Geology topics

C.J. Nye

Publications and source records attributed to C.J. Nye.

7 recordsLinked to original sources

USGS2018

The geomorphology of an Aleutian volcano following a major eruption: The 7-8 August 2008 eruption of Kasatochi Volcano, Alaska, and its aftermath

Analysis of satellite images of Kasatochi volcano and field studies in 2008 and 2009 have shown that within about one year of the 78 August 2008 eruption, significant geomorphic changes associated with surface and coastal erosion have occurred. Gully erosion has removed 300,000 to 600,000 m3 of mostly fine-grained volcanic sediment from the flanks of the volcano and much of this has reached the ocean. Sediment yield estimates from two representative drainage basins on the south and west flanks of the volcano, with drainage areas of 0.7 and 0.5 km2, are about 104 m3 km-2 yr-1 and are comparable to sediment yields documented at other volcanoes affected by recent eruptive activity. Estimates of the retreat of coastal cliffs also made from analysis of satellite images indicate average annual erosion rates of 80 to 140 m yr-1. If such rates persist it could take 35 years for wave erosion to reach the pre-eruption coastline, which was extended seaward about 400 m by the accumulation of erupted volcanic material. As of 13 September 2009, the date of the most recent satellite image of the island, the total volume of material eroded by wave action was about 106 m3. We did not investigate the distribution of volcanic sediment in the near shore ocean around Kasatochi Island, but it appears that erosion and sediment dispersal in the nearshore environment will be greatest during large storms when the combination of high waves and rainfall runoff are most likely to coincide. ?? 2010 Regents of the University of Colorado.

Arctic, Antarctic, and Alpine Research↗

USGS2016

Geologic map of the Valdez D-1 and D-2 quadrangles (Mount Wrangell Volcano), Alaska

Geologic Note Mount Wrangell (elev. 4,317 m) is the youngest and only active volcano in the Oligocene to Holocene-aged Wrangell volcanic field that extends from beyond the Alaska-Yukon border northwest through the Wrangell Mountains to the Copper River Basin. The volcano is a very large (900 km 3 ) broad shield containing an ice-filled, nonexplosive, collapse caldera measuring 3.2 by 5.6 kilometers. Three known craters, the West, North, and East occur along the north and west margins of the caldera; the caldera is open to the southeast. The volcano is best exposed on its southwest flank (this map area) where a number of deep glaciated canyons cut through hundreds of meters of shield lava flows creating routes for younger, valley-filling lava flows. The shield extends north into the Gulkana A-1 quadrangle, northeast into the Nabesna A-6 quadrangle, and east into the McCarthy quadrangle where it is almost entirely covered by ice. The present extent of the Mount Wrangell shield showing the entire caldera and locations of the three summit craters is depicted in figure 1. Mount Wrangell was built rapidly beginning about 650 ka by the outpourings of hundreds of voluminous lava flows from a vent, or vents, apparently in the present summit area. By 200 ka to 300 ka, activity waned and only an occasional lava flow coursed down the glacially carved valleys radiating from the summit or flowed over the upper summit area above the heads of the glacial valleys. The youngest dated valley-fill lava flow is approximately 25,000 years old; one or two undated flows may be younger. In historical times there have been several reports of lava flows issuing from the summit area. The most reliable and convincing of these were two independent observations from Copper Center, Alaska on September 3, 1899 that described great earth movements (the 1899 Yakutat Bay earthquake) followed by an eruption at Mount Wrangell’s summit, consisting of vigorous ash emission and flowing lava on the volcano’s northwest flank. This eruptive activity apparently continued for several years after the earthquake, as a photo taken around 1901–02 shows a large part of Mount Wrangell’s summit blanketed by ash. During this study, no evidence of young lava flows in the region were found, although it is very possible that a small-volume flow could be entirely hidden by snow and ice in the 100 years since the event. However, abundant juvenile andesitic pumice was found on the upper Chetaslina Glacier, strongly supporting a very young pyroclastic eruption. In addition to the 1899–1902 eruptions there have been accounts of strong ash-producing activity on at least four different occasions: 1912, July 3, 1921, April 6, 1930, and February 20, 1982. Of these, the 1921 activity was the most spectacular, and possibly erupted from the northeast side of the summit caldera. Present activity is limited to fumaroles in North and West Crater at the summit, at the summit ridge near East Crater, and at two localities at an elevation of 3,657 m on the southwest flank. The summit fumaroles frequently give rise to visible steam plumes, and occasionally sporadic explosive phreatic activity in North and West Crater will put a thin dusting of ash on the summit ice. This study was directed toward Mount Wrangell volcano and the older Wrangell volcanic field rocks that underlie the volcano. These older lavas include the Chetaslina lavas (867 ka–1,650 ka) and a basaltic andesite–dacite center (1,590 ka–1,640 ka) whose source areas are not well defined. Older Paleozoic and Mesozoic sedimentary, igneous, and metamorphic rocks of the Wrangellia terrane underlie the entire Wrangell volcanic field.

