The flood basalts that underlie Houghton are about 400 individual lava flows.  Each flow has an internal structure, with a bubbly top that is filled with colorful minerals.  We call these colorful tops amygdaloids.  If you count the amygdaloids, you are counting the flows.  Behind the Razorback Center, you can find the lava flow structure and see where one flow begins and the other ends.