Central Valley photographs

There is nothing spectacular or grand about the low-lying triangle by which California's Central Valley rivers seek the sea--except, at times, its sky. The skyscape can be a tremendous pile of billowing cumulus clouds, sometimes as dramatic as the firmament over the Arizona desert or the heavens off the Kona Coast. but the flattended horizon is broken only by the distant bulk of Mount Diablo's saddle.

Spectacle is the business of our desert mesas and buttes; the jagged and surf-battered Redwood Coast; or the High Sierra, where the Sacramento and San Joaquin are born in springs, snowbanks, and even glaciers.

The Delta, in contrast, is a bucolic land of peace, a tranquil place of ease largely unsullied by civilization. It is low-keyed; it must be approached on its own unhurried terms in order to be properly appreciated.

It is a backwater, a throwback in a few hidden "gunkholes," or anchorages, to the pristine landscape of the Spanish explorers and, everywhere else, to the easygoing rural and pastoral California of a century ago.

Time stands still. It is almost as much "an island in time" as Harold Gilliam's lonesome Point Reyes Peninsula.

Mima mounds are ~1-m-high hillocks found on every continent except Antarctica. Despite often numbering in the millions within a single field, their origin has been a mystery, with proposed explanations ranging from glacial processes to seismic shaking. One hypothesis proposes that mounds in North America are built by burrowing mammals to provide refuge from seasonally saturated soils. We test this hypothesis with a numerical model, parameterized with measurements of soil transport by gophers from a California mound field, that couples animal behavior with geomorphic processes. The model successfully simulates the development of the mounds as well as key details such as the creation of vernal pools, small intermound basins that provide habitat for endemic species. Furthermore, we demonstrate that the spatial structure of the modeled mound fields is similar to actual mound fields and provides an example of self-organized topographic features. We conclude that, scaled by body mass, Mima mounds are the largest structures built by nonhuman mammals and may provide a rare example of an evolutionary coupling between landforms and the organisms that create them.