Three months of camp life on Lake Tahoe would restore an Egyptian mummy to his pristine vigor, and give him an appetite like an alligator.–Mark Twain, Roughing It (1872)
When Mark Twain first laid eyes upon Lake Tahoe in 1861, he thought it “must surely be the fairest picture the whole earth affords.” More than a century and a half later, that opinion is still shared by another Missouri boy, and though I would gladly welcome three months of camp life over one week at a ski resort, I nevertheless remain confident that my vigor will be fully restored by the time I return to work next Monday. The journey that began some days ago in the foothills of my beloved, ancient Ozark Highlands has today taken me to one of the youngest of landscapes to grace Lake Tahoe – Emerald Bay. I have written previously about Lake Tahoe (one year ago almost to the day) in a post that also featured photos of Emerald Bay and its only island, the iconic Fannette Island. The Tahoe Basin itself is a relatively young landscape, forming within the last 5-10 million years as the basin floor dropped between two uplifted blocks. Volcanic flows in the valley on the north side of the present lake dammed the valley to form the lake, whose level has fluctuated drastically over time during the past 2 million years as Pleistocene glaciations have repeatedly damned the Truckee River that drains the lake into the lowlands of Nevada. At maximum, the level of the lake approached 7,000 feet in elevation – nearly 800 feet higher than today. It was the last of these glacial events – near the end of the Pleistocene just 10,000 years ago – that gave birth to Emerald Bay. Unlike the “ice sheets” that spread out across much of the continent, the ice age here manifested itself as individual glaciers that formed at the highest elevations and carved out individual valleys as their crushing weight ground them inexorably downward. The elongated shape characteristic of such glacial valleys is seen not only in Emerald Bay, but in the adjacent Fallen Leaf Lake and Donner Lake in the north as well. John Muir alludes to this glacial birth in a description of Emerald Bay that he wrote in his private journal in 1888:
Emerald Bay is about two miles long. Its mouth is nearly closed by a terminal moraine; the sides are formed by lateral moraines. The left lateral is very striking, well formed, three or four hundred feet high where it joins the shoulder of the mountain, timbered with pine and spruce¹ sparsely on the grayish slopes.
¹ Actually firs, of the genus Abies.
Unfortunately, the very existence of Lake Tahoe is under threat. While the mountain building processes that created the Sierra Nevada have ceased for now, the erosive forces caused by weathering continue unabated. The Sierra Nevada range is being gradually worn down, and Lake Tahoe is filling with sediment at an average rate of about 1/10th of a millimeter per year. At this rate, Lake Tahoe will become a meadow in just over 3 million years.[/humor]
Lake Tahoe facts:
- It is 22 miles long, 12 miles wide, and holds about 40 trillion gallons of water – enough to cover the entire state of California to a depth of 14.5 inches!
- Maximum elevation of the lake surface is about 6,229 feet above sea level.
- The lake is drained by the Truckee River, one of a few rivers that run inland to the desert rather than towards the ocean.
- It is the third deepest lake in North America, with an average depth of 989 feet. However, the deepest point is about 1,645 feet. It is the largest lake in North America above 600 feet elevation.
- Surface temperatures can reach as high as 75°F in summer, but at depths below 600 feet the water remains a constant 40°F.
- Lake Tahoe does not freeze over, although Emerald Bay has formed complete ice cover at least three times during the 20th Century and partial cover in more years.
Copyright © Ted C. MacRae