Death Valley geology field trip Shoreline Butte

Ice age Death Valley During the Pleistocene ice ages, climate cooled and became wetter, glaciers grew in the Sierra Nevada Mountains. Rivers flowed into what are now dry deserts and lakes formed in many of down-dropped valleys of the Basin and Range. Shoreline Butte reveals evidence of a large lake, Lake Manly, that filled what is now the driest desert of the United States. Imagine a time during the ice age, between 186,000 - 128,000 years ago, when Shoreline Butte was an island in a lake nearly 100 miles long and 600 feet deep! Lake Manly and other Pleistocene lakes of the Death Valley region. Note the location of Shoreline Butte at the south end of the Valley.

Shorelines etched into northeast flank of Shoreline Butte. Photo by Marli Miller. Waves left their mark Look carefully and you can see several horizontal lines carved into the northeast flank of Shoreline Butte. These lines are actually flat terraces called strandlines that are cut into the hillside by waves battering the shore. It takes some time for waves to gnaw away terraces like these, so these benches provide records of times when the lake level stabilized long enough for waves to leave their mark on the rock. The highest strandline is one of the principle clues that geologists use to estimate the depth of the lake that once filled Death Valley. Shorelines of ancient Lake Manly are preserved in several parts of Death Valley, but nowhere is the record as clear as at Shoreline Butte. Not so long ago Several lakes have occupied Death Valley since the close of the Pleistocene Epoch 10,000 years ago, but these younger lakes were quite shallow compared to Lake Manly.

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