Pumice kapena pumice ndi mtundu wa mwala womwe ndi wopepuka, wokhala ndi thovu lopangidwa ndi thovu lotchingidwa ndi magalasi, ndipo nthawi zambiri limatchedwa galasi lamoto wa silicate.
Miyala imeneyi imapangidwa ndi acidic magma chifukwa cha kuphulika kwa mapiri komwe kumatulutsira zinthu mumpweya; kenako mayendedwe yopingasa ndi kudziunjikira ngati thanthwe pyroclastic.
Pumice imakhala ndi mawonekedwe osinthika kwambiri, imakhala ndi ma cell ambiri (mapangidwe am’manja) chifukwa chakukula kwa thovu lachilengedwe lomwe lili mmenemo, ndipo nthawi zambiri limapezeka ngati zinthu zotayirira kapena zidutswa za volcanic breccia. Ngakhale mchere womwe uli mu pumice ndi feldspar, quartz, obsidian, cristobalite, ndi tridymite.
Pumice imachitika pamene acidic magma ikwera pamwamba ndipo mwadzidzidzi ikumana ndi mpweya wakunja. Chithovu chagalasi chachilengedwe chokhala ndi / gasi womwe uli mmenemo uli ndi mwayi wothawa ndipo magma amaundana mwadzidzidzi, pumice nthawi zambiri imakhala ngati zidutswa zomwe zimatulutsidwa pakaphulika mapiri kuyambira kukula kwake kuchokera ku miyala kupita ku miyala.
Pumice nthawi zambiri imapezeka ngati kusungunuka kapena kusefukira, zinthu zotayirira kapena zidutswa za breccias zamapiri.
Pumice imatha kupangidwanso ndi kutentha kwa obsidian, kuti mpweya uthawe. Kutentha kochitidwa pa obsidian kuchokera ku Krakatoa, kutentha komwe kumafunika kusintha obsidian kukhala pumice pafupifupi 880oC. Mphamvu yokoka ya obsidian yomwe poyamba inali 2.36 idatsikira ku 0.416 pambuyo pa chithandizo, chifukwa chake imayandama m’madzi. Mwala uwu wa pumice uli ndi mphamvu zamagetsi.
Pumice ndi yoyera mpaka imvi, yachikasu mpaka yofiira, mawonekedwe a vesicular ndi kukula kwa orifice, omwe amasiyana malingana ndi wina ndi mzake kapena osati mawonekedwe oyaka ndi orifices.
Nthawi zina dzenjelo limadzazidwa ndi zeolite / calcite. Mwala uwu umalimbana ndi mame oundana (chisanu), osati hygroscopic (madzi oyamwa). Lili ndi mphamvu zochepetsera kutentha. Kuthamanga kwamphamvu pakati pa 30 – 20 kg / cm2. Waukulu zikuchokera amorphous silicate mchere.
Kutengera momwe amapangidwira (deposition), kugawa kukula kwa tinthu (chidutswa) ndi zinthu zomwe zidachokera, ma depositi a pumice amagawidwa motere:
Dera laling’ono
Amadzimadzi
Ardante yatsopano; i.e. madipoziti opangidwa ndi yopingasa kutuluka kwa mpweya mu chiphalaphala, kuchititsa chisakanizo cha zidutswa za makulidwe osiyanasiyana mu mawonekedwe masanjidwewo.
Zotsatira za kubwezeretsanso (kubwezeretsanso)
Kuchokera ku metamorphosis, madera okhawo omwe ali ndi mapiri ophulika adzakhala ndi ma depositi otsika mtengo. M’badwo wa geological wa madipozitiwa uli pakati pa Apamwamba ndi apano. Mapiri amene ankaphulika m’nthawi ya nthaka imeneyi anaphatikizapo mphepete mwa nyanja ya Pacific Ocean ndi njira yochokera ku Nyanja ya Mediterranean kupita ku Himalaya ndi kum’mawa kwa India.
Miyala yofanana ndi ma pumice ena ndi pumicite ndi volcanic cinder. Pumicite ili ndi mankhwala omwewo, chiyambi cha mapangidwe ndi mawonekedwe a galasi monga pumice. Kusiyanitsa kumangokhala mu kukula kwa tinthu, komwe ndi kakang’ono kuposa mainchesi 16 m’mimba mwake. Pumice imapezeka pafupi ndi komwe idachokera, pomwe pumicite imatengedwa ndi mphepo kwa mtunda wautali, ndipo idayikidwa ngati phulusa kapena ngati dothi.
Chiphala chamoto chili ndi tizidutswa tambirimbiri tofiira mpaka takuda, tomwe tinayikidwa pa kuphulika kwa miyala ya basaltic kuchokera kuphulika kwa mapiri. Ambiri mwa ma depositi a cinder amapezeka ngati zidutswa zogona zoyambira kuyambira 1 inchi mpaka mainchesi angapo m’mimba mwake.
Kuthekera kwa Pumice yaku Indonesia
Ku Indonesia, kupezeka kwa pumice nthawi zonse kumalumikizidwa ndi mapiri angapo a Quaternary to Tertiary. Kugawa kwake kumakhudza madera a Serang ndi Sukabumi (West Java), chilumba cha Lombok (NTB) ndi chilumba cha Ternate (Maluku).
Kuthekera kwa ma depositi a pumice omwe ali ndi tanthauzo lachuma komanso malo osungira ambiri ali pachilumba cha Lombok, West Nusa Tenggara, chilumba cha Ternate, Maluku. Kuchuluka kwa nkhokwe zoyezedwa m’derali zikuyerekezeredwa kupitilira matani 10 miliyoni. M’dera la Lombok, kugwiritsidwa ntchito kwa pumice kwachitika kuyambira zaka zisanu zapitazo, pomwe ku Ternate kugwiriridwako kudangochitika mu 1991.