii: U.S. Geological Survey Miscellaneous Investigations Series Map I-2225, scale 1:24,000.

"Kilauea is an active shield volcano in the southeastern part of the Island of Hawaii (see index map). Its lower east rift zone (LERZ) forms the easternmost part of the island and extends about 70 km offshore as the submarine Puna Ridge (Fornari, 1987). Lava flows erupted during 1983 - 90 have reached as close as about 1 km from the map area. The map includes about 300 km2 of the LERZ and shows the distribution of the products of 112 separate eruptions during late Holocene time."

Neal, C.A. and Lockwood, J.P., 2003, Geologic map of the summit region of Kilauea Volcano, Hawaii: U.S. Geological Survey Geologic Investigations Series I-2759, scale 1:24,000 (available online).

Description

The area covered by this map includes parts of four U.S. Geological Survey 7.5' topographic quadrangles (Kilauea Crater, Volcano, Ka`u Desert, and Makaopuhi). It encompasses the summit, upper rift zones, and Koa`e Fault System of Kilauea Volcano and a part of the adjacent, southeast flank of Mauna Loa Volcano.

The map is dominated by products of eruptions from Kilauea Volcano, the southernmost of the five volcanoes on the Island of Hawaii and one of the world's most active volcanoes. At its summit (1,243 m) is Kilauea Crater, a 3 km-by5 km collapse caldera that formed, possibly over several centuries, between about 200 and 500 years ago. Radiating away from the summit caldera are two linear zones of intrusion and eruption, the east and southwest rift zones. Repeated subaerial eruptions from the summit and rift zones have built a gently sloping, elongate shield volcano approximately 1,500 square kilometers. Much of the volcano lies under water; the east rift zone extends 110 km from the summit to a depth of more than 5,000 m below sea level; whereas the southwest rift zone has a more limited submarine continuation. South of the summit caldera, mostly north-facing normal faults and open fractures of the Koa`e Fault System is interpreted as a tear-away structure that accomodates southward movement of Kilauea's flank in response to distension of the volcano perpendicular to the rift zones. Farther to the south and outside the map area, the large normal fault scarps of the Hilina Pali are structures related to the seaward subsidence of Kilauea's mobile south flank.

The map illustrates a succession of young basaltic lava flows erupted from Kilauea and Mauna Loa Volcanoes, as well as pyroclastic deposits erupted from Kilauea. No interfingering of Mauna Loa and Kilauea flows is known in this area, although interleaving of flows is seen outside the map area and should be common at depth in the border region between the two volcanoes.

Normark, W.R., Lipman, P.W., Lockwood, J.P., and Moore, J.G., 1978, Bathymetric and geologic maps of Kealakekua Bay, Hawaii: U.S. Geological Survey Miscellaneous Field Studies Map MF-986, scale 1:250,000.

"Kealakekua Bay is shaped largely by the Kealakekua fault, a major arcuate normal fault along which part of the seaward flank of Mauna Loa volcano has been downdropped (fig. 3). The on-land fault scarp has topographic relief greater than 250 m, even though it is extensively draped by prehistoric (pre-19th century) lava flows from Mauna Loa. A young lava delta from one of these flows built Cook Point (fig. 2), where Captain James Cook first landed in 1778. In 1951, a major earthquake (M = 6.1), accompanied by a local tsunami, had its epicenter on the seaward end of the fault, although there was no known surface rupture. Aftershock epicenters were distributed along the curving landward extension for a distance of about 25 km. The overall seismic-tectonic pattern demonstrates south-side-down normal faulting (Macdonald and Wentworth, 1954). A submarine eruption occurred offshore in the mapped area on February 24, 1877 (Anonymous, 1877) (fig. 3) This eruption reportedly occurred along a west-northwest-trending line extending out 1.7 km from Palemano Point, and no active fissure vents or lava appeared on land. The submarine activity was manifested by boiling water, a strong sulfurous odor, appearance of incandescent scoriaceous basalt blocks at the sea surface, and fish kills."

Peterson, D.W., 1967, Geologic map of the Kilauea Crater Quadrangle, Hawaii: U.S. Geological Survey Geologic Quadrangle Map GQ-667, scale 1:24,000.

"The southeastern part of the Kilauea Crater quadrangle contains the summit area of Kilauea Volcano, which consists of the summit caldera and the upper part of the broad volcanic dome or shield. The northern and western part of the quadrangle contains part of the eastern flank of Mauna Loa Volcano. Lava flows from the two volcanoes interfinger with each other in the broad, shallow, southwestward-trending trough that lies between them."

Peterson, D.W., 1979, Geologic map of the Kilauea Crater Quadrangle, Hawaii: U.S. Geological Survey Geologic Quadrangle Map Series GQ-667, scale 1:24,000.

