They are the small terraces at muscle shoals and other locations near and along the coast, east of the shoals. All date in the last few thousand years since sea level stabilized--all thought to be earthquake events.

An interesting map can be found at:

map

Looking at the aerial photos on Google Earth, it's clear that there are a number of shelf-like features around Mussel Shoals Beach, some of which are actual marine terraces and some ofwhich are artificial. The prominent series of steps on the hillside (Ain the next image) is certainly artificial:

image

There are, however,two old marine terraces that can be seen in the picture: one (B in the attached image) is lower and partially covered by younger stream and landslide deposits, while the other (C in the attached image) makes up much of the top of the adjacent hillside, although it is now cut by various streams.

shows that the terrace at B is between 1800 and 5800 years old, while the higher terrace at C is between 40,000 and 60,000 years old (it also shows other areas where you can find these terraces). Both of these terraces show the characteristic appearance of marine terraces in the Santa Barbara region--they are very broad flat expanses, often making up the tops of local hills.

Marine terraces are formed by winter waves crashing against the shoreline; the force of thousands of waves hitting each day for decades or centuries wears down a flat notch into the land; we are actually forming a new marine terrace on the shore today. The level at which the waves hit the land is controlled by two processes: the rise and fall of global sea level and the local uplift of the land by tectonic processes. The most important recent control on global sea level is the growing and shrinking of glaciers as the Earth's climate cools and warms; terraces are only formed when the relative sea level stays constant for a long time. These marine terraces are lifted overtime by tectonic activity. The Santa Barbara area was torn off from North America by the San Andreas Fault; it has become caught between the North American plate to the east and the Pacific plate to the west, and has rotated clockwise by 90 degrees. As the Santa Barbara block rotated, it collided with North America to the north & has buckled and folded like a piece of paper that is crumpled up. It is this compression that results in the formation of our local mountains,and this is what has lifted the marine terraces above sea level.