Ice Caps and Ice Fields Explained
When ice accumulates not just in individual valley glaciers but across entire mountain plateaus and elevated terrain, covering the underlying topography to form a continuous blanket of ice from which outlet glaciers radiate outward, the result is either an ice cap or an ice field. The distinction between these two terms is technical but useful. Both are distinct from the great polar ice sheets — Greenland and Antarctica — which are orders of magnitude larger and involve ice thick enough to overwhelm all underlying topography. Ice caps and ice fields represent an intermediate scale of glaciation, sitting atop mountains and plateaus rather than burying continents.
An ice cap is formally defined as a dome-shaped ice mass covering high ground, with ice flowing outward in all directions from a central ice divide. The underlying bedrock topography is subdued — buried beneath the ice — and the surface is relatively smooth and gently convex in profile, much like a smaller ice sheet. True ice caps cover their source terrain entirely. An ice field, by contrast, is an extended mass of interconnected glaciers atop a mountainous terrain, but the highest peaks — nunataks — protrude through the ice surface. The underlying topography influences the ice field surface significantly, and flow directions from different sectors of the ice field are controlled partly by the underlying bedrock valleys.
Iceland's Vatnajokull
Vatnajokull, covering approximately 8,100 square kilometres of southeastern Iceland, is the largest glacier in Iceland and one of the largest in Europe by area. It qualifies as an ice cap under the formal definition: its central plateau buries the underlying basaltic terrain, and numerous outlet glaciers flow outward in all directions. Breidamerkurjokull flows south toward the Atlantic and calves into the Jokulsarlon glacier lagoon. Skeidararjokull spreads west across the outwash plain of Skeidararsandur. Brúarjökull extends north toward the interior highlands.
Vatnajokull overlies several active volcanic systems, including Grimsvotn and Bardarbunga, which generate subglacial lakes and periodic subglacial eruptions. The geothermal heat from these volcanic systems maintains subglacial melting that contributes to jökulhlaup outburst floods. The 1996 eruption in the Grimsvotn caldera produced a flood discharge that briefly exceeded the discharge of the Amazon River. Vatnajokull is protected as part of Vatnajokull National Park and is accessible for guided glacier walks from multiple access points on its southern margins.
Norway's Jostedalsbreen
Jostedalsbreen, covering approximately 474 square kilometres in western Norway, is the largest glacier on mainland Europe. It sits atop a high plateau in the Jotunheimen and Breheimen highlands, and sends outlet glaciers down steep valley sides in all directions. The most visited outlets include Briksdalsbreen, Nigardsbreen, Bergsetbreen, and Boyabreen, each accessible by marked trails or guided tours from the valleys below.
Jostedalsbreen is an ice field in the formal sense: its highest point reaches approximately 1,957 metres above sea level at Lodalskapa, and several nunatak peaks punctuate the ice surface. The different outlet glaciers behave somewhat independently: Briksdalsbreen and Nigardsbreen retreated substantially through most of the twentieth century, then advanced between roughly 1990 and 2005 in response to increased precipitation, before resuming retreat. This behaviour illustrates the sensitivity of outlet glaciers to both temperature and precipitation inputs.
Canada's Columbia Icefield
The Columbia Icefield straddles the Continental Divide between Alberta and British Columbia in the Canadian Rockies, covering roughly 230 square kilometres at elevations between approximately 1,900 and 3,700 metres. It is the hydrological apex of North America in one sense: meltwater from the icefield drains to three oceans — the Pacific via the Columbia River, the Atlantic via the Saskatchewan and Nelson Rivers, and the Arctic via the Athabasca and Mackenzie Rivers.
The Columbia Icefield is a true ice field in the topographic sense, with peaks including Mount Columbia (3,747 m) and Snow Dome (3,456 m) serving as nunataks or near-nunataks within the ice mass. Outlet glaciers include the Athabasca Glacier, the most accessible in Canada due to its proximity to the Icefields Parkway, the Saskatchewan Glacier, and the Columbia Glacier. The Athabasca Glacier has retreated roughly 1.5 kilometres since the late nineteenth century and is regularly used for commercial glacier tours.
Iceland's Other Ice Caps: Langjokull and Hofsjokull
Iceland's second and third largest ice caps, Langjokull (approximately 920 square kilometres) and Hofsjokull (approximately 925 square kilometres), occupy central Iceland's highlands. Langjokull covers a plateau of Pleistocene volcanic rocks and has recently been the site of a remarkable engineering project: a system of tunnels bored directly into the ice from the side, creating an ice tunnel experience accessible to tourists. Hofsjokull is Iceland's central ice cap, broadly dome-shaped, and overlies a central volcanic caldera.
Both ice caps have thinned and retreated measurably since systematic surveys began in the twentieth century. Combined ice volume loss from all Icelandic ice caps has contributed a detectable signal to global sea level rise, though individually smaller than the contributions from Greenland and the major polar systems.
Patagonian Ice Fields: North and South
The Northern and Southern Patagonian Ice Fields in Chile and Argentina are the largest temperate ice masses in the Southern Hemisphere outside Antarctica. The Southern Patagonian Ice Field, covering approximately 12,400 square kilometres, straddles the Andes crest and sends outlet glaciers eastward onto the Patagonian steppe and westward into the fjords of Chilean Patagonia. Major outlet glaciers include Perito Moreno, Upsala, Viedma, and O'Higgins.
The Northern Patagonian Ice Field, covering approximately 4,200 square kilometres, lies further north and is more heavily dissected by deep fjords. San Quintin, San Rafael, and Steffen Glaciers are among its major outlets. The San Rafael Glacier is notable for being one of the lowest-latitude tidewater glaciers in the world, calving icebergs into the Laguna San Rafael at approximately 46.7 degrees South latitude.
Explore the locations of ice caps and ice fields worldwide, including those profiled here and many smaller examples in the Arctic, sub-Antarctic, and mid-latitude mountain ranges, by browsing the map.