"The southeastern part of the Kilauea Crater quadrangle contains the summit area of Kilauea Volcano, which consists of the summit caldera and the upper part of the broad volcanic dome or shield. The northern and western part of the quadrangle contains part of the eastern flank of Mauna Loa Volcano. Lava flows from the two volcanoes interfinger with each other in the broad, shallow, southwestward-trending trough that lies between them."

"All the lava within the quadrangle is basaltic in composition. The matrix is dark gray to black and consists of microscopic crystals of plagioclase, pyroxene, olivine, magnetite, and ilmenite; some quickly chilled rocks have a glassy matrix. Olivine phenocrysts are present in most lavas, but volume percent of megascopic olivine varies widely. Most rocks contain from about 1 to 10 percent olivine phenocrysts that average 1/4 to 2 mm in diameter. A few of the map units contain as much as 30 percent olivine crystals that reach 10 mm across. In other rocks olivine of megascopic size is absent. Small plagioclase laths that reach about 1 mm in length are discernible in some rocks. Other phenocrysts are rare."

Porter, S.C., 1979, Geologic map of Mauna Kea Volcano, Hawaii: The Geological Society of America Map and Chart Series MC-30, text 4 p., scale 1:24,000. ["A detailed discussion of stratigrapnic units shown on this map is given in Quaternary stratigraphy and chronology of Mauna Kea, Hawaii: a 380,000-yr record of mid-Pacific volcanism and ice cap glaciation: summary' in Geological Society of America Bulletin, Pt. 1, v. 90, p. 609-611; pt. 2, v. 90, p. 980-1093, July 1979."]

Mauna Kea (4,206 m), the highest of the five volcanoes that form the island of Hawaii. is the only Hawaiian volcano known to possess a record of Pleistocene glaciation. The interstratification of glacial sediments with volcanic rocks on the upper slopes of the mountain makes it possible to subdivide the volcanic pile into mappable rock-stratigraphic units. On the basis of their gross lithologic characteristics, these units fan into two major groups. The glacial and volcanic rocks of the younger group have been further subdivided into time-stratigraphic units that are controlled by 14C and K-Ar dates. The volcanic and glacial stratigraphy and the Chronology, Which have been discussed in detail elsewhere (Porter, 1972a, 1972b, 1973a, 1973b, 1979a, 1979b, 1979c; Porter and others, 1977), are summarized below and in Figure 1. Lava flows of Mauna Loa volcano that are included within the map area were assigned to the prehistoric and historic members of the Kau volcanic series by Stearns and Macdonald (1946), but these rocks were not part of this study, except for mapping their distribution and relative-age relationships.

Saint Ours, P., de, 1982, Structural map of the summit area of Kilauea Volcano, Hawaii: U.S. Geological Survey Miscellaneous Field Studies Map MF-1368, scale l:24,000.

This structural map is intended to serve as a base for current and future scientific investigations of the summit area of Kilauea and as a complement to earlier geologic maps (Peterson, 1967; Walker, 1969) and studies on the summit caldera (Macdonald, 1965), the upper parts of both rift zones (Moore and Krivoy, 1964; Stearns and Calark, 1930) and the Koae fault system (Duffield, 1975).

This map also identifies areas of ground fractures that are potentially hazardous to hikers, and areas of potential landslides and fault offsets that are closely related to the fracture system.

Simkin, T., Unger, J.D., Tilling, R.I., Vogt, P.R., and Spall, H., 1994, This dynamic planet: world map of volcanoes, earthquakes, impact craters, and plate tectonics: U.S. Geological Survey map, scale 1:30,000,000. [Prepared in cooperation with the Smithsonian Institution; revised from original map published in 1989]

Volcanic eruptions and earthquakes are awe-inspiring displays of the powerful forces of nature and can be extraordinarily destructive. Some societies have been devastated by them. About 60 of the Earth's 550 historically-active volcanoes are in eruption each year, but far more volcanism takes place unobserved on the ocean floor. Steady earth movements often culminate in rock fractures that produce earthquakes. In 1992 alone, 85 earthquakes worldwide exceeded magnitude 6.5 on the Richter scale, and many of them caused extensive damage.

The world's earthquakes and volcanoes are not randomly scattered over the Earth's surface. Most of them are concentrated along the edges of certain continents (for example, the western margins of the Americas), along island chains (for example, Japan and the Aleutians), or along oceanic ridge crests (for example, the Mid-Atlantic Ridge). Although geologists have long known this, it is only in the past 30 years that a concept has emerged to satisfactorily link these observations. The concept, called plate tectonics, is now widely accepted and has revolutionized the earth sciences.

