Geology 15                                                                                            West Valley College

Geology of California                                                                                  Robert Lopez

Study Questions 14: Glaciers and Sierra Glaciation


1)      What is the time interval and what is significant about the Pleistocene Epoch?


2)      What is the definitive characteristic of glaciers?


3)      What are continental glaciers and did California experience continental glaciation?


4)      What are the two remaining continental glaciers today?


5)      What were the names of the continental glaciers that existed in North America during the Pleistocene Epoch?


6)      What are Alpine glaciers and how do they differ from continental glaciers?


7)      What are cirques, crevasses, and ice falls (e.g. Harden, Fig. 8-40)?


8)      Be able to label the following large-scale glacial erosional landforms common to the Sierra Nevada: Aretes, cirques, tarns, horns, cols, hanging valleys, roches Moutennees, pater noster lakes, and U-shaped valleys.


9)      What is till and what is a moraine?


10)   Be able to identify the following small-scale features common in the Sierra Nevada: “roche moutonnees”, grooves and striations, glacial polish (p. 205).


11)   Be able to identify the following depositional landforms left by the retreating glaciers and common in the Sierra Nevada: terminal, recessional, medial, and lateral moraines.


12)   What are glacial erratics (dropstones) and how do we know they were transported by glaciers (p. 8-48)?


13)   What are four possible causes of Pleistocene glaciation?


14)   What are the three aspects of Milankovich Cycles (read info on Astronomical Cycles in side-bar box The Earth’s Climatic Cycles” on page 204)?  What is Precession of the Equinoxes? What is Changes in Obliquity?  What is Eccentricity?


15)   What is aphelion?


16)   What Sierran Glaciation formed the most conspicuous moraines now seen in the Eastern Sierra Nevada?


17)   Why are glacial moraine deposits more conspicuous on the east side of the Sierra than those on the west side?



Where to best see Glacial Moraines

Hwy 395


The Automobile Club of Southern California has a great map entitled Eastern Sierra that covers Lone Pine to Bridgeport.  If you are a AAA member, you can pick up a copy at the AAA office in Bishop or anywhere in southern California.  This map is detailed enough to show a lot of handy information.  For example, the dirt road to Lookout Mountain (the Resurgent Dome in Long Valley Caldera), which is the classic view point of the Long Valley Caldera, San Joaquin Ridge, Mammoth Mtn., and the Minarets and Ritter Range.


Large lateral moraines extend away from the Sierran Front between Big Pine and Bridgeport.  You can drive up moraines on Hwy. 168 from Bishop to Lake Sabrina and on the Glacier Lodge Road from Big Pine.  The trail head to the Palisade Glaciers is near in near Glacier Lodge.  A round trip to the glaciers involves two days of strenuous hiking at elevations up to 14,000 ft.


Glacial Geology of Yosemite

Know that Yosemite Valley was a broad valley during the mid-Tertiary before uplift and tilting of the Sierra Nevada that started about 5 to 10 m. y. ago. 


As a result of the uplift, the rate of erosion increased, and in the early Quaternary before glaciation, the Valley moved into the “canyon stage” a V-shaped valley.  The lower elevation portion of the Merced River west of Yosemite that was never glaciated is still V-shaped and in the canyon stage.


During the most intensive period of Pleistocene glaciation, glaciers reached near the tops of Clouds Rest, Half Dome, and El Capitan, but did not override them.  Glaciers plucked slabs of rocks off Half Dome along joints, forming the steep cliff.


At the end of Tioga glaciation, a terminal moraine stretched across the valley from El Capitan to Bridal Vail falls.  This moraine formed a dam for Lake Yosemite, and about 2000 ft. of lake sediments accumulated behind the dam.  Consequently, the floor of Yosemite Valley is much flatter than a typical U-shaped glacial valleys.


“Don’t Miss” points in Yosemite Valley

Tunnel View – Top view of the Valley according to PhotSecrets of Yosemite.  For even better views, hike to Inspiration Point or Old Inspiration Point.


Sentinel Dome – See the famous, twisted (and now dead) Jeffery Pine.


Glacier Point – One of the most inspirational viewpoints in the world (you may not be able to get to this view point because of recent rock slides along exfoliation sheets).


Olmsted Point – On Hwy. 120 to Tuolumne Meadows and Tioga Pass.  Great and unusual views of Half Dome, Clouds Rest, and Tenaya Lake.  A good place to see many glacial features and the Half Dome Granodiorite.


Toulumne Meadows – Many glacial features and Lembert Dome.


Lee Vining Canyoun – A few miles beyond Tioga Pass and out of the Park.  Drive down this spectacular glaciated canyon.  At the east end you will be driving between two enormous Tahoe age lateral moraines and finally through the terminal moraine.


Useful References for Yosemite

Yosemite Road Guide – Keyed to roadside markers.  A must.

Yosemite Trails – by Lew and Ginny Clark.  Great information on all the trials in the Park.

Domes, Cliffs, and Waterfalls – by W.R. Jones.  A brief summary on all the trails in the Park.

PhotoSecrets of Yosemite by Andrew Hudson.  If you want to take photos of classic views in Yosemite, but only have limited time there, this book can be most helpful.  It contains a list of the “Top Ten” sights of Yosemite Valley along with the best time of day to photograph them.