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F. A. Trusdell

Publications and source records attributed to F. A. Trusdell.

11 recordsLinked to original sources
USGS2006

Submarine radial vents on Mauna Loa Volcano, Hawai'i

A 2002 multibeam sonar survey of Mauna Loa's western flank revealed ten submarine radial vents and three submarine lava flows. Only one submarine radial vent was known previously. The ages of these vents are constrained by eyewitness accounts, geologic relationships, Mn-Fe coatings, and geochemical stratigraphy; they range from 128 years B.P. to possibly 47 ka. Eight of the radial vents produced degassed lavas despite eruption in water depths sufficient to inhibit sulfur degassing. These vents formed truncated cones and short lava flows. Two vents produced undegassed lavas that created “irregular” cones and longer lava flows. Compositionally and isotopically, the submarine radial vent lavas are typical of Mauna Loa lavas, except two cones that erupted alkalic lavas. He-Sr isotopes for the radial vent lavas follow Mauna Loa's evolutionary trend. The compositional and isotopic heterogeneity of these lavas indicates most had distinct parental magmas. Bathymetry and acoustic backscatter results, along with photography and sampling during four JASON2 dives, are used to produce a detailed geologic map to evaluate Mauna Loa's submarine geologic history. The new map shows that the 1877 submarine eruption was much larger than previously thought, resulting in a 10% increase for recent volcanism. Furthermore, although alkalic lavas were found at two radial vents, there is no systematic increase in alkalinity among these or other Mauna Loa lavas as expected for a dying volcano. These results refute an interpretation that Mauna Loa's volcanism is waning. The submarine radial vents and flows cover 29 km 2 of seafloor and comprise a total volume of ∼2×10 9 m 3 of lava, reinforcing the idea that submarine lava eruptions are important in the growth of oceanic island volcanoes even after they emerged above sea level.

Hawai'i↗
USGS2005

The 2003 phreatomagmatic eruptions of Anatahan volcano - Textural and petrologic features of deposits at an emergent island volcano

Stratigraphic and field data are used in conjunction with textural and chemical evidence (including data from scanning electron microscope, electron microprobe, X-ray fluorescence, X-ray diffraction, and instrumental neutron activation analysis) to establish that the 2003 eruption of Anatahan volcano was mainly phreatomagmatic, dominated by explosive interaction of homogeneous composition low-viscosity crystal-poor andesite magma with water. The hydromagmatic mode of eruption contributed to the significant height of initial eruptive columns and to the excavation and eruption of altered rock debris from the sub-volcanic hydrothermal system. Volatile contents of glass inclusions in equilibrium phenocrysts less abundances of these constituents in matrix glass times the estimated mass of juvenile magma indicate minimum emissions of 19 kt SO2 and 13 kt Cl. This petrologic estimate of SO2 emission is an order-of-magnitude less than an estimate from TOMS. Similarly, inferred magma volumes from the petrologic data are an order of magnitude greater than those modeled from deformation data. Both discrepancies indicate additional sources of volatiles, likely derived from a separate fluid phase in the magma. The paucity of near-source volcanic-tectonic earthquakes preceding the eruption, and the dominance of sustained long-period tremor are attributed to the ease of ascent of the hot low-viscosity andesite, followed by a shallow phreatomagmatic mode of eruption. Phreatomagmatic eruptions are probably more common at emergent tropical island volcanoes, where shallow fresh-water lenses occur at near-sea-level vents. These relations suggest that phreatomagmatic explosions contributed to the formation of many of the near-sea-level craters and possibly even to the small calderas at the other Mariana islands.

Northern Mariana Islands↗
USGS2003

Kilauea east rift zone magmatism: An episode 54 perspective

On January 29 30, 1997, prolonged steady-state effusion of lava from Pu'u'O'o was briefly disrupted by shallow extension beneath Napau Crater, 1 4 km uprift of the active Kilauea vent. A 23-h-long eruption ( episode 54 ) ensued from fissures that were overlapping or en echelon with eruptive fissures formed during episode 1 in 1983 and those of earlier rift zone eruptions in 1963 and 1968. Combined geophysical and petrologic data for the 1994 1999 eruptive interval, including episode 54 , reveal a variety of shallow magmatic conditions that persist in association with prolonged rift zone eruption. Near-vent lava samples document a significant range in composition, temperature and crystallinity of pre-eruptive magma. As supported by phenocryst liquid relations and Kilauea mineral thermometers established herein, the rift zone extension that led to episode 54 resulted in mixture of near-cotectic magma with discrete magma bodies cooled to ≤1100°C. Mixing models indicate that magmas isolated beneath Napau Crater since 1963 and 1968 constituted 32 65% of the hybrid mixtures erupted during episode 54 . Geophysical measurements support passive displacement of open-system magma along the active east rift conduit into closed-system rift -reservoirs along a shallow zone of extension. Geophysical and petrologic data for early episode 55 document the gradual flushing of episode 54 related magma during magmatic recharge of the edifice.

