de Anza’s Sea

As readers of this website know, California in ages past had a large inland sea, a mixture of salt and fresh water, known as the Temblor, and in times past, the San Joachin Sea. It varied in size over the many years, but sat in roughly the middle part of the state, the central valley, made infamously flat and sandy by the ceaseless ebb and flow of those ancient waters. Take a look at my California page for a depictions of how it looked during the middle Miocene. After the land rose, due to subduction by the Pacific Plate, the sea was drained. Later, however, it filled again with runoff from the Sierras, this time to become a vast freshwater lake called the Corcoran.

I recently ran across the following comments regarding a version of this “sea of fresh water” in the time of Juan Bautista de Anza, the noted 18th century Spanish explorer, which I thought worthy of reproduction here. It’s found on the website of the great California native plants outlet, Las Pilitas Nursery:

“We know the Sierran snow melt filled up much of the Sacramento and San Joaquin valley floors; there is just not enough information as to how much it filled and how long the water stood. If the soil stood for a month under water, it was probably a grassland. If the soil stood for three months or more it was probably more a seasonal marsh. Anza’s men measured an ebb and flow of 8 or 9 feet within the ‘vast inland freshwater sea’ and it was approximately “breadth some twenty-five or thirty leagues” [league=three miles] wide. Now the valley floor from his vantage point was only about 70 miles wide, so the water must have been present from the Sierran foothills to the coastal foothills. In a high snowfall year with a warm spring as Font saw it the water level in the San Joaquin Valley may have been to 60-70 feet above sea level (about the elevation of Los Banos).”

The wildflowers in between these floodings would have been spectacular! Unfortunately, as the nursery goes on to say, “It was discovered by Europeans in 1776 and almost completely destroyed (drained and plowed) by 1840 or 1850. It was one of the largest marshlands for waterfowl in North America; now, it is but a minuscule patch of its former self.”

You can read more about de Anza’s explorations here.


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