Volcanic Activity
Ruapehu is largely composed of andesite and began erupting at least 250,000 years ago. In recorded history, major eruptions have been about 50 years apart, in 1895, 1945 and 1995–1996. Minor eruptions are frequent, with at least 60 since 1945. Some of the minor eruptions in the 1970s generated small ash falls and lahars (mudflows) that damaged skifields.
Between major eruptions, a warm acidic crater lake forms, fed by melting snow. Major eruptions may completely expel the lake water. Where a major eruption has deposited a tephra dam across the lake's outlet, the dam may collapse after the lake has refilled and risen above the level of its normal outlet, the outrush of water causing a large lahar. In 2000, the ERLAWS system was installed on the mountain to detect such a collapse and alert the relevant authorities.
Read more about this topic: Mount Ruapehu
Famous quotes containing the words volcanic and/or activity:
“Pity the planet, all joy gone
from this sweet volcanic cone;”
—Robert Lowell (1917–1977)
“The Good of man is the active exercise of his soul’s faculties in conformity with excellence or virtue.... Moreover this activity must occupy a complete lifetime; for one swallow does not make spring, nor does one fine day; and similarly one day or a brief period of happiness does not make a man supremely blessed and happy.”
—Aristotle (384–322 B.C.)