Loihi Seamount

Lōʻihi Seamount
Yellow iron oxide-covered lava rock on the flank of Lōʻihi
Summit depth	975 m (3,199 ft).
Height	over 3,000 m (10,000 ft) above the ocean floor
Summit area	Volume—660 km3 (160 mi3)
Translation	Loʻihi means "long" in Hawaiian, so named in 1955. (Hawaiian)
Pronunciation	[loːˈʔihi]
Location
Location	Southeast of the island of Hawaiʻi
Coordinates	18°55′N 155°16′W / 18.92°N 155.27°W / 18.92; -155.27Coordinates: 18°55′N 155°16′W / 18.92°N 155.27°W / 18.92; -155.27
Country	Hawaiʻi, US
Geology
Type	Submarine volcano
Volcanic arc/chain	Hawaiian-Emperor seamount chain
Age of rock	At least 400,000 years old
Last eruption	February to August 1996
History
Discovery date	1940 – US Coast and Geodetic Survey chart number 4115
First visit	1978

Lōʻihi Seamount (also known as Loihi) is an active submarine volcano located about 35 km (22 mi) off the southeast coast of the island of Hawaiʻi. The top of the seamount is about 975 m (3,000 ft) below sea level. This seamount lies on the flank of Mauna Loa, the largest shield volcano on Earth. Lōʻihi, meaning "long" in Hawaiian, is the newest volcano in the Hawaiian-Emperor seamount chain, a string of volcanoes that stretches over 5,800 km (3,600 mi) northwest of Lōʻihi. Unlike most active volcanoes in the Pacific Ocean that make up the active plate margins on the Pacific Ring of Fire, Lōʻihi and the other volcanoes of the Hawaiian-Emperor seamount chain are hotspot volcanoes and formed well away from the nearest plate boundary. Volcanoes in the Hawaiian Islands arise from the Hawaiʻi hotspot, and as the youngest volcano in the chain, Lōʻihi is the only Hawaiian volcano in the deep submarine preshield stage of development.

Lōʻihi began forming around 400,000 years ago and is expected to begin emerging above sea level about 10,000–100,000 years from now. At its summit, Lōʻihi Seamount stands more than 3,000 m (10,000 ft) above the seafloor, making it taller than Mount St. Helens was before its catastrophic 1980 eruption. A diverse microbial community resides around Lōʻihi's many hydrothermal vents.