The Mauna Loa Volcano

Have you ever heard of Mauna Loa? Rising gradually to more than 4 km above sea level, Mauna Loa is the largest volcano on our planet. Its long submarine flanks descend to the sea floor an additional 5 km, and the sea floor in turn is depressed by Mauna Loa's great mass another 8 km. This makes the volcano's summit about 17 km (56,000 ft) above its base! The enormous volcano covers half of the Island of Hawaii and by itself amounts to about 85 percent of all the other Hawaiian Islands combined. Now let's get to finding out about lava.

Although, it is a little terrifying having an active volcano next to a big city like Hilo Hawaii, it also brings in money for the city. According to wikipedia “Hilo is the county seat of the County of Hawaii and
This is partly due to the fact that the volcano was covered in cloud at high elevation and helicopters were not in use; so, most of the information we have comes from what happened on Highway 11 during the eruption. In the months and years following the eruption, the vents and flows have been examined and mapped extensively, however. The eruption occurred along almost the entire length of the SW rift zone (from 8000 to 13,000 ft) and opened up almost simultaneously (like a zipper) from an essentially continuous vent system. Consequently, lava flows poured down at numerous places on both the west and east side of the rift. The eruption lasted only two weeks but the eruption of 1859 lasted almost a whole year. So, given that the flow volume is 4 to 5 times greater than the 1984 eruption (which lasted 3 weeks) it must have been a spectacular eruption. In places the flows were obviously very fluid and flowing rapidly, since they eroded the bases of prehistoric spatter cones during emplacement. It must have been coming downhill like gangbusters! The lava flow was compositionally very heterogeneous, with the upper part of the rift eruption evolved magmas (MgO 7 wt. %). Compositions became more primitive (MgO up to 10 wt. %) down rift. However, the lowest elevation flows were the somewhat more evolved (MgO 8 wt. %). The data are consistent with mixing of a relatively primitive magma with an evolved magma that may have been residing in the rift zone (this older magma has compositions very similar to the lava produced by the 1949 summit