Izintaba-mlilo—Ingabe Usengozini?
IZINTABA-MLILO eziqhumayo, ezikhipha umlotha oshisayo nodaka oluvutha ubuhanguhangu, zingeminye yemibukwane yamandla angokwemvelo ebabazeka kakhulu emhlabeni. Mhlawumbe awukasiboni ngawakho isenzakalo esinjalo, kodwa kungenzeka uye wajabulela ukubhukuda emithonjeni eshisayo yezintaba-mlilo noma wajabulela ukudla okutshalwe enhlabathini evundile enomlotha wentaba-mlilo. Abanye bathola ngisho nezinzuzo zikagesi ophehlwe ngokushisa okungaphansi komhlaba emakhaya abo.
Nokho, muva nje abaningi abahlala eduze nezintaba-mlilo ezisaqhuma baye babhekana nokufa nembubhiso okubangelwa izinhlekelele zezintaba-mlilo. Selokhu iMount St. Helens eningizimu-ntshonalanga yeWashington State, e-U.S.A., yaqhuma ngamandla ngo-May 18,1980, izingxenye ezihlukahlukene zomhlaba ziye zabhekana nobuthaphuthaphu bokuqhuma kwezintaba-mlilo okubulalayo. Abantu abafe phakathi nalenkathi baye badlula ingqikithi ehlanganisiwe eyabikwa emashumini eminyaka angu-7 ngaphambi kwalokho, futhi umonakalo wempahla uye wafinyelela emakhulwini ezigidi zamaRandi. Kuye kwacishe kwavela izinhlekelele lapho umlotha wentaba-mlilo osemoyeni ubangela ukuba izindiza ziphelelwe amandla, uziphoqelela ukuba zihlale phansi ngokuphuthumayo.
Okwabhubhisa kakhulu kuye kwaba ukuqhuma nokugeleza kodaka lweMount Pinatubo, ePhilippines, okwacekela phansi amashumi ezinkulungwane zamakhaya, neNevado del Ruiz, eColombia, okwabulala abantu abangaphezu kuka-22 000. Kungase kuvele nezinye izinhlekelele. Ochwepheshe bezintaba-mlilo uRobert Tilling noPeter Lipman, be-U.S. Geological Survey, bathi “ngonyaka ka-2000, abantu abasengozini yezinhlekelele zezintaba-mlilo cishe bayokwanda bafinyelele okungenani ezigidini ezingu-500.”
Ngakho-ke ungase ukuthole kuwukuhlakanipha ukubuza: ‘Ingabe ngihlala eduze nentaba-mlilo esaqhuma, noma engase iqhume? Ukuqhuma okunjani okuyingozi kakhulu, futhi kungazibangela yini ezinye izinsongo ezibulala ngisho nakakhulu? Uma ngihlala endaweni esengozini yentaba-mlilo, yini engingayenza ukuze nginciphise ingozi?’
Izintaba-mlilo Ezisaqhuma—Zikuphi?
Ungase umangale uma uzwa ukuthi uhlala eduze nentaba-mlilo engasaqhumi nokuthi uyothinteka nakanjani uma kungenzeka iqale ukuqhuma. Ososayensi abahlola izintaba-mlilo (abaziwa ngokuthi ama-volcanologist) abazange baphumelele emashumini eminyaka amuva ekuboneni izintaba-mlilo ezisaqhuma nezingasaqhumi kuphela kodwa futhi baye baphumelela nasekuqondeni isizathu esenza ukuba izintaba-mlilo zivame ezindaweni ezithile.
Ake ubheke ibalazwe (ekhasini 17), elibonisa ezinye zezindawo zezintaba-mlilo ezingaphezu kuka-500 okuye kwabikwa ukuthi zisaqhuma. Ingabe uhlala eduze kwenye yazo? Kwezinye izindawo, iziphethu nemithombo eshisayo kubonisa ukuba khona kwezintaba-mlilo ezingasaqhumi; nalezi zingase ziqhume esikhathini esizayo. Izintaba-mlilo ezingaphezu kwengxenye ezisaqhuma ziwuhele ngasemaphethelweni ePacific, zakha lokho okwaziwa ngokuthi Isiyingi Somlilo. Ezinye zalezi zintaba-mlilo zisemazwekazini, njengaseziNtabeni zaseCascade eNyakatho Melika naseziNtabeni zase-Andes eNingizimu Melika, kuyilapho ezinye zakha uxhaxha lweziqhingi olwandle, njenge-Aleutian Islands, iJapane, iPhilippines, neningizimu ye-Indonesia. Izintaba-mlilo zivamile futhi eMediterranean naseduze nakhona.
