Show devils tower wyoming Is years old devil devils s tower wyoming is the oldest national monument under the national park service of the de apartment part ment of the interior it is said to be 20 years old it is a unique and colossal geologic forma tion which stands in the black hills the striated stone measuring 1000 1 feet in diameter at its base occupies one and a halt half acres of territory and stands feet above ground geologists hold that about 50 years ago when the black hills were forming molten rock started to force its way through weak points in the limestone and sandstone in the area these formed surface flows sills and lava blis some of the molten masses came through passages that were nearly rounded or oval the cooling of the molten lava in the passages produced necks or plugs sometimes called pipes weathering frequently exposes these rocks which remain standing as promontories devil devils s tower was proclaimed a national monument by theodore roosevelt in 1906 |