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A mountain is a landform that extends above the surrounding terrain in a limited area. A mountain is generally not much higher and steeper than a hill, but there is considerable overlap, and usage often depends on local custom. Some authorities define a mountain as a peak with a topographic prominence over an arbitrary value: for example, the Encyclopędia Britannica requires a prominence of 2,000 feet (610 m).

24% of the Earth's land mass is mountainous; 10% of the world's 6 billion people live in mountainous regions. All the world's major rivers are fed from mountain sources, and more than half of humanity depends on mountains for water [1].

The nearly circular uninhabited island formed by Augustine Volcano is 12 km (7.5 mi) wide east-west, 10 km (6 mi) north-south; a nearly symmetrical central summit peaks at altitude 1,260 metres (4,134 feet). Augustine's summit consists of several overlapping domes emplaced during many historic and prehistoric eruptions. Most of the fragmental debris exposed along its slopes comprises angular blocks of dome-rock andesite, typically of cobble to boulder size but carrying clasts as large as 4 to 8 metres (10 to 25 feet), rarely as large as 30 metres (100 feet). The surface of such deposits is hummocky, a field of steep conical mounds and intervening depressions with many metres of local relief. En route to Katmai in 1913, Griggs (1920, p.341) had briefly inferred landslide (debris avalanche) as the origin of Augustine's hummocky coastal topography about Burr Point, by geomorphic analogy with the hummocky and blocky deposit of a 1912 landslide near Katmai. The hummocky deposits on Augustine's lower flanks resemble both topographically and lithologically those of the great landslide or debris avalanche that initiated the spectacular 18 May 1980 eruption of Mount St. Helens. The deposit of that landslide revealed the origin of coarse diamicts with hummocky topography at other stratovolcanic cones. Since 1980 many hummocky coarsely fragmental deposits on Augustine's lower flanks have come to be interpreted as deposits of numerous great landslides and debris avalanches. Recent eruptions A March 27, 1986, eruption deposited ash over Anchorage and disrupted air traffic in southcentral Alaska. In mid-December 2005 a sulfur dioxide-laden plume of steam, hundreds of miniature earthquakes and a new coating of ash over its currently snow-clad peak, taken together, suggested that Augustine was building to a new eruption, likely in 2006. CNNNews 15 December 2005. On January 11, 2006, Augustine erupted at 4:44 a.m. and 5:13 a.m. Alaska Standard time. Map of Augustine Volcano in Alaska, USA.

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