Some of the magma froze inside or just below the volcano. Later, after millions of years, the volcanic ash and lava layers that buried the landscape were eroded away. The mass of solid intrusive rock was exposed. This became Devil's Tower. Native American legend viewed these as scratches of a giant bear.
Geological view is that they formed when the rock cooled and contracted, and therefore cracked.
Because of time constraints, we can't cover all the parks listed in the syllabus, or we will fall behind the lab schedule. For the time being, we will skip Voyageurs, Cape Cod, and Everglades. If there's time at the end of the semester, we'll discuss these then. Parks Consisting of Caves and Karst In lecture, we will discuss some of the general concepts of cave formation. Groundwater and the Water Table Groundwater refers to the water that lies under the ground surface.