Earth is a dynamic planet. Its outermost shell (the lithosphere) is a mosaic of a dozen or so large, rigid slabs of rock (called lithospheric or tectonic plates) that move relative to one another at speeds measured in centimeters per year--or about the same rate as our fingernails grow. The plates average about 80 kilometers (km) thick and are composed of the Earth's relatively thin surface rind (the crust) and the topmost 60-75 km of its 2,900-km-thick mantle. The lithosphere is generally thicker under the continents than under the oceans.

The plates move very slowly on top of a flowing layer of hotter, softer mantle (the asthenosphere) several hundred kilometers thick. Plate movement represents the top of a large-scale circulation system (convection), driven by Earth's escaping heat, that extends deep into the mantle. Mantle flow can be imagined as the sluggish movement in a pot of thick soup boiling on a stove, and this movement transports the plates horizontally on the surface. Where the plates grind against each other, stress builds up and is relieved intermittently through earthquakes when rocks break along faults. Near plate boundaries, molten rock (magma) rises to the surface from as deep as tens of kilometers and erupts to form volcanoes.

The geologic processes associated with plate movements are concentrated in the narrow boundary zones between the shifting plates. This explains why most of our restless planet's earthquakes and volcanoes are found along or near plate boundaries. Nevertheless, some very active volcanic areas and large earthquakes also occur in the plate interiors.

Smoot, N.C., 1983, Detailed bathymetry of guyot summits in the North Pacific by multi-beam sonar: Surveying and Mapping, v. 43, p. 53-60.

The flat-topped seamount, or guyot, was recognized as a seafloor feature by Hess in the 1940's because sonar had progressed enough to begin delineating topography. Various studies were undertaken to pinpoint an exact guyot definition. A recapitulation of surveying hardware shows why this was inadequate. U.S. Naval Oceanographic Office surveys employing a multi-beam swath mapping system have covered most of the North Pacific guyots, and the bathymetric tops of six of the guyots are presented at a 10 m contour interval. These are used to show some fallacies in both the historical definition as well as some of the survey procedures. Alternatives are presented to correct these misconceptions.

Smoot, N.C., Delaine, K., and Gregory, R.L., 1985, A 3-D model of Nintoku Guyot to predict paleo-island morphology: Bulletin of the American Congress on Surveying and Mapping, v. 97, p. 23-27.

Based on a statement about eroded tops (Smoot, 1983 and lower flank slope angles, a comparison was made between a guyot and a still forming seamount. From this what the eroded island of Nintoku would have looked like many millions of years ago using Hawaii Island as a control was extrapolated. It was also demonstrated that a guyot has a lower flank slope angle, especially away from the prevailing current, than a seamount that is just reaching its peak.

Finally, it should be noted that Hawaii displays a different subaerial slope than the subaqueous portion, the upper slope being 13% and the submerged slope 20%. Partial buoyancy by water (Vogt, 1974) might explain this fact. In any case, it is clearly illustrated (Fig. 2).

Nintoku Island then would have had an elevation of 11,000 ft. above sea level at 58myBP (age interpolation from Dalyrmple et al., 1981). The extra 2400 ft. (400fm) is from the removal of isostatic compensation, that value having been derived from a comparison of moat depths around Nintoku and Hawaii. Nintoku Island is hypothesized in Figure 9.

Walker, G.W., 1969, Kau Desert Quadrangle, Hawaii: U.S. Geological Survey Geologic Quadrangle Map GQ-827, scale 1:24,000.

"The Kau Desert quadrangle is located mostly on the southern flanks of Kilauea Volcano, with only the northwest corner reaching a small section on the flank of Mauna Loa Volcano. Both volcanoes are typical basaltic shields built of countless thin flows of basalt and minor amounts of interstratified fragmental basaltic debris. A few of the lava flows erupted from identifiable vents - such as Puu Koae, Cone Crater, Mauna Iki, and the Kamakaia Hills - along fissure zones on the southwest flank of Kilauea; most of the lava flows are from summit caldera overflows or from now-buried vents on the southwest rift zone north of the mapped area. Most flows are about a meter thick, locally up to about 12 meters thick, and are dense, commonly with scoriaceous or fragmental zones at top and bottom."

Walker, G.W., 1977, Geologic map of the Kau Desert Quadrangle, Hawaii: U.S. Geological Survey Geologic Quadrangle Map Series GQ-827, scale 1:24,000.

Watts, A.B., and Talwani, M., 1975, Gravity field of the northwest Pacific Ocean basin and its margin: Hawaii and vicinity: Geological Society of America Map and Chart Series MC-9, text 6 p., scale 1:3,937,000.

