Southern Alps / Kā Tiritiri o te Moana

Two huge pieces of the Earth's crust push together here.

The push lifts the mountains up, very slowly.

UNESCO explains that the great Alpine Fault runs through this region. It marks where the Indo-Australian Plate and the Pacific Plate meet, and it is one of only three parts of the world's major plate boundaries that are on land.

The two plates collide here, and that collision builds the Southern Alps. NASA says the central part of the fault runs the length of South Island, and as the plates keep pushing together, the mountains should keep rising.

UNESCO: the great Alpine Fault marks the contact zone of the Indo-Australian and Pacific continental plates, one of only three segments of the world's major plate boundaries on land; collision between the plates constructs the main range.

NASA describes the Alpine Fault as the major surface expression of the plate boundary, its central section running the length of South Island; as the plates progressively converge, the Southern Alps should continue to rise over time.

The west side of the mountains gets lots of rain and snow. The east side is drier.

Some glaciers flow down into rainforest.

NASA says the mountains make a rain shadow. On the west side, the mountains and foothills get rain and snow all year. On the east side, the land is drier, with many days without clouds.

UNESCO says Ice Age glaciers carved deep U-shaped valleys, lakes and fiords in the southwest. Today the Franz Josef and Fox glaciers still flow down into temperate rainforest.

NASA: the range creates a rain-shadow effect; the west side and its foothills have frequent rain and snowfall year-round, while the downwind east has a more arid climate and many cloud-free days.

UNESCO: Pleistocene glaciers carved fiords, lakes, deep U-shaped valleys, hanging valleys, cirques and ice-shorn spurs; outwash gravels and moraine ridges west of the Alpine Fault outline former piedmont and Holocene valley glaciers; the Franz Josef and Fox Glaciers descend into temperate rainforest.

Rare birds live in the wild southwest, like the takahē and a kiwi called the rowi.

Tussock grass grows on the open hills.

UNESCO's Te Wāhipounamu – South West New Zealand, which reaches from Fiordland in the south to the Southern Alps in the north, holds the whole wild population of the rare takahē and of the rowi, New Zealand's rarest kiwi.

It also has large populations of the kākā and the yellow-crowned parakeet. UNESCO says its plants and animals are the world's best intact living example of the ancient life of Gondwana, the old southern supercontinent.

Te Wāhipounamu (UNESCO, 1990; 2.6 million ha, including the Mount Cook and Westland national parks) holds the entire wild population of the endangered takahē (Notornis mantelli) and of the rowi (Apteryx rowi), New Zealand's rarest kiwi, plus the only large remaining populations of kākā and kākāriki / yellow-crowned parakeet.

Its habitats run along altitudinal gradients from sea level to the permanent snowline, with extensive alpine plant endemism and tussock grasslands; UNESCO calls its biota the best intact modern representation of the ancient biota of Gondwana.

Mountain weather can change quickly. Stay with your grown-up.

Wear warm layers and sunscreen.

PlayOwl's advice: the western side of the Southern Alps gets rain and snow all year, so mountain weather can turn cold and wet. Walk only on marked tracks with a grown-up, carry warm, waterproof layers and check the weather first.

Snow and sun together can burn skin. The CDC says UV rays reflect off snow, so wear sunscreen, sunglasses and a hat.

PlayOwl's advice, based on NASA's account of year-round rain and snowfall on the western side: keep to marked tracks, carry warm and waterproof layers, and check forecasts and track conditions first.

CDC sun safety: UV rays reflect off surfaces such as snow, water and sand; use broad-spectrum sunscreen, UV-blocking sunglasses and a wide-brimmed hat.