Natural and Historical Setting

The Menlo Park offices of the U.S. Geological Survey are sited in the San Francisco Bay region, an area of complex and exciting geology. The region occupies the boundary zone between two of the major tectonic plates that make up the outer shell of the Earth—the Pacific Plate and the North American Plate. The many active faults slicing through the region, the frequent earthquakes, and the very young ranges of hills and mountains that have been pushed up in the region are results of the relentless motion of these plates.

San Francisco Bay occupies a depression formed long ago when a block of the Earth’s crust subsided between two of the region’s major faults. The rise of sea level at the end of the Pleistocene Epoch of Earth history (about 10,000 years ago) flooded this depression to form the Bay, an inlet of the Pacific Ocean.

The USGS campus was built atop sedimentary deposits—mostly sands, gravels, and silts—laid down during the past few thousand years on the margins of the bay by San Francisquito Creek and other streams carrying debris down from the nearby hills. These deposits continue to form today, and new layers are added to the land whenever the streams flood.

This area, like much of the lands around San Francisco Bay, was once home to the Ohlone people. The Spanish first explored the area in the late 1700s and established several large rancheros in the area. Settlers discovered the mild and sunny climate of the area in the 1850s, and soon many wealthy families from San Francisco acquired Menlo Park properties to serve as their summer homes. The present site of the USGS was once part of the estate of Mark Hopkins, of California railroad and hotel fame. During World War II, the site was part of the Dibble Army Hospital, the receiving area for wounded returning from the Pacific front. After the hospital was decommissioned in 1947, part of the site was designated by Congress for use by the USGS.

Related link:
History of the Menlo Park Campus

Back to index