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Tholus vulcanicus
From Wikipedia, the free encyclopedia
Tholus vulcanicus,[1] sive tholus lavae,[1] in vulcanologia est rotunda protrusio tumuli similis, quae ex lente lavae viscosae extrusione per eruptionem montis igniferi nascitur, Erupientes montes igniferi tholos lavae saepe gignunt, praecipue prope convergentes laminarum fines.[2] Circa 6 centesimae eruptionum in tellure tales tholos gignunt,[2] et eorum geochemia a basalte (e.g., Semeru anno 1946) ad rhyolitem (e.g., Chaitén anno 2010) variare possunt, sed plurimi a rebus permixtis componuntur (sicut Sancta Maria, a dacite et andesite hodie composita).[3] Propria tholi similis forma a viscositate fingitur quae prohibet ne lava procul effluat. Quae viscositas binis modis efficitur: ex dioxido silicii in magma et per degasificationem magmae fluentis. Quia tholi basaltici andesiticique celeriter effectu caeli dissolvuntur et facile a lava nuper exorienti confringuntur, plurimis tholis exstantibus est materies silicosa, atque ei in rhyolite vel dacite consistunt.
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Geologi credunt nonnullas conformationes tholiformes quae in Luna atque in Venere et Marte planetis videntur esse tholos lavae,[2] praesertim in superficie Martis in occidentali Arcadiae Planitiae regione atque intra Terram Sirenum.[4][5]