Stumbling across our once-great inland sea of Lahontan

Driving from Carson City to the Black Rock Desert where the annual Burning Man counterculture celebration is held can be an education in pre-history and a chance to stop off and do some hiking. We made that drive twice last week, first on Monday and then again on Friday for the Burn.

Highway 477 starts outside Fernley and runs roughly parallel with the Truckee River, which is on its way to Pyramid Lake, where it ends. At first it is Nevada desert, but then the scene changes and deep canyons cut by the Truckee descend on the right to the river. We passed up a stop at the Numana Hatchery Visitor Center where one can find out about the area's natural history and the tribe's fisheries program. We decided it might be fun later to look at the river along the road, so when Chicken Ranch Road appeared on the right, we took it.

This is a nicely paved road for about four miles and turns to dirt just after a ranch house (some warehouse buildings are up a side road about here). The dirt road is easily passable by almost any car and passes a river rehabilitation area before ending in a parking area.

There is the trailhead to the Wetlands Nature Trail and a leg of the Tahoe-Pyramid Bike Trail. The Tahoe-Pyramid Bikeway is a dream of following the Truckee River by foot or by bicycle from its source at Lake Tahoe to its desert end, Pyramid Lake. The route will descend more than 2,000 feet in 116 miles, using a combination of existing dirt and paved roads, plus some sections of new trail and bridges.

Some sections will suit families out for an hour, others horseback riders, and the entire route will entice adventure cyclists traveling the distance. Lands crossed will include both public and private land in two states, five counties, one Indian reservation, and three federal agencies. The trail is not completed yet, but many sections are open.

The sign at the trailhead said a permit was required from the Pyramid Lake tribes in Wadsworth, but we risked a short hike (in the name of Journalism) to the river along the wetlands nature trail where we got a quick peek at the unique habitats of the river valley. Next time we'll get a permit first.

On the way back to Highway 477 we took a dirt road that led to a magnificent overview of the river and mountains, green oases in the midst of the usual Nevada brown. This slight detour is a must because of the sprawling vistas.

On 477 again we noted that the valley to the right no longer offered the deep canyons but instead seemed to be a wide playa. Sometimes the playa came up to and crossed the road and sometimes it disappeared behind hills. The playa here, some 40 miles from the playa at Gerlach, raised some interesting questions. Was this all part of one dried up lake bed? And where did it end.

After the Burn we looked into the question and quickly discovered the very obvious reality. The playa that ends at the Black Rock Desert is all part of the original Lake Lahontan that stretched from the present reservoir to the south up to Gerlach. The Internet revealed more.

"Ancient Lake Lahontan was a large endorheic lake that existed during the ice age, covering much of northwestern Nevada, extending into northeastern California and southern Oregon. At its peak approximately 12,700 years ago (during a period known as the "Sehoo Highstand"), the lake had a surface area of over 8,500 square miles, with its largest component centered at the location of the present Carson Sink. The depth of the lake was approximately 900 feet at present day Pyramid Lake, and 500 feet at the Black Rock Desert. Lake Lahontan, during this earlier ice age, would have been one of the largest lakes in North America.

"Climate change around the end of the Pleistocene epoch led to a gradual desiccation of ancient Lake Lahontan. The lake had largely disappeared in its extended form approximately 9,000 years ago. As the surface elevation dropped, the lake broke up into series of smaller lakes, most of which rapidly dried up leaving only a playa.

These playas include the Black Rock Desert, the Carson Sink and the Humboldt Sink. The only modern day remnants existing as true lakes are Pyramid Lake and Walker Lake. Winnemucca Lake has been dry since the 1930s and Honey Lake periodically desiccates. The ancient shoreline is evidenced by tufa formations throughout the area."

Why did the lake disappear? Largely because of climate warming and high rates of evaporation. The existence of the lake coincided roughly with the first appearance of humans in that region of North America. Archaeological evidence exists along the ancient lake shore of early human habitation.

On the return leg from the Burn, Pyramid Lake loomed a rich, deep blue on the right. It is just a tiny reminder of the great lake that once covered this area. At times along 477 you can see high water marks on the lower hills - strata after strata show a high water rim.

Next time we visit this area we will get hiking and camping permits and perhaps try to trace the remains of the original inland sea that covered the area - reaching almost to Carson City.

• Contact Sam Bauman at 881-1236 or Sbauman@nevadaappeal.com.

What's left of the lake

The Lahontan Reservoir is but a shadow of the original lake.

However, it is an important recreation area for western Nevadans - but there are problems.

The discovery of the Comstock Lode in Nevada in 1859 initiated the use of liquid mercury or "quicksilver" to remove gold and silver from crushed ore. Today, mercury is present in historic mill tailings piles, in alluvial deposits adjacent to the Carson River and in Lahontan Reservoir.

The Lahontan Reservoir is 45 miles east of Carson City on Highway 50. Access is by paved and dirt roads. The surface area is about 11,200 acres at full reservoir storage with 69 miles of shoreline (both reduced by the current drought). Fishing is year-round. The reservoir supports white bass, walleye, white crappie, catfish, and brown and rainbow trout. A health advisory has been issued by Nevada urging limited consumption of fish caught in the reservoir due to the mercury contamination.