Geological SeriesVirginia Geological Survey, 1918 - Geology |
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40 feet altitude Amelia quadrangle Appomattox River Bermuda Hundred quadrangle Blandford Blue Ridge bluff Bollingbrooke broad BULLETIN XVI PLATE Camp Lee channel Chowan City Point clay cliff Coastal Plain continental platform contour lines Country About Camp Courtesy of W. B. divides Drainage Dutch Gap Canal east EASTERN VIRGINIA eastward edge estuaries extends Facing page Facing Farrar Island feet above sea-level flat flow formation formed gentle slope granite higher plain Hopewell illustrated booklet entitled inches James River land landward lower plain Meadowville meanders miles narrow navigable Pamlico Petersburg quadrangle Piedmont Plateau places provinces publisher of illustrated Richmond roads sand and gravel sea bottom seaward shallow valleys shore line side soil steep slope stream terraces Sunderland swamps Swift Creek terrace plains tidal reaches tide level Tidewater Virginia Topographic map tributary U. S. Geol undertow UNIVERSITY OF VIRGINIA upland VIRGINIA GEOLOGICAL SURVEY W. B. Harrison weather WESTMORELAND DAVIS Wicomico terrace
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Page 13 - In the foreground is the sea, with a bay that is partly inclosed by a hooked sand bar. On each side of the valley is a terrace into which small streams have cut narrow gullies. The hill on the right has a rounded summit and gently sloping spurs separated by ravines. The spurs are truncated at their lower ends by a sea cliff.
Page 12 - The features represented on the topographic map are of three distinct kinds: (1) inequalities of surface, called relief, as plains, plateaus, valleys, hills, and mountains; (2) distribution of water, called drainage, as streams, lakes, and swamps; (3) the works of man, called culture, as roads, railroads, boundaries, villages, and cities.
Page 13 - Ideal view and corresponding contour map. 1. A contour indicates a certain height above sea level. In this illustration the contour interval is 50 feet; therefore, the contours are drawn at 50, 100, 150, and 200 feet, and so on, above mean sea level. Along the 250foot contour lie all points of the surface 250 feet above sea; along the 200foot contour, all points that are 200 feet above sea, and so on.
Page 14 - ... 3. Contours show the approximate grade of any slope. The vertical space between two contours is the same, whether they lie along a cliff or on a gentle slope; but to rise a given height on a gentle slope one must go farther than on a steep slope, and therefore contours are far apart on gentle slopes and near together on steep ones.
Page 12 - The heights of many points are accurately determined, and those which are most important are given on the map in figures. It is desirable, however, to give the elevation of all parts of the area mapped, to delineate the horizontal outline, or contour, of all slopes, and to indicate their grade or degree of steepness. This is done by lines connecting points of equal elevation above mean sea-level, the lines being drawn at regular vertical intervals.
Page 14 - In the space between any two contours are found elevations above the lower and below the higher contour. Thus the contour at 150 feet falls just below the edge of the terrace, while that at 200 feet lies above the terrace; therefore all points on the terrace are shown to be more than 150 but less than 200 feet above sea. The summit of the higher hill is stated to be 670 feet above sea; accordingly the contour at 650 feet surrounds it. In this illustration all the contours are numbered, and those...
Page 14 - ... it is not desirable to number all the contours, and then the accentuating and numbering of certain of them — say, every fifth one — suffice, for the heights of others may be ascertained by counting up or down from a numbered contour. 2. Contours define the horizontal forms of slopes. Since contours are continuous horizontal lines, they wind smoothly about smooth surfaces, recede into all re-entrant angles of ravines, and project in passing about prominences. These relations of contour curves...
Page 14 - In the space between any two contours are found all elevations above the lower and below the higher contour. Thus the contour at 150 feet falls just below the edge of the terrace, while that at 200 feet lies above the terrace; therefore all points on the terrace are shown to be more than 150 but less than 200 feet above sea. The summit of the higher hill is stated to be 670 feet above sea; accordingly the contour at 650 feet surrounds it. In this illustration...
Page 14 - Contour lines show the approximate grade of any slope. The vertical interval between two contours is the same, whether they lie along a cliff or on a gentle slope ; but to attain a given height on a gentle slope one must go farther than on a steep slope, and therefore contours are far apart on gentle slopes and near together on steep ones. A small contour interval is necessary to express the relief of a flat or gently undulating country ; a steep or mountainous country can, 'as a rule, be adequately...