New Zealand is located near the centre of the water hemisphere and is made up of two main islands and more than 700 smaller islands. The two main islands (the North Island, or Te Ika-a-Māui, and the South Island, or Te Waipounamu) are separated by Cook Strait, 22 kilometres (14 mi) wide at its narrowest point. Besides the North and South Islands, the five largest inhabited islands are Stewart Island (across the Foveaux Strait), Chatham Island, Great Barrier Island (in the Hauraki Gulf), D'Urville Island (in the Marlborough Sounds) and Waiheke Island (about 22 km from central Auckland).
New Zealand is long and narrow—over 1,600 kilometres along its north-north-east axis with a maximum width of 400 kilometres - with about 15,000 km of coastline and a total land area of 268,000 square kilometres.
The South Island is the largest landmass of New Zealand. It is divided along its length by the Southern Alps. There are 18 peaks over 3,000 metres (9,800 ft), the highest of which is Aoraki / Mount Cook at 3,724 metres (12,218 ft) Fiordland's steep mountains and deep fiords record the extensive ice age glaciation of this southwestern corner of the South Island.
The North Island is less mountainous but is marked by volcanism. The highly active Taupō Volcanic Zone has formed a large volcanic plateau, punctuated by the North Island's highest mountain, Mount Ruapehu (2,797 metres (9,177 ft)). The plateau also hosts the country's largest lake, Lake Taupō, nestled in the caldera of one of the world's most active super volcanoes. New Zealand is prone to earthquakes and volcanic eruptions.
The country owes its varied topography, and perhaps even its emergence above the waves, to the dynamic boundary it straddles between the Pacific and Indo-Australian Plates.
New Zealand is part of Zealandia, a microcontinent nearly half the size of Australia that gradually submerged after breaking away from the Gondwanana supercontinent. About 25 million years ago, a shift in plate tectonic movements began to contort and crumple the region. This is now most evident in the Southern Alps, formed by compression of the crust beside the Alpine Fault.
Before the arrival of humans, an estimated 80% of the land was covered in forest, with only high alpine, wet, infertile and volcanic areas without trees. Massive deforestation occurred after humans arrived, with around half the forest cover lost to fire after Polynesian settlement. Much of the remaining forest fell after European settlement, being logged or cleared to make room for pastoral farming, leaving forest occupying only 23% of the land.