U.S. DEPARTMENT OF THE INTERIOR GEOLOGIC INVESTIGATIONS SERIES I–2723 U.S. GEOLOGICAL SURVEY Pamphlet accompanies map

121°30' 121°27'30" 626200 626400 121°35' 121°32'30" 626600 626800 btb CORRELATION OF MAP UNITS 627000 627200 wf22 [Symbols on map in parentheses indicate buried units.Units indicated by magenta brackets have uncertain age relations] p22 or btb p22 or abm wv22 whe

or (dlp) or or p17 ch wv22 fh wv22 atu or wv22 ch oa wf22 btb p22 pf22 or abw dlp d19 wv22 atu atu btb abm atu btb atu f19 4483400 dlp btb w19 dlp 4483400 or btb s19 wf22 (atu) wf22 p22 btb p19 dlp d14

~0.3 ka scj btb fh lh ch (sh) or or whe

rcf ccf Holocene sce

arp rce cce (mrm) p1 7 scd dlp f19 rcd ccd fh fa arp rcc ccc or rcb ccb 4483200

rca pc 4483200 mrm fa ~1 ka wv22 ~8 ka whe p1 7 arp arp arp the dlp dlp p1 7 tal fr ta oa fa ch tb d14 40°35' trl dlp 40°35' or clp slp ch 27±1 ka ch pc pflp dlp dlp oa tb dlp slp tr or fr fr fa rk 4483000 d14 dlp QUATERNARY

oa 35±3 ka abw pfk 35±1 ka 4483000 tr abm fk ch tb slp dlp abm abm 41±1 ka psf rsf dlp oa ch abm d19 pc slp acr fh f19 wf22 dlp dlp oa abm dcr ch tr ch ahm 25±21 ka apr oa slp tr 43±2 ka rkr arp abm atb slp abm r27 dlp tr ch tr abm fa oa ch axe tr oa abm slp tr p22 fh ta bnt re pc arp fh slp pfe 66 4 ka psf ± ta tr

