A weekly feature provided by scientists at the Hawaiian Volcano Observatory. Among the many tools earth scientists use, the measurement of gravity variations over the earth's surface is one of the most useful for studying Hawaiian volcanoes. Gravity varies from location to location on the Big Island, and the gravity measurements can be easily corrected for the expected variations. After correction, any remaining variations in gravity must be caused by volcanic structures below the island's surface.
Gravity is even weaker at the top of Mt. Everest.
On the Big Island, the values of corrected gravity are highest over the summits of each of our volcanoes and their rift zones. A high value of corrected gravity generally signifies that the deep rocks are denser than average lava flows. These dikes are the conduits by which magma is brought up to the surface and erupted. Variations in gravity can be a way of mapping the internal magma plumbing and storage chambers of each of the island's volcanoes, without waiting for erosion to expose them. First, Kohala Volcano used to be much larger and longer, extending from its current summit in an east-southeast direction across the shoreline between Laupahoehoe and Hakalau.