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Surveying Ice and Fire: Mapping Iceland’s Glaciers and Subglacier Volcanic Calderas
An image of a Jökulhlaup from Vatnajökull. Dark blue water cascades from the white and gray ice cap, flowing underneath a small bridge

Photograph of the large j√∂kulhlaup that spread out across Skei√įar√°rsandur (glacial outwash plain) from the terminus of Skei√įar√°rj√∂kull, an outlet glacier of Vatnaj√∂kull. The photo of Skei√įar√°rsandur was made on 6 Nov. 1996. Photo credit: Oddur Sigur√įsson, Icelandic Meteorological Office.

Ice and fire form compelling imagery through their opposing natures. Perhaps nowhere on Earth are these two forces brought together with more spectacular results than Iceland. Home to hundreds of glaciers and a few hundred volcanoes [Iceland has experienced several hundred eruptions during the past 1,100 years, with a volcanic eruption occurring about every three to five years], Iceland is exposed to both fiery volcanic eruptions, flowing masses of ice, and large glacier-outburst floods (jökulhlaups). In addition, because of their proximity to each other, Iceland’s volcanoes and glaciers regularly interact, pitting the fire from deep within the Earth against the overlying ice caps.

Now, for the first time, the Icelandic Meteorological Office, the U.S. Geological Survey, and Iceland Geosurvey have illustrated cartographically the complex relationship between Iceland’s glaciers and underlying volcanic calderas on one map. Made for emergency managers, scientific researchers, and the general public, this map shows the full extent of Iceland’s glaciers and which volcanic calderas they overlie.

The Stories a Map Can Tell

Contained within this map of glaciers and volcanoes are stories of climate change and altering landscapes; natural hazards and cryologic oddities; technological advancement and scientific collaboration; and cultural history and language.

LISTEN: Career of the Cryosphere-An Interview with Dr. Richie Williams

The Paradoxes of Climate Change

In 1890, the overall glacier coverage of Iceland was at its highest since the end of the Ice Age. Since then, as global temperatures have begun to climb, Iceland’s glaciers have retreated, with a few periods of advance during cooler climate periods, but at a fast rate, particularly during the last two decades, altering the landscape in areas adjacent to the glaciers.

Glaciers result when so much snow falls that the resulting ice does not fully melt during the warmer months. Over time, the snow builds up and compacts into glacier ice when thick enough to deform and creep from its own weight.

Glaciers often take hundreds of years to form, so climatic changes can have significant effects on them. If warmer temperatures result in more snow melting, the glacier is unable to sustain itself and begins to thin and retreat.

However, an unexpected side effect of that melting snow was revealed in this map of Iceland‚ÄĒmore glaciers have been discovered. Some of these glaciers lay underneath such a large snowpack that they were unknown, effectively hidden from human eyes.

A cutout of the new map of Iceland's Glaciers and volcanoes, showing the overall ice cap as a pale shade of cyan with surge glaciers in a darker shade of cyan.

An excerpt from the map showing the Katla volcano beneath the M√Ĺrdalsj√∂kull ice cap. Eyjafjallaj√∂kull is just to the west.

What’s in a Name?

The discovery of ‚Äúnew‚ÄĚ glaciers in Iceland, revealed from melting of snow pack in late summer, has provided the impetus to provide names to these glaciers. As is often the case, geographic names are an important part of Iceland‚Äôs cultural heritage, and are often inspired from Iceland‚Äôs history. For instance, one of Iceland‚Äôs largest glaciers,¬†Hofsj√∂kull, is named for a farmstead which takes its name from the pre-Christian temples (‚ÄúHof‚ÄĚ) that were part of the Norse religion.

Often the names of the glaciers are descriptive‚ÄĒVatnaj√∂kull translates to ‚ÄúGlacier with many streams,‚ÄĚ and Langj√∂kull, the ‚ÄúLong Glacier.‚Ä̬†Eyjallafjallaj√∂kull, the famous volcano and glacier from 2010, translates to ‚ÄúIslands Mountains Glacier.‚ÄĚ

Other times, the glacier’s name can come from local legends. The Torfajökull glacier is named for Torfi of Klofi, who fled an epidemic with his family into the meadowlands near the glacier.