atu Pleistocene wv22

arp 4482800 abk bnt rsf tr meh ch sd tb clp 4482800 atb atb ta mrl d19

tb ta mrm rsf pc ch lh rsf pc 199±2 ka psf 193±11 ka rdm bec dlp bnt ch 212±5 ka dr atb abk p1 9 ta slp meh ta 244±10 ka dsh ahm 261±5 ka w19 fh abk rsf wf22 d83 dvc dpl arp 270±18 ka fa tr mrl dum trl (mrl) rsf 297 1 ka ta ± rmz dlp sd amc fr ta dlp (meh) wv22 rsf rsf fh sd ta rl av 313±8 ka dlp ta pfe (sd) pc sd pc rrp 4482600 dlp pc 40°32'30" amc 40°32'30" amc slp pfk 4482600 mrl scj tr abk amc dlp dlp amc pc ta arp (sd) scj wf22 pfe 708±21 ka abm amc amc bnt ch rsf pc atb fh amc btb ch pfe cce ccc ch ch ta av fh tr ch bec fh ta dlp fh wf22 arp pc ch ch amc tr fr scd ch rcf ch wf22 dlp amc rcc rcc sce slp ch ch fh LIST OF MAP UNITS ta rcb ccc rcc dlp rsf All units are Quaternary in age. Symbols on map in parentheses indicate buried units. Initial letter ch rcf wv22 ta rrp slp ch of each map symbol indicates dominant lithology of unit, as follows: abk fh (ch) rmz tb rce fh ta ccc ccf Volcanic units Sedimentary units ch tr ahm dlp ch pc abk b, basalt (<53% SiO ) c, colluvium, including talus dlp ch cce 2 fa pc d83 w19 ta m, mafic andesite (<57% SiO ) f, fluvial deposits, including most alluvium 4482400 tr rcd 2 ch fa ta ch rcc(?) fh tr a, andesite (<63% SiO ) l, lacustrine deposits s19 (arp) s19 2 rcb ta w19 4482400 ch d, dacite (<68% SiO2) o, glacial outwash deposits rcd d83 pfk ta rcd ccd d83 pc ta w19 (ahm) r, rhyodacite (<72% SiO ) and rhyolite s, landslide and avalanche deposits amc ccb wf22 s19 (ta) 2 ta (≥72% SiO ) t, till abk pc abk abk ta fh 2 (sh) p, pyroclastic deposits (pf, pyroclastic-flow w, mudflow and other debris-flow deposits tr d83 whe w19 ta ccb ch (sh) pf22 fh (pfk) wf22 deposits) ta r27 s19 dlp ch ch rkr ta s19 (sh) dlp (tal) HOLOCENE dlp tr rkr ta pc pflp s19 d83 ta ta (ch) w19 rcb dcr w19 p17 Pyroclastic deposit of May and June, 1917, from Lassen Peak ch 626200 rl lh ch d83 wf22 626400 626600 rkr (rkr) ta pfk w19 626800 pflp pfk wv22 Viscous debris-flow deposits of May 22, 1915, from Lassen Peak Base from U.S. Geological Survey, Branch of Astrogeology, 627000 627200 ta ta SCALE 1:2 500 pc rkr wf22 (pfk) Photogrammetry Section, 1988. Compiled on AS11-B1 tr fh 0 0.05 0.10 0.15 0.20 0.25 MILES rkr wf22 pfk p22 Pumice-fall deposit of May 22, 1915, from Lassen Peak analytical stereoplotter using U.S. Department of Agriculture tr rca fk color aerial photographs 1673-089 and 1673-090 taken August ta ta pkf 0 0.05 0.10 0.15 0.20 0.25 KILOMETERS ta wv22 28, 1973 (Project LA02-06089). Control points obtained from d83 rrk wf22 Fluid debris-flow deposits of May 22, 1915, from pyroclastic flow ch pf22 1:24,000 Lassen Peak and Reading Peak quadrangles. Grid is ta rkr (ta) ta pf22 fk CONTOUR INTERVALS 2 (ABOVE 3100) AND 5 (BELOW 3100) METERS rl pc d83 rkr tr ta UTM of zone 10. ccb pc (t r) (abk) rdm pf22 Pyroclastic-flow deposit of May 22, 1915, from Lassen Peak dcr pflp fh fh (dcr) d38 d83 wf22 (rdm) d19 Dacite flow of May 19-20, 1915, on Lassen Peak dum rkr ch GEOLOGIC MAP OF THE LASSEN PEAK SUMMIT AREA pc d83 d83 pc r2 7 pflp pf22 fh whe f19 Flood deposits of May 19-20, 1915, in Hat Creek pf22 fh rdm rl ch (ch) rkr pf22 dum (r27) r27 pc (ch) w19 Debris-flow deposits of May 19-20, 1915, from avalanche deposit acr (tal) w19 (ch) pc pfk Pyroclastic-flow deposit of Kings Creek Contact rsf rkr pc pflp —Contacts shown within unit indicate contacts between separate pc (r27) (s19) ta r27 (ch) ch (ta) s19 Avalanche deposit of May 19, 1915, from Lassen Peak volcanic domes whe pflp fk Sediments beneath pyroclastic-flow