| 词汇 | caldera |
| 释义 | caldera noun[ C ] geology specializeduk /kælˈdeə.rə/ us /kælˈder.ə/ a very large, circular hollow that remains when the central part of a volcano falls in after an eruption喷火山口（火山爆发后，中心塌陷而形成的巨大中空） Photography by Mangiwau/Moment/GettyImages Geography: hills & mountains acclivity alpine tundra clifftop craggy esker highlands hillock Marilyn mesa mid-ocean ridge motte Mount Kilimanjaro pike scarp slope spur steep the Adirondack Mountains the Alaska Range the Alps Examples of calderacaldera A small, possibly ephemeral caldera lake is a likely source. Cooling units and composite sheets in relation to caldera structure. Eruption of the ignimbrites is envisaged as a series of poorly expanded flows possibly with incorporated fall material generated by foundering of a caldera floor. The sedimentary breccias were probably formed from talus and/or other types of colluvium that were shed from the ring-fracture fault scarp of the caldera. These minerals may have formed by recrystallization of pre-existing weak advanced-argillic alteration at the southern margin of the caldera structure. This suggests that eruptive hiatuses in the extracaldera record may reflect effusive activity and stratovolcano or shield-building phases within the summit caldera. A caldera lake is occasionally established in the present caldera following snowmelt. It is possible that this embayment is a caldera or lateral collapse structure. This northern caldera was formed in the 21 000 year explosive eruption. This igneous activity was focused on the southwest margin of the dormant caldera. Fractionation was repeatedly interrupted by eruption of material from the roof zone such that seven stages of caldera development have been identified. They have been interpreted to represent part of a caldera-related succession, possibly intra-caldera. The caldera has chemical characteristics that could result in ambiguous or incorrect tectonic discrimination if the entire rock suite was not considered as a whole. Many of the major eruptions recorded by the extensive lithic brecciabearing ignimbrite sheets may have involved caldera collapse. The caldera is partially filled and surrounded by crystal-rich ignimbrite (f). These examples are from corpora and from sources on the web. Any opinions in the examples do not represent the opinion of the Cambridge Dictionary editors or of Cambridge University Press or its licensors. |
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