R. V. DENENBERG is a writer who lives in the Hudson Valley. BY R.V.DENENBERG

In darkness they gather at the summit of the volcano, like Druids awaiting a solstice. The sun's hot orange ball peeks above the crater rim, illuminating an ashen landscape and turning the clouds below a golden purple. Fingers numbed by pre-dawn cold grope for camera buttons and a wave of sighs and gasps ripples through the audience: Haleakala, Maui's awesome mountain, has made its appearance.

It is a scene that repeats itself each daybreak at Haleakala, ''the house of the sun'' and the apex of Maui. Although the shivering band of spectators changes from day to day, the response is remarkably uniform. There is a vicarious sense of being present at the creation - the fiery upthrust of ocean floor about a million years ago that shaped this giant cone and linked it with another volcano to form a narrow-waisted landmass, anchored in a cluster of sister islands.

The 10,000-foot-high summit of Haleakala commands a sweeping view of the 700-square-mile island and much of the rest of the Hawaiian archipelago. Nearly barren and often fog-bound or frigid, it is hardly as inviting as the lush beaches, the island's primary lure. Yet those who drive up for the sunrise spectacular often linger on.

Volatile, explosive Haleakala set the pattern for Maui's progress. In the early 19th century it was the sandalwood boom: Whole forests of aromatic lumber were exported to fuel the incense burners of China. Later, Maui became the base from which determined Yankee missionaries proselytized the entire Hawaiian chain.

By the 1850's, Maui was coping with its first tourist influx. As many as 80 ships at one time stood in the roadstead off Lahaina, on the northwest of the island. Then the capital of the native Hawaiian kingdom, Lahaina suddenly found itself a port of respite for seaweary whaling men plying the Pacific from Alaska to the Antarctic. The whalers were followed by the sugar planters and their field hands, immigrants from Japan who raised Buddhist temples beside the churches. In 1898, at the squat courthouse in Lahaina, the Stars and Stripes was hoisted aloft to signal the annexation of Hawaii by the United States.

Despite its long association with international commerce and politics, Lahaina (population: 10,000) has remained little more than a seaside village. It nestles beneath soft, tropical hills, but the whaling and missionary connection has lent it a crusty New England flavor. Front Street, the narrow main thoroughfare, is a South Seas version of Cape Cod: a collection of weathered wooden shops with overhanging galleries under which scrimshaw sellers stand cheek-byjowl with muumuu merchants.

The white-walled home of Dwight Baldwin, an early medical missionary, would not be out of place in his native Connecticut, except for the lanai (veranda) and the mosquito net hanging like a birdcage over the four-poster bed. Restored to its mid-19th-century appearance, the house reflects a blend of practicality and piety. On display are a set of primitive surgeon's tools and, on the piano, the sheet music for ''Rejoice in the Lord.''

The whalers occasioned less savory monuments. On a side street stands the imposing, fortress-like walls of Hale Paahao, whose Hawaiian name means ''stuck-in-irons house.'' This jail was built to confine seamen who, after months under sail, had become obstreperous on shore leave. Judging by the stoutness of the prison, made of white coral-stone blocks, the sailors had earned a fearsome local reputation for disorderly conduct.

At the wharf, the Pioneer Inn, a mellow, turn-of-the-century hostelry with a two-story veranda facing the sea, seems to be keeping watch for the return of some ghostly fleet; well-worn harpoons stand at the ready along the one wall of the bar.

An impressive recreation of a whaler floats at dockside just across from the hotel. The Carthaginian II (named after the ship in the James Michener novel, ''Hawaii'') was a cement carrier in the Baltic before the nonprofit Lahaina Restoration Foundation (which also refurbished the Baldwin House) bought it and installed hand-finished fir masts, eucalyptus deck planking and other authentic details. The dashing, fully-rigged replica of a brig opened in 1980 as a museum of whaling.

The other craft moored in the little artificial harbor - Lahaina has no natural port - are mostly of the sightseeing variety. The wharf is a carnival of booths selling tickets for an astonishing variety of excursions: coral-reef-viewing cruises, sunset cruises, dinner cruises, snorkeling cruises, fishing cruises and cruises to the nearby islands of Lanai and Molokai. They sail aboard glassbottom boats, catamarans, trimarans and yachts, and serve everything from breakfast to evening cocktails.

When they are not strolling Lahaina's streets or bobbing offshore in a boats, visitors are usually lolling under the palms at such beachside resorts as Kaanapali, about six miles north of town. A narrow strip of former brushland has here been converted into a hotel enclave of high-rise towers, cottages and elevated freeways for golf carts.