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Features of Lava Lake Filling and Draining and Their Implications for Eruption Dynamics

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Features of Lava Lake Filling and Draining and Their Implications for Eruption Dynamics Bull Volcanol (2009) 71:767–780 DOI 10.1007/s00445-009-0263-0 RESEARCH ARTICLE Features of lava lake filling and draining and their implications for eruption dynamics W. K. Stovall & Bruce F. Houghton & Andrew J. L. Harris & Donald A. Swanson Received: 13 March 2008 /Accepted: 7 January 2009 /Published online: 13 February 2009 # Springer-Verlag 2009 Abstract Lava lakes experience filling, circulation, and roughly horizontal lava shelves on the lakeward edge of the often drainage depending upon the style of activity and vertical rinds; the shelves correlate with stable, staggered lake location of the vent. Features formed by these processes stands. Shelves either formed as broken relict slabs of lake have proved difficult to document due to dangerous crust that solidified in contact with the wall or by accumula- conditions during the eruption, inaccessibility, and destruction tion, accretion, and widening at the lake surface in a dynamic of features during lake drainage. Kīlauea Iki lava lake, lateral flow regime. Thin, upper lava shelves reflect an Kīlauea, Hawai‘i, preserves many such features, because lava initially dynamic environment, in which rapid lake lowering ponded in a pre-existing crater adjacent to the vent and was replaced by slower and more staggered drainage with the eventually filled to the level of, and interacted with, the vent formation of thicker, more laterally continuous shelves. At all and lava fountains. During repeated episodes, a cyclic pattern lava lakes experiencing stages of filling and draining these of lake filling to above vent level, followed by draining back processes may occur and result in the formation of similar sets to vent level, preserved features associated with both filling of features. and draining. Field investigations permit us to describe the characteristic features associated with lava lakes on length Keywords Lava lake . Kīlauea . Hawai‘i . Filling . scales ranging from centimeters to hundreds of meters in a Draining . Lava shelves . Vertical rinds fashion analogous to descriptions of lava flows. Multiple vertical rinds of lava coating the lake walls formed during filling as the lake deepened and lava solidified against vertical Introduction faces. Drainage of the lake resulted in uneven formation of Lava lakes are a common occurrence at basaltic volcanoes Editorial responsibility: M. Clynne and are defined as either ‘active’ or ‘inactive’ (Swanson W. K. Stovall (*) : B. F. Houghton et al. 1973). Active lava lakes are located directly over the Department of Geology and Geophysics, source vent, so that lava enters and circulates within the University of Hawai‘iatMānoa, lake. Active lava lake convection may proceed for years-to- 1680 East-West Road, decades before supply ceases and lava drains. Such activity Honolulu, HI 96822, USA ī ‘ ‘Ō‘ō e-mail: [email protected] has been observed at K lauea in U.S.A. (Pu u : Heliker and Wright 1991; Halemaumau: Jaggar 1947), Erta Ale in A. J. L. Harris Ethopia (Harris et al. 2005), Nyiragongo in The Democratic ‘ Hawai i Institute of Geophysics and Planetology, Republic of the Congo (Tazieff 1984), and Villarrica in University of Hawai‘iatMānoa, 1680 East-West Road, Chile (Witter et al. 2004). Inactive lava lakes are located Honolulu, HI 96822, USA adjacent to, or down flow from, the source vent and typically form as a result of lava flowing into a previously D. A. Swanson formed depression. These have been observed in various pit Hawaiian Volcano Observatory, U.S. Geological Survey, ī ‘ P.O. Box 51, Hawai‘i National Park, craters on K lauea, such as Alae (Swanson et al. 1979) and Honolulu, HI 96718, USA Makaopuhi (Wright and Kinoshita 1968), as well as on 768 Bull Volcanol (2009) 71:767–780 Masaya, Nicaragua (Harris 2008b). In inactive lava lakes, While lake level was below the vent, the lake was inactive. most of the crater-trapped lava does not drain back down Lava fountains from the vent ponded lava in the crater, the feeder vent when supply ceases, but remains within the causing lake level to rise. In each fountaining episode, lake confining pit to stagnate and cool in place (Peck et al. 1966; level reached the height of the vent, and the geometry Wright and Okamura 1977). became that of a classic active lava lake. Lake level often Throughout the life time of a lava lake, processes of lava rose above the level of the vent, and fountaining burst movement within the lake vary in time and space. through the lake. When fountaining ended, lava drained Convection and influxes of new magma circulate the lava from the lake back into the vent, which acted much like the and transfer heat (Harris 2008a;Harrisetal.2005); overflow drain on a bath tub, until lake level reached the consequent