Hverfjall

Deutsch: Der Tuffring Hverfjall (auch Hverfell) gehört zum Vulkansystem der Krafla im Norden Islands beim See Mývatn. Er entstand in großen phreatomagmatischen Explosionen vor ca. 2800 Jahren.

English: Hverfjall (also known as Hverfell) is a tephra cone or tuff ring in northern Iceland, to the east of Mývatn. It erupted in 2800 BP in the southern part of the Krafla fissure swarm.

Français : Le Hverfjall (en islandais la « montagne de la source chaude ») est un volcan situé sur le site du lac Mývatn, en Islande.Il est apparu il y a 2 500 ans et est le résultat d'une seule éruption appartenant au cycle de Hverfjall du Krafla.

Íslenska: Hverfjall (eða Hverfell) er fjall austan við Mývatn og vestan við Búrfellshraun í Skútustaðahreppi. Hverfell er eldgígur og hlut Kröflukerfisins sem talinn er hafa myndast í öflugu en stuttu þeytigosi fyrir um 2800 árum.

Nederlands: De Hverfjall is een kegelvulkaan in het noorden van IJsland in het Mývatn gebied. De Hverfjall wordt ook wel de Hverfell genoemd, over de juiste naamgeving zijn de IJslanders het onderling nog niet eens. Beide namen betekenen hete-bronnen-berg. De vulkaan is ongeveer 2800 jaar geleden in een aantal dagen ontstaan. De uitgestoten lava koelde door water vrijwel onmiddellijk af waardoor de ringvormige vulkaan vrijwel geheel uit tefra, as en fijn gruis is opgebouwd.

Norsk nynorsk: De Hverfjall (òg kalla Hverfell, uttale kvˈerfjadl) er ei tefrakjegle eller ein tuffringvulkan nord på Island, like aust for Mývatn. Han hadde utbrot for 2800 år sidan i den sørlege delen av Krafla-svermen.

Maps

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  Mývatn with Hverfjall to the east

Aerial pictures of Hverfjall

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Views of Hverfjall

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The crater

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The surroundings of Hverfjall

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  View in direction of Krafla caldera, Hlíðarfjall, Jarðbaðshólar with Jarðböðin, Námafjall and another much smaller tuff ring nearby
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  Walking down the flank of Hverfjall
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  Seen from the remnants of a lava lake, Dimmuborgir

Origins of tuff rings

Maar diatreme and tuff ring origin (Kereszturi, Gábor and Németh, Károly, 2012)

Schematic cross-section through a maar-diatreme (upper diagram) and a tuff ring (lower diagram), showing the typical volcano-sedimentary processes, deposits and geomorphological features. Note that the left-hand side represents the characteristics of a maar-diatreme volcano formed in a hard-substrate environment, while the right-hand side is a soft rock environment. (Abbreviation: PDC = pyroclastic density current).

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Origin of Hverfjall

In this case the phreatomagmatic and explosive eruptions which had commenced on an eruption fissure, were very intensive due to an important reservoir of groundwater which the magma encountered on its way, so that copious amounts of ash and debris were produced and formed the wide ring wall of the tuff ring, closed the vent, and the water evaporated. Today, there is no surface access to the groundwater table which makes the difference to maars like the Víti crater in the same volcanic system.

Phreatomagmatic eruptions

	1: Water vapour cloud
	2: Volcanic bomb
	3: Magma conduit
	4: Layers of magma and ash
	5: Stratum
	6: Water table
	7: Explosion
	8: Magma chamber