Monowai lies at the northern end of the Kermadec Arc north of New Zealand, in the Southwestern Pacific Ocean about halfway between Tonga and the Kermadec Islands. The Kermadec Arc is the southern part of the about long Tonga-Kermadec arc; this volcanic arc contains about 12 volcanic islands and at least 37 submarine volcanoes, which occur about every . Many of these volcanoes were only recently discovered and are poorly studied; hydrothermal activity has been observed at many. The Osbourn Trough and the Louisville seamount chain are being subducted close to Monowai and might have influenced the development of the seamount and the volcanic arc and back-arc in general. Monowai is one of the most active volcanoes in the Kermadec arc; two other active volcanoes are Raoul Island and Rumble III while Clark, Rumble V, Healy, Brothers, Volcano-W, Macauley, and Giggenbach are hydrothermally active.