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Geology lessons as you hike...5 Tahoe choices.

Geology lessons as you hike . . . 5 Tahoe choices

Volcanoes, glaciers, and faulting formed the Tahoe region over millions of years. The result is a land of incredible beauty, scarred by eons of geologic activity.

We've selected a handful of scenic hikes, ranging from 2 to 9 miles round trip, where the forces that shaped the Tahoe Sierra are clearly in evidence. As always in the mountains, check weather reports before heading out, dress in layers, and carry ample food and water.

Formed by the powerful forces of plate tectonics (continental drift), the Sierra Nevada as we know it today was created by a series of dramatic collisions which made an uplifted range of granitic rock 40 to 80 miles wide and more than 400 miles long. Later uplifts, volcanic eruptions, and slow-moving glaciers gradually sculpted the range into its present form.

The Tahoe basin evolved 2 to 4 million years ago, likely the result of land slip-page from faulting. Lava filled the middle of the basin and dammed it at one end. At times, Lake Tahoe was hundreds of feet deeper than it is today--and occasionally glacier dams on the Truckee River gave way, causing enormous floods.

The last glaciers receded about 10,000 years ago, leaving behind polished barren tracts like Desolation Wilderness and soft alluvial soil where conifers flourished.

1. Eagle Lake . . . a little like Yosemite's Mist Trail, without the mist

The Eagle Lake Trail takes you up a dramatic glacial "staircase' with intermittent flat stretches containing lakes and meadows; Eagle Lake itself perches on one step of the deep glaciated canyon.

You need a free wilderness permit for this hike; get it at Lake Tahoe Visitor Center on State 89, 3 miles northwest of U.S. 50. From State 89, turn into the Eagle Falls picnic parking area, or park in the scenic turnout for the Emerald Bay trail and walk back 1/4 mile on the highway. (Both parking areas are often overflowing.)

On your way to the lake, look for xenoliths --fragments of ancient dark rock that have been "absorbed' over time into the now dominant granite. They resemble gray blemishes in the speckled atone.

A mile from the trailhead, Eagle Lake is hemmed in on three sides by cliffs and steep slopes. In the center is a fairy-book island you can swim to with little trouble. For a full-day trip, continue hiking-- you'll need a good topo map--to the three Velma lakes. Or take the steep, easy trail down to Emerald Bay.

2. Burton Creek . . . moderate 3-mile loop up a V-shaped ravine

On this walk, the prevailing rock you see is basalt lava from explosions of Mount Watson some 3 million years ago.

From Tahoe City, take State 28 north 1 mile to Tamarack Lodge and turn left onto the dirt road; bear left past the lodge about 1/4 mile and park near the Burton Creek State Reserve sign.

The loop road/trail starts and ends here. Take the main (left) road over the creek. Just 1/4 mile in, you'll see large angular fragments covering a slope--victims of frost wedging, which occurs when water freezes and thaws in the cracks.

A little farther on are tall, fissured, volcanic outcrops. These are examples of columnar jointing, solid rock divided into prismatic columns by contraction as the lava flow solidified (Devil's Postpile is the greatest example in the West). Some hikers like to scale the face of these rock formations, but it's safer to follow the trail to the flat, grassy area on top, dotted with white firs and Jeffrey pines. There's a small reservoir here, and you can see Mount Watson to the north.

Continue on the main trail as it loops back to your car, about 500 feet below.

3. Five Lakes . . . well-traveled 5-miler is beautiful and interesting

You climb steadily on this hike, gaining great views of the glacial valley now threaded through by Bear Creek. As of June 1, a wilderness permit will be required; get it at USFS Truckee Ranger District, I-80 and State 89, Truckee.

From State 89, take Alpine Meadows Road; in about 2 miles, park on the shoulder opposite Deer Park Drive. A large sign marks the trailhead.

As June ends, wildflowers will be coloring the slopes near trailside. As you hike, note how successive glaciers have exposed increasing depths of granite and volcanic rock. Huge outcrops--light, smooth granite and dark, rough lava--surround you during the middle part of the hike.

