Elements of GeologyAmerican book Company, 1911 - 475 páginas |
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animals Appalachian Appalachian Mountains Archæan basins beds beneath bottom brachiopods Cambrian cañon carbon changes clay cliffs climate coal coast Comanchean contain corals cracks Cretaceous crystals delta deposits developed Devonian Diagram drift dunes earth eastern eroded erosion faults fauna feet feldspar Figure flood plain flow folded formation fossils geologic glacial glaciers granite gravel ground water horizontal ice sheet igneous rocks lakes land later lava layers less limestone lower mammals marine marshes material Mesozoic metamorphic rocks miles minerals Mississippi moraines mountains North America ocean Ordovician origin Paleozoic period Permian plants Plate plateaus Proterozoic quartz region reptiles ridges rivers salt sand sandstone schists sea level sedimentary rocks sediments shale shallow shells shore showing side Silurian slope strata streams structure surface Surv tains terraces Tertiary thick tion to-day Triassic tributary trilobites U.S. Geol unconformity United valley glaciers volcanic waves weathering western wind worn
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Página 3 - Using their own words, — they have " sought to give the student (1) an understanding of the general principles and processes of the science, (2) a few of its fundamentad facts, (3) an interest in the subject, and especially (4) training in clear thinking.
Página 110 - Unlike sea water, brackish waters differ in quality, quantity, and composition not only from place to place, but also from time to time even at a given location.
Página 274 - A few of them reach elevations above sea level or nearly 30,000 feet, or about 5! miles. Compared with the diameter of the earth, even the loftiest mountains are insignificant protrusions of the lithosphere. "Mountain ridges and peaks are grouped commonly in relatively long and narrow belts, called mountain ranges. When several more or less parallel ranges are grouped together, they constitute a mountain system. Thus, one speaks of the Wasatch Range of Utah, but of the Rocky Mountain System.
Página 286 - Most lake plains are small. Extensive plains, like the Atlantic and Gulf coastal plains of the United States and the vast interior plain which stretches from the Appalachians to the Rockies, cannot in most cases be put in any of the above classes. They commonly contain many smaller plains of several or all of the types mentioned. In general, extensive coastal plains are former marginal sea-bottoms, exposed either by elevation of the land or by lowering of the sea.
Página 115 - The surface material creeps faster than that at a slight depth, tipping the trees toward the axis of the valley (Plate 14, B).
Página 93 - Fig. 20 the above lines are shown alone; this is a contour map of the region represented by the model. By comparison of the model and map it will be seen that where the slopes of the former are steep, the lines of the latter are close together, and vice versa. The vertical distance between two adjacent contour lines is the contour interval. The contour interval varies on different maps. In regions of low relief an interval of 10 or 20 feet is used...
Página 274 - A mountain is an elevation which rises prominently above the surrounding country, and which has a comparatively small area on top. On a low, flat plain, a mountain may have a height of only a few hundred feet; in more rugged surroundings, a much higher elevation may be called a hill. The matter is therefore a relative one, and no fixed height is necessary in order that an elevation may be classed as a mountain. Certain plains — for example, the western portion of the Great Plains — are higher...
Página 162 - NARROWS. — When the rocks in the sides of a valley are of unequal strength, the valley is widened at unequal rates at different points, and if the difference in the character of the rocks is great, the valley may become wide where they are weak, while still narrow where they are strong. The places where valleys have much less than their usual width are called narrows or water gaps. Delaware Water Gap and Harper's Ferry on the Potomac are among the more famous of many narrows in the Appalachian...
Página 189 - The Physical Geography of Southern New England, in Physiography of the United States, pp. 269-304. (New York, 1895.) DAVIS AND WOOD: The Geographic Development of Northern New Jersey, in Proc. Bost. Soc. Nat. Hist., Vol. XXIV, pp. 365-423DODGE: The Geographical Development of Alluvial River Terraces, in Proc. Bost. Soc. Nat. Hist., Vol. XXVI, pp. 257-273. DUTTON: Tertiary History of the Grand Canyon District; Mono.