Tuyas

Deutsch: Tafelvulkane sind Vulkane mit relativ flachem Gipfelbereich, die einen teilweise subglazialen Ursprung haben. Dabei hat nur der Gipfelbereich aus dem jeweiligen Gletscher herausgeragt und besteht daher aus Laven bzw. Tephra. Tuyas existieren in allen vergletscherten Vulkangebieten wie der Arktis und Antarktis, in heute gemäßigteren Zonen wie Island stammen die meisten Tuyas aus der Eiszeit.

English: w:'''Tuyas''' are flattopped volcanoes of partially subglacial origin, only the summit region has surmounted the glacier and consists of subaerial volcanic products (w:Lavas and w:Tephra). Tuyas are to be found in all the regions characterised by the combination of volcanism and glaciers, esp. the w:Arctic and w:Antarctica, in zones of today moderate climate like w:Iceland, are the tuyas of w:Ice Age origin.

Français : Un volcan de table est un volcan dont la partie inférieure a son origin dans des éruptions sous-glaciaires tandis que la partie supérieure de structure assez plate a surmonté le glacier et consiste de tephras et de laves. Il y a des volcans de table dans toutes les régions qui sont characterisées par un volcanisme sous-glaciaire, surtout l'Arctique et Antarctique, les tuyas dans des zones d'un climat aujourd'hui plutôt modéré comme l'Islande datent de la glaciation.

Typical tuyas

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  Bláfjall and Sellandafjall
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  Sellandafjall
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  Herðubreið
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  The Table
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  Lake Garibaldi with tuya
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  Tuya Butte
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  Ring Mountain
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  Ring Mountain
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  The Table
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  Hoodoo Mountain

Tuyas in Iceland

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  Sellandafjall near Mývatn
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  The inselberg Hjörleifshöfði belongs to the volcanic system of Katla.
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  Búrfell (Þjórsá) is located not far from Hekla.
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  Eiríksjökull
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  Hrafnabjörg, perhaps a central volcano
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  Rhyolitic tuyas: Kerlingarfjöll

Tuyas in the United States

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  Hayrick Butte
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  Hayrick Butte
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  Hayrick Butte with Mount Washington
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  Hogg Rock
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  Hogg Rock seen from Santiam Pass with Three Fingered Jack in the background

The origin of tuyas

Tuyas have their origin in a often rather complicated mixture of subglacial and subaerial eruptions which depend on the height of the mountain vs. the surrounding glacier and also the cycle of deglaciations and glaciations over thousands of years.

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  The subglacial eruption produces the base of the volcano consisting of pillow lavas and hyaloclastites.
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  When the eruption has broken through the ice cover of the glacier, it produces tephra and lavas.

The following pictures of the Icelandic tuya w:Herðubreið clearly show the subaerial pyroclastic cone and lavas on her top:

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Satellite pictures of tuyas

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  Satellite picture of Hoodoo Mountain
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  Hoodoo Mountain