South Falls has tree casts in the ceiling, but the caves formed by gas bubbles in the lava are the dominant features seen by hikers. Basalt with many holes is referred to as vesicular basalt. Both North and South Falls show evidence of much larger streams with more powerful waterfalls flowing at the end of the last ice age as glaciers in the Cascades melted. An analogy by Frank Nulty, Geologist Introduction Drawing an analogy can help one more easily understand unfamiliar concepts. A guided trip through a stack of pancakes has been chosen to help explain the layers of rocks and the occurrence of waterfalls in Silver Falls State Park.
Pancakes closely match the cliff forming nature of lava flows.
The geology of Silver Falls State Park can be visualized as a stack of pancakes. Think of one of those pancake eating contests hosted by the area radio station. The local pancake house has offered to cook a stack of eight pancakes, each three feet in diameter. The morning of the big day arrives with the pancake house stacking three chocolate, each separated by raspberry preserves. Next are stacked two buttermilk, each separated by blueberry preserves.