Hawaii↗
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↗
USGS1998

The probability of lava inundation at the proposed and existing Kulani prison sites

The State of Hawai`i has proposed building a 2,300-bed medium-security prison about 10 km downslope from the existing Kulani medium-security correctional facility. The proposed and existing facilities lie on the northeast rift zone of Mauna Loa, which last erupted in 1984 in this same general area. We use the best available geologic mapping and dating with GIS software to estimate the average recurrence interval between lava flows that inundate these sites. Three different methods are used to adjust the number of flows exposed at the surface for those flows that are buried to allow a better representation of the recurrence interval. Probabilities are then computed, based on these recurrence intervals, assuming that the data match a Poisson distribution. The probability of lava inundation for the existing prison site is estimated to be 11- 12% in the next 50 years. The probability of lava inundation for the proposed sites B and C are 2- 3% and 1-2%, respectively, in the same period. The probabilities are based on estimated recurrence intervals for lava flows, which are approximately proportional to the area considered. The probability of having to evacuate the prison is certainly higher than the probability of lava entering the site. Maximum warning times between eruption and lava inundation of a site are estimated to be 24 hours for the existing prison site and 72 hours for proposed sites B and C. Evacuation plans should take these times into consideration.

Open-File Report↗
USGS1993

Geology of kilauea volcano

This paper summarizes studies of the structure, stratigraphy, petrology, drill holes, eruption frequency, and volcanic and seismic hazards of Kilauea volcano. All the volcano is discussed, but the focus is on its lower cast rift zone (LERZ) because active exploration for geothermal energy is concentrated in that area. Kilauea probably has several separate hydrothermal-convection systems that develop in response to the dynamic behavior of the volcano and the influx of abundant meteoric water. Important features of some of these hydrothermal-convection systems are known through studies of surface geology and drill holes. Observations of eruptions during the past two centuries, detailed geologic mapping, radiocarbon dating, and paleomagnetic secular-variation studies indicate that Kilauea has erupted frequently from its summit and two radial rift zones during Quaternary time. Petrologic studies have established that Kilauea erupts only tholeiitic basalt. Extensive ash deposits at Kilauea's summit and on its LERZ record locally violent, but temporary, disruptions of local hydrothermal-convection systems during the interaction of water or steam with magma. Recent drill holes on the LERZ provide data on the temperatures of the hydrothermal-convection systems, intensity of dike intrusion, porosity and permeability, and an increasing amount of hydrothermal alteration with depth. The prehistoric and historic record of volcanic and seismic activity indicates that magma will continue to be supplied to deep and shallow reservoirs beneath Kilauea's summit and rift zones and that the volcano will be affected by eruptions and earthquakes for many thousands of years. ?? 1993.

Geothermics↗
USGS1993

Preliminary results from an isotope hydrology study of the Kilauea Volcano area, Hawaii

Deuterium (D) content of groundwater and precipitation, and tritium content of selected groundwater samples are used to infer flowpaths for groundwater in the Kilauea Volcano area. The spatial distribution of calculated recharge elevations and residence times for groundwater samples tends to support the idea that Kilauea's rift zones comprise leaky boundaries within the regional groundwater flow system, partly isolating the groundwater in the area bounded by the rift zones and the Pacific Ocean. The southwest rift zone also appears to act as a conduit for groundwater recharged at relatively high elevation. The relation between precipitation ??D values and elevation differs between areas receiving frequent rainfall and areas where most rainfall occurs during storm events.

Conference Paper↗
USGS1991

Volcanologic investigations in the Commonwealth of the Northern Mariana Islands, September-October 1990

U.S. Geological Survey volcanologists examined the ten volcanoes in the active Mariana Arc north of Saipan in May 1992, at the request of the Governor and the Disaster Control Office of the Commonwealth of the Northern Mariana Islands (CNMI). A shallow earthquake swarm on Anatahan in March-April 1990 and reports of possible new fuming on Agrigan in August 1990 had prompted the evacuation of all CNMI islands north of Saipan. None of the volcanoes in the chain erupted during our visit. Five uninhabited islands (Farallon de Pajaros, Maug, Asuncion, Guguan, and Sarigan) were inspected only from the air, while the other four were studied in more detail. The previously installed seismic stations on Anatahan, Alamagan, and South Pagan were upgraded. A new station was established at the southwestern base of the intermittently active Mount Pagan, on the northern end of Pagan Island. Portable seismometers were operated on Anatahan, Alamagan, Pagan, and Agrigan. The seismometers on Anatahan, Alamagan, and Agrigan recorded no local shallow earthquake swarms nor volcanic tremor indicative of shallow magmatic movement. On Mount Pagan, intermittent low-amplitude tremor indicated the continuing possibility of occasional small ash eruptions, which prior to our visit had been witnessed in April 1992. Ash eruptions resumed in February 1993. Electronic distance measurement (EDM) lines were remeasured on Agrigan, Mount Pagan, and Anatahan. Line length changes were generally insignificant, in accord with the absence of significant shallow seismicity. Hot spring waters were collected on Agrigan, Pagan, and Anatahan, and fumarole temperatures were measured on Agrigan, Pagan, Alamagan, and Anatahan. The temperature data showed no indication of an impending significant change in the state of these volcanoes. We mapped the geology of Alamagan, collected charcoal to date eruptions of Alamagan and Mount Pagan, and collected rocks on Agrigan, Pagan, Alamagan, and Anatahan for petrographic and chemical studies. We conclude that the low shallow seismicity, lack of significant deformation, and low fumarole temperatures suggest that no eruption is likely soon on Agrigan, Alamagan, or Anatahan. The persistent low-level volcanic tremor on Mount Pagan suggests that intermittent small explosive eruptions may continue to occur.

Open-File Report↗