The Geomorphic Evolution of Oceanic Volcanoes in the Southwest Pacific
This thesis examines the post-eruptive geomorphic evolution of oceanic volcanoes in the southwest Pacific, specifically, the Tasmantid Seamount Chain, Norfolk Island, and its surrounding shelf. These volcanoes are compared with the Lord Howe Seamount Chain and geomorphic processes are investigated at both regional and local scales. Volcanoes erupting in a submarine environment form a seamount; if they build above sea level, they develop into a volcanic island. Over time, a volcanic island will be eroded to form a flat-topped truncated submerged volcano known as a guyot, except in lower latitudes when protected by a carbonate reef.
Geomorphic mapping is undertaken on nineteen volcanoes in the Tasmantid Seamount Chain. High-resolution bathymetric data reveals the geomorphic detail of the northern volcanoes (~30 Ma), whereas lower-resolution data enables morphometric analysis of the southerly volcanoes, including the three southernmost guyots (~6 Ma). Volcanoes erupted sequentially as the Australian plate moved northwards. Subsidence rate of each volcano varies based on age and type of supporting lithosphere; faster on oceanic (Tasman seafloor) and slower on continental lithosphere (Zealandia). Marine erosion is estimated to have truncated the guyots at a rate of 2.45 kmMyr-1. A conceptual model of the volcano evolution within the Tasmantid Seamount Chain from the Oligocene to the present is generated, illustrating that the evolution of each volcano is the product of erosion, carbonate accretion in the Mid-Miocene and drowning in the Late-Miocene.
History
Year
2024Thesis type
- Doctoral thesis