[Illustration: Located in the middle of the Pacific Plate, the volcanoes of the Hawaiian Island chain are among the largest on Earth. The volcanoes stretch 2,500 km across the north Pacific Ocean and become progressively older to the northwest. Formed initially above a relatively stationary “hot spot” in the Earth’s interior, each volcano was rafted away from the hot spot as the Pacific Plate moves northwestward at about 9 cm per year. The island of Hawaii consists of the youngest volcanoes in the chain and is currently located over the hot spot.] HAWAII NIIHAU KAUAI OAHU MOLOKAI LANAI MAUI KAHOOLAWE PACIFIC PLATE Oceanic Crust Fixed “Hot Spot” Zone of magma formation extends to Kilauea & Mauna Loa Direction of place movement Recent Eruptions From U.S. Volcanoes Hawaiian volcanoes Few places on Earth allow closer or more dramatic views of volcanic activity than Mauna Loa and Kilauea volcanoes on the island of Hawaii. Their frequent but usually non-explosive eruptions make them ideal for scientific study. Kilauea’s eruptions are so intensely monitored that scientists have assembled a detailed picture of the volcano’s magma reservoir “plumbing” system and how it behaves before and during eruptions. Studies of these volcanoes and the surrounding ocean floor continue to improve our understanding of the geologic history of the Hawaiian Island chain and the ability of scientists to determine volcanic hazards that threaten island residents. [Illustration: Hawaiian Volcanoes] EXPLANATION Volcano active during past 2,000 years Potentially active volcano Population centers · 50,000 to 100,000 • 350,000 to 1,000,000 _PACIFIC OCEAN_ NIIHAU KAUAI OAHU •Honolulu MOLOKAI MAUI Haleakala LANAI KAHOOLAWE HAWAII Kohala Mauna Kea ·Hilo Hualalai Mauna Loa Kilauea Lohi Eruptions of Hawaiian volcanoes are typically non-explosive because of the composition of the magma. Almost all of the magma erupted from Hawaii’s volcanoes forms dark gray to black volcanic rock (called _basalt_), generally in the form of lava flows and, less commonly, as fragmented lava such as volcanic bombs, cinders, pumice, and ash. Basalt magma is more fluid than the other types of magma (andesite, dacite, and rhyolite). Consequently, expanding volcanic gases can escape from basalt relatively easily and can propel lava high into the air, forming brilliant fountains sometimes called “curtains of fire.”