THE GREAT PLEISTOCENE LAKE OF NORTHWESTERN NEVADA

There is a secret that lies hidden in the valleys of northwestern Nevada. No it is not gold, or silver though there is plenty of that as well. It is the story of a huge lake that once filled these valleys. A lake so large that it would take weeks and weeks to walk around it. A lake so deep that the sun never penetrated its depths. A lake rich with fish, and surrounded by woodlands and grassy steppe. Large herds of now extinct animals like American camel, horse and shrub ox, giant bison, and the majestic Columbian mammoth roamed the shores of this lake. Even deer, pronghorn antelope and big horn sheep grazed the grassy slopes. Giant cats, probably including saber or dirk-toothed, dire wolves and other terrifying carnivores hunted these animals. And people? They had probably not even arrived yet or were just beginning to venture around the cold windy shores of this lake. Why do we know about this lake? And what do we know about this lake? It is a story of the Ice Age and what it did to western North America.

It is through the observations of European visitors to the region during the 1800s that we began to learn about this lake. They noticed shore lines, river deltas, and gravel bars high above the now dry valley floors. They examined caves that had been cut into rocky outcrops by the action of waves. During this century many scientists and students began examining the evidence of this lake in earnest. Soon we knew how big this lake had been and how long it had lasted. We knew the kinds of animals that had roamed its shores and the plants that had covered the surrounding mountain slopes.

Today we can tell the tale of a much colder period when rainfall could collect in the valley floors where today it can only evaporate from the numerous barren and salty playas that lie there. It was probably a time when for extended periods cold storms brought rain from the Pacific. At other times, such as around 18,000 years ago, it may have been extremely cold and dry...a continental desert. And of the lake? Before 12,000 years ago the northwestern portion of Nevada was dominated by the cold, gray waters of Pluvial Lake Lahontan. It filled the low-lying valleys in a large sinuous, O-shaped lake that stretched from beyond present-day Winnemucca in the north to modern Hawthorne in the south. If power boats had been available one could have sailed from Lockwood just east of Reno/Sparks eastward through the Truckee Valley, north above where Pyramid Lake now lies into the Smoke Creek and Blackrock deserts to the north and then east to Winnemucca. From there one could have sailed south high above the towns of Lovelock and Fallon to Hawthorne. Finally turning north and then west again one would have returned to Reno/Sparks. The cold clear waters held huge Lahontan cut-throat trout that fed in the rich waters.

The silts, sands, and gravels that fill the bottoms of caves that were carved by the waves that lashed these shores 13,000 years ago contain the bones of both animals that still live in the area today and of animals that have disappeared from the face of the earth. The remains of both small and large animals are found. These bones tell of a similar though different world. A world were large herds of animals grazed and where large carnivores hunted them. These sediments also contain volcanic ashes that came from distant volcanic eruptions and suggest disasters that must have taken a terrible toll in plant and animal life, and terrified anyone or thing that witnessed them.

The calcium carbonate deposits called tufa which were left on the outcrops and in the caves surrounding the lake tell us how cold the lake was and about its chemistry. Some were formed in deep, cold lakes. Others reflect warmer water temperatures, and still others suggest periods when the lake was dying and its waters were rapidly evaporating at the end of the Ice Age. Formed over tens of thousands of years they provide detailed information that scientists, such as Dr. Larry Benson of the U.S. Geological Survey, use to reconstruct the lakes history.

In the mid 1960s Roger Morrison pioneered studies of the ancient deposits of pluvial Lake Lahontan. Later others such as Jonathan Davis, who dated the history of the lake with the aid of volcanic ashes of known origin and age, and Fred Nials, who studied the geomorphology of the northern basins of Lake Lahontan, continued the collection of knowledge. Today the tradition is being continued by students such as Kurt Cupp, who studied the Fernley Basin deposits, and Dr. Ken Adams, who has examined high shore line deposits around the Carson Sink and elsewhere to unravel the complicated history of this immense lake. Others, such as Jerry Miller and his students, have studied the histories of smaller sub-basins in hopes that the record will be less complex then in the main basins were the rise and fall of the lakes have destroyed much of the earlier sedimentary archive.

Finally, pollen from the ancient plants that once grew here is being recovered from the sediments of the lake-shore caves and from marshes in the bottoms of the valleys. These pollen can tell us what plants grew around the lake thousands of years ago. They have recorded the changes that occurred in the vegetation as the climates changed from interglacial to glacial and back to interglacial climates. They reveal that plants that now grow much higher in the nearby mountains once grew around the lake itself. They also indicate that many plants which grow in the region today were here during the Ice Age as well. It is the changes that we see in the plant communities that provide us with some of our best information of past changing climates.