Lahar in Glass Creek and Owens River During the Inyo Eruption, Mono^Inyo Craters, California

Available online at www.sciencedirect.com

Journal of Volcanology and Geothermal Research 131 (2004) 321^331

www.elsevier.com/locate/jvolgeores

Lahar in Glass Creek and Owens River during the Inyo eruption, Mono^Inyo Craters, California

M. Bursik a;Ã, J. Reid b;1

a Department of Geology, State University of New York at Bu¡alo, Bu¡alo, NY 14260, USA b School of Natural Science, Hampshire College, Amherst, MA 01002, USA

Received 5 September 2002; accepted 4 November 2003

Abstract

Nested fluvial and lahar terraces are inset in a volcanic surface where Glass Creek has created an embayment in the Sierran range front, on the north rim of Long Valley caldera, California. The geomorphic and stratigraphic relationships among these terraces indicate that they record events at the time of the pre-1472 AD Inyo eruption. The volcanic surface records the deposition of the Inyo pyroclastic materials over pre-existing landforms. Somewhat younger terraces contain volcanic beds at depth, overlain by alluvium. The youngest, lowest terraces comprise lahar deposits overlying alluvium and the pyroclastic debris. Downstream from the embayment, in the canyon of Glass Creek, levees line the walls to a maximum height of 35 m above the present stream level. The canyon opens onto a lahar fan, the surface of which is covered with cobbles and pebbles of Inyo pumice. Further downstream, in the floodplain of the Owens River, an abandoned meander belt is filled with graded debris containing large amounts of Inyo pumice. At the distal end of the floodplain, 30 km from the embayment, coarse pumiceous debris occupies low mounds scattered in the abandoned meander belt. The deposits that comprise the mounds are massive-bedded muds and sandy muds. These features record the excavation of V1.9U105 m3 of material from the Glass Creek embayment, and perhaps an additional amount up- and downstream, which was transported in a non-cohesive lahar down the Glass Creek and Owens River drainage to a distance of at least 30 km from the source region. Lahars are a previously uncharacterized volcanic hazard in the Long Valley caldera region. It may be important to consider them in any future assessment of hazards in this restless system. ß 2003 Elsevier B.V. All rights reserved.

Keywords: lahar; debris £ow; Long Valley caldera; Inyo Craters; Inyo eruption; Owens River; California; terrace; levee; oxbow; £oodplain

1. Introduction Long Valley caldera^Mono Craters volcanic area discusses how the most likely event to plan The volcanic hazards response plan for the for is a moderate-sized rhyolitic eruption from the Mono^Inyo Craters chain Hill et al. (2002). The description of the nature of this potential eruption 1 Deceased. is based on a hazards analysis ¢nished in the * Corresponding author. 1980s (Miller et al., 1982; Miller, 1989), which E-mail address: [email protected]¡alo.edu (M. Bursik). discusses pumice fall, pyroclastic £ow and surge,

VOLGEO 3013 13-2-04 Cyaan Magenta Geel Zwart 322 M. Bursik, J. Reid / Journal of Volcanology and Geothermal Research 131 (2004) 321^331 and dome-forming eruptive episodes. At the time Glassy Beds phase (the last ashfall phase) of the of the completion of the hazards analysis, there North Mono eruption. Although the evidence had been no descriptions of lahar deposits among from the Bodie Hills shows that small lahars oc- the pyroclastic products of the Mono^Inyo Cra- curred at the time of the most recent events, no ters. assessment of potential lahar hazards was under- The major pyroclastic deposits of the Inyo Cra- taken to help fully characterize eruption hazards ters volcanic chain were erupted during the Inyo in the Long Valley region. eruption of 1325^1472 AD from vents now under- We have studied what we believe to be the most lying Obsidian Flow, Glass Creek Flow and substantial lahar deposits and related landforms South Deadman Dome (Miller, 1985). The Inyo that resulted from the Inyo and North Mono eruption followed the 1325^1368 AD North eruptions. The goal of the present contribution Mono eruption from the Mono Craters (Sieh is to ¢ll the gap in our understanding of eruptions and Bursik, 1986) by at most a few decades. in the region by describing what we have inter- Sieh and Bursik noted small lahar deposits of re- preted as lahar deposits. We furthermore seek to mobilized North Mono airfall ash in the Bodie consider the mode of formation and implications Hills, north of Mono Lake. The data suggested for lahar hazards in the Long Valley^Mono Lake that the remobilization occurred after the Gray region.

