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Espenberg reported activity

ESPENBERG LINKS

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EVENT SPECIFIC INFORMATION

Event Name : Espenberg Devil Mountain Lakes Maar

Start: 17500 Years BP C-14 (raw)

Tephrafall: BibCard
Pyroclastic flow, surge, or nuee ardente: BibCard
Maar, tuff cone, tuff ring: BibCard BibCard
Eruption Type:Explosive
Other""

Description: From Hopkins (1988): "The youngest and most spectacular volcanic features in the Devil Mountain-Cape Espenberg area consist of a group of five maars (shallow, broad, low-rimmed explosion craters formed by eruptions rich in steam)."

"The Devil Mountain Lakes are the freshest in appearance and the most tightly dated of the maars; the north lake is the fresher and younger maar. The basin of North Devil Mountain lake has maximum and minimum diameters of 5.1 and 3.3 kilometers. South Devil Mountain Lake is the smallest of the Espenberg maars, having maximum and minimum diameters of 3.4 and 2.2 kilometers."

From Beget and others (1996): "...Devil Mountain Maar, which is an irregular composite crater containing North and South Devil Mountain Lakes (Fig. 1 [in original text]). North Devil Mountain Lake (5.1 km in diameter) is partly separated from South Devil Mountain Lake (3.4 km diameter) by a small sand spit."

"Sequences of bedded surge deposits, airfall lapilli beds, massive pyroclastic flows, and explosion breccia can be traced through many fresh exposures in 10-40 m high cliffs around the Devil Mountain Lakes Maar (Fig. 2a, 2b [in original text]). Stratigraphic sections were measured through the volcanic pile at many sites around the lakes, and complex but uninterrupted sequences of plane-bedded and cross-bedded surge deposits, massive explosion breccia, and scoria beds were found. No trace of nonvolcanic sediment or paleosol development was found at any level within the sequence of volcaniclastic sediments (Fig. 2b [in original text]). Similarly, radiocarbon dates from organic material preserved at numerous sites beneath a widespread tephra deposit on the northern Seward Peninsula produced by the eruptions of the Devil Mountain Lakes Maar all indicate an age of about 17 500 years B.P. (Table 1 [in original text]). The existence of only a single tephra deposit at numerous sites around the maar, the similarity of all radiocarbon dates from beneath the tephra deposits, and the absence of significant stratigraphic breaks in either the distal ash or the proximal volcaniclastic sequence indicate the Devil Mountain Lakes Maar formed during one complex eruptive episode about 17 500 years B.P. The crater produced during those eruptions, measured from rim to rim across the maar lake, is 8 km long by 6 km wide, as much as 200 m deep, and covers over 30 km2 (Fig. 1 [in original text])."

"The bottom of the Devil Mountain Lakes Maar is extensively cratered, with at least eight separate depressions visible in the contour data (Fig. 4 [in original text]). These well-defined craters range from 0.1-1 km in diameter and are 50-100 m deep. The underwater craters seem to trend north-south in South Devil Mountain Lake, but east-west in North Devil Mountain Lake, paralleling the ellipitical asymmetry of each lake basin. Similar but partly infilled craters are also visible in depth profiles from the somewhat older Killeak Lakes."

"We interpret the closed depressions on the floors of the Espenberg maars as small explosion craters, as they are similar in size to typical, small hydromagmatic craters observed elsewhere. These craters evidently mark the sites of explosive activity during the eruption; other explosion craters may have formed earlier in the eruption sequence, only to be obliterated or filled in by later eruptions. Although we are unable to find any published bathymetric data from other maars, we speculate that multiple craters may exist on other maar lake floors. Similar groups of coeval explosion craters have recently been documented at sites like Cerro Xalapaxco in central Mexico, where multiple phreatomagmatic eruptions occurred at a site with an especially abundant water supply (Abrams and Siebe, 1994)."

"Radiocarbon dates and tephrochronology, together with relative age estimates based on the degree of erosion and sedimentation in the lake basins, indicate that the Devil Mountain Maar is the youngest, formed ca. 17 500 years B.P. (Table 1 [in original text])..."

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