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Geology of Selected Lava Tubes in the Bend Area, Oregon

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Geology of Selected Lava Tubes in the Bend Area, Oregon STATE OF OREGON DEPARTMENT OF GEOLOGY AND MINERAL INDUSTRIES 1069 State Office Building Portland, Oregon 97201 BUL LETI N 71 GEOLOGY OF SELECTED LAVA TUBES IN THE BEND AREA, OREGON By Ronald Greeley Space Sciences Division National Aeronautics and Space Administration Moffett Field, California 1971 GOVERNING BOARD Fayette I. Bristol, Rogue River, Chairman R. W. deWeese, Portland Harold Banta, Baker STATE GEOLOGIST R. E. Corcoran FOREWORD Oregon probably has the greatest diversity of volcanic rock types and landforms of any region in the conterminous United States. The area centering around Bend has come to be known as Oregon's "moon country" because the very young volcanic rocks in this vicinity show features similar to what have been photographed on the lunar surface. The National Aeronautics and Space Administration has, therefore, spent considerable time studying various aspects of the terrain in central Oregon because its scientists have interpreted certain lunar forms, such as the sinuous rilles, as volcanic structures. Mr. Ronald Greeley, the author of this report, believes that some of the smaller lunar rilles probably resuI ted from I ova-tube coli apse. Up to the present time, there has been relatively little study of lava tubes in the western United States to determine their origin, nor have these unusual structures been described in sufficient detail to be classified into different types. Mr. Greeley has selected several lava tubes in the Bend area for such a study because of their excellent development and relative ease of access. The Department presents this publication with the hope that it will stimulate the interest of others in exploring the many unusual and fascinating geologic features that occur in our "moon country. " R. E. Corcoran Oregon State Geologist ii CONTENTS Page -- Abstract . 1 Introduction Field methods 3 Geology and physiography 3 Lava tube formation . 5 Lava tube descriptions 12 Arnold Lava Tube System 12 Upper section . 12 Charcoal Cave 12 Arnold Ice Cave 15 Middle section 15 Collapsed Lava Pond No. 15 Deg Cave 18 Bat Cave 18 Lower section . 18 Wind Cave 18 CoII apsed Lava Pond No. 2 22 Pictograph Cave 22 Coli apsed Lava Pond No. 3 24 2 24 Charcoal Cave No. Collapsed Lava Pond No. 4 24 Stookey Ranch Cave 27 Collapsed Lava Pond No. 5 27 Horse Lava Tube System 27 Lewis Farm Caves 27 Garbage Caves 31 Garbage Cave No. 2 31 Stevens Road Cave 31 Horse Cave 31 Wilson Cave 31 Barlow Cave 31 iii Page Miscellaneous lava tubes . 33 Lava Top Butte Caves 33 Log Crib Cave 33 South Ice Cave 34 Skeleton Cave 34 Boyd Cave 36 Lava River Cave . 40 Conclusions 45 Acknowledgments 45 References cited 46 Appendix (location of surveyed lava tubes near Bend) 47 iv ILLUSTRATIO NS Figures Page Marius Hills region of the Moon . Structure interpreted to be a partly col l apsed lava tube l. 2 2. Location map and physi ography of central Oregon showing area of investigation near Bend 4 3. D iagram of a minor lava tube system in north ern California 6 4a. Bear Trap Lava Tube , Idaho, showing layered lava 7 4b. Jug Cave, Washington, showing layered lava 7 5. W ind Cave showi ng flow lines and cut bank at meander bend 8 Rim of col l apse pit, Barlow Cave, sh owing plastic deformation of lava crust 10 6. Boyd Cave Lava Tube sh ow ing sand at surface draining into tube 11 7. Boyd Cave Lava Tube sh owing sand draining through roof fracture 8. 11 Map of Arnold LavaTube System . 9. 13 10. Obl ique aerial view of upper Arnold Lava Tu be System 14 . Arnold Ice Cave near entrance 11 16 12. Arnold Lava Tube System; cross sections transverse to lava tube axis ; 7 o . 13. Diagrams of coll apse lava ponds f Ar nold Lava Tu be System 17 Bat Cave sh owing p lastically deformed lining curling from wa ll 14. 19 Wind Cave sh owing plastic deformation of wall lining 15. 21 Entrance to Pictograph Cave . 23 16. En trance to Pictograph Cave showi ng possible gas pocket 23 17. Pictograph Cave downtube from entrance 18. 25 Oblique aerial view of Collapsed Lava Ponds No . 3 and No . 4 26 19. 20. Map of Horse Lava Tu be System . 28 Di agrams of Le wis Farm Cave, Horse Lava Tube System 21. 29 v Page Diagrams of Garbage Caves Nos . and Horse Lava Tube System 30 22. I 2, 23. Diagrams of Horse Cave, Horse Lava Tube System 32 24. South Ice Cave viewed toward entrance 35 25. Diagram of South Ice Cave 37 26. Skeleton Cave Interior . 