Fig. 1. Location map of the Glass Creek^Owens River drainage, Long Valley caldera, CA, USA, showing lettered localities and map areas (A^D) at which lahar deposits or erosional features were studied. The Inyo Craters and Mammoth Mountain, parts of the Mono^Inyo volcanic chain, are ¢lled. Mono Craters and Mono Lake are north of the area depicted. Mammoth Pass, which marks the divide between the Mammoth Creek and San Joaquin River basis, is on the northwest shoulder of Mammoth Mountain. A, Glass Creek embayment; B, Glass Creek canyon; C,D, Owens River £oodplain.

VOLGEO 3013 13-2-04 Cyaan Magenta Geel Zwart M. Bursik, J. Reid / Journal of Volcanology and Geothermal Research 131 (2004) 321^331 323

2. Methods Flow, were constructed (Map area A). A base topographic map was drawn from a dataset of Field work involved mapping landforms and position readings made with a commercial total deposits along four reaches of Glass Creek and station geodimeter. Relative elevations were accu- Owens River (Fig. 1). Detailed topographic and rate at the cm level. We also excavated and logged geomorphologic maps of a possible source region, 11 pits up to 2 m deep. Further downstream, in a 200 mU400 m embayment in the Sierran range the canyon of Glass Creek (Map area B), lahar front between Glass Creek Flow and Obsidian levees and fans were mapped on an enlarged copy

Fig. 2. (Map area A) Topographic and geomorphic map of the £uviovolcanic terraces within an embayment of the Sierran range front has been used to show the sequence of events at the time of the Mono and Inyo eruptions. The small dome of Glass Creek is just out of the map area to the north. The Sierran range front wraps around the map area on the west, south and north sides.

VOLGEO 3013 13-2-04 Cyaan Magenta Geel Zwart 324 M. Bursik, J. Reid / Journal of Volcanology and Geothermal Research 131 (2004) 321^331 of a 71=2 arcmin quadrangle map. In the Owens escarpment at the southern boundary of the em- River £oodplain (Map areas C and D), observa- bayment, and also comprises its eastern bound- tions were made of landforms and deposits asso- ary. Near its southwestern corner, Glass Creek ciated with two major meander belts of the river. enters the embayment via a cascade V100 m Landforms were mapped on USGS aerial photo- high down the range front escarpment. The creek graphs, then transferred to a 71=2 arcmin quadran- exits the embayment near its northeastern corner. gle map by comparing positions of stream mean- Five terraces occur within the embayment. In ders, abandoned stream meanders, and roads. planform, many of the terrace risers and treads Several pits were dug into the £oodplain deposits are subparallel to the path of Glass Creek, sug- to characterize internal stratigraphy and relation- gesting that they were formed by its erosive ac- ships with surrounding units. tion. In several localities, the terraces are dissected by paleochannels of Glass Creek. Some of the terraces have boulders on their treads that are 3. Data derived from the adjacent Sierran granites and older Neogene volcanic rocks. Cobbles are the 3.1. Glass Creek embayment largest clasts on other terrace treads. Some of the treads are relatively planar, with little topo- The range front of the Sierra Nevada is em- graphic variation or roughness, while others are bayed where Glass Creek crosses it (Map area characterized by mounds or piles of clasts; many A, Fig. 1). Glass Creek has followed various of the piles are elongated in the downstream di- courses within the embayment, as indicated by rection. the existence of abandoned terraces and channels The stratigraphy within the outer, higher surfa- (Fig. 2). The small dome of Glass Creek marks ces di¡ers considerably from that within the inner, the northern boundary of the embayment. The lower terraces (Fig. 3). The most outboard surface Glass Creek Flow abuts against the range front (I), occurs on both sides of Glass Creek, has a

Fig. 3. Summary stratigraphic columns for the deposits found along Glass Creek and the Owens River. Deposits in Glass Creek canyon are not depicted.