deposit of Kings Creek dum wf22 ta (pfk) p19 Pyroclastic deposit of May 19, 1915, on Lassen Peak Certain (whe) pf22 (pfk) pc (clp) pf22 psf Pyroclastic-flow and proximal fall deposits of Sunflower Flat rl clp wf22 whe ta Approximately located (whe) r27 ch d14 Dacite dome of May 14-19, 1915, on Lassen Peak dpl ch pf22 40°30' rsf Rhyodacite domes of Sunflower Flat Inferred p22 wv22 40°30' wf22 scj Avalanche deposits of Chaos Jumbles, from dome C of Chaos Crags wf22 pfk Concealed 121°30' ch wv22 whe p22 ahm Andesite flow of Hat Mountain clp wf22 pf22 wv22 p22 (tal) rcf Rhyodacite dome F of Chaos Crags Bear Wallow Butte (dlp) Fault—Bar and ball on downthrown side Chaos Jumbles avalanche deposits dlp p22 acr Andesite scoria deposit on west rim of Crescent Crater ch ccf Talus, emplaced hot from dome F of Chaos Crags Certain Lassen dacitic dome field ta wv22 clp p22 tal dr dcr Dacite dome and flow of Crescent Crater Approximately located 1915 dacitic flow and dome (historic) ch the sce Avalanche deposit from partial collapse of dome E of Chaos Crags ch fh clp rkr Rhyodacite dome and flow of Krummholz Younger prehistoric dacitic domes dlp whe Concealed clp dlp rce Rhyodacite dome E of Chaos Crags (clp) rk Twin Bridges p22 ta r27 Rhyodacite flow of Section 27 on north flank of Lassen Peak Flow direction of landslide Older dacitic domes ch e k p1 7 H a t C r e e k ch cce Talus, emplaced hot from dome E of Chaos Crags r e dlp Vent of unnamed dacitic dome C d14 Moraine crest t clp axe Andesitic mixed lava of Eagle Peak s Map Area o ch p22 clp scd Avalanche deposit from partial collapse of dome D of Chaos Crags Vent of named dacitic dome L dlp Concealed moraine crest dlp re Rhyodacite dome and flow of Eagle Peak dlp ta dvc clp p1 9 rcd Rhyodacite dome D of Chaos Crags Crater rim clp clp pfe wv22 d19 ch Pyroclastic-flow deposit of Eagle Peak ch fh ccd Talus, emplaced hot from dome D of Chaos Crags Concealed crater rim fh sd Highway 44 dlp Avalanche deposit from dacite older than pyroclastic-flow deposits of dlp wv22 dlp tal Red Lake ta rcc Rhyodacite dome C of Chaos Crags Eagle Peak Volcanic vent Badger wv22 wv22 clp Mountain Red tal Mountain Mountain fh tal atu Andesite flow of Tumble Buttes older than Bear Wallow Butte ccc Talus, emplaced hot from dome C of Chaos Crags Concealed volcanic vent fh dlp clp ch ch ch dlp meh Mafic andesite flow of Eskimo Hill Lateral limits of tree destruction by snow-laden pyroclastic flow of May Table the tal rcb Rhyodacite dome B of Chaos Crags Eskimo dlp M Mountain LASSEN VOLCANIC NATIONAL PARK ch re Hill ch 22, 1915 a n z a n i t a C h u t e tal tal dlp mrl Mafic andesite flows of Red Lake Mountain ccb Talus, emplaced hot from dome B of Chaos Crags Lateral limits of snow and hot-debris avalanche of May 19-20, 1915 Sunflower Flat ch rk mrm Mafic andesite flow of Red Mountain ch ch ch rca Rhyodacite dome A of Chaos Crags clp 122° 121° 120° Chaos tb Till of Badger Mountain ta Jumbles pc Pumiceous pyroclastic-flow and fall deposits of Chaos Crags 42° OREGON dvc Dorris Tulelake Anklin ch Meadows Raker fh CALIFORNIA C r e e k M k whe Debris-flow deposits from the northeast side of Lassen Peak a n a L Peak e MIDDLE PLEISTOCENE a n z i t a Manzanita n e M o r Lake z s dpl a t C n CENTRAL PLATEAU ch the Till or protalus-rampart debris of early Holocene age C Emigrant axe dsh rdm Rhyodacite flow of Dersch Meadows i t t r 97 395 Deep e Pass a a e Hole k H pfe fh Fluvial deposits of Holocene age bec Tholeiitic basalt flow of Eagle Canyon C A S C A D E R A N G E 139 C Chaos LOCATION OF GEOLOGIC MAP OF r e Crags

