There is a lot going on in this picture. In the foreground is San Bruno Mountain, which separates San Francisco from the rest of the Peninsula. The flat expanse just beyond contains the cities of South San Francisco, San Bruno, and Daly City, known as “Gateway to the Peninsula.”
What this picture reveals, however, is that this flat little expanse between San Francisco and the rest of the Peninsula beyond is actually an isthmus. What’s more, we are looking at two separate tectonic plates. Do you see that thin blue line of water coming in diagonally at the top-middle left hand side of the picture? That is the San Andreas Fault which divides the Pacific Plate from the North American Plate. It continues in a straight line right out to sea and then hits land again in Marin County, just north of San Francisco.
The thin blue line of water is actually two narrow lakes, formed when runoff collects in the narrow gorge between the two plates. The lake closest to us in the center of the picture is called San Andreas Lake. The fault was named after the lake and not the other way around.
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L.A.’S TWO STREET GRIDS
Los Angeles began as a city that belonged to the king of Spain. Its street grid, based on a traditional Spanish plan, was a three mile square centered on the Los Angeles River, whose streets were at a 45 degree angle to the cardinal points.This city plan served Los Angeles for its first hundred years, even for its first several decades under U.S. dominion. By the 1880s, Anglo-Americans from the Midwest began arriving and settling in Los Angeles in droves, and they wanted a city laid out with the standard U.S. grid aligned to the cardinal points, N,S,E,W. In the two photos below, you can see this dividing line where the original Spanish city ends and the American city begins, and the two street grids collide.
