where did the magma that erupts from mauna loa likely form
The volcano's magma comes from the Hawaii hotspot.
Mauna Loa
Mauna Loa has probably been erupting for at least 700,000 years, and may have emerged above sea level about 400,000 years ago. The oldest-known dated rocks are not older than 200,000 years. The volcano's magma comes from the Hawaii hotspot, which has been responsible for the creation of the Hawaiian island chain over tens of millions of years. The slow drift of the Pacific Plate will eventually carry Mauna Loa away from the hotspot within 500,000 to one million years from now, at which point it will become extinct.
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Mauna Loa [SEP] Introduction
No recent eruptions of the volcano have caused fatalities, but eruptions in 1926 and 1950 destroyed villages, and the city of Hilo is partly built on lava flows from the late 19th century. Because of the potential hazards it poses to population centers, Mauna Loa is part of the Decade Volcanoes program, which encourages studies of the world's most dangerous volcanoes. Mauna Loa has been monitored intensively by the Hawaiian Volcano Observatory since 1912. Observations of the atmosphere are undertaken at the Mauna Loa Observatory, and of the Sun at the Mauna Loa Solar Observatory, both located near the mountain's summit.