37 27. Planimetric diagram of Lava River Cave 38 28. Longi tudinal profi le of Lava River Cave 39 29. Lava River Cave near entrance . 41 30. Lava River Cave interior showing roof col lapse and multiple flow lines on wa lls 42 31. Lava River Cave interior partly fi lled with sand 42 32. Lava River Cave interior at the Sand Gardens 43 33. Lava River Cave interior cross sec ti on 44 Plates (fo ld-outs at end of bul letin) 1. Arnol d Lava Tube System Selected lava tubes n ear Bend, Oregon 2. 3. Ph otogeolog ic map of th e lava tubes of parts of Bend and Newberry 30' quadrangles, Oregon VI GEOLOGY OF SELECTED LAVA TUBES IN THE BEND AREA, OREGON by Ronald Greeley ABSTRAC T Lava tubes in the vicinity of Bend, Oregon, we re mapped and studied in detail to determine their geomorphology and mode of formation . Longitudinal profiles representing 5872.5 m of mapped lava tubes and a photogeologic map relating lava tube s to surface geology, regional structure and topography are prese nted. Three sets of lava tubes we re examined: 1) Arnold Lava Tube System (7km long) composed of col l apsed and uncal lapsed tube segments and lava ponds, 2) Horse Lava Tube System (11 km long) composed of parallel and anastomosing lava tube segments, and 3) miscell aneous lava tubes. Results of this study te nd to confirm the "l ayered lava" hypothesis of Oilier and Brown (1965) for lava tube forma­ tion; however, th ere are probably several modes of formation for lava tubes in general . Arnold System is a single series of tubes apparently formed in a single basalt flow on a relatively steep gradient. The advancing flow in wh ich the tubes formed wa s apparently temporarily halted, resulting in the formation of lava ponds wh ich we re inflated and later drained by the lava tube system. Horse System probably fo rmed in multiple, interconnected flaws . Pre-flow gradient appears to have been less than for Arnold System, and resulted in meandrous, multiple tube networks. INTRO DUCTION Interpretation of certain lunar surface features as vol canic structures has resulted in increased in terest in the geomorphology of te rrestrial val conic ana logs. A recent report (Oberbeck an d others, 19 69) propose d that some smaller lunar sinuous rilles (general ly, those less than about 0.5 km wide) probably resulted from lava tube collapse . Other structures (figure l) may be partially col l apse d lunar I avo tubes (Greeley, 1970) Unfortunately, I ittle is known about the formational mechanisms and geomorphology of lava tubes an d it is difficul t to establish criteria to distinguish lunar lava tubes, both collapsed and partly col l apsed, from oth er lunar structures without data on terrestrial counterparts. For th is reason , some of th e major lava tu bes in th e western United States were examined and surveyed to gain an understanding of the geology of these complex structures . The tubes are of interest to several groups besides geol ogists, including zool o­ gists interested i n cave biota, an thropo logists concerned with historic and preh istoric inhabitants, U. S. Forest Service personnel responsible for recreational facilities and safety of National Fo rest visi tors, an d the National S peleological Society, an organization of amateur and professional cave expiorers. The Bend, Oregon area is characterized by relatively young, unweathered vol canic fe atures that are we ll suited for study . In the initial stages of examination of te rre strial analogs to lunar strudures, a field conference was held in Bend to study some of the volcan ic structures (Peterson Groh, 1965). and L a tubes, ho wever, we re only br iefly considered during the conference. This report presents de ta i led av de scriptions of se lected lava tubes, theory of tube formation, and a sketch of the general geology of the Be nd are a. There are many lava tubes in the Bend area. Those th at we re se lected for mapping and study I ie mai nl y an d southeast of Bend. They comprise the Arnold Lava Tube System, i·he Horse Lava Tube east Sy stem, and miscellaneous lava tubes such as Skeleton Cave, Boyd Cave , an d South Ice Cave . Lava River Cave so uth of Bend has al so been in cluded because of its general interest to the publ ic and its ac cessibility as a State Park. 2 LAVA TUBES IN THE BEND AREA MAR IUS HILLS LO ::2:-51 M-212 � N � 0 5 km Figure l. Morius Hills region of the Moon (west-central Oceanus Procellorum). Structure is interpreted to be a portly collapsed lava tube originating from on endogenous crater-vent. From its morphology, the Iorge crater is consid­ ered impact generated. Photograph from NASA Lunar Orbiter V, Site 51, Frome M-21 2.
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