Geology

All the Hawaiian islands were formed from volcanic activity initiated at an undersea magma source called a hotspot. As the tectonic plate beneath much of the Pacific Ocean moves to the northwest, the hot spot remains stationary, slowly creating new volcanoes. Due to the hotspot’s location, the only active volcanoes are located around the southern half of the Big Island. The newest volcano, Lōʻihi Seamount, is located south of the Big Island’s coast.

The last volcanic eruption outside the Big Island occurred at Haleakalā on Maui before the late 18th century, though it could have been hundreds of years earlier. In 1790, Kīlauea exploded with the deadliest eruption  known to have occurred in what is now the United States.As many as 5,405 warriors and their families marching on Kīlaueawere killed by that eruption.

Volcanic activity and subsequent erosion have created impressive geological features. The Big Island has the third highest point among the world’s islands.

Slope instability of the volcanoes has generated damaging earthquakes with related tsunamis, particularly in 1868 and 1975.

 Nā Pali coast, Kauaʻi

Pāhoehoe and ʻAʻā lava flows side by side at the Big Island of Hawaiʻi in September, 2007