Mid-Atlantic Rift zone, Thingvellir National Park, UNESCO World Heritage Site, Iceland, Polar Regions. Photography. Encyclopædia Britannica ImageQuest. Web. 23 Feb 2015.

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Thingvellir National Park, Iceland.. Photography. Encyclopædia Britannica ImageQuest. Web. 23 Feb 2015. http://quest.eb.com/#/search/137_3123767/1/137_3123767/cite

Moss and lichens on rock at mid-Atlantic ridge rift in Iceland

Cooled lava from recent eruption, Kilauea Volcano, Hawaii Volcanoes National Park, UNESCO World Heritage Site, Island of Hawaii (Big Island), Hawaii, United States of America, North America . Photography. Encyclopædia Britannica ImageQuest. Web. 23 Feb 2015.

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Kilauea Volcano crater, Hawaii Volcanoes National Park, Island of Hawaii, Hawaii, USA. Photograph. Encyclopædia Britannica ImageQuest. Web. 23 Feb 2015.

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Yellowstone National Park. Photography. Encyclopædia Britannica ImageQuest. Web. 23 Feb 2015.

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Colorful terrace atop Mammoth Hot Springs, Yellowstone National Park, Montana.

Yellowstone National Park. Photography. Encyclopædia Britannica ImageQuest. Web. 23 Feb 2015.

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Dormant volcano, Mt St. Helens. Photography. Encyclopædia Britannica ImageQuest. Web. 23 Feb 2015. http://quest.eb.com/#/search/165_3346871/1/165_3346871/cite

Steam Rising From Mount St. Helens. Photography. Encyclopædia Britannica ImageQuest. Web. 23 Feb 2015. http://quest.eb.com/#/search/139_1939472/1/139_1939472/cite

Mt. Kilimanjaro, Amboseli, Kenya, Africa. Photography. Encyclopædia Britannica ImageQuest. Web. 23 Feb 2015. http://quest.eb.com/#/search/151_2492040/1/151_2492040/cite

Laureus Sport for Good Foundation - Martina Navratilova Mt. Kilimanjaro Climb Day One. Photography. Encyclopædia Britannica ImageQuest. Web. 23 Feb 2015. http://quest.eb.com/#/search/115_3808143/1/115_3808143/cit

The Dead Sea. Photography. Encyclopædia Britannica ImageQuest. Web. 23 Feb 2015. http://quest.eb.com/#/search/139_1970271/1/139_1970271/cite

Jerusalem and the Dead Sea. Photography. Encyclopædia Britannica ImageQuest. Web. 23 Feb 2015.

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Trona Pinnacles, California. Photography. Encyclopædia Britannica ImageQuest. Web. 23 Feb 2015.

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Trona Pinnacles National Natural Landmark, located in the Mojave Desert near the mining town of Trona, California, is a vestige of a former inland sea. The spires were formed underwater in the same manner as the tufa formations at Mono Lake, California.

Pinnacles National Monument, California.. Photography. Encyclopædia Britannica ImageQuest. Web. 23 Feb 2015. http://quest.eb.com/#/search/137_3093714/1/137_3093714/cite The volcanic dome at Pinnacles National Monument.

Cotopaxi Volcano (5890 meters), Cotopaxi National Park, Ecuador. Photograph. Encyclopædia Britannica ImageQuest. Web. 23 Feb 2015.

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Cotopaxi Volcano. Photography. Encyclopædia Britannica ImageQuest. Web. 23 Feb 2015. http://quest.eb.com/#/search/149_2086868/1/149_2086868/cite

World map . IMAGE. Encyclopædia Britannica. Web. 23 Feb. 2015. <http://media3.school.eb.com/eb-media/94/75394-004-D63D96A5.gif>.

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