Geoscience Reference
In-Depth Information
h e Great Basin lakes reached their peak in extent about 15,000 years ago.
Lake Lahontan reached a high stand during the late Pleistocene, 15,500 years
ago, then began to shrink, reaching an area of only one-seventh the size by the
early Holocene, 10,000 years ago. Other lakes showed similar declines, such
as the Great Basin's Owens Lake in California and Lake Bonneville in Utah,
and, outside the Great Basin, Tulare Lake in California's Central Valley, all
of which reached low stands coinciding with the end of the Pleistocene and
the start of the Holocene.
climate and the first westerners
Humans arrived in the western landscape around 13,500 years ago. h ese
stone-age hunter-gatherers, the so-called Clovis people who let behind
pointed spears fashioned from stone, migrated south from Alaska into the
Plains and Great Basin and continued into the Southwest and California.
h ey settled close to sources of reliable water: lakes, springs, and perennial
streams. When the climate deteriorated and water sources dried up, they
moved on. h eir low population numbers gave them l exibility and mobility,
which were key to their survival. From the coast to inland valleys, these earli-
est westerners could choose from a wide diversity of foods: i sh, including
salmon during their spring and fall migrations upstream to spawn; small
and large game; wild plants; and migratory birds that stopped over in wet-
lands like California's Central Valley en route to more southerly or northerly
feeding and breeding grounds. Strange ice age animals—the Pleistocene
“megafauna”—also roamed the region, including giant sloths, herds of mast-
odons and mammoths, native camels, horses, and elk, as well as fearsome
predators like the saber-toothed tiger and the grizzly bear.
Along the coast, food would have been plentiful—particularly mollusks,
i sh, and sea mammals—but the early inhabitants would have had to con-
tend with rapidly changing environments during the late Pleistocene and
early Holocene. During this time of transition, the coast was perhaps one
of the most rapidly changing environments in the West, its coni guration
changing dramatically with the meltwaters of glacial ice l owing into the
oceans. Between about 18,000 and 6,000 years ago, sea level rose an average
of three-quarters of an inch per year, transforming coastal river valleys into
shallow bays and estuaries.