Even the Icelandic word for glacier, j√∂kull, has interesting history‚ÄĒ it was brought from Norway by early settlers to Iceland and has the same origin as the English word icicle.


More than half of Iceland‚Äôs glaciers lie nearby or flow directly over volcanoes. Knowing which volcanic calderas lie beneath glaciers is important for disaster preparation and mitigation. When a volcano erupts beneath a glacier, it can result in the unleashing of a massive flood known as a j√∂kulhlaup. This volcano-glaciological hazard is well-known to Icelanders, and the largest known j√∂kulhlaup occurs when the Katla volcano under the M√Ĺrdalsj√∂kull ice cap [just to the east of the Eyjafjallaj√∂kull ice cap; see graphic] erupts, resulting in a flood that exceeds the normal flow of the Amazon, Earth‚Äôs largest river in terms of volumetric discharge of water per second.

Large black boulders piled in a line on top of a white ice sheet. A geologist stands next to one of the boulders for scale.

Photograph of rounded boulders of glacier ice rafted across and deposited on the Skei√įar√°rsandur. Note geologist in the left background for scale. Photograph taken on 4 January 1997. Credit: Oddur Sigur√įsson

Jökulhlaups don’t just bring massive floods; they also carry enormous boulders, transport huge blocks of ice, and icebergs. The Vatnajökull eruption in 1996 carried ice blocks weighing more than 2,000 tons. These floods can destroy bridges and roads, making them a serious hazard for Icelandic emergency managers.

Hundreds of Years in the Making

Incorporated into this map are geological, cartographic, and glaciological investigations and techniques from three different centuries. First came the pioneering work by Sveinn P√°lsson in 1795 (see ‚ÄúIcelandic Ice Mountains‚Äú published in English¬†in 2004 and translated from Danish and edited by Richard S. Williams, Jr., and Oddur Sigur√įsson), mapping and surveys in the 1890s, geologists and glaciologists mapping glacier termini and glacial deposits. ¬†From their work, the farthest extent of the Iceland glaciers at the Little Ice Age maximum (ca. 1890) was determined. From 1902 to 1939, the Danish Geodetic Survey compiled maps of Iceland with plane-table methods.

The next stage of mapping came in the mid-20th Century, at the end of World War II. Aerial mapping surveys in 1945/1946 were taken all across Iceland as part of a U.S. Army Map Service mapping endeavor. This latest map integrates the next level of surveying technology‚ÄĒsatellite remote sensing. More than 40 years of remote sensing imagery provided by the Landsat and SPOT satellite programs, as well as cutting-edge airborne sensing techniques like LiDAR , allowed Iceland‚Äôs glaciers to be mapped and studied to a degree not previously possible.

Mapping the Future

The map of Iceland‚Äôs glaciers represents just the latest collaborative effort between the Icelandic Meteorologic Office and the USGS. Operating from a multi-decade Memorandum of Understanding between the USGS and the Icelandic Research Council of Iceland (Rann√≠s), Icelandic and U.S. scientists have studied Iceland‚Äôs glaciers, volcanoes, tectonics and seismology, and geothermal activity, seeking to better understand these processes for the benefit of both countries and earth science as a whole. Iceland is the world leader in geothermal exploration, technology, and exploitation; geothermal energy for space heating and generation of electricity is an important local source of ‚Äúgreen‚ÄĚ energy.

Future research goals of the Icelandic Meteorological Office (IMO) and the USGS include furthering the mapping efforts, completing the third book on the glaciers of Iceland (with 10 Icelandic scientists); [the second book, published by the USGS and in collaboration with the IMO in 2008 was ‚ÄúGeographic Names of Iceland‚Äôs Glaciers: Historic and Modern‚ÄĚ by Oddur Sigur√įsson and Richard S. Williams, Jr.; ], documenting historical science archives, and pursuing additional opportunities for seismological, geothermal, volcanological research, and geologic and hydrologic hazards.

A snow-covered mountain erupting against a yellow sky with the sun peeking through the ash cloud

Photograph from the southwestern wall of the Gr√≠msv√∂tn caldera in Vatnaj√∂kull on December, 19 1998. Photo credit: Oddur Sigur√įsson, Icelandic Meteorological Office

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