A tour boat takes its chances near a spectacular sight: lava pouring into the ocean on Hawaii's Big Island. Flowing from the unstable Pu'u 'O'o vent on Kīlauea, the lava traveled seven miles to the coast from Hawai'i Volcanoes National Park, home to two of the most active volcanoes on the planet. When lava reaches the water, it cools and hardens.