Māhukona is a submerged shield volcano on the northwestern flank of the Island of Hawaiʻi. A drowned coral reef at about 3,770 feet (-1,150 m) below sea level and a major break in slope at about 4,400 feet (-1,340 m) below sea level represent old shorelines. A roughly circular caldera marks its summit. A prominent rift zone extends to the west. A second rift zone probably extended to the east but has been buried by younger volcanoes. Māhukona is the oldest volcano to build Hawaiʻi island, older than Kohala and Mauna Kea. It was named for the area known as Māhukona, on the shore to the northeast.