Class Note for GEOS 218 at UA
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Date Created: 02/06/15
LecTure 12 Volcanoe Collapse Geological DisasTers and SocieTy No gmduaTe of EOSZlB should ever buyahuse in such a locaTionl The conTribuTing products of sTraTavolcanoes This happens to be MT ETna GraviTaTional collapse and spreading The faTe of large sTraTavalcanaes is To collapse Lmder Their own weighT in parT because They are raTTen To The care39 Insides of volcanoes are canverTed Ta weak clay aITeraTian maTeriaIs as a resLIIT of The inTense acTian of haT sulfuricacidrich fluids Where The bedrock beneaTh a volcanic edifice is weak e g clay rich The LOAD exerTed downward by The volcano can cause The subvolcano basemenT39 Ta flow and spread IaTeraIIy Imagine if The basemenT of your house did ThaT LocaTion of MT ETna Sicin LurgesT ucTive volcano n Europe EIevuTion is 10924 A H or 3329 m Satellite image of Mt Etne Beganm turn suuiuuu Veavsaga amne mast mSiuW Migvmedm tadaVs median BPPVDX 17u uuu veavs saw it is a smavaimrm win anemmmg eiumiuns m inter and sen Virgil s description of Mt Etne A Spreading hay i ineie impregnd e Ta aH invading Siding and Ae m trim Wiin iuai af tiignitui iuin thderimgh Nuwiuine ieain afhg ii h xacim Ofpi chrhiatk whirhngimake andfieiydux Shammgamgiahexaf ame Wiinnmgiei imgue mu hck ire 901 MW nuge mags af MEN 0m af ire hawei af ire mmnmin mm It mow dngmgBS wniie ire nuiien rack RaH Screaming Swain ham ire mm deep The fa hamiesx mg make ebb and aw Etne39s eruptions in the 21339 Century Not neariy as grand as ih21669 eruption wnicn produced a cubic kiiomzizr of voicanic stuff and Wiped om viHagBS Volcanoes are wonderful vacafion spofs so is M1 Rainizrlll Fm 2x3mp 2 Ena a evs skung mthe VWHEV mumhs and bvea makmg mkes m We Wands dunng We Summev Them ave am 3 mnme smaHev peaks my me s upes mans and same mteveshng cavems Smce Ema s a wamvu canu wnh ve awe y sum ava empevamves and numevuus upemngs may quotmay evevknuws pvemse ywheve an M5 vas1 su aceme next empth Wm be Geological Framework of Mt Emu rmmamg ma whys m2 Structure map of Mt Etna B ack duvs are under curves Thm suhd sz are erup ve ssures Shaded remanst are mm zunes Arruws are smke shp fauHs km W miewmanwm m This map shows the faulT paTTem on the east flank of Mt Etna a paTTern reflecting an eastward movement of the east flank of Mt Etna The MT ETna graviTaTional collapse sTory as described by Borgia and oThers 2000 Nice summary of The geologic map relations The acTive folding and faulTing deTails and The larger concepTual cross secTion of whaT is happening beneaTh Spreading beneaTh volcano due To weak clays ThaT can39T handle The massive load of This volcano The cancepT of graviTaTional spreading of sTraTavalcanoes Volcanic spreading produces exTension in The summiT regions of volcanoes and compression around Their peripheries The exTension can be measured Through GPS The compression is more difficulT To measure buT can be done Through deTermining The area and volume of uplift e g by Folding Borgia and oThers 2000 did This for The densely populaTed urban area of CaTania aT The fooT of MT ETna They used as aTool DifferenTial SynTheTic AperaTure Radar InTerferomeTry39 whew Here are The inTerferograrns quot SE movemem is 15 minyr vertical 0pm is 7 mmyr From Borgia and others 2000 JusT To be sure The deformaTion ThaT is being produced is noT wimpy The fold creaTed by The laTeral spreading ranges from 400 rn To 1000 rn in verTical relief And The ThrusT faulT ThaT is carrying39 The deformaTion is aT a depTh of 3 km This is noT superficial in The normal sense Andrea Borgia39s geological cross secTion of acTive ThrusT faulTing and folding along souThern margin of MT ETna stislmunno Emgiq Ferariand Paxquare 1992 Oui cr op exposure of faulfing and folding along SE margin of MT Efna Crefaceous clays and silfs me Burgla Feran and Pasquare 1992 Now let39s shift over To The big island of Hawaii where There is evidence for volcanoe collapse Full T o um imiasi Map showing The volcanoes and sfr uci ur es of The Island of Hawaii 4 Direciion of View of nzxi slide mm Emgiq 1994 This is The zasf side of Hawaii Easl rift zone Fauil scarp Movemeni s along SE margin of Hawaii during period 1970 1390 1989 i a pr zGPS anemerit Was 4m an EaS39LEm and and ll m an Western E di mare than can be accuunted fat by inieelian 0f magma in feed Kliauea v benillnger and quotquot 39 quot39mm min 1995 umm mm Vertical cross section of seismicity along