Ososayensi baye bathola ukuthi lezi zintaba-mlilo zivela emingceleni yezingqimba ezinkulu, ezihambayo, ikakhulukazi lapho ungqimba olusolwande lungena ngaphansi kongqimba olusezweni. Lenqubo ibizwa ngokuthi i-subduction. Ukushisa okuphehlwa yilenqubo kukhipha i-magma (amadwala ancibilikile) ekhuphukela phezulu. Ngaphezu kwalokho, ukunyakaza okungalindelekile phakathi kwalezi zingqimba kubangela ukuzamazama komhlaba okunamandla ezindaweni eziningi ezifanayo ezinezintaba-mlilo eziqhumayo.
Kungase kuvele izintaba-mlilo nalapho kuhlukana khona izingqimba ezisolwandle. Okuningi kwalokhu kuqhuma kwenzeka ekujuleni kolwandle futhi abantu abakuboni. Nokho, uma uhlala ezweni eliyisiqhingi lase-Iceland, usendaweni ephezu kweReykjanes Ridge, exhumana ne-Mid-Atlantic Ridge, lapho izingqimba ezihlanganisa iNyakatho neNingizimu Melika zihlukana khona nalezo ezihlanganisa iYurophu ne-Afrika. Kwezinye izimo ezimbalwa, izindawo ezishisayo ezihlukene ezingaphansi kwezingqimba ziye zabangela izintaba-mlilo ezinkulu eHawaii nasezwekazini lase-Afrika.
Ziyini Izingozi?
Izinga lenhlekelele ebangelwa intaba-mlilo lixhomeke emlandweni wayo wamuva wokuqhuma, kuhlanganise nobukhulu bokuqhuma kwayo nezingozi ezihlobene nakho. Ingozi ilinganiswa ngobukhulu nokuzilungiselela komphakathi ophila endaweni esengozini. Ake siqale ngokuhlola izingozi.
Ngokuvamile, ukuqhuma okuyingozi kakhulu kubangelwa udaka olugcwele i-silica. Lolu hlobo lodaka lujiyile, futhi lungavala intabamli-lo okwesikhashana kuze kube yilapho amagesi enza umfutho owanele ukuqhumisa intaba-mlilo. Udaka oluncibilikile olugcwele i-silica luqina lube amadwala akhanyayo futhi luvame kakhulu ezintaba-mlilweni ezisemaphethelweni ezingqimba. Kungavela futhi ukuqhuma lapho amadwala ancibilikile akhuphukayo ehlangabezana namanzi futhi awaphendule isisi. Udaka olushisayo olukhiqizwa ukuqhuma okunamandla lungabulala—izintaba-mlilo ezintathu endaweni yaseCaribbean-Central America zabulala abantu abangaphezu kuka-36 000 enkathini eyizinyanga eziyisithupha ngo-1902.
Ngakolunye uhlangothi, izintaba-mlilo zezindawo ezishisayo olwandle nezingqimba ezihlukanayo, nezinye eziningi, ngokuyinhloko zakhiwa amadwala amnyama, angenayo i-silica eningi kodwa agcwele insimbi ne-magnesium. Amadwala ancibilikile amnyama awuketshezi futhi ngokuvamile abangela ukuqhuma okuncane noma ukuqhuma okungenamsindo kanye nokugeleza kodaka oluhamba kancane abantu abangalugwema kalula. Nokho, lokhu kuqhuma kungathatha isikhathi eside—intaba-mlilo iKilauea esiqhingini saseHawaii ibilokhu iqhuma ngokunganqamuki kusukela ngo-January 1983. Nakuba ukuqhuma okunjalo kuye kwabangela umonakalo omkhulu wempahla, akuvamile ukubangela ingozi noma ukufa.
