{"id":391,"date":"2017-07-19T14:35:24","date_gmt":"2017-07-19T21:35:24","guid":{"rendered":"https:\/\/blogs.ubc.ca\/arsgeophysica\/?p=391"},"modified":"2017-07-19T15:59:52","modified_gmt":"2017-07-19T22:59:52","slug":"391","status":"publish","type":"post","link":"https:\/\/blogs.ubc.ca\/arsgeophysica\/2017\/07\/19\/391\/","title":{"rendered":"Pre-reading for the Field: Volcanism of the Eastern Snake River Plain, Idaho"},"content":{"rendered":"

Summary of Selected Chapters from “Volcanism of the Eastern Snake River Plain, Idaho: A Comparative Planetary Geology Guidebook”\u00a0<\/strong>(NASA 1977)<\/p>\n

_______________________________<\/p>\n

Chapter 1: Introduction (Greeley and King) <\/em><\/p>\n

-Basaltic volcanism appear to cover substantial areas of the terrestrial planets<\/p>\n

-The Snake River Plain (SRP)<\/em> is similar in morphology to many volcanic regions on the Moon\/Mars\/Mercury<\/p>\n

-SRP is an optimal analogue owing to its good preservation state, lack of forests \/ heavy vegetation (which would impede radar), and good network of jeep trails<\/p>\n

-Study is restricted to central and Eastern sections of SRP<\/p>\n

 <\/p>\n

_______________________________<\/p>\n

Chapter 2: Volcanic Morphology (Greeley) <\/em><\/p>\n

-A VOLCANIC CONSTRUCT* is an accumulation of volcanic products. Examples include stratovolcanoes, basaltic plains, cinder cones, etc.<\/p>\n

-Factors influencing the morphology of Volcanic Constructs*:<\/p>\n

    \n
  1. a) Eruption style (Strombolian, Plinian, etc.)<\/li>\n
  2. b) Proportion of liquids (lava), gases (volatiles), solids (tephra)<\/li>\n
  3. c) Lava Viscosity (Temperature, composition, volatiles, degree of crystallization, flow character (laminar vs.<\/li>\n<\/ol>\n

    turbulent)<\/p>\n

      \n
    1. d) Vent characteristics (shape, number, arrangement)<\/li>\n
    2. e) Effusion rate\/duration<\/li>\n
    3. f) Pre-flow topography<\/li>\n<\/ol>\n

      -Volcanic morphology is largely a function of eruption style; for example:<\/p>\n

      -BASALTIC FLOODS: produce large volumes of hot, fluid lava that often form LAVA PONDS<\/p>\n

      -STROMBOLIAN ACTIVITY: repeated eruptions of tephra and pasty lava ejected short distances from the<\/p>\n

      vent, deposited to form CINDER CONES<\/p>\n

      -PELEEAN ERUPTIONS: Thick, pasty block lava flows in low volumes, forming DOME volcanoes<\/p>\n

      \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/em>-Block lavas often characterized by \u2018corded\u2019 large-scale textures<\/p>\n

      -Volcanic materials include liquids (lava), gases (eg. Steam), and solids (pyroclastics, tephra such as ash\/lapilli\/blocks\/bombs)<\/p>\n

      – Higher proportion of lava erupted = Lower profile (ie. flatter) volcanic profile (eg. Hawaiian)<\/p>\n

      -Higher proportions of solid ejecta = Steepening<\/p>\n

      -High volatile content = fire fountaining \/ cinder cones \/ spatter cones<\/p>\n

      -Low volatile content = high lava fluidity (ie. volatiles remain in solution)<\/p>\n

      -LAVA VISCOSITY<\/p>\n

      –>One of the most complex parameters governing lava morphology<\/p>\n

      –>Controlled by primarily by Temperature \/ Composition \/ Volatiles \/ Degree of Crystallization \/ Flow Regime (laminar\/turbulent)<\/p>\n

      *Inverse exponential relationship between temperature\/viscosity (ie. visc = exp(1\/T) )<\/p>\n

      *Lunar \u2018lavas\u2019 (impact melt flows) are more fluid than any terrestrial ones<\/p>\n

      –>Composition: Governed by felsic vs. mafic content (ie. silica distribution)<\/p>\n

      –>Silica can form 3D networks that retard flow and increase lava viscosity!<\/p>\n

      -VOLCANIC VENTS<\/p>\n

      –>Shape: Central\/Point (eg. Craters) vs. linear (fissures)<\/p>\n

      –>Central vents: spatter cones\/ cinder cones \/ shields \/ domes<\/p>\n

      –>Linear vents: Plateaus \/ plains<\/p>\n

      –>Fissures feeding flood basalts can be huge: eg. Yakima Basalt (of Columbia River Plateau) is >130km long<\/p>\n

      –>Each fissure produces one eruption; subsequent fissures with new eruptive material are commonly ~parallel to previous fissures<\/p>\n

      –>Valley floors typically contain the thickest \/ most active part of a lava flow<\/p>\n