Alaska↗

USGS2003

Preliminary geologic map of Kanaga Volcano, Alaska

Kanaga Volcano is a 1,300 m (4,287-foot) high, historically active cone-shaped stratovolcano located on the north end of Kanaga Island in the Andreanof Islands Group of the Aleutian Islands. The volcano is undissected, symmetrical in profile, and is characterized by blocky andesitic lava flows, with well-developed levees and steep flow fronts, that emanate radially from, or near, the 200-m-wide summit crater. The lack of dissection of the cone suggests the entire edifice was constructed in post-glacial Holocene time. Historical eruptions were reported in 1791, 1827, 1829, 1904-1906, and 1993-95 (Miller and others, 1998); questionable eruptions occurred in 1763, 1768, 1786, 1790, and 1933. The upper flanks of the cone are very steep (>30°) and flows moving down these steep flows commonly fragment into breccias and lahars. A non-vegetated lahar, or group of lahars, extends from high on the southeast flank of the cone down to the northeast shore of the intracaldera lake. This lahar deposit was observed in 1999 but does not appear to be present on aerial photos taken in 1974 and is assumed to be part of the 1994-95 eruption. Most recent eruptions of Kanag a, including the 1994-95 eruption, were primarily effusive in character with a subordinate explosive component. Lava was extruded from, or near, the summit vent and moved down the flank of the cone in some cases reaching the ocean. In 1994, lava flows going down the very steep north and west flanks broke up into incandescent avalanches tumbling over steep truncated sea cliffs into the Bering Sea. A common feature of Kanaga central vent eruptions is the occurrence of widespread ballistics and accompanying craters. Steam and fine ash plumes rose to 7.5 km ASL and drifted a few tens of kilometers downwind. Plumes such as these are unlikely to deposit significant (i.e., sufficiently thick to leave a permanent record) tephras on other islands downwind.

Alaska↗

USGS2002

The 1999 eruption of Shishaldin Volcano, Alaska: Monitoring a distant eruption

Shishaldin Volcano, in the central Aleutian volcanic arc, became seismically restless during the summer of 1998. Increasing unrest was monitored using a newly installed seismic network, weather satellites, and rare local visual observations. The unrest culminated in large eruptions on 19 April and 22-23 April 1999. The opening phase of the 19 April eruption produced a sub-Plinian column that rose to 16 km before rapidly dissipating. About 80 min into the 19 April event we infer that the eruption style transitioned to vigorous Strombolian fountaining. Exceptionally vigorous seismic tremor heralded the 23 April eruption, which produced a large thermal anomaly observable by satellite, but only a modest, 6-km-high plume. There are no ground-based visual observations of this eruption; however we infer that there was renewed, vigorous Strombolian fountaining. Smaller low-level ash-rich plumes were produced through the end of May 1999. The lava that erupted was evolved basalt with about 49% SiO2. Subsequent field investigations have been unable to find a distinction between deposits from each of the two major eruptive episodes.

Bulletin of Volcanology↗

USGS1998

Catalog of the historically active volcanoes of Alaska

Alaska hosts within its borders over 80 major volcanic centers that have erupted during Holocene time (< 10,000 years). At least 29 of these volcanic centers (table 1) had historical eruptions and 12 additional volcanic centers may have had historical eruptions. Historical in Alaska generally means the period since 1760 when explorers, travelers, and inhabitants kept written records. These 41 volcanic centers have been the source for >265 eruptions reported from Alaska volcanoes. With the exception of Wrangell volcano, all the centers are in, or near, the Aleutian volcanic arc, which extends 2500 km from Hayes volcano 145 km west of Anchorage in the Alaska-Aleutian Range to Buldir Island in the western Aleutian Islands (fig. 1). The volcanic arc, a subduction-related feature associated with underthrusting of the Pacific plate beneath the North American plate is divided between oceanic island arc and continental margin segments, the boundary occurring at about 165° W longitude (fig. 1). An additional 7 volcanic centers in the Aleutian arc (table 2; fig. 1 A) have active fumarole fields but no reported historical eruptions. This report discusses the location, physiography and structure, eruptive history, and geology of those volcanoes in Alaska that have experienced one or more eruptions that have been recorded in the written history (i.e., in historical time). It is part of the group of catalogs entitled Catalogue of Active Volcanoes of the World published beginning in 1951 under the auspices of the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI). A knowledge of the information contained in such catalogs aids in understanding the type and scale of activity that might be expected during a particular eruption, the hazards the eruption may pose, and even the prediction of eruptions. The catalog will thus be of value not only to the inhabitants of Alaska but to government agencies concerned with emergency response, air traffic operations, and weather, as well as to industry and scientists. The combination of the hazard posed by volcanic ash to jet aircraft and the heavy use of international air routes located parallel to, and on either side of, the Aleutian volcanic arc means that even remote volcanoes in Alaska now pose significant hazards to life and property. Although this report is concerned with historical eruptions from Alaskan volcanoes, other volcanoes in Alaska have erupted in the past 10,000 years and might therefore be expected to erupt again. Several Holocene volcanic centers in the Aleutian arc have no reported historical activity. Elsewhere in Alaska the Bering Sea basalt fields cover large areas of the Yukon Delta, Seward Peninsula, and several of the islands of the Bering Sea. Holocene centers also occur in the Wrangell Mountains and in isolated occurrences in the interior and southeastern Alaska. Eruptions from these centers have occurred within the past several hundred years but none were transcribed in the written record. Moodie and others (1992), however, report oral traditions among the Northern Athapaskan Indians of the southwestern Yukon Territory that may record the second and younger deposition of the White River Ash circa A.D. 720. This lobe of the White River Ash was deposited during the paroxysmal eruption of Churchill volcano in the Wrangell Mountains of eastcentral Alaska (McGimsey and others, 1992; Richter and others, 1995).

