Tower falls in yellowstone

You might be interested in a  copy of the USGS “Geologic Map of Yellowstone National Park,” Misc. Geologic Investigations Map I-711.  You could also check out some road logs.  I like the “Roadside Geology of Yellowstone Country” by Fritz and Thomas.

More to your question, there are two lava flows in the vicinity of Tower Falls.  The older, the 2.2 million yr old Junction Butte Basalt is the flow that forms the prominent overhang on the road just north of the Tower store.  The younger set of flows (1.3 m.y) is referred to as the basalt of the Narrows and can best be seen in the narrow section of the Yellowstone River canyon .  Both of these flows are characterized by prominent columnar columns – you know them when you see them.

Yellowstone is a very special place.  Out of curiosity, why are you so interested in the basalts in the north end of the Park?

Sheepeater cliffs. You can find them on a map.