      -EFFUSION RATE\/DURATION<\/p>\n

      –>Effusion rate is the primary factor controlling lava flow LENGTH<\/p>\n

      –>Units\u00a0 = [Lava Volume \/ Time]<\/p>\n

      –>ie. High effusion = extensive, \u2018simple\u2019 flows (ie. a single cooling unit, such as a flood basalt);<\/p>\n

      Low effusion\u00a0 = layered, \u2018compouned\u2019 flows comprised of multiple cooling units<\/p>\n

       <\/p>\n

      -BASALTIC LANDFORMS<\/p>\n

      –>Diverse: range from highly fluid to very viscous flows<\/p>\n

      -FLOOD BASALTS: Form extensive, thick flows erupted at very high rates from fissure vents, producing<\/p>\n

      vast basalt plateaus<\/p>\n

      -VOLCANIC SHIELDS: Produced by high eruption rate, though resulting in lower total lava volumes than for flood basalts<\/p>\n

      –>Central vents<\/p>\n

      –>Sporadic eruptions, as opposed to continuous eruptions for flood basalts<\/p>\n

      –>Thinner flow thicknesses<\/p>\n

      –>Can have rapid outbursts of high volume, short duration flow<\/p>\n

      -BASALTIC PLAINS: Combine characteristucs of both flood basalt and volcanic shields<\/p>\n

      –>SRP epitomizes this: Lava flows 10m thick, erupting both from central vents producing low lava shields (LOW SHIELDS) and short fissures<\/p>\n

      *Size\/surface feature morphology resembles smaller lunar maria<\/p>\n

      *Lava tubes \/ Lava flow channels common (as for shield volcanoes)<\/p>\n

      –>COMPOSITE CONES: Steep volcanoes surrounding central vents<\/p>\n

      –>Composed of alternating lava flows \/ tephra deposits<\/p>\n

      –>Indicates episodic eruption styles (Hawaiian\u00e0Strombolian)<\/p>\n

      –>Eruptive phase results in extensive size (10-20km across)<\/p>\n

      —>Tephra phase produces steep slopes<\/p>\n

      –>Cinders accumulate ~at angle of repose (~30 degrees)<\/p>\n

      *Tephra accumulations are WELDED TOGETHER by the episodic lava flows, resulting in the<\/p>\n

      massive composite cone<\/p>\n

       <\/p>\n

      \u00a0_______________________________<\/em><\/p>\n

      Chapter 3: Basaltic \u201cPlains\u201d Volcanism (Greeley)\u00a0 <\/em><\/p>\n

      -The central Snake River Plain may represent a distinctive style of volcanism, combining aspects of both flood basalts and classic basaltic shield volcanoes; the term \u2018basaltic plains\u2019 has been tentatively proposed for this intermediate volcanic regime<\/p>\n

      -Compound vs. Simple Lava Flows: Compound consist of multiple flow units (5cm-10m thick), while simple consist of single (typically thicker) flow units that cooled as one single body<\/p>\n

      –> Correlates to effusion rate: low = compound, high = simple<\/p>\n

      -In the Snake River Plain, predominant flow type is compound, manifested by typically thin units<\/p>\n

      -Typical features include hummocky pahoehoe, collapse depressions, pressure plateaus, pressure ridges, flow ridges<\/p>\n

      -4 main types of volcanic constructs in eastern Snake River Plain: <\/em><\/p>\n

        \n
      1. a) Low shields<\/em><\/li>\n
      2. b) Fissure flows<\/em><\/li>\n
      3. c) Major tube flows<\/em><\/li>\n
      4. d) Intra-canyon flows <\/em><\/li>\n<\/ol>\n

        -b) Fissure Flows<\/em><\/p>\n

        \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 -Most fissure vents assoc. with rift zones <\/em><\/p>\n

        \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 -Typically compound flows <\/em><\/p>\n

        -COTM flows consist of both aa and pahoehoe flows erupted from fissures along Great rift, covering nearly 1500km^2<\/em><\/p>\n

        \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 -Characteristically, continuous effusion occurs along several km of the fissure <\/em><\/p>\n

        \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 -However, \u2018point-source effusion\u2019 may occur either independently or contemporaneously with fissure-wide effusion,<\/em>\u00a0producing spatter cones (or cinder cones, as in COTM); or phreatic eruptions along fissures at King\u2019s Bowl, where <\/em>rising magma encounters ground water<\/em><\/p>\n

         <\/p>\n

        \u00a0_______________________________<\/em><\/p>\n


        \nChapter 11: Guide to the Geology of King\u2019s Bowl Lava Field (Greeley et. al.) <\/em><\/p>\n

        -Kings Bowl flow amongst youngest, at only ~2100 years old<\/p>\n

        -Compound lava flow, fissure-fed; erupted as lava sheets from the fissure, as well as from numerous point sources along the fissure (identified by small spatter cones)<\/p>\n

        -Different parts of fissure active at different times (perhaps separated by as few as a couple hours)<\/p>\n