The shallow lakes at the top (2 1/2 miles) are water-filled depressions scoured out by glaciers. Take off your shoes, or brave a plunge--the water's chilly but oh so refreshing (it warms a bit by late July). All around the lakes stand random boulders called erratics--fragments of the granite mass chipped off by glaciers, tumbled along, and left behind like orphans.

4. Castle Peak . . . challenge its ruined ramparts and bastions of volcanic rock

About 10 miles northwest of Truckee, 9,103-foot Castle Peak looks like a conquered ancient fortress. From high on the shoulder of this extinct volcano, you can see the ski runs at Northstar, Squaw Valley, and Boreal; on super-clear days, Sierra Buttes and Mount Shasta appear to the northwest, the Coast Range to the west. From I-80, take the Castle Peak exit; proceed north of the freeway on a paved road that shortly becomes a dirt road. You can proceed with caution if you have a high-clearance vehicle--but it's wiser to park here and continue on foot, following the road/trial angling steadily northwest. The hike, 6 miles round trip, gains almost 2,000 feet from the road to the mountain's west shoulder and craggy adjacent summit. At the top of the initial saddle (Castle Pass), look for an unsigned fork to your right leading up along a spiny ridge toward Castle Peak's jagged formations. (The main trail continues down to the Sierra Club's Peter Grubb hut.)

From the fork, Sierran granite gives way to sharp, almost eerie outcrops of reddish-black agglomerate--mainly erupted mudflow breccias. The darkest rock at the top is the neck of the volcano (the remains of its cooled core).

5. Mount Tallac . . . rugged, rewarding; a steep climb to spectacular views

This 9-mile round-trip hike takes you to the 9,735-foot summit--a vertical ascent of about 3,300 feet from the trailhead. To hike beyond Floating Island Lake, you need a wilderness permit; see listing under Eagle Lake on page 59.

From State 89, turn inland opposite Baldwin Beach Road and follow signs to the trailhead. Initial views along the rocky path take in Fallen Leaf Lake, which resembles Emerald Bay and would, like it, be joined to Tahoe but for a broad moraine --in effect, glacial landfill.

About 1 3/4 miles up, you reach curious little Floating Island Lake. Sometimes pieces of the matted-grass shore break away and float in the middle of the pool. About 3/4 mile farther is Cathedral Lake, a good rest stop before heading on. From boulders near the east shore, you'll have fine views of Fallen Leaf Lake.

The next section is steep and demanding. You labor up through the thinning air for about 2 miles to reach a gently sloping brush- and wildflower-covered pleateau. To your left, the dazzling Crystal Range springs into view. Nearly round Gilmore Lake appears below, in a cirque--a bowlshaped recess gouged out by glaciers.

The trail turns steep again. Tallac is principally metamorphic rock--rock that's been changed by intense pressure and heat; it's dark and jagged in contrast to the smoother light granite. The last 1/4 mile, you scramble a bit to the stunning, windswept peak, where you will be greeted by hungry golden-mantled ground squirrels and the spectacular view: nearly all of Lake Tahoe, much of Desolation Wilderness, and far beyond.

Note: A superior trail guide, The Tahoe Sierra, by Jeffrey P. Schaffer (Wilderness Press, Berkeley, 1984; $13.95), describes 106 hikes in detail, with accompanying maps and photographs.

Photo: Fractured block of basalt lava along Burton Creek trail shows columnar jointing

Photo: At 2 miles round trip, hike 1 is easiest; at just over 9 miles, hike 5 is the most demanding

Photo: Looking out from miniature island, he gazes across placid Eagle Lake, on one step of a glacial staircase. Maggies Peaks in back stayed above ancient glaciers

Photo: Solitary hiker ponders glacial handiwork from top of Mount Tallac. Polished face of Crystal Range rises beyond Gilmore Lake

Photo: Volcanic ash and layers of lava lie exposed on southfacing slope of Castle Peak. Each layer represents a separate eruption dating as far back as 20 million years

Photo: Tenacious pines and scrub brush struggle to survive on exposed shoulder of Castle Peak. Talus slope is sign of centuries of weathering
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Copyright 1986 Gale, Cengage Learning. All rights reserved.

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Date:Jun 1, 1986
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