A famous example of volcano running was the Kilauea Volcano Wilderness Run, a full marathon that existed for 3 decades up to 2008 and typically attracted some 200 runners. Now the route descends 400 meters to El Reventon (if the full race is a bit much, you can also start just before this point at El Pilar and only do the marathon), before climbing up to the Pico de la Cruz (2300 meters) and the observatory at the Roque de los Muchachos (2400 meters) where the race comes past the Isaac Newton Telescope.