New Zealand; Geysers and snug pastureland

Visiting New Zealand is like having Devonshire tea in the middle of adventureland - the customs and food are very British, but the terrain is bizarre, as are the fauna, from parrots to century-old tuatara lizards, whose ancestors predate the dinosaur.

It's a land the size of Colorado, lying midway between the Equator and the South Pole, 1,200 miles east of Australia. New Zealand's north is warmer than its south; summer begins in December; and, instead of the Big Dipper, they gaze at the Southern Cross. If it's Tuesday in New Zealand, it's sometime Monday in the United States.

Patches of New Zealand seethe, bubble, and percolate, while the land around it, as if too polite to notice, is snugly pastoral. In this country the earth is at its most primitive - and its most nurturing. Some 60 million sheep (20 for every person) graze unopposed by any predator. Mirroring this duality, the country is divided in two. The North Island accommodates two-thirds of the population and volcanic parks, and the South Island boasts mountains, fiords, streams, and plains. Beautiful beaches outline the island nation.

New Zealand is not a place of urban wonders, though the cities are pleasant. Having come a great distance to see the country, visitors should get out and see as much as they can.

Whether they arrive in Auckland, the city with the largest population (400, 000); Wellington, the capital; or the very English Christchurch, they must see Rotorua, 146 miles (239.8 kilometers) south of Auckland. It is a pungent place. Underground thermal activity unleashes a sulphur gas, whose smell (which one becomes accustomed to) would seem to be the price extracted for its individuality. As the rest of the world perfects solar heat, Rotorua - and national power plants - harnesses terrestial energy. Most of the dwellers here tap the steam below.

From the terrace of Rotorua's Polynesian Pools of naturally hot water, one sees black swans gliding through the mists and inky clouds on a pink sky. Nearby is Whakarewarewas, ''Whaka'' for short, the best-known thermal area and nature's theater of the absurd. Here the Pohutu Geyser sleeps or spews according to its own dictates (alas for the tourist on a schedule, but the most likely time is between 9 and 10 a.m.). It announces itself with a roar and a spit heralding another larger geyser that will send a plume as high as 300 feet.

To stand before its might or sit eagerly Indian-style on a lava rock (authorities have marked the spots where it is safe) is to know an exhilaration and a daring that is a sassy response to the geyser's misty threats. As the spray subsides, one sees silica terraces where black shale rocks are as smoky as logs with steam and green pools are turning blue in the sun. In dun-colored pools, bubbling squirts work themselves into messy cones that end with a pop and a fizzle.

In a country of ying and yang, of action and reaction, there are the Maoris, a formerly primitive Polynesian people that make up the non-European component of the populace. A quarter-million strong, they waved to the Dutch navigator Abel Tasman when he found New Zealand in 1642, declining to go ashore. They supposedly came from Southeast Asia, though their ancient belief in one God leads some elders to think they might even be Greek. Carpenters, lawyers, and teachers by day, some Maoris perform their traditional dances by night (one of which, unfortunately, is done to the tune of ''Canadian Sunset''). They and the Pakeha (Europeans) agree there is racial harmony now, although they were at war until the beginning of the 20th century.

Maori (pronounced Mau-ree) life is New Zealand life. Their villages are ranch or A-frame houses around a traditional square meeting house with a pointed roof. They are digging for the cultural roots they have lost and cultivating those which remain.

''If it weren't for the tourists, we would have lost our craft,'' says Emily Schuster, director of women's crafts at the Maori Arts and Crafts Center. ''They have always come to Rotorua and asked us questions, and so we remembered.'' The two chief crafts are weaving and carving. Maoris are the only people who weave by hand without a loom.

To the Maoris, art is the expression of a people, not an individual. Two women work on each woven-wood panel, one on each side, passing the strips through to each other.