VOLGEO 3013 13-2-04 Cyaan Magenta Geel Zwart M. Bursik, J. Reid / Journal of Volcanology and Geothermal Research 131 (2004) 321^331 325 relatively planar upper surface and is underlain by clastic apron extending eastward from the Glass pumiceous, poorly sorted, generally massive beds Creek vent. containing angular volcanic clasts. These beds are Terraces III and IV are underlain by up to 0.5 m bioturbated at top and contain only a small per- of lithic-rich, massive and inverse-graded, poorly centage of lithic rhyolite and rhyodacite. The de- sorted, silty^sandy gravels and gravelly sands; posits constitute a sequence of coarse-grained then 0.8 m of lithic-rich, poorly strati¢ed, thin- tephra fall, and poorly sorted pyroclastic-£ow bedded gravelly sands of granite, and redeposited and blast-£ow beds, and are therefore the beds lithic rhyolite, dacite and obsidian; pumice lapilli of the pyroclastic sequence from the Glass Creek occur at depth. Terrace IV has a hummocky sur- vent (cf. Miller, 1985). Surface I is thus the dis- face with abundant granitic and andesitic clasts. sected remnant of the original volcaniclastic The deposits suggest that the terraces were formed apron that surrounded the vent. by cut-and-¢ll stream£ow and non-cohesive, boul- The tread of Terrace II is £at and littered with dery lahar. lithic cobbles and boulders. The deposits within Terrace V occurs near the present stream level are planar and cross-bedded sands and gravels in and has a locally hummocky surface. Terrace V the uppermost 0.5^1 m, overlying poorly sorted, could perhaps be inundated by Glass Creek dur- massive pumice-rich lapilli. These are £uvial beds ing £ooding. The right terrace is partially covered overlying pyroclastic fall and £ow deposits similar by the blocky talus of the Glass Creek rhyolite to those underlying Terrace I. £ow. Terraces II^IV do not occur on the right Two paleochannels (K and L in Fig. 2) separate side of Glass Creek, nor does the present talus Terrace II from Terrace I. At its upstream termi- margin of the £ow show any evidence of £uvial nus, K is overlain by a bouldery debris-£ow levee, reworking. It is possible therefore that formation whereas L has been beheaded by later stream mi- of the Glass Creek rhyolite £ow postdates the gration and downcutting. The position of K and creation of all but the lowest terraces, if the talus the westward dip of the tread of Terrace II sug- slopes were formed for the most part during em- gest £uvial planing of a westward-sloping pyro- placement of the £ow.

Fig. 4. Lahar levee along Glass Creek canyon; note eight-year-old boy (arrow) for scale standing on the proximal end of the levee. The levees are continuous along this entire reach. The highest levees are approximately 35 m about the present stream bed.

VOLGEO 3013 13-2-04 Cyaan Magenta Geel Zwart 326 M. Bursik, J. Reid / Journal of Volcanology and Geothermal Research 131 (2004) 321^331

Fig. 5. (Map area B) Map of levees and deposits in Glass Creek canyon. Bold lines indicate outer edge of terrace treads in the Glass Creek embayment (compare map area A) and levee treads in Glass Creek canyon. Stippled area is lahar fan at downstream end of canyon where it widens as Glass Creek joins Deadman Creek to form Owens River.

3.2. Glass Creek canyon The deposits consist of 6 m of ¢nes-poor breccia, overlain by 2 m of pebbly, planar-bedded pumice Downstream from the embayment, Glass Creek deposits. Clasts within the deposits are angular to passes into a narrow canyon between Obsidian sub-rounded pumices of the Inyo eruption. Flow and Glass Creek Flow on its western end, The canyon opens onto a gently sloping surface which ends on the northwestern £oor of Long that conveys the waters of Glass Creek to the Valley caldera (Map area B, Figs. 1, 4 and 5). juncture with Deadman Creek to form the Owens The canyon was originally cut by stream action River. The surface is strewn with a high concen- after formation of the caldera. The steep, V- tration of pumice cobbles and boulders of the shaped walls are lined with local bedrock covered Inyo eruption. Modern Glass Creek has incised by pyroclastic material, colluvium and alluvium the surface along its southern edge. The deposits associated with the Inyo eruption. underlying the surface include a very poorly Numerous £at-topped surfaces sloping down- sorted pumice gravel throughout an exposed stream, covered with pumice boulders and cob- depth of V5m. bles, line the canyon along both banks (Fig. 4). The geomorphological and stratigraphic fea- The widths of the surfaces range from several me- tures in Glass Creek canyon are consistent with ters to 10 m. The more substantial surfaces are deposition from lahar(s) in the canyon following continuous for much of the length of the canyon. the Inyo eruption. The fact that the highest levees The larger surfaces are so regular that they can be are underlain by massive-bedded, coarse-grained mistaken for roads. The highest surface is the breccia, with planar beds at top, is consistent with most substantial, and is nearly continuous along non-cohesive lahar origin, and more dilute, hyper- both banks of the creek. At the upstream end of concentrated(?) stream£ow following lahar prop- the canyon, the highest surface is V5 m above agation, or in the lahar tail. Deposition from stream level, while at the downstream end, it is pulses within the lahar may have generated the V35 m above stream level. lower surfaces, although there is little evidence Near the upstream end of the canyon, the de- for pulses at other sites. The observation that posits underlying the surfaces are exposed in the the alluvial surface at the mouth of Glass Creek outer banks of incised meanders of Glass Creek. canyon, which is coplanar with some of the lowest

