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<br />FISHES AND FISHERIES OF NEVADA 71
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<br />all have peaks rising more than 10,000 feet above sea level, the tallest
<br />being 11,807 ft. Mt. Jefferson in the Toquimas. To the northeast of this
<br />block, and northwest of Wheeler Peak, the massive Ruby :Mountains
<br />scale up to 11,400 ft. in Ruby Dome. The Rubies have more than pass-
<br />ing interest in being the site of more extensive glaciation than any of
<br />the other interior Nevada ranges.
<br />Along Nevada's northern margins the Columbia Plateau sweeps
<br />briefly into the State-the country here is generally high, but peaks
<br />are not impressive.
<br />The.lofty Sierra Nevada '.Mountains invade west-central Nevada in
<br />the vicinity of Lake Tahoe. The Nevada spur here culminates in 10,800
<br />ft. Mt. Rose near Reno. The main body of the Sierras is not much
<br />higher here, for the range becomes progressively lower in its northern
<br />latitudes. To the south, below Nevada's 13,145 it. Boundary Peak, the
<br />southern Sierras exceed 14,000 feet in height, terminating in `IL Whit-
<br />ney, the 14,500 ft. sovereign of all mainland United States crags.
<br />The only other prominent eminence in the State is a great limestone
<br />block called Mt. Charleston in the Spring Mountains of southern
<br />Nevada west of Las Vegas (11,910 ft.). Here, in the south, where
<br />bottomlands along the Colorado River are the lowest elevations in the
<br />State (500 ft.), Charleston Peak towers far above all others in Nevada,
<br />rising 9,500 feet above its 2,500-foot plain. The high Toquima Moun-
<br />tains are not as impressive, for their valley floors are already 5,000
<br />feet above sea level.
<br />Larger expanses of west-central Nevada have bottomlands of not
<br />much under 4,000 feet, this rising progressively toward the State's
<br />northern border, where the valley lows average better than 5,000 feet.
<br />In summary, the lowest section of the State is its southern tip, where
<br />levels of around 2,500 feet prevail in bottollands around Las Vegas.
<br />Land swells upward toward the center of the State until the Toiyabe
<br />block is reached where major valleys may have a base elevation of more
<br />than 6,000 feet. They drop off gradually on all sides from this highland,
<br />most prominently to the west and southwest, where basins of less than
<br />4,(X1) feet are common. Northward, the dip down to 4,500 and 5,000-
<br />foot valleys Dently begins to ascend again toward the Columbia Plateau
<br />country.
<br />(2) DYNAMICS
<br />LI order to understand the origin of the native fish fauna of Nevada,
<br />one must not only have it knowledge of external landscape features,
<br />but know how these have moved and isolated or brought together
<br />drainage systems in the past to produce the distinctive associations of
<br />fishes we have today.
<br />Ueomorphology,?which deals with the visible form and shape of the
<br />Iand. is the final but never completed expression of dynamic forces
<br />which are continually altering the face of the earth. There is a cyclic
<br />halanre, going first one way and then another, between those agmeies
<br />which elevate and add to the heights of various portions of the earth's
<br />rrust. and those which counter these movements by wearing away rocks
<br />and soil.
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