linguistic:paraphrasing, quality:corruption
Volcanoes

There are four extinct volcanoes in the South Island, all located on the east coast.

Banks Peninsula forms the most prominent of these volcanic features. Geologically, the peninsula comprises the eroded remnants of two large shield volcanoes (Lyttelton formed first, then Akaroa). These formed due to intraplate volcanism between about eleven and eight million years ago (Miocene) on a continental crust. The peninsula formed as offshore islands, with the volcanoes reaching to about 1,500 m above sea level. Two dominant craters formed Lyttelton / Whakaraupō and Akaroa Harbours.

The Canterbury Plains formed from the erosion of the Southern Alps (an extensive and high mountain range caused by the meeting of the Indo-Australian and Pacific tectonic plates) and from the alluvial fans created by large braided rivers. These plains reach their widest point where they meet the hilly sub-region of Banks Peninsula. A layer of loess, a rather unstable fine silt deposited by the foehn winds which bluster across the plains, covers the northern and western flanks of the peninsula. The portion of the crater rim lying between Lyttelton Harbour / Whakaraupō and Christchurch city forms the Port Hills.

The Otago Harbour was formed from the drowned remnants of a giant shield volcano, centred close to what is now the town of Port Chalmers. The remains of this violent origin can be seen in the basalt of the surrounding hills. The last eruptive phase ended some ten million years ago, leaving the prominent peak of Mount Cargill.

Timaru was constructed on rolling hills created from the lava flows of the extinct Mount Horrible, which last erupted many thousands of years ago.