Almannagja, a large canyon-like fault in Thingvellir National Park, is actually the exposed eastern boundary of the North American geologic plate.

A dike (volcanic feeder tube) merging into layered strata in Thingvellir National Park.

Downchannel from the volcanic dike in Thingvellir National Park.

Mini stream between banks of eroding basalt in Thingvellir National Park.

Rainbow envelopes the peak of Hekla volcano.

Snow-filled crater from the 2000 eruption of Hekla volcano.

Pyroclastic rock bombs scattered about a crater in the Hekla Mountain Range.

Descent down Hekla across the snowpack. Hekla is a stratovolcano located in the south of Iceland; it is one of the island's most active volcanoes, having erupted more than 20 times since the ninth century A.D.

Descent down Hekla across the snowpack. Hekla is an active volcano located in the south of Iceland; it is 1,491 m (4,892 ft) high.

A hauntingly luminous view down the southwest flank of Hekla volcano.

A geyser field and stream runoff.

An azure blue hot pool.

The many channels of a glacial river.

On 21 May 2011, Grimsvoetn volcano rumbled to life and sent off a plume of ash and steam about 20 km (12 mi) into the atmosphere. Above Grimsvoetn's summit, volcanic ash formed a circular brown plume that towered above the surrounding clouds. In the southeast, ash colored the snow surface dark brown. Ash from the volcano also reduced visibility to about 50 m (160 ft) in some areas, causing night-like darkness in the middle of the day. Image courtesy of NASA.

Plumes of dust blowing off the southern coast of Iceland in late June 2007. The dust appears as grayish blurs emanating from the coast southward over the North Atlantic Ocean. Blue-green algal blooms also fringe the coastline. Relatively light winter snow in 2006-07 followed by arid spring weather created the conditions for this dust storm. Photo courtesy of NASA.

The West Fjords are a series of peninsulas in northwestern Iceland, shown in this false-color satellite image. They represent less than one-eighth the country's land area, but their jagged perimeter accounts for more than half of Iceland's total coastline. Black areas represent the sea; light blue snow and ice. Image courtesy of USGS.

Summer temperatures melt snow and ice on much of Iceland's surface, as shown on this satellite image. The lack of uniform snow cover allows permanent (though shrinking) icefields to show through (particularly Vatnajokull in the southeast), and highlights the island's rugged coastline. Scores of fjords edge the island, resembling feathers waving out into the waters of the northern Atlantic Ocean (bottom) and Greenland Sea (upper left). Though Iceland's climate is relatively mild and humid thanks to the North Atlantic Drift, and though the island's active volcanism provides inexpensive heating, only about the a quarter of the island is habitable, most of that along the coastlines. Photo courtesy of NASA.

Summer is winding to a close on 9 September 2002, but even Iceland is still showing some summer color, its perimeter tinged with green, while its large permanent ice caps stand out brightly against the volcanic rock surrounding them. The largest ice cap, Vatnajokull, actually rests on top of three active volcanoes. The heat from these volcanoes causes the underside of the ice cap to melt, slowly filling the calderas. Eventually the caldera spills over and releases a torrent of water known as a glacial melt flood. This volcanic activity happens because a tectonic boundary runs roughly northeast-southwest through the island country, and the two plates are pulling away from each other, causing magma to well up from deep in the Earth. The brightly colored lakes and coastal waters are the result of very fine, and highly reflective sediment that is ground to bits by the immense weight of the glaciers and washed out with glacial runoff. Image courtesy of NASA.

Sunset over a frozen lake-filled caldera.

An eruption of the geyser Strokkur.

A river with volcanic black sand banks meanders to the sea through farm fields near the southern coast of Iceland.

Photo taken from the Eurasian continental plate (foreground rock ledge) looking across to the North American plate and to the Thingvellir, the plains on which the Icelandic republic was founded in 930 and independence declared in 1944. The tabletop mountain on the horizon was formed by a volcanic eruption beneath a glacial ice sheet when Iceland was covered by ice.

Menntaskolinn i Reykjavik (Reykjavik Junior College). Founded in 1096; building erected in 1846. Oldest school in full-time use in Iceland.

City Hall in Reykjavik.

Hofthi House in Reykjavik, site of the summit between Ronald Reagan and Mikhail Gorbachev in 1986.

National Parliament (Althing) building in Reykjavik, erected in 1880-81.

A roundup of Icelandic horses.

Hardy Icelandic sheep exhibit a variety of wool colors: white, grays, browns, black, and spotted.

The Gullfoss Waterfall (Golden Falls) seen from a distance.

The Gullfoss (Golden Falls) Waterfall in southern Iceland.

Mist rises above the Gullfoss Waterfall.

A closeup of the churning Gullfoss Waterfall.

The Gullfoss Waterfall has a distinctive stairstep configuration.

Closeup of some of the stairsteps in the Gullfoss Waterfall.

The thundering waters of the Gullfoss Waterfall.

Channel downstream from the Gullfoss Waterfall.