VOLGEO 3013 13-2-04 Cyaan Magenta Geel Zwart M. Bursik, J. Reid / Journal of Volcanology and Geothermal Research 131 (2004) 321^331 327 surfaces within the canyon, is underlain by coarse, take on the waters of Big Spring to become the massive beds suggests that it too is of non-cohe- Owens River. In the caldera £oor, the river £ows sive lahar origin. around the eastern edge of the resurgent dome in a single meandering channel for about the ¢rst 3.3. Owens River £oodplain 8 km below Big Spring. Continuing further around the dome to Crowley Lake, the £oodplain There are two environments on the £oodplain widens and is occupied by two parallel and com- of the Owens River in Long Valley caldera where parably sized meander belts that are separated by concentrated deposits of Inyo pumice are found a roughly 300 m wide strip of land lacking evi- (Map areas C and D, Fig. 1). In each case, the dence of river channels. Reid (1992) interpreted deposition appears to have occurred during lahar these parallel meander belts to indicate that, as £ow from the Inyo source region with some re- the resurgent dome in£ates and de£ates, the riv- working in the time following. One concentration er’s £oodplain changes in its cross-valley tilt, pos- occurs in an abandoned oxbow, where pumice ¢lls sibly inducing the river to alternately occupy one an old channel to its brim, resulting in slight relief of the two meander belts. With the dome cur- (Map area C). The surface expression of the pum- rently in£ating (Hill et al., 2002), the river is in ice-¢lled paleochannel is de¢ned by sagebrush the outboard of the two belts, and, based on early rather than the wetland grasses of a typical in- land surveys, has been so since at least the late ¢lled oxbow. The second concentration is a thin 19th century. debris £ow/£ood sheet of pumice blocks that cov- The pumice-¢lled oxbow is found in the now- ers large parts of the £oodplain and is thickest in abandoned inboard (toward the resurgent dome) a region about 0.5 km2 in area, in the southeast- meander belt about 2 km downstream of the ern reaches of the Owens River £oodplain just point where the two channels diverge (Fig. 6). upstream from Crowley Lake. Cross-cutting relationships in map view between In the northwest corner of Long Valley caldera, this channel loop and those near it indicate that Deadman Creek and Glass Creek join and then the pumice-¢lled loop is among the older channels

Fig. 6. (Locality C) Oblique aerial photograph showing the two meander belts of the Owens River in the £oodplain. The outer belt (top) is active today. The inner belt is ¢lled with permeable pumice deposits allowing good drainage and growth of sagebrush within the channel. Plants outside the channel in the £oodplain are mostly grasses.

VOLGEO 3013 13-2-04 Cyaan Magenta Geel Zwart 328 M. Bursik, J. Reid / Journal of Volcanology and Geothermal Research 131 (2004) 321^331 in the inboard belt; several nearby meander scars A pit (5.5 m in length, 1.5 m deep) dug in the at slightly lower elevations truncate it, suggesting pumice-¢lled channel cross-cut the outer channel that the river remained in this belt gently down- bank and perhaps the outer two-thirds of the cutting for some time after the pumice deposition. channel ¢ll (Connolly, 1997)(Fig. 3). The outer 14C accelerator mass spectrometry dating of 12 bank and the bed of the stream beneath the pum- conifer charcoals recovered from the layers within ice consist of volcanic and plutonic pebbles and the oxbow ¢ll cluster at about 600 yr, with several gravels representative of the Glass Creek and older, but none younger than that age (Reid et al., Deadman Creek headwater landscape, and con- 1998). The charcoal may represent debris from tain no pumice. The pumice deposit is crudely ¢res both during and before the Inyo eruptions. layered with coarse 15^20 cm pumice blocks in

Fig. 7. (Map area D) Map of low pumice-bearing hummocks near the distal margin of the lahar deposits. Star indicates excavation site. Darker gray means greater frequency of sur¢cial pumice boulders.