SE murg n of the island of Hawaii 24000 earthquakes between 1970 and 1989 K lun nan awn mu um MIunlUm isiLPugmis n Note how the earthquakes go me benilngzrand claim ma no deeper than 10 or 12 km Map of Kilaue Volcano Dark region is ocean39s bathyrrretry Light shaded dots are earthquakes between 5 and 12 km depth Dark shaded dots betweerr 0 arrd 5 km depth Earthquakes from 1990 1996 From Owen arrd others 2000 GPS measurements were er m mwmmm m mum VDLCANO awao acem am39m zn 39w zos w umrzuinm om tummucus mom marrow zana 204 40 au39sa WW Tli tumor 0 m hm hnmu we as This is how Omen and others see things moving based on earthquakes and GPS Eargm s m4 mmrwemhan Hi we gum aeiamamn mkmg p ace n HawaH a ang m2 205mm margm and dawn mm m subsurface A suddzn want on W Bus ank of HuwaH Novzmbzr 2000 The mm evemwas an we mm Hank af mmmxma Mavemems were recarded hymn nuaus evs recewers 5 p mak p ace war 0 3a m permd Wm max mum S p WhamHf a armday The energy m eased wasequwa emm a sng e E720thuok2 5 12 Hi we fauh surface an m shp mk p ace was m x7 km 5 p a rechan was saumzasvward Dwsp aczmzms recorded on m SE margm of HawaH durmgtthmzmber 2000 s zm shpevzm rum and who am Imerprzmnon of the nature of H12 s zm shp zvzm szragexhpwax 57cm Oneme eraframMWda hefme heevem A mew 2 of maps of HawaH ms map gm m2 5th Di HawaH am as we as m 9mm andshdesfarm quot9 an apmn mm acea v Submarme andshdes m mm m9 0 an s ands quotmmquot Landshd Hg 5 c ear ya Way af w m m m and fa af va ca mesaf m We Mummmn m ms map gm m2 NW mm Hawau am and we bammmy m mg We Mock Swan an m mm 012 mmquot m Wm cang amerme up W 10 Conglomerates found well up on dry land date39 at N110 000 years and are a mix of broken up marine shells and coral and volcanic rock They are thought to be the product of a tsunami that ran up39 the island at least 400 m and across the island at least 6 km There was a giant landslide Alika 2 that took place approximately 120 000 years ago a segment of Mauna Loa Volcano This may have triggered the run up39 We39ll now look of flank failures39 of Socompa Chile n In we a mu a 71mm remcg Socompu i39he bes i expsosure of one of These Pun Biost 180 III The scale of this collapse is mind boggling The scar goes From So to 5c 12 km Note bar scale For vertical rel 2F Most of the debris n foreground was squeezed up From underneath Socompu The mouth of the scar is 12 km wide There is 4000 m of vertical relief represented Distance of flow was 40 km quotfquot refers to giant blocks transported on debris Van Wyk de Vries at al 2001 11 Here s Me Warm swam and we pmmgmpm mmm Ava a vche s campased af 3a Sq km afmamma Tms awe took p acz about 1000 yzars do but n s not as Mgh y davzd as H needs 390 b2 Thrusts and fo ds dzvszzd m spreadmg Mk2 Ema When We VHNJSVS then broke evzryvhmg wzm m S hes my devwapedhy van WK a2 vnexand mm 2001 mam Gravwmmnal spremmg Farmmmnaf Mum md mm mm m m Dem ava mcheli 12 a a ma m quotmammaa Nice reconstruction Failure of Mombucho volcano in Nicaragua is also a result of subvolcanic spreading and collapse 3 Van WW a mag and Wm m7 Th2 deNS created GYl archlzlago W the lake blocks from We deNS avalanche Look at the dlslancz ll The archipelago n this map is shown 3 Lus Isletus Eammnnl m m mum mpwu yNuvmal hm a quotlambum m m deem mm mm m m a cum amquot y mm lum Satan mm m 510mm quot39W39 1 inlmsmmmsmflcmver mm Reconstruction by Van Wyk de Vries and Francis 1997 39 39qu u mum 2 in mm Mummy mm 94 m m n Wm 5 Mug m um Wooler and others 2004 created a physical analogue model of flank collapse Silicone pLItty is underlying strata Volcanoe made of dry sand and plaster 1 my w ml my nfs me 11 WSW m vymmm l W 7m a in him g n Kyla l vmmmx 14 Dip of mafer39ials beneafh The volcano defermines oufcome Even dip changes of 1 degree maH39er39 Nofice combinafion of sfr39ike slip fhr usf and normal faulfing A am E D m w Thrus r faul rs in sand 15 I39m mpressed with the beautiful correspondence between strike slip faults in the model and the dra nage pattern on the Tumisa volcanic complex Chile ulnere the underlying surface dips 5 degrees Borgia worries that flank collapse could take place in Merapi Java and Orosi Costa Rica Both have bulging toe areas Ought to be possible to continuously measure the growth of the bulge What about gravitational spreading andor flank collapse in the more ancient geologic record 16 17 18 H mm UMTF 19 20 MM mu nmm syi wm 93m Manna anmbnan Dmmmbmn 21 22
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