Sierra Nevada: Range of Snow and Ice

Note: This article is taken from material prepared for the 2005 exhibit at the California Academy of Sciences called “Hotspot: California on the Edge.”


About 1.8 million years ago, after the Sierra Nevada began to rise, the Earth’s atmosphere turned cold, marking the beginning of the Pleistocene, the last ice age. Glaciers grew high in the mountains and moved slowly down former stream channels, carving U-shaped valleys as they advanced. Small glaciers still exist at the highest elevations in the Sierra Nevada, where they continue to scour the landscape.  The plants and animals that live at high elevations have special adaptations for surviving the cold, harsh environments.


About 1.8 million years ago, the last ice age began. A period of long-term cooling of Earth’s climate resulted in the expansion of continental and polar ice sheets and mountain glaciers.


During this ice age, no massive ice sheets covered California. Glaciers were confined to high mountains, advancing and retreating 4 to 7 times.

The last ice age ended just 10,000 years ago, but several small glaciers still persist in California at high elevations.


A species that lived during the last ice age and still persists today is called a Pleistocene relict. Its present-day distribution is a remnant of its wider range during the last ice age. The grizzly bear and California condor are both Pleistocene relicts – one is extinct in California, the other is barely clinging to existence.

California condor  Gymnogyps californianus


Destruction of habitat, poaching, and lead poisoning led to the California condor’s decline. By 1985 populations plummeted to fewer than 9 birds in the wild.


Captive breeding programs have released birds back into the wild, but their long-term survival is still in question. Today [2005], 85 of the 222 birds in existence, are in the wild [The population estimate in May 2013 was 198 birds in captivity and 237 in the wild for a total of 435].   The California condor is the largest land bird in North America.  An adult can weigh up to 25 pounds (11 kg) and have a wingspan up to 9.5 feet (3 m).   Condors can soar for hours at altitudes of 15,000 feet (4572 m), cover hundreds of miles, and reach speeds over 55 mph (89 kph). Like most other vultures, condors eat carrion.

Grizzly bear  Ursus arctos californicus




The story of “Monarch”  Monarch was captured from the wild and died of old age in captivity in 1911. After his death, he was donated to the California Academy of Sciences by the de Young Museum. He remains a legacy to the once mighty California grizzlies.





Conservation -  In 1913, after a bitter battle, Congress gave San Francisco permission to dam the Tuolumne River at Hetch Hetchy Valley in Yosemite National Park. Following this action, legislation was passed that made it illegal to ever put a dam in any national park again. Studies by the University of California, Davis show it may be possible to restore the valley by impounding Tuolumne River water at existing dams further downstream.