        -Kings Bowl flows: cover ~3km^2, consisting of several flow units, some of which ponded as small lava lakes, with individual<\/p>\n

        flow thickness typically <1.5m; feeder dike exposed in some places<\/p>\n

        -Includes many fresh basaltic features, including: spatter cones, feeder dikes, drainback of lava into the fissure, squeeze-ups (mushrooms?), \u2018grooved\u2019 lava, cross-cutting relations of lava and fractures, overlap relations of flow units, and a phreatic explosion crater, lava mounds<\/p>\n

        -\u2018Squeeze-ups\u2019 described as bulbous masses of lava ranging in size from 0.5m to >2m, many being hollows<\/p>\n

        -Hypothesized to have resulted from molten lava that \u2018squeeze\u2019\/oozed through crack on the lava lake crust, possibly in response to the pressure generated by the crust\u2019s subsiding<\/p>\n

        -Others observed to have been impacted by ejecta from King\u2019s Bowl<\/p>\n

        -Describe some \u2018linear squeeze-ups\u2019<\/p>\n

         <\/p>\n

        _______________________________<\/p>\n

        Chapter 14: Geological Guide To Craters of the Moon National Monument (Papson) <\/em><\/p>\n

        -Situated along northern border of Snake River Plain<\/p>\n

        -Contains many typical features of basaltic volcanism, including Quaternary lava flows, cinder cones, spatter cones, lava tubes, volcanic bombs, tree molds, etc..<\/p>\n

        -\u2018Plains\u2019 volcanism dominant<\/p>\n

        -55 cones w\/ associated lava flows + 14 fissures (many with spatter cones)<\/p>\n

        -27 distinct cinder cones; many other cones, but partly buried by younger flows<\/p>\n

        -Great Rift (part of Idaho Rift System) passes through COTM as a set of en echelon fissures striking N35W, up to 3km wide<\/p>\n

        -These fissures are major vents for the youngest lavas<\/p>\n

        -The entire rift system may be a continuation of the normal faulting that produced the mountain ranges to the N and S of the SRP<\/p>\n

        -Basalt Geochemistry: Highly evolved olivine basalt of an Fe\/alkali-enriched lava series<\/p>\n

        -Basalt Mineralogy\/Petrology: Sunset Cone flow contains phenocrysts of andesite, fayalitic olivine, titanomagnetitte, and fluorapatite in an intersertal brown glass matrix; could imply >80% crystallization of the parent magma<\/p>\n

        -Pioneer Mountains close to COTM consist of 2 rock types:<\/p>\n

          \n
        1. a) Oligocene quartz latite vitrophyres and basaltic vitrophyres (known as Challis Volcanics)<\/li>\n
        2. b) Miocene quartz monzonite to granodiorite intrusives<\/li>\n<\/ol>\n

          -All flows (except Highway) contain monoliths (fragments of cinder cones) from 0.5-200m long and up to 25m high<\/p>\n

          -Highway Flow: Flow units include pahoehoe, aa, and blocky<\/p>\n","protected":false},"excerpt":{"rendered":"

          Summary of Selected Chapters from “Volcanism of the Eastern Snake River Plain, Idaho: A Comparative Planetary Geology Guidebook”\u00a0(NASA 1977) _______________________________ Chapter 1: Introduction (Greeley and King) -Basaltic volcanism appear to cover substantial areas of the terrestrial planets -The Snake River Plain (SRP) is similar in morphology to many volcanic regions on the Moon\/Mars\/Mercury -SRP is an optimal analogue owing to its good preservation state, lack of forests \/ heavy vegetation (which would impede radar), and good network of jeep trails -Study is restricted to central and Eastern sections of SRP…read more<\/a><\/p>\n","protected":false},"author":20223,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2372365],"tags":[],"class_list":["post-391","post","type-post","status-publish","format-standard","hentry","category-craters-of-the-moon","et-no-image","et-bg-layout-dark","et-white-bg"],"_links":{"self":[{"href":"https:\/\/blogs.ubc.ca\/arsgeophysica\/wp-json\/wp\/v2\/posts\/391","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.ubc.ca\/arsgeophysica\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.ubc.ca\/arsgeophysica\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.ubc.ca\/arsgeophysica\/wp-json\/wp\/v2\/users\/20223"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.ubc.ca\/arsgeophysica\/wp-json\/wp\/v2\/comments?post=391"}],"version-history":[{"count":6,"href":"https:\/\/blogs.ubc.ca\/arsgeophysica\/wp-json\/wp\/v2\/posts\/391\/revisions"}],"predecessor-version":[{"id":399,"href":"https:\/\/blogs.ubc.ca\/arsgeophysica\/wp-json\/wp\/v2\/posts\/391\/revisions\/399"}],"wp:attachment":[{"href":"https:\/\/blogs.ubc.ca\/arsgeophysica\/wp-json\/wp\/v2\/media?parent=391"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.ubc.ca\/arsgeophysica\/wp-json\/wp\/v2\/categories?post=391"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.ubc.ca\/arsgeophysica\/wp-json\/wp\/v2\/tags?post=391"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}