Dutsen Kirsimeti na Caldera

Tsarin caldera na Dutsen Kirsimeti wani hadadden caldera ne wanda ke cikin Dutsen Kirisimeti a cikin Big Bend National Park a yammacin Texas .  Ita ce mafi tsufa irin wannan rikitarwa da aka adana a Texas  kuma ita ce irin misalin laccocaldera (eruptive laccolith ).

 Kafawa 
Tsarin caldera ya fara samuwa shekaru miliyan 42 da suka gabata a cikin Eocene Period tare da samar da laccolith. Wannan wani ɓarna ne wanda Magma ya tashi daga zurfi a cikin Duniya ya bazu tsakanin gadaje na dutsen da ke akwai (dutse na ƙasa) kuma ya tilasta gadaje masu rufi sama zuwa cikin siffar rufi. Daga baya magma ya fashe zuwa farfajiyar yayin fashewar fashewa, sannan ya biyo bayan rushewar caldera. An gano calderas guda huɗu, duk 1-1.5 kilomita (0.6-0.9  a diamita, a saman dome, kuma an gano jerin biyar na volcaniclastic, tuff, da gadaje na lava a kusa da dome. Uku daga cikin wadannan jerin sun ƙunshi manyan ajiyar ash flow tuff. Tsarin yaduwar ash na farko yana da alaƙa da rushewar caldera a gefen yammacin dome. Gudun toka na biyu yana da alaƙa da caldera na biyu, wanda ya rufe caldera na farko. Tsarin yaduwar ash na ƙarshe ya haifar da samar da ƙarin calderas guda biyu a saman dome. Abubuwan da suka faru daga baya sun fi alkaline da porphyritic fiye da fashewar da ta gabata.

Caldera yana da alamar adadi mai ban mamaki na gadon gado a cikin karyewar zoben. Ana zaton wannan ya samo asali ne daga matsanancin doming kafin fashewar caldera.

Gidan caldera yana kewaye da wani babban sashi mai zurfi wanda ya kai sama da kilomita 35 (22  daga hadaddun. Sashe na wannan apron a cikin kilomita 8 (5.0  na calderas galibi yana gudana da toka da iska mai faduwa tare da wasu tsaunuka da tarkace, inda jerin fashewa guda biyar ke bayyane. Bugu da ƙari, daga kilomita 18 zuwa 23 (11 zuwa 14 , apron ya ƙunshi mafi yawan laka da kuma ajiyar kwararar da aka raba ta hanyar rikice-rikice daban-daban, wuraren rushewa, wanda ke nuna cewa saurin saurin saukowa na sediments a lokacin abubuwan da suka faru na dutsen wuta an katse shi ta lokutan rushewa. Sashe mafi nisa na apron, daga kilomita 30 zuwa 35 (19 zuwa 22  daga hadaddun caldera, ya ƙunshi jerin laka da iska mai faduwa wanda ambaliyar ruwa da tashar rafi suka rufe shi ba tare da bambancin rashin daidaituwa ba. Wannan ya nuna cewa zubar da turɓaya ya kusan ci gaba a cikin farfajiyar nesa, kuma irin waɗannan farfajiyoyin ba za su iya yin rikodin yanayin aikin dutsen wuta ba.

 Muhimmancin yanayin ƙasa 
A yau, hadaddun caldera na Kirsimeti, da kuma dome, sun lalace sosai, suna fallasa zurfin tsarin hadaddun. Gidan yana da nau'in wuri don laccocalderas. Laccocalderas sun bambanta da calderas na al'ada, kasancewar suna da ɗan ƙarami kuma suna tasowa a kan ƙananan ɗakunan magma na laccolithic maimakon jiki mai zurfi a ƙarƙashin ɓawon duniya. Koyaya, suna da kama da cewa suna fashewa kamar yadda calderas na yau da kullun ke yi, suna nuna irin waɗannan fasalulluka na caldera kamar fashewar iska na farko wanda ya biyo bayan rushewar caldera, raguwar piston-kamar ƙasa na caldera, wurin da ke da ƙura mai laushi, da kuma maimaita fashewa daga wannan ɗakin magma. Ginin Solitario laccolith na kusa da Big Bend National Park, wanda aka raba shi a matsayin laccolith, yanzu an sake kimanta shi a matsayin laccocaldera.

 Manazarta