For much of the last 50 million years, the San Joaquin Valley (Bakersfield area) was under a shallow ocean. It was like a large protected bay along the coast. Abundant plants and animals lived in this bay over Bakersfield. When they died their bodies sank into the mud at the bottom and were preserved as the mud was altered to rock. One particularly rock layer that formed 14-16 million years ago, called the Round Mountain Silt contains an especially fossil-rich layer referred to as “the Sharktooth Hill Bone Bed”. The Bone Bed contains abundant fossils of marine mammal, shark teeth and plants. This is one of the best marine mammal fossil location from this period in geologic time (the Miocene) in the world.
This module has two parts. The first, Subduction Model, has students create a physical model of subduction, the process that created the shallow ocean over Bakersfield. The second, has two parts; 1) Students create and interpret a map of the rocks that we see at the surface near Hart Park, just NE of Bakersfield, and 2) Students create and interpret 2 cross sections, vertical slices through the rock units that show what the rock units look like under the ground. Both geologic maps and cross sections are valuable tools to the geologist and the combination of these two activities creates a three dimensional image of what the rock units in this area look like.