Friday, September 21, 2007

Lake Lahonton, Nevada: Climate Change

The Black Rock Desert and ancient Lake Lahontan in northwestern Nevada bring back fond memories for me. To those who know and remember, this is a tribute to "Bruno's Country Club", in Gerlach, Nevada, to days gone by.

Searching for Lake Lahontan
Evidence of the giant, ancient lake can be seen throughout northern Nevada.
Mark Vanderhoff RENO GAZETTE-JOURNAL Posted: 5/17/2003
There was a time when a giant lake covered much of northwestern Nevada. Between 9,000 and 20,000 years ago, the same mountains that exist today dipped into its deep, dark blue waters. Junipers or limber pine carpeted the slopes from the snowcapped peaks to its shores. Nearby, prehistoric camels, mammoths, bison and horses grazed. Cheetahs chased antelope. Huge sloths and the giant short-faced bear, larger than a Kodiak bear and fast on its long legs, roamed.
Fingers of the lake reached into mountain valleys and the tops of large hills poked out of the water, forming little islands. What is now the high country beginning in the Truckee Range north of Fernley to the Jackson and Kamma Mountains forming the eastern border of the Black Rock Desert once was a large island in the middle of the ancient lake.

Lake Lahontan, as the giant lake was called, reached its high point 15,000 years ago.
The climate then was much different than it is today because a massive glacier of the last ice age stretched down to the Canadian border, deflecting polar jet streams toward the southwestern United States. An abundance of rain and snow filled the Great Basin with hundreds of feet of water. During its highest years, the lake was almost 900 feet deep at present-day Pyramid Lake.

Lake Lahontan at its highest stretched from the Oregon border to Walker Lake, as far east as Winnemucca and as far west as Honey Lake up U.S. 395 in California. Although Reno and Carson City were high and dry, the Black Rock Desert, Lovelock and Fallon were under water.
Climate changes eventually dried up the lake, but today, clues about Lake Lahontan remain all across its former domain.
“You can see a world that was different from today,” said Pat Barker, the Bureau of Land Management’s Nevada archaeologist.

The beach
The playa of the Black Rock Desert may be the most famous remnant of Lake Lahontan.
“I think one of the coolest things is it’s one of the biggest, flattest surfaces on the planet,” said Ken Adams, a Desert Research Institute geologist who studies Lake Lahontan.
Playa means beach or shore in Spanish, but in the days of Lake Lahontan, the playa was at the bottom of the lake. The fine silt and clay that compose the playa was light enough to be carried in by the rivers and streams that flowed into Lake Lahontan. That sediment eventually settled to the bottom.

Today, the playa owes its flat surface to the water table, Adams said.
A water table, standing water that sits underground, has a flat upper surface, just like a lake.
The winds that blow over the playa only blow off the loose items — they can’t pick up the cohesive, moist sediment wetted by the upper surface of the water table. Essentially, the playa surface has been “planed off by the wind,” Adams said.

Part of Adams’ research consists of finding remnants of the ancient shorelines and measuring their heights in the hills that once surrounded Lake Lahontan.
He has found the highest shorelines in the hills surrounding the Black Rock Desert and the Carson Sink. Those areas may have been under as much as 450 feet of water at one point, he said.

Shorelines and seashells
The highest shorelines may have been around the Black Rock Desert and Carson Sink, but the deepest waters stood at what is now Pyramid Lake.
Today, it is easy to see where the waves of Lake Lahontan also lapped at the hills surrounding Pyramid Lake.
“They’re very obvious if you know what to look for,” Adams said. “There’s a lot of places I could bring my mother and she’d understand what she was looking at.”
Look at the mountainsides that surround the lake, and white or light tan splotches will begin to appear among the brown dirt. Those spots consist of very fine silts that were deposited by Lake Lahontan on these hills thousands of years ago.

Next, search the slopes of the mountains for horizontal lines. Look closer and notice the terraces cut into the mountains like giant steps. Those terraces formed as crashing waves eroded soil from the hillsides. As the lake level dropped, the waves tore at successively lower spots on the slopes.

