Kilauea, in Hawaii Volcanoes National Park is just a short flight away and a 30 mile drive from Oahu. Make sure you do the flight first.

The park has hiking trails, a visitor center, and several programs. Kilauea is an active volcano; you will find steam vents, current and old lava flows, and a "lovely" odor.
A must-see for any geology student!

The crater looks better than it smells.

As the lava pours into the Pacific creating a giant steam cloud

Lava flow from the mid-1980s