کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4712848 1638405 2011 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Toothpaste lava from the Barren Island volcano (Andaman Sea)
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات ژئوشیمی و پترولوژی
پیش نمایش صفحه اول مقاله
Toothpaste lava from the Barren Island volcano (Andaman Sea)
چکیده انگلیسی

Toothpaste lava is a basaltic lava flow type transitional between pahoehoe and aa and has been described from Paricutin, Kilauea and Etna volcanoes. Here we describe a spectacular example of toothpaste lava, forming part of a recent (possibly 1994–95) aa flow on the active volcano of Barren Island (Andaman Sea). This flow of subalkalic basalt shows abundant squeeze-ups of viscous toothpasate lava near its entry into the sea. The squeeze-ups are sheets and slabs, up to several meters across and tens of centimeters thick, extruded from boccas. They are often prominently curved, have striated upper surfaces with close-spaced, en echelon linear ridges and grooves, broad wave-like undulations perpendicular to the striations, and sometimes, clefts. Textural, geochemical, and Sr–Nd isotopic data on the squeeze-ups and the exposed aa flow core indicate very crystal-rich, viscous, and isotopically very homogeneous lava. We envisage that a greatly reduced speed of this viscous flow at the coastline, possibly aided by a shallowing of the basal slope, led to lateral spreading of the flow, which caused tension in its upper parts. This, with continued (albeit dwindling) lava supply at the back, led to widespread tearing of the flow surface and extrusion of the squeeze-ups. The larger slabs, while extruding in a plastic condition, curved under their own weight, whereas their surfaces experienced brittle deformation, forming the en echelon grooves. The extruded, detached, and rotated sheets and slabs were carried forward for some distance atop the very slowly advancing aa core, before the flow solidified.

Research Highlights
► Toothpaste lava - transitional between aa and pahoehoe.
► Described previously from Paricutin, Kilauea, and Etna.
► New, spectacular example from Barren Island, Andaman Sea.
► Crystal-rich, viscous and isotopically homogeneous lava.
► Late-stage extrusion as viscous squeeze-ups from boccas due to tearing of aa flow surface.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Volcanology and Geothermal Research - Volume 202, Issues 1–2, 30 April 2011, Pages 73–82
نویسندگان
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