The westward-facing flank of Hualālai forms a large underwater slump known as the North Kona slump. An area of about , the slump consists of an intricate formation of beaches and scarps below the waterline. This area was explored more closely in a 2001 joint Japan-United States project to explore the volcano's flanks, utilizing the remotely operated vehicle ROV "Kaikō". Data collected showed that the lava flows there originated in shallow water deep, and that unlike similar slumps at other volcanoes, the slump at Hualālai formed gradually.