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M. T. Mangan

Publications and source records attributed to M. T. Mangan.

7 recordsLinked to original sources
USGS1998

Observations on basaltic lava streams in tubes from Kilauea Volcano, island of Hawai'i

From 1986 to 1997, the Pu'u 'O'o-Kupaianaha eruption of Kilauea produced a vast pahoehoe flow field fed by lava tubes that extended 10–12 km from vents on the volcano's east rift zone to the ocean. Within a kilometer of the vent, tubes were as much as 20 m high and 10–25 m wide. On steep slopes (4–10°) a little farther away from the vent, some tubes formed by roofing over of lava channels. Lava streams were typically 1–2 m deep flowing within a tube that here was typically 5 m high and 3 m wide. On the coastal plain (<1°), tubes within inflated sheet flows were completely filled, typically 1–2 m high, and several tens of meters wide. Tubes develop as a flow's crust grows on the top, bottom, and sides of the tubes, restricting the size of the fluid core. The tubes start out with nearly elliptical cross-sectional shapes, many times wider than high. Broad, flat sheet flows evolve into elongate tumuli with an axial crack as the flanks of the original flow were progressively buried by breakouts. Temperature measurements and the presence of stalactites in active tubes confirmed that the tube walls were above the solidus and subject to melting. Sometimes, the tubes began downcutting. Progressive downcutting was frequently observed through skylights; a rate of 10 cm/d was measured at one skylight for nearly 2 months.

Journal of Geophysical Research B: Solid Earth↗
USGS1998

The character of long-term eruptions: Inferences from episodes 50-53 of the Pu'u 'Ō'ō-Kūpaianaha eruption of Kīlauea volcano

The Pu'u 'Ō'ō-Kūpaianaha eruption on the east rift zone of Kīlauea began in January 1983. The first 9 years of the eruption were divided between the Pu'u 'Ō'ō (1983&ndash;1986) and Kūpaianaha (1986&ndash;1992) vents, each characterized by regular, predictable patterns of activity that endured for years. In 1990 a series of pauses in the activity disturbed the equilibrium of the eruption, and in 1991, the output from Kūpaianaha steadily declined and a short-lived fissure eruption broke out between Kūpaianaha and Pu'u 'Ō'ō. In February 1992 the Kūpaianaha vent died, and, 10 days later, eruptive episode 50 began as a fissure opened on the uprift flank of the Pu'u 'Ō'ō cone. For the next year, the eruption was marked by instability as more vents opened on the flank of the cone and the activity was repeatedly interrupted by brief pauses in magma supply to the vents. Episodes 50&ndash;53 constructed a lava shield 60&thinsp;m high and 1.3&thinsp;km in diameter against the steep slope of the Pu'u 'Ō'ō cone. By 1993 the shield was pockmarked by collapse pits as vents and lava tubes downcut as much as 29&thinsp;m through the thick deposit of scoria and spatter that veneered the cone. As the vents progressively lowered, the level of the Pu'u 'Ō'ō pond also dropped, demonstrating the hydraulic connection between the two. The downcutting helped to undermine the prominent Pu'u 'Ō'ō cone, which has diminished in size both by collapse, as a large pit crater formed over the conduit, and by burial of its flanks. Intervals of eruptive instability, such as that of 1991&ndash;1993, accelerate lateral expansion of the subaerial flow field both by producing widely spaced vents and by promoting surface flow activity as lava tubes collapse and become blocked during pauses.

Bulletin of Volcanology↗
USGS1997

Littoral hydrovolcanic explosions: A case study of lava-seawater interaction at Kilauea Volcano

A variety of hydrovolcanic explosions may occur as basaltic lava flows into the ocean. Observations and measurements were made during a two-year span of unusually explosive littoral activity as tube-fed pahoehoe from Kilauea Volcano inundated the southeast coastline of the island of Hawai'i. Our observations suggest that explosive interactions require high entrance fluxes (??? 4 m3/s) and are most often initiated by collapse of a developing lava delta. Two types of interactions were observed. "Open mixing" of lava and seawater occurred when delta collapse exposed the mouth of a severed lava tube or incandescent fault scarp to wave action. The ensuing explosions produced unconsolidated deposits of glassy lava fragments or lithic debris. Interactions under "confined mixing" conditions occurred when a lava tube situated at or below sea level fractured. Explosions ruptured the roof of the tube and produced circular mounds of welded spatter. We estimate a water/rock mass ratio of 0.15 for the most common type of littoral explosion and a kinetic energy release of 0.07-1.3 kJ/kg for the range of events witnessed.

Journal of Volcanology and Geothermal Research↗
USGS1993

Emplacement and differentiation of the york haven diabase sheet, Pennsylvania

Many of the high-Ti quartz-normative tholeiitic intrusive sheets in the early Mesozoic rift basins of the Eastern USA exhibit lateral differentiation from mafic cumulate units, through diabase, to relatively evolved iron-rich rock types. We have investigated a representative example in detail, the York Haven sheet in the Gettysburg basin of south-central Pennsylvania. It ranges in thickness from 330 m to 675 m, and we have sampled it from base to top along four separate stratigraphic sections evenly spaced over the extent of the intrusion. The easternmost section (York Haven) is entirely basaltic bronzite cumulate (average 15 vol. % bronzite), whereas the westernmost (Reesers Summit) consists of diabase and low-MgO diabase with a middle to upper 'sandwich zone' of ferrogabbro. The intervening sections feature rock types transitional between the two end-member sequences. Chemically, the rock series shows a gradual east to west depletion of compatible elements (Mg, Ca, Ni, and Cr), and enrichment of incompatible elements [Ti, Fe, Na, K, P, Cu, Zr, Th, Ta, Hf, Sb, Cs, As, platinum group elements (PGEs), and rare earth elements (REEs)].We suggest two main processes for the trends observed in the York Haven sheet. First, flow differentiation during ascent and lateral injection of the parental magma produced a tongue of basaltic bronzite cumulate that thins from southeast to northwest and passes laterally into diabase, and, at the distal end of the intrusion, into low-MgO diabase. Then, in the latter stages of crystallization, densitydriven hydrothermal fluids transported incompatible elements westward, into structurally higher parts of the intrusion. Reaction of this residual aqueous fluid with partly crystallized low-MgO diabase produced a zone of ferrogabbro rich in hydrothermal replacement products (e.g., Cl-amphibole, biotite, ferrohypersthene, and skeletal ilmenite) and precipitates (e.g., quartz, fayalite, Cl-apatite, sulfides, and PGE minerals). © 1993 Oxford University Press.

Pennsylvania↗