Pyramid Lake yields other clues about Lake Lahontan.
Walk to the beach and examine the sediment in the escarpments cut by the waves. Pick up a handful of sediment and look closely, and some white shells will appear among the sand and pebbles. “They look like snail shells, but there are no aquatic snails in the lake today,” Adams said. Those snail shells, called gastropods, have been dated to as far back as 25,000 years ago, suggesting they lived in Lake Lahontan. While the snails no longer live in Pyramid Lake, one species that swam Lake Lahontan does still call Pyramid Lake home. The qui-ui, a bottom-feeding fish that is now endangered because its spawning habitat on the Truckee River has been altered, thrived for thousands of years in Lake Lahontan and now only lives in Pyramid Lake.
“That’s one reason why we know Pyramid has never dried up since Lake Lahontan,” Adams said.
Pyramid Lake is, in fact, the real heir to Lake Lahontan. Walker Lake is also a remnant of Lahontan, but it has dried up numerous times over the years because of climate change and the diversion of the Walker River.

Surf’s up
If humans existed during Lake Lahontan’s prime, they could have stood on a sandy finger reaching into the lake now called the Russell Spit. Russell Spit looks like a long, wide pile of sand sticking out of the hills south of Fallon like an earthen finger. It was formed when Lake Lahontan’s waves crashed on nearby slopes at a slight angle, tearing away soil and then redepositing it down the shoreline. “You can stand on this beach and look north and go ‘Wow, there must have been huge waves here,’” Adams said. The waves here got so big because they had a large fetch, Adams said. Fetch is the area of open water where waves are built by the wind.

From the Russell Spit, it’s more than 50 miles as the wave rolls to the north end of the Carson sink. Back then, the Desert Mountains, on the edge of which Russell Spit stands, rose out of the water. Today, someone standing on Russell Spit can see where that giant expanse of water stood, clear beyond Fallon.

The human element
Throughout its long life, Lake Lahontan grew and shrank as the climate of the Great Basin gradually changed. After its high point, the lake dried up as the ice sheets retreated. A long drought ensued, followed by a very cold period that probably froze any water left.
Then the lake returned one final time. Scientists believe humans lived at the lake during this last incarnation, and the proof lies in sites like the Grimes Point-Hidden Cave Archaeological Area.

This site, south of Fallon, consists of caves hidden among hills and large boulders and is managed by the Bureau of Land Management. “Those boulders would have been on the shore lines,” said Amy Dansie, a retired Nevada State Museum anthropologist. The Spirit Cave Man might have lived on this shore and caught giant Lahontan cutthroat trout from its waters. This mummified human was found in nearby Spirit Cave in 1940 by two archaeologists who thought the remains were only 2,000 years old.

The remains were boxed and forgotten for six decades until the Nevada State Museum tested them as part of a program to return the remains to the Fallon Paiute-Shoshone tribe, who claim the Spirit Cave Man as their ancestor. The tests showed the mummy was about 10,630 years old. That places him at the Spirit Cave around the time Lake Lahontan was a dying lake.
But Dansie and other archaeologists believe humans may have seen Lake Lahontan in its prime.
Their theories are based on artifacts believed to have come from a period before this marshy time.

Some artifacts found at high elevations appeared to be “water tumbled,” Dansie said, suggesting they existed around the time of Lake Lahontan’s high stand. Dated bones belong to horses that appear to have been butchered using tools that predate the Spirit Cave Man’s culture. One spearhead called the McGee point is believed to be more than 13,000 years old, putting humans at Lake Lahontan no later than its high stand.

Any people that lived around Lake Lahontan through its varied life would have had to put up with — or perhaps retreated from — the changing climate. “They may have existed here but gone south and come back up multiple times,” Dansie said. Dansie is searching for a smoking gun, some artifacts that can be positively dated using the most modern technology. Those artifacts might be buried deep in layers of lake silt.

She believes such artifacts might prove humans appeared about 1,000 years before the Clovis Man, a member of a culture that lived 11,000 years ago — the earliest accepted date of a human presence in the New World. “It’s only another 1,000 years,” she said. “It’s not like we’re proposing 30,000 years.”

No comments: