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GEOLOGY ON POST STAMPS |
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GEOLOGY ON POST STAMPS |
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Stany Zjednoczone Ameryki / United States of America
Diablelska Wieża w stanie Wyoming, ostaniec utworzony przez skały komina
wulkanicznego wyerodowane ze skał osadowych; znaczek wydany w roku 1956.
Devils Tower in
Wyoming, a monadnock formed by rocks filling the ancient volcanic vent, eroded
from the surrounding sedimentary rocks; the stamp issued in 1956.
Coll. A. Kozlowski
Devils Tower. The nearly vertical monolith known as Devils Tower rises 1,267 feet above the meandering Belle Fourche River. Once hidden below the earth's surface, erosion has stripped away the softer rock layers revealing Devils Tower. Known by several northern plains tribes as Bears Lodge, it is a sacred site of worship for many American Indians. The rolling hills of this 1,347 acre park are covered with pine forests, deciduous woodlands, and prairie grasslands. Deer, prairie dogs, and other wildlife are abundant. Proclaimed September 24, 1906 as the nation's first national monument by President Theodore Roosevelt.
Z / From: http://www.nps.gov/deto/
Park geology. Although Devils Tower has long been a prominent landmark in northeastern Wyoming, the origin of the mammoth rock obelisk remains somewhat obscure. Geologists agree that Devils Tower formed from molten rock forced upwards from deep within the earth. Debate continues, however, as to whether the rock cooled underground or whether Devils Tower magma reached the surface. Current research supports the conclusion that Devils Tower was not a volcano, but was injected between sedimentary rock layers and cooled underground. The characteristic furrowed columns are the result of contraction which occured during the cooling of the magma. Geologic estimates have placed the age of Devils Tower at greater than 50 million years, although it is likely that erosion uncovered the rock formations only one or two million years ago. The unique geological attributes of Devils Tower stimulated several early preservation efforts. In 1892 Wyoming Senator Francis E. Warren persuaded the General Land Office to create a timber reserve which surrounded the Tower. Senator Warren also launched an unsuccessful effort to declare the entire area a national park. In 1906 Congress passed the Antiquities Act which empowered the President to bestow historic or prehistoric structures, and other significant historic or scientific objects. President Theodore Roosevelt quickly invoked the Antiquities Act, designating Devils Tower the nation's first National Monument in 1906. The National Park Service was created in 1916 and eventually assumed administrative control of all national monuments.
About 60 million years ago molten rock forced its way into overlying sedimentary rocks and cooled underground. The cooling igneous rock contracted, fracturing into columns. An earlier intrusion formed the nearby Missouri Buttes.
Over millions of years the sedimentary rock eroded to expose Devil's Tower and accentuate Missouri Buttes. The Tower rises 867 feet from its base, 1,267 above the river, and 5,117 above sea level. The area of its tear-drop shaped top is 1.5 acres. Its base diameter is 1,000 feet.
Z / From: http://www.aqd.nps.gov/grd/parks/deto/