VOLGEO 3013 13-2-04 Cyaan Magenta Geel Zwart M. Bursik, J. Reid / Journal of Volcanology and Geothermal Research 131 (2004) 321^331 329 a basal layer overlain by successively ¢ner pumice in the inner meander belt for some time after the in mainly sandy and ^ in one locality ^ clayey lahar event(s). In fact, the youngest river channel matrices. The material on which the sagebrush is in the inner belt lies inboard of the highest concen- growing is a small pumice lens much poorer in tration of lahar pumice, suggesting that the river ¢ne clays (and thus more permeable) than the migrated toward the resurgent dome in the years underlying channel-¢lling pumice deposits. This following the Inyo eruptions, opposite to its mod- clean pumice may have been deposited by normal ern outward-migrating behavior. Two pits exca- stream£ow rather than as part of a lahar, as it sits vated where the surface is heavily littered with within a small channel in the more extensive de- pumice blocks reveal that the block layer is at posit. Its presence suggests that the river was di- most 20 cm thick, overlying V0.6 m of massive- verted progressively to a new channel as the loop bedded sandy mud and V0.3 m of normally ¢lled with pumice. The sur¢cial layer of the land- graded muddy sand to mud. These ¢ne-grained scape immediately bordering the sagebrush loop is deposits within the bounds of coarse-pumice a 15^20 cm layer of ¢ne soil that may be in part mounds most likely represent distal deposition aeolian. from a non-cohesive(?), non-diluting lahar that X-ray £uorescence trace-element data for the formed coarse margins and bifurcating £ow ¢ngers pumices from the excavated meander-loop pit de- at its distal limit (Scott, 1988; Vallance, 2000). ¢ne scatter-plot trends indistinguishable from ones derived from pumices collected at the Inyo Domes (Connolly, 1997), suggestive of a common 4. Discussion origin. In addition to the oxbow ¢ll, sparse pumice blocks are widely scattered over the £oodplain 4.1. Possible chronology of the abandoned inner meander belt, but are not found in the vicinity of the modern Owens River. Based on the stratigraphy and morphology These, like the ¢nal in¢ll of the sage-brush oxbow, found along the lahar path, the following history may represent river-deposited £otsam, rather than can be reconstructed. Before the Inyo eruption, a lahar deposition. The stratigraphy and geomor- £uvial surface covered the Glass Creek embay- phology are consistent with channel facies depo- ment. The products of the Inyo eruption, partic- sition from a small, (generally) non-cohesive lahar ularly those from the Glass Creek vent, covered having a sole layer, overall normal grading, and the surface with a pyroclastic apron that thinned a ‘whaleback bar’ surface morphology (Scott, to the west from the locus of the vents towards 1988). the base of the range. These deposits were at least Farther down-valley, about 2 km upstream of 20 m thick in the embayment. Remnants of this Crowley Lake and 30 km downstream from the apron occur as Terrace I. Because of the thinning Glass Creek embayment, the river’s two meander and consequent westward dip of the Glass Creek belts are more widely separated (Map area D, volcaniclastic apron toward the base of the range, Figs. 1 and 7). Here, much of the £oodplain sur- Glass Creek was initially constrained to follow a face of the inner meander complex is very densely course along the juncture of the apron and the littered with varying concentrations of pumice range front escarpment, forming the £uvial sur- blocks on low-lying mounds (Bryce, 1991). They face of Terrace II. With time, the stream began apparently represent the toe of a lahar. They do downcutting, and occupied Channel K, where it not cover all parts of the inner meander belt sur- remained for a time until an upstream avulsion face; the point bar surfaces that were most re- related to the deposition of the debris-£ow levee cently generated (before the river’s late 19th cen- forced it into a new course in L. tury avulsion to the modern meander belt) lack The creek at some time abandoned Channel L, pumice blocks, suggesting both that there was rel- and downcut dramatically to Terraces III and IV atively little reworking of this lahar material dur- and Q, which mark cut and ¢ll from normal ing later £ood events, and that the river remained stream£ow and lahar £ow. The highest levees in

VOLGEO 3013 13-2-04 Cyaan Magenta Geel Zwart 330 M. Bursik, J. Reid / Journal of Volcanology and Geothermal Research 131 (2004) 321^331