THE LASSEN PEAK SUMMIT AREA MODOC e lh Hill 7241 k Crescent Hat Mountain Lacustrine deposits of Holocene age dr Dacite domes of Reading Peak Hill SISKIYOU COUNTY Crater 299 8283 Dersch COUNTY ch Colluvium and talus of Holocene age evastated Area dsh Dacite dome of Ski Heil Peak Alturas Hill 6924 D 299 40°30' Meadows Weed (sh) Landslide deposits of Holocene age—Buried unit only bnt Tholeiitic basalt flow of Nobles Trail 1915 flow Loomis Lassen B a i l e y and dome Paradise Mount Shasta C r Peak Peak e e Meadows dvc Dacite dome of Vulcans Castle McCloud k LATE PLEISTOCENE 89 Dunsmuir Eagle dpl Dacite flow of Lassen Peak Trail Parking Lot Vulcans Peak tal 5 Castle Late till of Anklin Meadows PARKING Reading d83 Dacite dome and flow of hill 8283 LOT 299 Peak 121°35' 121°32'30" 121°30' 121°27'30" INTERIOR—GEOLOGICAL SURVEY, RESTON, VA—2002 ta Till of Anklin Meadows Ski Heil Kings Creek k 16 1/ SHASTA Park Road e 2° SCALE 1:24 000 41° Mt. Diller Peak Meadows r e Base from U.S. Geological Survey, dum Dacite flow of upper Manzanita Creek COUNTY C 1 1/ 2 0 1 MILE Geology mapped 1982-1996; digital compilation by Reading Peak, Lassen Peak, West oa Outwash deposits coeval with till of Anklin Meadows 395 s TH K i n g R R.L. Christiansen Burney Prospect Peak, and Manzanita Lake, O arp Andesite flows of Raker Peak 1985 N 1 .5 0 1 KILOMETER CALIF. Edited by Jan Zigler and Theresa Iki; digital TIC fa Alluvium coeval with till of Anklin Meadows E 299 cartography by Kathryn Nimz 89 139 Lambert Conformal Conic projection TRUE NORTH GN LASSEN BROKEOFF STRATOCONE A rmz Rhyodacite flow of Manzanita Chute M CONTOUR INTERVAL 40 FEET Manuscript approved for publication April 12, 2000 COUNTY clp Talus of Pleistocene age on Lassen Peak Brokeoff Diamond Peak APPROXIMATE MEAN Old Station CALIFORNIA e 0 1 2 3 km H C r e k DECLINATION, 2001 MAP LOCATION rl Rhyodacite flow of Loomis Peak Mountain o t g s MAP AREA NEVADA S p r i n trl Post-maximum till of Raker Peak, consisting of Lassen Peak avalanche LASSEN VOLCANIC NATIONAL PARK debris av Andesite flow of Viola Redding 44 Figure 2. Map showing Lassen dacitic dome field (shaded) in relation to Brokeoff stratocone and slp 273 44 Avalanche debris spread across glacial ice from Lassen Peak rrp Rhyolite dome of the west side of Raker Peak Anderson Central Plateau, the area of the geologic map (heavy magenta line), and place names used in the text. Susanville pflp Pyroclastic-flow deposit from partial dome collapse of Lassen Peak abk Andesite flows and debris flows of the composite Brokeoff volcano Mineral LVNP 36 36 5 89 Chester dlp Dacite dome of Lassen Peak Westwood amc Andesite flow and cinder cone (black-stippled area) of lower Manzanita 36 Creek (part of Brokeoff volcano) TEHAMA tr Till of Raker Peak 89 PLUMAS Red Bluff COUNTY Herlong GEOLOGIC MAP OF THE LASSEN PEAK, CHAOS CRAGS, AND UPPER HAT CREEK AREA, CALIFORNIA Greenville COUNTY or Outwash deposits coeval with till of Raker Peak EARLY PLEISTOCENE AND EARLY PLEISTOCENE(?) 395 Los Molinos 40° 70 By fr Alluvium coeval with till of Raker Peak abm Andesite flows of Badger Mountain 70 Quincy 0 10 20 30 km For sale by U.S. Geological Survey, Information Services, 99 32 BUTTE Corning Box 25286, Federal Center, Denver, CO 80225, Robert L. Christiansen, Michael A. Clynne, and L.J. Patrick Muffler abw Andesite flow of Bear Wallow Butte btb Tholeiitic basalt flows of Twin Bridges COUNTY or call 1–888–ASK–USGS Figure 1. Map of northeastern California showing location of Available on World Wide Web at Printed on recycled paper rk Rhyodacite flow of Kings Creek atb Andesite flows of Table Mountain 2002 Lassen Volcanic National Park (LVNP) and area of geologic map. http://geopubs.wr.usgs.gov/i-map/i2723