The Macquarie Fault Zone is a major right lateral-moving

transform fault A transform fault or transform boundary, is a fault along a plate boundary where the motion is predominantly horizontal. It ends abruptly where it connects to another plate boundary, either another transform, a spreading ridge, or a subductio ...

along the seafloor of the south

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

which runs from

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

southwestward to the

Macquarie Triple Junction The Macquarie Triple Junction is a geologically active tectonic boundary located at at which the Indo-Australian Plate, Pacific Plate, and Antarctic Plate collide and interact. The term Triple Junction is given to particular tectonic boundaries ...

. It is also the

tectonic Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents k ...

plate boundary between the

Indo-Australian Plate The Indo-Australian Plate is a major tectonic plate that includes the continent of Australia and the surrounding ocean and extends northwest to include the Indian subcontinent and the adjacent waters. It was formed by the fusion of the Indian an ...

to the northwest and the

Pacific Plate The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate. The plate first came into existence 190 million years ago, at the triple junction between the Farallon, Phoenix, and Iza ...

to the southeast. The Macquarie Fault Zone includes a component of convergence which increases as it approaches the South Island of New Zealand. Many researchers conclude that the fault zone here is an incipient subduction zone, with oblique motion corresponding to the transition from lateral (strike-slip) motion. In the area known as the

Puysegur Trench The deepStern, Robert J. (2004)Subduction initiation: spontaneous and induced Earth and Planetary Science Letters 226, 275–292. . Puysegur Trench is a deep cleft in the floor of the south Tasman Sea formed by the subduction of the Indo-Austral ...

, the Indo-Australian Plate appears to be starting to sink beneath the Pacific Plate, the reverse of what is occurring off of New Zealand's North Island (see

Kermadec-Tonga Subduction Zone The Kermadec-Tonga subduction zone is a convergent plate boundary that stretches from the North Island of New Zealand northward. The formation of the Kermadec and Tonga Plates started about 4–5 million years ago. Today, the eastern boundary ...

). A major geographic feature which runs along the Macquarie Fault Zone is known as the Macquarie Ridge. This ridge represents both the different relative heights of the abutting plates as well as the component of compression between the plates. The namesake

Macquarie Island Macquarie Island is an island in the southwestern Pacific Ocean, about halfway between New Zealand and Antarctica. Regionally part of Oceania and politically a part of Tasmania, Australia, since 1900, it became a Tasmanian State Reserve in 197 ...

, named after

Lachlan Macquarie Major-general (United Kingdom), Major General Lachlan Macquarie, Companion of the Order of the Bath, CB (; gd, Lachann MacGuaire; 31 January 1762 – 1 July 1824) was a British Army officer and colonial administrator from Scotland. Macquarie se ...

lies atop a segment of the Macquarie Ridge. The Macquarie Fault Zone merges into the

Alpine Fault The Alpine Fault is a geological fault that runs almost the entire length of New Zealand's South Island (c. 480 km) and forms the boundary between the Pacific Plate and the Indo-Australian Plate. The Southern Alps have been uplifted on the f ...

which cuts across the

continental crust Continental crust is the layer of igneous, sedimentary, and metamorphic rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called ''sial'' be ...

of New Zealand's South Island.

References

Transform and Subduction Tectonics Along the Macquarie Ridge, University of Texas
{{Oceanic features of Zealandia, state=collapsed Zealandia Seismic faults of New Zealand Seismic faults of Australia Macquarie Island Plate tectonics Underwater ridges of the Pacific Ocean