<P> Mauna Loa is one of five subaerial volcanoes that make up the island of Hawaiʻi, created by the Hawaii hotspot . The oldest volcano on the island, Kohala, is more than a million years old, and Kīlauea, the youngest, is believed to be between 300,000 and 600,000 years of age . Lōʻihi Seamount on the island's flank is even younger, but has yet to breach the surface of the Pacific Ocean . At 1 million to 700,000 years of age, Mauna Loa is the second youngest of the five volcanoes on the island, making it the third youngest volcano in the Hawaiian--Emperor seamount chain, a chain of shield volcanoes and seamounts extending from Hawaii to the Kuril--Kamchatka Trench in Russia . </P> <P> Following the pattern of Hawaiian volcano formation, Mauna Loa would have started as a submarine volcano, gradually building itself up through underwater eruptions of alkali basalt before emerging from the sea through a series of surtseyan eruptions about 400,000 years ago . Since then, the volcano has remained active, with a history of effusive and explosive eruptions, including 33 eruptions since the first well - documented eruption in 1843 . Although Mauna Loa's activity has been overshadowed in recent years by that of its neighbor Kīlauea, it remains active . </P> <P> Mauna Loa is the largest subaerial and second largest overall volcano in the world (behind Tamu Massif), covering a land area of 5,271 km (2,035 sq mi) and spans a maximum width of 120 km (75 mi). Consisting of approximately 65,000 to 80,000 km (15,600 to 19,200 cu mi) of solid rock, it makes up more than half of the surface area of the island of Hawaiʻi . Combining the volcano's extensive submarine flanks (5,000 m (16,400 ft) to the sea floor) and 4,170 m (13,680 ft) subaerial height, Mauna Loa rises 9,170 m (30,085 ft) from base to summit, greater than the 8,848 m or 29,029 ft elevation of Mount Everest from sea level to its summit . In addition, much of the mountain is invisible even underwater: its mass depresses the crust beneath it by another 8 km (5 mi), in the shape of an inverse mountain, meaning the total height of Mauna Loa from the start of its eruptive history is about 17,170 m (56,000 ft). </P> <P> Mauna Loa is a typical shield volcano in form, taking the shape of a long, broad dome extending down to the ocean floor whose slopes are about 12 ° at their steepest, a consequence of its extremely fluid lava . The shield - stage lavas that built the enormous main mass of the mountain are tholeiitic basalts, like those of Mauna Kea, created through the mixing of primary magma and subducted oceanic crust . Mauna Loa's summit hosts three overlapping pit craters arranged northeast - southwest, the first and last roughly 1 km (0.6 mi) in diameter and the second an oblong 4.2 km × 2.5 km (2.6 mi × 1.6 mi) feature; together these three craters make up the 6.2 by 2.5 km (3.9 by 1.6 mi) summit caldera Mokuʻāweoweo, so named for the Hawaiian ʻāweoweo fish (Priacanthus meeki), purportedly due to the resemblance of its eruptive fires to the coloration of the fish . Mokuʻāweoweo's caldera floor lies between 170 and 50 m (558 and 164 ft) beneath its rim and it is only the latest of several calderas that have formed and reformed over the volcano's life . It was created between 1,000 and 1,500 years ago by a large eruption from Mauna Loa's northeast rift zone, which emptied out a shallow magma chamber beneath the summit and collapsed it into its present form . Additionally, two smaller pit craters lie southwest of the caldera, named Lua Hou (New Pit) and Lua Hohonu (Deep Pit). </P>

Which is bigger kīlauea and mauna loa or mount everest