Nova spoznanja o nastanku piroduktov Galapaškega otočja, Ekvador

There has been little research on the genesis and development of pyroducts (or lava tubes) originating from Gala´pagos volcanoes. Pyroducts are responsible for the lateral, post-eruptive transport of lava because they are highly effective as thermal insulators. After eruptions terminate, these conduits often become accessible as caves. In March 2014 the 16th International Symposium on Vulcanospeleology brought a large group of vulcanospeleological specialists to the Islands. During the meeting a number of pyroducts were visited and studied in context on the island of Santa Cruz and around Isabella’s Sierra Negra volcano in the western, most active, part of the Gala´pagos. The longest of the caves, Cueva del Cascajo, about 3 km in length, was partly surveyed and nine other caves were visited. Structural features such as thickness of roof, evidence of downcutting, presence of oxbows, secondary ceilings, lavafalls, collapses and pukas were particularly studied for evidence they reveal about developmental stages of pyroducts. The resulting data show that the pyroducts were formed by "inflation" with the primary roof consisting of uninterrupted paŻhoehoe sheets. No pyroducts were identified that developed by the crusting-over of channels. The studies strongly confirm inferences drawn from other hot-spot related islands, such as Hawai’i.Raziskav o nastanku in razvoju piroduktov ali lavinih cevi na galapaških vulkanih je malo. Pirodukti so pomembni za bočni transport lave po izbruhu in so toplotni ščit med tokom lave in zunanjim ozračjem. Po končanem izbruhu ti kanali ostanejo dostopni kot lavine cevi. Marca 2014 je na Galapaškem otočju potekal 16. mednarodni simpozij o vulkanospeleologiji. V okviru tega smo obiskali in proučevali številne pirodukte na otoku Santa Cruz in v okolici vulkana Isabella's Sierra Negra na zahodnem, najaktivnejšem delu Galapaškega otočja. Delno smo izmerili najdaljšo, 3 km dolgo jamo Cueva del Cascajo in obiskali še devet drugih jam. Pri tem smo bili pozorni na strukturne elemente, ki kažejo na razvojne faze piroduktov, kot so debelina stropa, vrezovanje, prisotnost obvodnih rovov (oxbow), ostankov lavinih slapov, sekundarnih stropov, odprtin na površje (puka) in vdorov. Podatki in opažanja kažejo, da so jame nastale z zaporednim napredovanjem in napihovanjem, na kar kaže tudi primarni strop iz neprekinjenih plasti pahoehoe lave.. Nobeden od piroduktov ni nastal zaradi strjevanja lave nad tokom. Podobne ugotovitve veljajo tudi jame na vulkanih drugih vročih točk, kot na primer na havajskih vulkanih