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

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At least 145 records · Page 8Linked to original sources
USGS1999

Bathymetry of the Republic of the Marshall Islands and vicinity

The bathymetric map of the Republic of the Marshall Islands and vicinity is bounded by a window of latitude 3 to 17 degrees North, longitude 153 to 175 degrees East. The map was compiled from surveys conducted by the USGS, Korean Ocean Research and Development Institute, and published gridded data. In addition to national jurisdictions, island and atoll coastlines are indicated on the map.

Miscellaneous Field Studies Map↗
USGS2002

Map showing lava inundation zones for Mauna Loa, Hawai'i

The Island of Hawai‘i is composed of five coalesced basaltic volcanoes. Lava flows constitute the greatest volcanic hazard from these volcanoes. This report is concerned with lava flow hazards on Mauna Loa, the largest of the island shield volcanoes. Hilo lies 58 km from the summit of Mauna Loa, the Kona coast 33 km, and the southernmost point of the island 61 km. Hawaiian volcanoes erupt two morphologically distinct types of lava, aa and pahoehoe. The surfaces of pahoehoe flows are rather smooth and undulating. Pahoehoe flows are commonly fed by lava tubes, which are well insulated, lava-filled conduits contained within the flows. The surfaces of aa flows are extremely rough and composed of lava fragments. Aa flows usually form lava channels rather than lava tubes. In Hawai‘i, lava flows are known to reach distances of 50 km or more. The flows usually advance slowly enough that people can escape from their paths. Anything overwhelmed by a flow will be damaged or destroyed by burial, crushing, or ignition. Mauna Loa makes up 51 percent of the surface area of the Island of Hawai‘i. Geologic mapping shows that lava flows have covered more than 40 percent of the surface every 1,000 years. Since written descriptions of its activity began in A.D. 1832, Mauna Loa has erupted 33 times. Some eruptions begin with only brief seismic unrest, whereas others start several months to a year following increased seismic activity. Once underway, the eruptions can produce lava flows that reach the sea in less than 24 hours, severing roads and utilities. For example, the 1950 flows from the southwest rift zone reached the ocean in approximately three hours. The two longest flows of Mauna Loa are pahoehoe flows from the 50-kilometer-long 1859 and the 48-kilometer-long 1880-81 eruptions. Mauna Loa will undoubtedly erupt again. When it does, the first critical question that must be answered is: Which areas are threatened with inundation? Once the threatened areas are established, we can address the second critical question: What people, property, and facilities are at risk? These questions can be answered by estimating the areas most likely to be affected by eruptions originating on various parts of the volcano. This report contains such estimates, based on the known source vents and areas affected by past eruptions. We have divided the volcano into potential lava inundation zones and prepared maps of these zones, which are presented here on the accompanying map sheets.

Hawaii↗
USGS1972

Maps showing distribution of anomalous amounts of selected elements in stream-sediment and rock samples, Eagle quadrangle, Alaska

Maps showing the distribution of anomalous amounts of selected elements found in more than 1,600 stream-sediment and more than 1,500 rock samples have been prepared form results of semiquantitative spectrographic analyses. The samples were collected in the Eagle quadrangle, east-central Alaska, in the summers of 1968, 1969, 1970, and 1971. Figure 1 is a map showing localities for all stream-sediment samples analyzed and indicates by symbols those containing anomalous amounts of one or more of the following elements: gold (Au), silver (Ag), arsenic (As), bismuth (Bi), copper (Cu), chromium (Cr), molybdenum (Mo), nickel (Ni), lead (Pb), antimony (Sb), tin (Sn), tungsten (W), and zinc (Zn). Figure 2 shows the localities for analyzed rock samples and indicates those containing specified amounts of the same elements as selected from the stream-sediment samples. Maps similar to these which showed the distribution of anomalous amounts of selected elements in stream-sediment and rock samples from the Eagle quadrangle were compiled in 1971 and issued as a U.S. Geological Survey open-file report (Foster and Yount, 1971). The maps of this report are revised from the open-file maps to include the sampling in the summer of 1971.

Alaska↗