It is an active shield volcano with relatively gentle slopes, with a volume estimated at approximately 18,000 cubic miles (75,000 km 3), although its peak is about 120 feet (37 m) lower than that of its neighbor, Mauna Kea.Lava eruptions from Mauna Loa are silica-poor and very fluid, and they tend to be non-explosive.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.t is an active shield volcano with relatively gentle slopes, with a volume estimated at approximately 18,000 cubic miles (75,000 km 3), although its peak is about 120 feet (37 m) lower than that of its neighbor, Mauna Kea.