At Whaka's Maori Center (and at museums such as Auckland's War Memorial), one learns how this people survived before white settlements were started in 1824. There were only two mammals, a dog species and bats. They depended on fish and bird flesh - and, to a certain extent, on human flesh, for they were cannibals. Early Maoris named four varieties of grapes and 50 kinds of flax, which weavers used for baskets, cloaks, fishing lines, and so on. The wooden panels and the carving tell, in Maori pictograms, the history of the people. Maureen Waaka, a former Miss Universe, now a hotel manager, showed me a panel and said confidently, ''Here you see the fish.'' I saw only a geometric diamond pattern, but I would not see a finned creature in the letters f-i-s-h, had I not had a certain amount of training.

The carvings, stained a mahogany color or washed with volcanic red clay, consist of flowing, somewhat grotesque forms with protruding tongues and abalone eyes and patterns, which tell those who can read them the story of the makers' family and tribe.

The outskirts of Rotorua reward a visit. About six miles to the south is the Waimangu Valley, a very active area in a setting of bush and sloping vegetation. Until 1886 this was the site of one of the wonders of the natural world - glittering solid flows of silica, known as the Pink and White Terraces and the Waimangu Geyser, which reached a height of 1,600 feet. In June 1886 Mount Tarawera erupted, and these wonders were no more.

Some might prefer Waimangu to Whaka, because the setting is more natural. Here, instead of pools, one has craters and cauldrons and rock-faced cliffs. A walk past the Southern Crater with its Emerald Pool, Bird's Nest Terrace, and Echo Crater - all interplays of silica, clay, and algae - leads to Lake Rotomahana, a five-acre filling the crater of the 1886 eruption. Also outside Rotorua is Rainbow and Fairy Springs, a preserve of 6,000 rainbow, brook, and brown trout and a variety of ferns and ducks.

The Agrodome should be seen, even by those who normally avoid ''country fair'' situations. The Agrodome offers a sort of ''merino follies.'' In the show , the 19 breeds of sheep come out of their stalls one by one as their attributes and origins are explained. The merino ram, backbone of the industry, fittingly stands above them all, but the Dorset horn, with huge curlicues above his head, steals the show - he's as funny and incongruous as a meek-mannered person wearing a Napoleonic hat.

After sheep-shearing comes a demonstration of a small sheep round-up, where a dog drives a few sheep round a pen, through a gate, and even through a man's knees. The Bowen brothers, two men in their 60s, alternate as master of ceremonies, shear the sheep, and call the dogs. In 1953 Godfrey Bowen set the world's hand-shearing record of 456 sheep in a nine-hour day.

Sheep are everywhere. With 60 million of them, it is hard to find a mountain or a field that is not ornamented by the woolly creatures. This is especially so on the South Island, an eminently benign place, where there are neither deadly animals nor pollution.

On the South Island are seven of New Zealand's 10 national parks. Mount Cook is the most famous; its centerpiece is Mt. Cook itself, New Zealand's highest, at 12,349 feet. One can see it in its majesty from the Mt. Cook Airport en route to Queenstown, or from a ski plane to the glacier.

Fiordland National Park with its 23 million acres, much of it explored only by air, is twice as large as the other nine combined. Fiords are steep-walled bays created by glaciers. Milford Sound, carved out by a piece of ice 6,000 feet thick, is actually a fiord with bottle-green water and verdant mountains. Ten miles long, it is best experienced on a 90-minute boat trip. Granite cliffs soar thousands of feet to the sky, waterfalls cascade and bounce, seals play along the rocks. Past Mitre Peak, the launch sails into the Tasman Sea, once a highway for navigators and whalers, before turning around for the trip back. One grows sated with beauty until it can't be seen anymore and the majesty is reduced to mountains and water.

New Zealand abounds in watery experiences, even in mountain areas. Queenstown is New Zealand's ski resort set on S-shaped Lake Wakatipu, 52 miles long. It is known as ''The lake that breathes,'' because its waters rise and fall three inches every 15 minutes. Maori legends say it was caused by a sleeping giant's heartbeat, but scientists attribute it to atmospheric pressure.