A total of 14,425 surface-ship and pendulum gravity measurements have been combined with land measurements in a new free air gravity anomaly map of the Hawaiian Islands and adjacent sea areas. The maps been contoured at 25-mgal intervals, and gravity anomaly values have been annotated at maxima and minima between contours. Defined on this map is a narrow belt (about 120 to 180 km wide) of large-amplitude positive anomalies (as much as +700 mgal) associated with the Hawaiian ridge, a narrow belt (about 120 to 180 km) of large-amplitude- negative anomalies (as much as -136 Mgal) that flank the ridge, and a broad belt (about 200 to 300 km) of positive anomalies (as much as 25 mgal) that border the negative anomalies. We discuss here the significance of these belts of positive and negative anomalies, which extend for distances of as much as 1,000 km across the map area, and their correlation with features of sea-floor topography.

Wolfe, E.W., and Morris, J., compilers, 1996, Sample data for the geologic map of the island of Hawaii: U.S. Geological Survey Miscellaneous Investigations Series Map I-2524-B, text 51 p., 3 map sheets, scale 1:100,000.

These maps and tables give locations, results, and documentary data for 1,783 analyzed rocks (table 1) and 242 radiocarbon ages (table 2). These data support the Geologic Map of the Island of Hawaii (Map 1-2524-A), which provides descriptions of all map units and geologic context for the samples. Most samples were collected during the course of the geologic mapping, and all were related to specific geologic map units. Sample data are also available on diskette as U.S. Geological Survey Open-File Report OF 96-0504.

Samples are listed by 7 1/2 minute topographic quadrangle, and each quadrangle is represented by a two-letter code (fig. 1). Within each quadrangle, analyzed rock samples are numbered in sequence from south to north, beginning with 1 (for example, BO-1). Gaps in numbering represent analyzed samples that were culled from the set either because of poor quality, indicated by excessive analyzed H2O or loss on ignition, or redundancy.

Some radiocarbon ages are irreconcilable with well established stratigraphic constraints and have been omitted from the data set. Such ages are generally too young and are commonly determined for charcoal collected at the bases of aa flows. Repeated experience indicates that charcoal fragments (for example, from forest fires long after a lava flow was emplaced) readily sift through and contaminate any charcoal that might have been preserved when the flow was emplaced.

Wolfe, E.W., and Morris, J., compilers, 1996, Geologic map of the island of Hawaii: U.S. Geological Survey Miscellaneous Investigations Series Map I-2524-A, text 18 p., 3 map sheets, scale 1:100,000.

This is the first map of the entire Island of Hawaii to show in detail the age and distribution of both prehistoric and historic lavas. Its chronologic detail reflects the application of isotopic-dating techniques that were unavailable when its predecessor, the classic geologic map of Stearns and Macdonald (1946), was prepared. The recent geologic mapping has greatly refined our understanding of the geology and evolution of the Island of Hawaii. Nevertheless, the major elements of the stratigraphy and distribution of rock units established by Stearns and Macdonald still largely stand, testifying to the extraordinary geologic insight and mapping skill of those pioneering Hawaiian geologists. Others made important geologic mapping contributions in the 1960's and 1970's. Geologic maps were published for the Kilauea Crater quadrangle (Peterson, 1967), Kau Desert quadrangle (Walker, 1967), Mauna Loa quadrangle (Macdonald, 1971), middle part of the east rift zone of Kilauea (Moore and Koyanagi, 1969), and upper flanks and summit of Mauna Kea (Porter, 1979a); theses that include geologic mapping were completed for the Kawaihae quadrangle (Malinowski, 1977) and the northwestern part of Kohala (Giza, 1979). Our current work rests upon the solid geologic foundation laid by all of these previous workers.

Wright, T.L., Chu, J.Y., Esposo, J., Heliker, C., Hodge, J., Lockwood, J.P., and Vogt, S.M., 1992, Map showing lava-flow hazard zones, island of Hawaii: U.S. Geological Survey Miscellaneous Field Studies Map MF-2193, text 1 p., scale 1:250,000.

This map shows lava-flow hazard zones for the five volcanoes on the Island of Hawaii. Volcano boundaries are shown as heavy, dark bands, reflecting the overlapping of lava flows from adjacent volcanoes along their common boundary. Hazard-zone boundaries are drawn as double lines because of the geologic uncertainty in their placement. Most boundaries are gradational, and the change in the degree of hazard can be found over a distance of a mile or more. The general principles used to place hazard-zone boundaries are discussed by Mullineaux and others (1987) and Heliker (1990). The differences between the boundaries presented here and in Heliker (1990) reflect new data used in the compilation of a geologic map for the Island of Hawaii (E.W. Wolfe and Jean Morris, unpub. data, 1989).

The primary source of information for volcano boundaries and generalized ages of lava flows for all five volcanoes on the Island of Hawaii is the geologic map of Hawaii (E.W. Wolfe and Jean Morris, unpub. data, 1989). More detailed information is available for the three active volcanoes. For Hualalai, see Moore and others (1987) and Moore and Clague (1991); for Mauna Loa, see Lockwood and Lipman (1987); and for Kilauea, see Holcomb (1987) and Moore and Trusdell (1991).