The Geology and Petrography of Crater Lake National Park, Ausgaben 105-107U.S. Government Printing Office, 1902 - 167 Seiten |
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abundant allotriomorphic analysis Anna Creek apatite appear augite microlites basalts brachypinacoid brown glass brownish canyon Cascade Range cavities color colorless conspicuous contain Crater Lake crest dacite dark-colored secretions described developed diameters dike Diller distinctly Eagle Cove edge eruption extinction angles feet feldspar fragments glacial glass base glass inclosures glass inclusions globulites grains granophyric granular groundmass hand specimen holocrystalline holocrystalline andesites hornblende hyalopilitic hypersthene hypersthene and augite hypersthene-andesite hypocrystalline type inclosures interstitial basalts irregular Klamath lava lithoidal Llao Rock magnetite Magnified mass microscope miles millimeter mineral minute Mount Mazama nearly numerous occurs olivine parallel pinacoid plagioclase crystals plagioclase laths plagioclase phenocrysts pleochroism polarized light portion present prismatic prisms pseudobrookite pumice pyroxenes quartz rectangular Red Cone refraction resemblance resorption roundish Sand Creek sanidine seen slender slope spherulites subtype summit Sun Creek thin section Trace tridymite twinning U. S. Geol usually vitrophyric volcanic Wizard Island
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Seite 14 - ... range, it is evidently the basal portion of a great hollow cone in which the lake is contained. In addition to the strong contrast between the outer and inner slopes of the rim the map shows the occurrence of a number of small cones upon the outer slope of the great cone. These adnate cones are of peculiar significance when we come to consider the volcanic rocks of which the region is composed. The rim is ribbed by ridges and spurs radiating from the lake, and the head of each spur is marked...
Seite 48 - They appear to be correlated to the remarkably quiet habits of the Hawaiian volcanoes, to their habitual modes of eruption, and to the special structure of the volcanic piles, which do not rise in steep conical peaks, but are very broad and flat. At Crater Lake, neither in the walls themselves, nor in the immediate neighborhood back of the crest line, have any traces of sinkage been observed as yet. Nothing can at present be pointed out which suggests the Hawaiian mode of origin, beyond the fact...
Seite 14 - ... The eye beholds 20 miles of unbroken cliffs ranging from over 500 to nearly 2,000 feet in height, encircling a deep blue sheet of placid water, in which the mirrored walls vie with the originals in brilliancy and greatly enhance the depth of the prospect. The first point to fix our fascinated gaze is Wizard Island, lying nearly 2 miles away, near the western margin of the lake. Its irregular western edge and the steep but symmetrical truncated cone in the eastern portion are very suggestive of...
Seite 118 - Under the microscope the greater part of the rock is seen to be composed of spherulites of distinctly recognizable fibers and shreds that radiate in branching.
Seite 7 - It affords some flue views of the canyons and rapids of that turbulent stream and of the high falls, where it receives its affluents. Striking features along both roads, within 20 miles of the lake, are the plains developed upon a great mass of detritus filling the valleys. Across these plains Anna Creek and Rogue River have carved deep, narrow canyons with finely sculptured walls, which the roads follow for some distance. Approaching the lake from any side, the observer sees...