Alaska↗

USGS1994

Geochemistry of the 1989-1990 eruption of redoubt volcano: Part II. Evidence from mineral and glass chemistry

Early stages (December 1989) of the 1989-1990 eruption of Redoubt Volcano produced two distinct lavas. Both lavas are high-silica andesites with a narrow range of bulk composition (58-64 wt.%) and similar mineralogies (phenocrysts of plagioclase, hornblende, augite, hypersthene and FeTi oxides in a groundmass of the same phases plus glass). The two lavas are distinguished by groundmass glass compositions, one is dacitic and the other rhyolitic. Sharp boundaries between the two glasses in compositionally banded pumices, lack of extensive coronas on hornblende phenocrysts, and seismic data suggest that a magma-mixing event immediately preceeded the eruption in December 1989. Textural disequilibrium in the phenocrysts suggests both magmas (dacitic and rhyolitic glasses) had a mixing history prior to their interaction and eruption in 1989. Sievey plagioclase and overgrowths of magnetite on ilmenite are textures that are at least consistent with magma mixing. The presence of two hornblende compositions (one a high-Al pargasitic hornblende and one a low-Al magnesiohornblende) in both the dacitic and rhyolitic groundmasses indicates a mixing event to yield these two amphibole populations prior to the magma mixing in December 1989. The pargasitic hornblende and the presence of Ca-rich overgrowths in the sievey zones of the plagioclase together indicate at least one component of this earlier mixing event was a mafic magma, either a basalt or a basaltic andesite. Eruptions in 1990 produced only andesite with a rhyolitic groundmass glass. Glass compositions in the 1990 andesite are identical to the rhyolitic glass in the 1989 andesite. Cognate xenoliths from the magma chamber (or conduit) are also found in the 1990 lavas. Magma mixing probably triggered the eruption in 1989. The eruption ended when this rather viscous (rhyolitic groundmass glass, magma capable of entraining sidewall xenoliths) magma stabalized within the conduit. ?? 1994.

Journal of Volcanology and Geothermal Research↗

USGS1994

Geochemistry of the 1989-1990 eruption of redoubt volcano: Part I. Whole-rock major- and trace-element chemistry

The 1989-1990 eruption of Redoubt Volcano produced medium-K calc-alkaline andesite and dacite of limited compositional range (58.2-63.4% SiO2) and entrained quenched andesitic inclusions (55% SiO2) which bear chemical similarities to the rest of the ejecta. The earliest (December 15) magmas are pumiceous, often compositionally banded, and the majority is relatively mafic (< 59% SiO2). The most silicic magmas of the eruption are the late December to early January domes (up to 63.4% SiO2). Subsequent magmas formed domes and rare pumices which converge on 60% SiO2. Chemical variations among ejecta comprise tight, linear, two-component arrays for all elements for which the analytical uncertainty is much less than the compositional range. The two-component arrays are interpreted as mixing arrays between unrelated magmas because several of the arrays are at steep angles to the normal liquid line of descent. Additionally, the felsic endmember cannot be easily related to the mafic endmember by normal high-temperature igneous processes (e.g., the silicic endmember has higher Zr yet lower Hf than the mafic endmember). Also relative enrichments of highly incompatible elements are dramatically different across the arrays. The mixing event must have preceded eruption by a significant, yet unspecified amount of time because groundmass glass compositions are homogeneous for all post-December samples (Swanson et al., 1994-this volume), in spite of the whole-rock chemical diversity. This implies time for additional crystallization after the mixing event. Swanson et al. (1994-this volume) discuss evidence for a potentially different mixing event recorded only in December 15 magmas. Cognate cumulate xenoliths composed of pl+cpx+opx+hb+mt+melt were recovered from January and April deposits. These blocks differ from local batholithic country rock in their low concentrations of incompatible elements (e.g., Rb < 5 ppm vs 20-90 ppm, Ba < 150 ppm vs 300-2000 ppm) and low SiO2 (< 50 wt.% vs > 60 wt.%). They have Mg, Cr, Ni, Sc, and V contents higher than the andesites, but lower than Redoubt basalts and basaltic andesites. Thus, they may be crystallization products of andesites, but do not represent the cumulate residue of basalt fractionation. The xenoliths were probably derived from a shallow or intermediate crustal chamber. ?? 1994.

Journal of Volcanology and Geothermal Research↗