Okunye ukuqhuma kuchitha inqwaba yomlotha emlonyeni wentaba-mlilo, okungabangela ukubhidlika komhlaba, noma okungabangela izinguzunga zenhlabathi ezisindayo ezingaguguleka ezintabeni lapho kuhlangene neqhwa, noma amanzi amaningi. Udaka olunjalo (olwaziwa nangokuthi ama-lahar, kususelwa egameni lesi-Indonesia elisho udaka olushisayo) lungafinyelela ebangeni elide kakhulu kusuka entaba-mlilweni, mhlawumbe isikhathi eside ngemva kokunqamuka kokuqhuma.
Okufinyelela kude kakhulu, kodwa okungavamile emlandweni, ama-tsunami—amaza olwandle amakhulukazi abangelwa ukuqhuma olwandle noma ukugidlika komhlaba ngaphansi kolwandle eduze nentaba-mlilo equbukayo. Lamaza anamandla angahamba ngejubane elingamakhulu amakhilomitha ngehora. Nakuba ama-tsunami engaphakeme kakhulu olwandle olujulile, empeleni engelona neze usongo emikhunjini edlulayo, aphakama ngokushesha lapho esondela ezweni. Lamaza aphakama ngaphezu kwezindlu nezakhiwo eziningi. Ngo-1883 lapho kuqhuma iKrakatau, kwafa abangu-36 000 lapho ama-tsunami egadla ezingwini zaseJava naseSumatra.
Ezinye izingozi zezintaba-mlilo ezingalimaza noma ziphazamise ukuphila zihlanganisa umlotha nezingcezu zamadwala eziphuma kuzo, ukuphazamisa kokuqhuma okukhulu, isisi esinobuthi, imvula ene-asidi, nokuzamazama komhlaba. Njengoba kunenqwaba yezintaba-mlilo eziyingozi kakhulu ezitholwe emhlabeni wonke kanye nezingozi eziningi ezingase zivele, ukuhlaziya izingozi zezintaba-mlilo kuwumsebenzi oyinkimbinkimbi noyinselele ngempela.
Ingabe Ungayinciphisa Ingozi?
Njengoba kwanda inani labantu emhlabeni, abantu abaningi bahlala ezindaweni ezisengozini yezintaba-mlilo. Ngenxa yalesi sizathu, kanye nokwanda kwamuva nje kokuqhuma kwezintaba-mlilo emhlabeni wonke, izazi zezintaba-mlilo ziye zaqinisa imizamo yazo yokunqanda ingozi yezintaba-mlilo. Kwezinye izimo, izibikezelo zokuqhuma kwezintaba-mlilo ziye zaphumelela, futhi kwasindiswa ukuphila. Siyini isisekelo salezi zibikezelo?
Ngokuvamile ukuqubuka kwandulelwa ukuzamazama komhlaba entaba-mlilweni noma emhubheni wayo ongaphansi, okubangela ukukhuphuka kodaka olushisayo. Njengoba lolu daka lunqwabelana phezulu entaba-mlilweni, umfutho uyanda. Kuphuma amagesi, futhi izinga lokushisa nobu-asidi bamanzi angaphansi komhlaba lingase likhule. Kungase kube khona nokuqhuma okuncane ngaphambi kokuqhuma okukhulu. Zonke lezi zenzakalo zingahlolwa.
Esikhathini eside ngaphambi kokuqhuma, izazi zokuma komhlaba zingaba nombono wezingozi ezingase zivele ngokuhlola umlando wamadwala. Ngokuvamile uhlobo lodaka olukhishwa intaba-mlilo nezingozi zakamuva kuyaphindeka, noma ukuqhuma kufana nokwezinye izintaba-mlilo ezihloliwe. Ngokusekelwe kulokho kwaziswa, kuye kwadwetshwa amabalazwe ezintaba-mlilo eziningi abonisa izindawo ezisengozini enkulu.
