movement on the proto-Alpine Fault was exclusively strike-slip. The Southern Alps had not yet formed and most of New Zealand was covered in water. Then uplift slowly began as the plate motion became slightly oblique to the strike of the Alpine Fault. In the last 12 million years, the Southern Alps have been uplifted approximately 20 kilometres, however, as this has occurred more rain has been trapped by the mountains leading to more erosion. This, along with isostatic constraints, has kept the Southern Alps less than 4,000 m. Uplift on the Alpine Fault has led to the exposure of deep metamorphic rocks near the fault within the Southern Alps. This includes mylonites and the Alpine Schist, which increases in metamorphic grade towards the fault. The eroded material has formed the Canterbury Plains. The Alpine Fault is not a single structure but often splits into pure strike-slip and dip-slip components. Near the surface, the fault can have multiple rupture zones. Fault zone geology The fault zone is exposed at numerous locations along the West Coast, and typically consists of a 10–50 m wide fault gouge zone with pervasive hydrothermal alteration. Most of the movement along the fault occurs in this zone. In outcrop, the fault zone is overlain by mylonites which formed at depth and have been uplifted by the fault. Earthquakes There have been no major historical earthquakes on the Alpine Fault. Because of this, during the mid-20th century it was speculated that the Alpine Fault creeps without making large earthquakes. However, it is now inferred by multiples lines of evidence that the Alpine Fault ruptures, creating major earthquakes approximately every few hundred years. Prehistoric The Māori arrived in New Zealand c.1300 but never reached a high population density in the colder South Island. Therefore, while earthquakes are an important part of Māori oral tradition, no stories have been passed down about South Island earthquakes. Over the last thousand years, there have been four major ruptures along the Alpine Fault, causing earthquakes of about magnitude 8. These had previously been determined to have occurred in approximately 1100, 1430, 1620 and 1717 CE, at intervals between 100 and 350 years. The 1717 quake appears to have involved a rupture along nearly of the southern two-thirds of the fault. Scientists say that a similar earthquake could happen at any time, as the interval since 1717 is longer than the intervals between the