Glass Creek canyon, and the deposits at the can- in the embayment suggest that normal stream£ow yon mouth and in the £oodplain of Owens River existed in Glass Creek for a time after the pyro- are likely the products of the lahar generated by clastic eruption. The period of normal stream£ow the downcutting. Trailing lahar and stream£ow was terminated by generation of lahars, which pulses may have resulted in the deposits at the downcut through the pyroclastic apron within head of Glass Creek canyon, some of the lower the embayment and along the upper reach of surfaces within the canyon itself, and the upper Glass Creek canyon. Although much of the pum- deposits in the £oodplain. ice-rich material within the resulting lahar(s) must Terrace V is locally only a fraction of a meter have been eroded from the embayment, the occur- above present stream level. It represents minor rence of the levee at the upstream end of Channel downcutting, lahar and £uvial activity following K means that some debris £ows initiated further abandonment of Terrace IV. Some of the lowest upstream, within the Sierra Nevada. No direct surfaces in the canyon, the uppermost layers of evidence has been found that the Inyo pyroclastic the canyon fan, and the pumice-depleted deposits eruptions melted snow to initiate lahar forma- of the £oodplain may be the products of the Ter- tion, although the volume of pyroclastic material race V-cutting events. erupted during the Inyo eruptions was substantial The Glass Creek tephra ^ the youngest of the (V0.3 km3)(Miller, 1985), and there can be deep Inyo tephras ^ and associated £ow beds comprise snowpack in the Glass Creek basin. The average the uppermost layers of the oldest terraces of the April 1 snowpack at the nearest measurement sta- embayment. Therefore, the downcutting postdates tion, Mammoth Pass (Fig. 1), is over 1 m of water the pyroclastic phases of the Inyo eruptions. The equivalent (CDEC, 2003). It may be possible that Glass Creek lava £ow overlies all terraces in con- the pyroclastic deposits were remobilized during tact with it, down to and including Terrace V spring runo¡, because spring stream£ow on the (Fig. 2). Therefore, the time of terrace downcut- eastern side of the Sierra can be more than 10 ting and lahar formation occupies the interval be- times the £ow in summer and autumn. Traveling tween the pyroclastic and dome-forming phases of downstream from the Sierra and carrying mostly the Inyo eruption sequence. Miller (1985) points bedrock debris, debris £ows eroded preferentially out that there are no reasonable limiting ages on in the embayment because of the adverse slope of the eruption of the Inyo Domes. However, if oth- the thick pyroclastic debris (the surface of the er volcanoes, such as Mount St. Helens, can be apron must have dipped toward the range). Given considered analogous, then it seems likely that the the adverse slope, it is furthermore possible that domes were erupted within one decade of the py- water ponded there for a short time and broke roclastic phases of the sequence (Fink et al., out, although there are no pond deposits. 1990). Thus it seems reasonable to assume that Some, perhaps most, of the material in the la- most of the terrace downcutting took place within har(s) was eroded from the embayment. By recon- a span of several years following the deposition of structing a relatively smooth initial post-eruption the pyroclastic deposits, most probably during a surface linking all the highest terrace remnants in relatively short timespan (possibly only one sea- the embayment and subtracting the current eleva- son) directly following deposition of the pyroclas- tions of the terraces from the elevation of this tic layers. At Pinatubo, it has been observed that reconstructed surface, a volume V1.9U105 m3 downcutting of pyroclastic deposits and the vol- of terrace deposits is found to have been eroded. ume of lahar debris generated by the downcutting drop exponentially in the years following initial lahar deposition (Pierson et al., 1996). 5. Conclusions

4.2. Lahar origin We conclude that at least one lahar was generated during the Inyo eruption. The lahar £owed The stratigraphic and geomorphic relationships down the Glass Creek drainage, and into the

VOLGEO 3013 13-2-04 Cyaan Magenta Geel Zwart M. Bursik, J. Reid / Journal of Volcanology and Geothermal Research 131 (2004) 321^331 331

