From the World Heritage inscription:
Hawaii Volcanoes National Park contains Mauna Loa and Kilauea, two of the world’s most active and accessible volcanoes where ongoing geological processes are easily observed. This property serves as an excellent example of island building through volcanic processes. Through the process of shield-building volcanism, the park’s landscape is one of relatively constant, dynamic change.
Criterion (viii) This property is a unique example of significant island building through ongoing volcanic processes. It represents the most recent activity in the continuing process of the geologic origin and change of the Hawaiian Archipelago. The park contains significant parts of two of the world’s most active and best understood volcanoes, Kilauea and Mauna Loa. The volcano Mauna Loa, measured from the ocean floor, is the greatest volcanic mass on earth.
This is a panoramic photo of the Kilaeua caldera in Hawaii Volcanoes National Park. Volcanoes National Park includes the Kilaeua and Mauna Loa volcanoes. Kilaeua has been eruption almost continuously since the 1980′s. Mauna Loa hasn’t erupted in several years but it still considered active and many geologists expect an eruption at any time. I always advise people who are going to Hawaii to visit the Big Island. There you will find the most significant cultural and natural features in all of Hawaii. The beaches aren’t the best, but it is more than made up for by everything else the island has to offer. If you go to the Big Island I have three words for you: green sand beach.
View my complete list of UNESCO World Heritage sites.