If moonbows, starry skies and volcanic activity peak your interest, head to one of the two national parks on these remote Pacific islands.
As the USA's National Park Service celebrates its centenary, we're profiling the wilderness areas it manages.
Today: The national parks of Hawaii . . .
"An unique example of significant island building through ongoing volcanic processes. The volcano Mauna Loa, measured from the ocean floor, is the greatest volcanic mass on Earth."
- Statement of Significance, UNESCO World Heritage Centre
Here on the big island of Hawaii, 48 kilometres from Hilo, are two of the world's most active volcanoes: Kilauea, whose name means spreading, much spewing; and Mauna Loa, which translates to long mountain. Mauna Loa last erupted in 1984; Kilauea has been erupting since early in 1983, with its ongoing activity at Halema'uma'u Crater in the park. After dark, it produces a vivid glow that illuminates the clouds and its plume.
Although flowing lava, craters and steam are undeniable draws, this park is also home to historic sites and endangered flora and fauna. Hiking and biking are popular ways to take in the scene. Driving routes also offer a dramatic overview. Crater Rim Drive and Chain of Craters Road include a number of vantage points. Fumes and glow from the lava lake within the vent at Kilauea's summit may be seen along Crater Rim Drive.
Other stops on the driving route include the Thurston Lava Tube (which Hawaiians call Nahuku), a walk-in tube that ends in a tropical rain forest. Tubes are formed when an underground channel of molten lava creates a hollow chamber.
In-park lodging is available at the Volcano House Hotel, which overlooks Halema'uma'u Crater. It has been operating since 1846, when it began as a grass shack.
Size: 323,431 acres
Attendance: 1,832,660 (2015)
"I felt like the Last Man . . . left pinnacled in mid-heaven."
- Mark Twain, as quoted by John F. Stone in the Mid-Pacific Magazine (1920)
In a park whose name means "house of the sun" in Hawaiian, it's appropriate that visitors' eyes are often drawn skyward. Rapidly changing cloudscapes, rainbows, moonbows and nighttime celestial bodies are highlights. Views can reach as far as 185km out to sea.
On land, there are rare plants and animals with memorable names. This is one of the last sanctuaries of the vibrant honeycreeper bird. And the protected silversword plant, which lives up to 90 years, flowers just once and then dies.
Botanists also call this the geranium capital of the world, which hardly sounds exotic. But, species of the flower here appear nowhere else.
Two sections — the summit and coast — make up this park on the island of Maui. They are not connected by road. Above, is a crater formed by erosion. It's a 49-square-km wilderness area that's popular with backpackers. Visitors flock to the summit for spectacular sunrise and sunset views. Below, in a lush landscape of forest, waterfalls, meadows and ocean, visitors watch for sea turtles, monk seals, dolphins, seabirds and humpback whales.
Overnighters may reserve wilderness cabins, which are accessible by hiking. Two car-accessible campgrounds also are options. All visitors are advised that the wild environment here includes the weather, which can be changeable.
Size: 33,265 acres
Founded: 1916 (separated from Volcanoes Park in 1961)
Attendance: 1,216,772 (2015)
The essential guide to Alaska's national parks
The essential guide to the National Park of American Samoa
The essential guide to Arkansas' Hot Springs National Park
The essential guide to California's national parks
The essential guide to Colorado's national parks
The essential guide to Kentucky's Mammoth Cave National Park
The essential guide to Utah's national parks
The essential guide to Virginia's Shenandoah National Park