Hawaii hotspot
Hawaiian volcanoes are characterized by frequent rift eruptions, their large size (thousands of cubic kilometers in volume), and their rough, decentralized shape. Rift zones are a prominent feature on these volcanoes, and account for their seemingly random volcanic structure. The tallest mountain in the Hawaii chain, Mauna Kea, rises above mean sea level. Measured from its base on the seafloor, it is the world's tallest mountain, at ; Mount Everest rises above sea level. Hawaii is surrounded by a myriad of seamounts; however, they were found to be unconnected to the hotspot and its volcanism. Kīlauea has erupted continuously since 1983 through Puʻu ʻŌʻō, a minor volcanic cone, which has become an attraction for volcanologists and tourists alike.
Lōʻihi Seamount
Lōʻihi Seamount's first depiction on a map was on Survey Chart 4115, a bathymetric rendering of part of Hawaiʻi compiled by the US Coast and Geodetic Survey in 1940. At the time, the seamount was non-notable, being one of many in the region. A large earthquake swarm first brought attention to it in 1952. That same year, geologist Gordon A. MacDonald hypothesized that the seamount was actually an active submarine shield volcano, similar to the two active Hawaiian volcanoes, Mauna Loa and Kīlauea. Macdonald's hypothesis placed the seamount as the newest volcano in the Hawaiian-Emperor seamount chain, created by the Hawaiʻi hotspot. However, because the earthquakes were oriented east–west (the direction of the volcanic fault) and there was no volcanic tremor in seismometers distant from the seamount, Macdonald attributed the earthquake to faulting rather than a volcanic eruption.
Geologists suspected the seamount could be an active undersea volcano, but without evidence the idea remained speculative. The volcano was largely ignored after the 1952 event, and was often mislabeled as an "older volcanic feature" in subsequent charts. Geologist Kenneth O. Emery is credited with naming the seamount in 1955, describing the long and narrow shape of the volcano as "Loihi". The Hawaiian word lōʻihi means "long". In 1978, an expedition studied intense, repeated seismic activity known as earthquake swarms in and around the Lōʻihi area. Rather than finding an old, extinct seamount, data collected revealed Lōʻihi to be a young, possibly active volcano. Observations showed the volcano to be encrusted with young and old lava flows. Fluids erupting from active hydrothermal vents were also found.