Shortly after a volcanic mudflow had buried the redwood forest, a lahar flowed into the valley several kilometers to the south creating the second natural dam and allowing the stream to flood the valley once again. The middle shale unit of the Florissant Formation is the shale that is most often seen by visitors. It is the unit outcropping near the visitor center, and is the unit that was collected historically by Scudder, Cockerell, and MacGinitie.
The Scudder Pit as seen along the Petrified Forest Walk. Here visitors can observe the middle shale unit and the caprock conglomerate. Samuel H. Scudder (1837 - 1911) was one of the first paleontologists to visit Florissant and publish on its fossils.
A view of the caprock conglomerate overlying the middle shale unit on the Petrified Forest Walk near the Visitor Center.
A view of "Big Stump" along the Petrified Forest Walk. Visitors can observe the lower mudstone that encases the fossil stumps, the middle shale unit, and the caprock conglomerate. You can also see the two saw blades that were embedded in Big Stump when collectors failed in their attempt to cut it up and haul it away.
A labeled sample of shale clearly showing alternating layers of volcanic ash and paper shale.
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