surface motion results in formation, growth, vent level, when drainage ceased and the lake was once and destruction of crustal plates (Duffield 1972). In active again technically inactive. lava lakes, the final period of lava drainage largely destroys At Kīlauea Iki, we found preserved features associated any record of the earlier history of the lake. Since the lava with lake filling, drainage, and stagnation and link them to has nowhere to drain in inactive lakes, freezing preserves the lake dynamics that constructed them. In particular, we some of the features associated with lake processes. In this are able to interpret the timing of processes in the last paper, we examine the preserved features of a lava lake that episodes of the eruption that contribute to a greater was sometimes active and sometimes inactive. understanding of generic lava lake processes. The 37-day-long lava fountaining eruption in 1959 at Kīlauea Iki, Kīlauea, Hawai‘i (Fig. 1) resulted in the formation, repeated filling, and partial drainage of a lava Kīlauea Iki 1959 lake within an existing pit crater adjacent to the principal vent. Throughout the eruption, the lake level rose and fell During the November–December 1959 eruption of Kīlauea, during waxing and waning of fountaining at the vent, a ∼46×106 m3 lava lake (Fig. 1) was formed in the Kīlauea nearly half way up the ∼200-m-high wall of the crater. Iki pit crater (Richter et al. 1970). The eruption comprised 17 episodes over 37 days and produced the highest a recorded lava fountaining events in Hawai‘i (Richter et al. 1970). The vent was 110 m above southwestern floor of the crater, and some of the ejecta from the fountains entered the 20˚N crater, forming the 110-m-deep lava lake, which eventually overtopped and interacted with the vent (Richter et al. Hilo 1970). Each episode can be divided into two stages: an early stage of fountaining and lake filling (Fig. 2a) and a - late stage of drainage and lake lowering (Fig. 2b). After K Ilauea Iki fountaining stopped, excess lava drained from the lake into the vent. Only the upper portion of the lake (that which km 19˚N overtopped the vent) could drain; the residual lava 0 10 remained trapped, cooling in situ, until the onset of the -156˚W -155˚W next episode. This two-fold cycle of fountaining and lake b filling, then draining and lake lowering, repeated through the 17 episodes of the eruption (Fig. 3a). When the eruption N ceased, the remaining lava cooled as a stagnant body, preserving intact surface features of the lake. NM The final Kīlauea Iki lava lake is approximately 1.5× 0.8 km in diameter and contains features formed through V the life of the lava lake. Some key features and their C inferred mechanism of formation were described by Richter et al. (1970). These are summarized in Table 1 and are used throughout this paper. T 200m Episodes 16 and 17 ‘ Fig. 1 Location maps: a Island of Hawai i with star marking location ī of Kīlauea Iki and b IKONOS image of Kīlauea Iki lava lake with The features preserved on the surface of the K lauea Iki north margin (NM), vent (V), cone (C) and tephra (T) highlighted lava lake are remnants of the final two episodes (16 and 17) Bull Volcanol (2009) 71:767–780 769 Fig. 2 Photographs taken by Fountaining and filling a Draining and lowering b Jerry Eaton during Kīlauea Iki eruption with dashed arrows in- dicating direction of lava flow in lake. a Episode 16 fountaining and lake filling stage, showing clear flow pathway along north margin (NM, solid white line along trace of wall). LI indicates location of partially-submerged lava island; note flow pathways diverted around island. b Episode 16 draining stage approximately 1 h after end of fountaining, when 60-m-wide channel within NM lake fed backflow down vent. LI NM with arrow points toward north margin, slightly out of view in photograph around edge of channel flow. Photographs cour- tesy of Hawaiian Volcano Ob- servatory (HVO) library 19-Dec 3:45 AMNM 19-Dec 7:30 AM of the 1959 eruption. Episode 16 started 35 h after the 16 and 17 except where erosion of the surface allows cessation of fountaining during episode 15 (Fig. 3a). observation of products from earlier episodes. Episode 16’s fountaining stage lasted 3 h 36 min and, although shorter in duration and producing fountains lower Rates of filling and drainage than those of episode 15, it fed a lake that reached a level 2 m higher (123 m deep, Fig. 3a). This was likely due to an Rates of filling and drainage varied for each eruptive increased flux during episode 16 fountaining. After the episode (Fig. 3b). Rates of filling were lowest during the fountain died, drainback of lava into the vent began earlier, longer fountaining stages and highest during the immediately, and an hour later the backflow channel very high, but shorter, fountaining stages, such as episodes stretched 60 m across the lake surface as a lava river 15 and 16, which occurred toward the end of the eruption.
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