OFFSHORE EXTENTS OF HOLOCENE HAWAIIAN LAVA FLOWS

Over the past 5,000 years, many lava flows from Hualālai and Mauna Loa volcanoes have entered the ocean on the northwest side of the Island of Hawai‘i. In order to quantify the offshore extent of the lava flows we use recently-acquired high-resolution bathymetry and near-shore LiDAR .

Surprisingly, the youngest lava flows did not advance far beyond the modern coastline even after advancing several tens of kilometers from their vents to the coast. For example, the Hu‘ehu‘e and Ka‘ūpūlehu lava flows from Hualālai and the 1859 lava flow from Mauna Loa did not extend farther than 3.5 km from the current coastline. In comparison, the Mauna Loa lava flows along the northwest coast that were channeled northwest between Hualālai and Mauna Kea volcanoes 3,000-5,000 years ago, appear to have advanced almost 8 km beyond the current coastline. These flows overlay the 125-m submerged terrace along this flank of the island and may represent higher eruption rates during a period of time when there was a surge in volcanic activity from the summit of Mauna Loa volcano that may have led to a collapse of the summit caldera, Moku‘āweoweo (Lockwood, 1995).

Future studies of these submarine lava flow will allow comparison with the work of Mitchell and others in the Azores identifying submarine lava flow features in near-shore areas and evaluation of the effect of submarine lava flow advancement.