Owens River. The total volume was in excess of excavation over the years. This work was sup- 1.9U105 m3, maximum run-up height within ported in part by NASA Grants NAG52273 and Glass Creek canyon was 35 m, and the run-out NAG510648. C. Waythomas and P. Kokelaar are distance was at least 30 km, near the shoreline of thanked for very helpful reviews. present-day Lake Crowley. The volume of the £ow represents a signi¢cant amount of material that could have an important impact on the References watershed, including Lake Crowley, the reservoir Bryce, J.G., 1991. Master’s Thesis, Univ. Virginia. used by the city of Los Angeles for drinking water CDEC (California Data Exchange Center), 2003. http://cdec. storage. water.ca.gov. A lahar during future eruptions may pose a Connolly, N.T., 1997. Bachelor’s Thesis, Hampshire College, signi¢cant volcanic hazard that has not heretofore MA. been considered explicitly for this most active vol- Fink, J.H., Malin, M.C., Anderson, S.W., 1990. Intrusive and extrusive growth of the Mount St. Helens dome. Nature 348, canic area of the southwestern U.S. Future erup- 435^437. tions from the Mono^Inyo Craters could occur Hill, D.P., Dzurisin, D., Ellsworth, W.L., Endo, E.T., Gallo- anywhere in the 50-km-long chain. Eruptions way, D.L., Gerlach, T.M., Johnston, M.S.J., Langbein, J., near Mammoth Mountain or the southern Mono McGee, K.A., Miller, C.D., Oppenheimer, D., Sorey, M.L., Craters could potentially occur near streams like 2002. Response plan for volcano hazards in the Long Valley caldera and Mono Craters region California. U.S. Geol. Glass Creek. At Mammoth Mountain, a lahar in Surv. Bull. 57. Mammoth and Hot Creeks could a¡ect the resort Miller, C.D., 1985. Holocene eruptions at the Inyo volcanic town of Mammoth Lakes and reach Lake Crow- chain, California: implications for possible eruptions in ley, which is 30 km away from potential eruptions Long Valley Caldera. Geology 13, 14^17. sites. In the southern Mono Craters, the resort Miller, C.D., 1989. Potential hazards from future volcanic eruptions in California. U.S. Geol. Surv. Bull. 1847, 17 pp. town of June Lake could be a¡ected by lahars Miller, C.D., Mullineaux, D.R., Crandell, D.R., 1982. Poten- within Reversed and Rush Creeks. The impact tial hazards from future volcanic eruptions in the Long Val- on Grant Lake, another reservoir used for water ley-Mono Lake area, east-central California and southwest storage by Los Angeles, could be greater than the Nevada: a preliminary assessment. U.S. Geol. Surv. Circ. impact on Lake Crowley for a lahar of similar 877, 10 pp. Pierson, T.C., et al., 1996. Flow and deposition of posterup- volume to that described here. Grant Lake is tion hot lahars on the east side of Mount Pinatubo, July- only 15 km downstream from a potential eruption October 1991. In: Punongbayan, R., Newhall, C. (Ed.), Fire site, and has a volume much smaller than Lake and Mud: Eruptions and Lahars of Mount Pinatubo, Phil- Crowley. ippines Quezon City/Seattle. Philippine Institute of Volca- The work has some implications for analysis of nology and Seismology/University of Washington Press. Reid, J.B., Jr., 1992. The Owens River as a tiltmeter for Long lahar hazards at other volcanoes. It may be that Valley Caldera, California. J. Geol. 100, 353^363. lahar has not yet been characterized for the Reid, J.B., Jr., Reynolds, J.L., Connolly, N.T., Getz, S.L., Mono^Inyo Craters because some of the evidence Polissar, P.J., Winship, L.J., Hainsworth, L.J., 1998. Carbon is erosional, and because the deposits that do exist isotopes in aquatic plants, Long Valley Caldera, California are relatively restricted in lateral extent and not as records of past hydrothermal and magmatic activity. Geophys. Res. Lett. 25, 2853^2856. near active stream channels. Entire stream can- Scott, K., 1988. Origins, Behavior, and Sedimentology of La- yons and £oodplains should be explored for the hars and Lahar-runout £ows in the Toutle-Cowlitz River existence of lahar deposits. System. U.S. Geol. Surv. Prof. Pap. 1447-A, 74 pp. Sieh, K., Bursik, M., 1986. Most recent eruption of Mono Craters, Eastern Central California. J. Geophys. Res. 91, 12539^12571. Acknowledgements Vallance, J.W., 2000. Lahars. In: Sigurdsson, H. (Ed.), Ency- clopedia of Volcanoes. Academic Press, San Diego, CA, pp. Many students were helpful in mapping and 601^616.

VOLGEO 3013 13-2-04 Cyaan Magenta Geel Zwart