The T.S.S. Earnshaw (a twin-screw steamer) plies these waters past a mountain range that forms an unbroken chain of sheep stations. The Earnshaw calls at the Mt. Nicholas sheep station which is comprised of 100,000 acres of mountain, 20, 000 adult sheep and 15,000 Hereford cattle. Here, Alan Harris, wearing slouch hat, jacket, and plaid shirt, and leaning on a gnarled walking stick, is ringmaster for a dog and sheep show. A retired station manager, he is a natural and unaffected showman. With a blow of his whistle, the dogs turn a straggling flock of Merinos into a fuzzy arrow shooting around the field and behind the bunk house.

Mr. Harris says, ''It's wise for the dog to sort things out for herself and not to give too many commands. The best dogs have a facility for letting the stock settle down and not agitating them.'' Training is a matter of picking a dog with talent and then teaching it to understand commands. Harris says it takes three years to begin to properly train a dog. Asked one's value, he replied, ''No one gets his hands on my dogs, but one recently sold at auction for $2,000.''

As the sky darkens from lavender to gray, Mr. Harris explained, ''Dog work allows four men to manage an entire herd.'' Pointing at the face of the mountain , he says: ''There's a top man at the peak, a middle man who handles the terrain about where you see that cloud, and someone for the lower fields. It's an arduous calling, but exciting. It is not lonely - as long as one enjoys isolation.''

The dogs have all the hallmarks of any profession - they are constantly alert , constantly learning, and totally concentrated. ''A good dog won't see the truck because his eyes are on the sheep. The dog that takes it a bit easier lives longer,'' he observes. Dogs may be divided into three sorts - backing dogs that leap over or ride the sheep, huntaways that bark from the rear, and the headers that lead the herd.

Inside the woodshed, Harris demonstrates shearing. Legs and one hand pinning a merino, his right hand clips with the fury of a hummingbird wing; then he shows how speed is doubled or trebled with electric clippers.

Harris is in fact half of a team. His wife, Hazel, runs the Earnshaw snack bar and gives her own demonstration of spinning in the Earnshaw's hold. Foot at the treadle, she shows how to spin wool, thick or thin, and how to card it into fibers for spinning. In a gesture at once poetic and instructive, she holds the wool to the porthole to show its colors in the light. She is said to be an accomplished knitter, but her production is parcelled out to her grandchildren. Of her husband, whose quiet merriment and good sense had won over most of the passengers, she says: ''Alan is a natural. He has no guile. He wouldn't have made an espionage agent.''

Such a description typifies one's impression of New Zealand in general. To drive through the countryside is to see it as the earliest explorers saw it - hills and mountains slide to the sea unfettered by hot-dog stands, condominiums, or any other dubious development. Here, nature is benign; a bubbling volcanic field is simply to be enjoyed. Practical information:

When in New Zealand, stay with New Zealanders. They call themselves Kiwis - after their national, noctural, and flightless bird - and are at home to foreign visitors through several meet-the-Kiwi programs. For example, Greg and Diane Gascoigne are sheep farmers who take in visitors as a way to experience the world from their 381-acre farm near Cambridge, 90 miles northwest of Rotorua. Young parents of five sons ranging from age 16 to babyhood, they tell wonderful stories of buying their farm by milking cows and shearing sheep by day, then baking Pavlovas (fruity meringue pies, which are a national treasure) by night. They are part of Rural Tours, P.O. Box 228, Cambridge, New Zealand.

There is also Homestay and Farmstay, P.O. Box 630, Rotorua, N.Z. Costs vary from $25 to $45 a person a night. Arrangements can also be made through New Zealand Tourist Offices at 630 Fifth Avenue, New York, N.Y. 10111; One Maritime Plaza, San Francisco, Calif. 94111; 10960 Wilshire Boulevard, Los Angeles, Calif. 90024; or 2 Bloor Street East, Toronto, Ontario, Canada M4W 1A8.