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.
Tamu Massif
The Tamu Massif was formed about 145 million years ago during the Late Jurassic to Early Cretaceous period over a relatively short period of time (a few million years) and then became extinct. If confirmed, the suggestion that it could be a single volcano would make the Tamu Massif the largest known volcano on Earth, dwarfing the current record-holder, Mauna Loa on the Hawaiian Islands. Tamu's rounded dome extends over an area of , totaling more than , many times larger than Mauna Loa, which has an area of , and about half the area of the Martian volcano Olympus Mons. The entire mass of Tamu consists of basalt. Its slopes are very gradual, ranging from less than half a degree to one degree near its summit. While the Shatsky Rise oceanic plateau is comparable in size to California or Japan, Tamu Massif, which is the plateau's oldest and largest edifice, is comparable in size to New Mexico or Britain and Ireland together.