Glacial Lake Modoc

During the cool, wet climate of the Pleistocene, a large lake formed east of the Cascades in southern Oregon and northeastern California.  Known today as Glacial Lake Modoc, it had a surface area of 1100 square miles; its surface was 100 feet higher than that of Upper Klamath Lake, its largest remnant. Tule Lake and Lower Klamath Lake and their adjacent wetlands are also remnants of Lake Modoc, which extended eastward along the Lost River Valley and northward along the Wood, Williamson and Sprague Rivers that now feed Upper Klamath Lake.

Current geologic evidence suggests that the Upper Klamath Basin formed as a vast graben, divided by north-south trending fault-block ridges.  Glacial meltwater from the Cascades balanced outflow through the Klamath River which carved a spectacular canyon through the Northern Coastal Ranges of California to reach the Pacific.

Toward the end of the Pleistocene, as the climate warmed, the mountain glaciers retreated, inflow to Lake Modoc diminished and the lake level fell, exposing vast wetlands between the remnant lakes.  Of course, once European settlers colonized the region, wetlands were drained, rivers were dammed and tributaries were diverted for irrigation, producing the landscape that we find today.  Fortunately, some recovery has occurred with the establishment of the Lower Klamath, Tule Lake and Clear Lake National Wildlife Refuges and spectacular congregations of migrant waterfowl and shorebirds still visit the Basin.

Point Reyes National Seashore

Southwest of Petaluma, California, the Coast Range mellows into a chain of grass covered hills, traversed without mind-numbing switch-backs.  It was across this scenic landscape that we returned to the Pacific Coast, headed for Point Reyes National Seashore.

More than a peninsula along the California Coast, Point Reyes, like much of Southern California, lies on the Pacific Plate, geologically separated from the North American Plate by the San Andreas Fault; the latter passes below Tomales Bay, the Olema Valley and the Bolinas Lagoon, east of the preserve.  Established in 1962, the National Seashore is a mosaic of public and private lands, home to both the Philip Burton Wilderness Area (established in 1976) and a large swath of cattle ranches that date back to the 1850s; it is also home to a herd of tule elk and harbors the Point Reyes Lighthouse, constructed in 1870.  Renowned as an excellent site for whale watching, the lighthouse point was our first destination this morning; unfortunately, high winds and choppy seas impaired our effort to observe whales.  However, we were entertained by a noisy congregation of elephant seals on Drake Beach and were inspired by spectacular seascapes across the peninsula.

After leaving Point Reyes, we headed for San Francisco, enduring innumerable hairpin turns as we climbed over the Coast Range for a final time.  We then traversed the majestic Golden Gate Bridge, clogged with vehicles and walkers alike on this mild, sunny Sunday and headed for famous attractions along the city's waterfront.  Though we enjoyed a pleasant meal overlooking the Bay, the congestion of San Francisco was hard to take after a week on the road and we set our sights on Yosemite National Park; after a night in the Great Central Valley, we'll head to the Park tomorrow.

Crossing the Great Basin

West of Salt Lake City, Interstate 80 passes between the north end of the Oquirrh Range and the Great Salt Lake.  As we drove west, black-necked stilts were feeding in the roadside shallows, cliff swallows swooped about the highway bridges and flocks of California gulls moved across the morning sky.  Throughout western Utah, flat plains, remnants of Lake Bonneville, alternated with stark fault-block ranges, many of which were capped with snow.

In eastern Nevada, the ranges were more numerous and the intervening valleys were both rolling and green, covered by sage grasslands that were grazed by horses, cattle and pronghorn.  Just west of Wells, the highway began to follow the Humboldt River, passing the majestic Ruby Mountains; we would parallel that river all the way to Lovelock, where it enters its terminal sink.  Beyond that point, the greenery of eastern Nevada gave way to desert landscape, characterized by vast lake flats where American avocets patrolled the alkaline pools.  This low desert, lying within the rain shadow of the Sierra Nevada, ended at Fernley where we climbed into the Sierra foothills along the Truckee River.  Passing through Reno, we continued westward and upward on Interstate 80 before turning south to Lake Tahoe.

Backed by the high spine of the Sierra Nevada, this beautiful lake is renowned for both its resorts and its fabulous alpine scenery; after a full day on the road,  it seemed like a great place to spend the night.  Tomorrow we head into the California Cascades.

From Denver to Salt Lake

Beginning the first leg of our California road trip, we left Denver this morning, headed west on Interstate 70.  Climbing through the Front Range, we crossed the Continental Divide at the Eisenhower Tunnel and entered the vast watershed of the Colorado River.  After dipping through the Blue River Valley, we crossed Vail Pass and descended along Gore Creek and the Eagle River to the Colorado itself.

Following the Colorado, we snaked down Glenwood Canyon and, just west of Glenwood Springs, cut through the Grand Hogback, entering the Colorado Plateau, a landscape of mesas, buttes, plateaus and cliff-lined valleys.  Passing Battlement and Grand Mesas to our south and the Roan Plateau to our north, we then drove along the Book Cliffs (Cretaceous in age), that rise along the north side of the Interstate from Grand Junction to Green River, Utah.  Leaving the Colorado, we entered Utah where the La Sal Mountains, a massive laccolith near Moab, loomed to the SSW; after crossing the Green River, just east of the Waterpocket Fold, we turned north on US 6 toward Price, Utah, passing formations of Mancos Shale carved by the Price River and its tributaries.

Beyond Price, the highway climbs onto the Wasatch Plateau where, at Soldier Summit (7477 feet), we left the watershed of the Colorado River and entered the Great Basin, dropping from the Plateau and through the Wasatch Range to the urban corridor of Provo and Salt Lake City.  Tomorrow, we cross the Great Basin on Interstate 80, headed for Reno and Lake Tahoe.