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Shield Volcanoes

Shield volcanoes are built almost entirely of fluid lava flows. Flow after flow pours out in all directions from a central summit vent, or group of vents, building a broad, ge…

Lava Domes

Volcanic or lava domes are formed by relatively small, bulbous masses of lava too viscous to flow any great distance; consequently, on extrusion, the lava piles over and aroun…

Submarine Volcanoes

Submarine volcanoes and volcanic vents are common features on certain zones of the ocean floor. Some are active at the present time and, in shallow water, disclose their prese…

Earth's Greatest Volcanic Field

The largest known concentration of active volcanoes on Earth was discovered by scientists aboard the research vessel Melville (Nov. 1992–Jan. 1993). The vast volcanic cluster …

Continental Drift and Plate-Tectonics Theory

Source: U.S. Dept. of the Interior, Geological Survey According to the theory of continental drift, the world was made up of a single continent through most of geologic time. T…

Interesting Caves and Caverns of the World

The following list names interesting caves and caverns of the world, including Aggtelek in Hungary, Blue Grotto in Italy, Kent's Cavern in England, Mammoth Cave in Kentucky, W…

The Continental Divide

The Continental Divide is a ridge of high ground that runs irregularly north and south through the Rocky Mountains and separates eastward-flowing from westward-flowing streams…

Rivers of the United States

(350 or more miles long)Alabama-Coosa (600 mi.; 966 km): From junction of Oostanula and Etowah R. in Georgia to Mobile R.Altamaha-Ocmulgee (392 mi.; 631 km): From junction of Y…

Geysers in the United States

Geysers are natural hot springs that intermittently eject a column of water and steam into the air. They exist in many parts of the volcanic regions of the world such as Japan…

Michigan and Huron: One Lake or Two?

It is a widely accepted fact that Lake Superior, with an area of 31,820 square miles, is the world's largest freshwater lake. However, this fact is based on a historical inacc…