New Zealand is a country in which sheep outnumber people by a factor of six, and its serene pastures have a timelessness that feels exempt from change. But Monday’s magnitude-7.8 earthquake, centered near Kaikoura, sixty miles north of Christchurch, was a brutal reminder that, beneath its verdant carpet, New Zealand is still under active construction. It occupies one of the most complex geologic venues on the globe, at the messy boundary of two tectonic plates. The North Island, where the capital, Wellington, lies, is part of the Australian plate, and its landscape is dominated by two dozen active volcanoes. (One of these, the Taupo caldera, is notorious in the annals of volcanology as the site of Earth’s most recent super-eruption, twenty-six thousand years ago, which covered parts of the island in ejecta six hundred feet deep. Outside geophysical circles, the region is more generally famous as the home of Mt. Doom in the “Lord of the Rings” films.) The plate boundary lies about forty miles offshore, at the Hikurangi trench, a deep warp in the ocean floor where the Pacific crust slides westward beneath the Australian plate. Meanwhile, off the southern end of the South Island, the configuration is reversed—that is, the Australian plate sinks eastward beneath the Pacific plate.
Source: New Zealand’s Tectonic Dragon Awakens – The New Yorker