Ngakho-ke izihluthulelo zokusindisa ukuphila ezingozini zezintaba-mlilo zihlanganisa ukuhlaziya izingozi nokuhlola izintaba-mlilo kwezazi zezintaba-mlilo kanye nokuxwayisa kweziphathimandla zendawo kusengaphambili ngenhlekelele esongelayo. Ngokungafani nokuzamazama komhlaba, okuseyinkinga ukukubikezela, izintaba-mlilo eziningi eziqhumayo zingahlolwa ngokunembile kangangokuthi abantu abasengozini bangase basuswe ngaphambi kwesenzakalo esibhubhisayo. Kuyaphuthuma ukushiya indawo esengozini, ngoba izakhiwo ezenziwe abantu ngokuvamile azinikezi sivikelo entukuthelweni nasekushiseni kodaka nokuqhuma kwentaba-mlilo namandla abhubhisayo okubhidlika komhlaba, ukugeleza kodaka, nama-tsunami.
Nakuba kwenziwa imizamo etusekayo yokunciphisa inani labantu ababulawa ukuqhuma kwezintaba-mlilo nezingozi ezihlobene nakho, umuntu usahluleka ukukubikezela ngokunembile ukuqhuma nezingozi ezibhubhisayo ezihambisana nakho ukuze aqinisekise ukuvikeleka okuphelele ezingozini zezintaba-mlilo. Ngisho nabathile kulabo abahlola izintaba-mlilo baye bafa ngenxa yokuhlaselwa ukuqhuma bengalindele. Nokho, uma uhlala eduze nentaba-mlilo engase iqhume, kufanele ulalele noma iziphi izixwayiso ezikhishwa iziphathimandla zendawo. Ngokwenza kanjalo, uyokwandisa amathuba onawo okusinda enhlekeleleni yentaba-mlilo.—Inikelwe isazi se-“astrogeology.”
[Ibhokisi ekhasini 18]
Ukubikezela Ukuqhuma Kwentaba-mlilo Emkhathini?
Ake ucabange ulinganisa okwenzeka ekujuleni kwentaba-mlilo ngokunemba okufinyelela esentimitheni elilodwa ngeziphuphutheki ezingamakhilomitha angu-20 000 ngaphezu komhlaba—ezihamba ngesivinini esingamakhilomitha amahlanu ngomzuzwana! Lokhu sekuyenzeka nge-Global Positioning System (GPS), eyakhiwa idlanzana leziphuphutheki kanye nezithungathamaza ezibekwe ngobuchule emhlabeni. Ukuze kwenziwe ukubala ngakunye, kulandelelwa ukuma kweziphuphutheki okungenani ezine. Isikhathi sibalwa ngama-atomic clock, ashaya emhloleni. Lokhu kubala, okungenziwa ezimweni zezulu eziningi, kuphumelela kangcono kunezinqubo zokuhlola ezisemhlabeni. Ukubala kwe-GPS kungase kukuthuthukise ngokuphawulekayo ukubikezela ukuqhuma kwezintaba-mlilo, okungase kwandulelwe iminyaka eminingi yokukhula kwentaba-mlilo. Lobu buchwepheshe sebuyasetshenziswa kakade ezintaba-mlilweni zase-lceland, e-ltaly, eJapane, nase-United States.
[Ibalazwe ekhasini 17]
(Ukuze ubone ukuthi indaba ihlelwe kanjani, bheka encwadini)
Izintaba-mlilo ezisaqhuma nezingqimba zomhlaba
Izintaba-mlilo ezisaqhuma
Imingcele yezingqimba.
Okuboniswe ngenhla ezinye zezintaba-mlilo ezingaphezu kuka-500 ezisaqhuma
[Umthombo]
Mountain High Maps™ copyright © 1993 Digital Wisdom, Inc.
[Isithombe ekhasini 16]
Umlotha wentaba-mlilo I-Unzen, eJapane, ugelezela endawenl eyakhlwe
[Umthombo]
Orion Press-Sipa Press
[Isithombe ekhasini 16]
Ukuqhuma kweMount St. Helens
[Umthombo]
USGS, David A. Johnston, Cascades Volcano Observatory
[Isithombe ekhasini 16]
IMount Etna, eSicily, muva nje yakhipha udaka olushisayo izinyanga ezingu-15
[Umthombo]
Jacques Durieux/Sipa Press
[Isithombe ekhasini 17]
IMount Kilauea, eHawaii, iye yanezela ama-hektare angaba
ngu-200 kulesi siqhingi
[Umthombo]
©Soames Summerhays/Photo Researchers