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R.L. Christiansen

Publications and source records attributed to R.L. Christiansen.

26 records · Page 2Linked to original sources
USGS1976

Tragedy at Kilauea

The following article is a reconstruction of events surrounding the deaths of a party of Hawaiian warriors in 1790 on Kilauea Volcano. It suggests that they were killed by a very hot, ash-free, base-surge cloud that rushed from the volcano. Much more recently than that, in the early morning hours of November 29, 1975, the largest earthquake in more than 100 years struck the southern part of the Island of Hawaii, causing widespread faulting and subsidence, an eruption at the summit of Kilauea Volcano, the loss of at least one life, and widespread damage to property. The effects of this earthquake are still being analyzed by the staff of the Geological Survey's Hawaiian Volcano Observatory, but preliminary results indicate that much of the south flank of Kilauea Volcano moved seaward in an abrupt, slump-like manner. The eruption that followed was small by the usually Kilauea standards and is regarded as a leakage of lava from the volcano's underground reservoir system in response to the effects of the earthquake. A more detailed account of these events will be included in a future issue of the Earthquake Information Bulletin.

Hawaii↗
USGS1975

Magma beneath Yellowstone National Park

The Yellowstone plateau volcanic field is less than 2 million years old, lies in a region of intense tectonic and hydrothermal activity, and probably has the potential for further volcanic activity. The youngest of three volcanic cycles in the field climaxed 600,000 years ago with a voluminous ashflow eruption and the collapse of two contiguous cauldron blocks. Doming 150,000 years ago, followed by voluminous rhyolitic extrusions as recently as 70,000 years ago, and high convective heat flow at present indicate that the latest phase of volcanism may represent a new magmatic insurgence. These observations, coupled with (i) localized postglacial arcuate faulting beyond the northeast margin of the Yellowstone caldera, (ii) a major gravity low with steep bounding gradients and an amplitude regionally atypical for the elevation of the plateau, (iii) an aeromagnetic low reflecting extensive hydrothermal alteration and possibly indicating the presence of shallow material above its Curie temperature, (iv) only minor shallow seismicity within the caldera (in contrast to a high level of activity in some areas immediately outside), (v) attenuation and change of character of seismic waves crossing the caldera area, and (vi) a strong azimuthal pattern of teleseismic P-wave delays, strongly suggest that a body composed at least partly of magma underlies the region of the rhyolite plateau, including the Tertiary volcanics immediately to its northeast. The Yellowstone field represents the active end of a system of similar volcanic foci that has migrated progressively northeastward for 15 million years along the trace of the eastern Snake River Plain. Regional aeromagnetic patterns suggest that this course was guided by the structure of the Precambrian basement. If, as suggested by several investigators, the Yellowstone magma body marks a contemporary deep mantle plume, this plume, in its motion relative to the North American plate, would appear to be "navigating" along a fundamental structure in the relatively shallow and brittle lithosphere overhead. The concept that a northeastward-propagating major crustal fracture controls the migration path of the major foc

Wyoming↗
USGS1974

Meteoric water in magmas

Oxygen isotope analyses of sanidine phenocrysts from rhyolitic sequences in Nevada, Colorado, and the Yellowstone Plateau volcanic field show that δ 18 O decreased in these magmas as a function of time. This decrease in δ 18 O may have been caused by isotopic exchange between the magma and groundwater low in 18 O. For the Yellowstone Plateau rhyolites, 7000 cubic kilometers of magma could decrease in δ 18 O by 2 per mil in 600,000 years by reacting with water equivalent to 3 millimeters of precipitation per year, which is only 0.3 percent of the present annual precipitation in this region. The possibility of reaction between large magmatic bodies and meteoric water at liquidus temperatures has major implications in the possible differentiation history of the magma and in the generation of ore deposits.

Colorado, Nevada, Wyoming↗
USGS1971

Evolving subduction zones in the western United States, as interpreted from igneous rocks

Variations in the ratio of K 2 O to SiO 2 in andesitic rocks suggest early and middle Cenozoic subduction beneath the western United States along two subparallel imbricate zones dipping about 20 degrees eastward. The western zone emerged at the continental margin, but the eastern zone was entirely beneath the continental plate. Mesozoic subduction apparently occurred along a single steeper zone.

western United States↗