534 STUDIES FOR STUDENTS 



Should the storm continue, the sheets of water in the valleys will expand, 

 and possibly become many square miles in area. Such lakes are always shallow, 

 and always yellow with mud in suspension. When the sun breaks through the 

 storm clouds, evaporation becomes active, and the lakes gradually contract their 

 boundaries, and perhaps in a few hours or in a few days are entirely dissipated. 

 When the water has disappeared, absolutely barren mud plains remain, which 

 harden under the sun's heat, and become cracked in all directions as their surface 

 contracts in drying. The lake beds then have a striking resemblance to tesse- 

 lated pavements of cream-colored marble, and soon become so hard that they 

 ring beneath the hoof beats of a galloping horse, but retain scarcely a trace of 

 his foot-prints. 



Such bare, level mud plains are characteristic features of the greater part 

 of the valleys of Nevada, and are known in Mexico and adjacent portions 

 of the United States as playas. The lakes to which they owe their origin are 

 termed playa lakes. .... The largest ephemeral lake of Nevada is formed 

 during winter months on what is known as Black Rock Desert in the north- 

 western part of the State. This desert valley is irregular in shape, and has 

 lateral valleys opening from it. Its length from northeast to southwest is over 

 one hundred miles, and its average breadth twelve or fifteen miles. In summer 

 it is almost entirely without tributary streams, except such as are fed by hot 

 springs. In winter many brooks descend the mountains to the east and west; 

 and the channel of Quinn River, which enters the basin from the northeast, is 

 transformed into a veritable river. The course of this stream in summer is 

 marked only by a dry channel, with an occasional water hole; but in winter it 

 is flooded so as frequently to be impassable to a man on horseback, and has a 

 length of upward of a hundred miles. Its waters then spread out on Black 

 Rock Desert, and at times form a long narrow lake from 450 to 500 square miles 

 in area. Although seldom over a few inches deep, it is impassable on account 

 of the softness of the mud forming its- bottom. Many times the "lake" is a vast 

 sheet of liquid mud, and for this reason is known as "Mud Lake" by the settlers 

 of the region. This name is not distinctive, however, as many other playas 

 have the same name attached to them 



The winter lakes on Black Rock and Smoke Creek deserts, as in many other 

 similar instances, do not occupy the entire valley bottom, but are surrounded 

 by a broad fringe of what to the eye appears level land. This broadening tract 

 is covered with sagebrush and other desert shrubs. In early spring many flowers 

 beautify the ground, and fill the air with a faint perfume. The playas left by 

 the desiccation of the lake, however, are always barren. Not a plant takes 

 root in their baked and hardened surfaces. Where these mud -plains meet the 

 surrounding areas clothed with desert shrubs, there is often a belt of ground 

 that is soft and marshy in winter, and frequently retains something of this char- 

 acter after the lakes have disappeared. In summer it becomes white with salts 

 brought from below by ascending water, and left on the surface when evapora- 

 tion takes place. These efiiorescent deposits become unusually abundant 



