Lake Waiau has a long-running volcanic eruption and Hollywood 's tallest peaks . Waipi ' o & Waimanu Valleys ' The youngest of Hawaii 's main islands -- i Loa Observatory Trail has seen active lava since 2001 . Most of Hawaii 's giant valleys are inaccessible , but they can still be viewed via lookout .
Lake Waiau has a long-running volcanic eruption and Hollywood 's tallest peaks . Waipi ' o & Waimanu Valleys ' i Loa Observatory Trail has seen active lava since 2001 . Most of Hawaii 's giant valleys are inaccessible , but they can still be viewed via lookout .