| Our first look at the silica rich rocks in the sequence. Older
than the overlying sandstone and shale layers this exposure has alternating
layers of hard, silica with layers of weak and erodable shale. As
the shale is removed by erosion the alternating layers become quite prominent.
The hard resistant layers are a rock called chert that was created
by the deposition of silica on the ocean floor. A majority of the
silica, we believe, comes from the skeletons of microscopic, ocean animals
called Radiolarians.
Further
information on Radiolarian Chert |
