National Park Guide: Hawaii's Volcanoes

— -- On a recent trip to Hawai'i Volcanoes National Park on Hawaii's Big Island, Marlene and Ellwood Johnson from Peterborough, Ontario, hiked through the rain forest and explored a lava tube at some points roughly twice as tall as they are.

"It's like a huge sewer pipe of black rock," Marlene Johnson says.

The couple then stuck around to watch one of the park's main attractions — the Kilauea volcano's Halemaumau crater. As of early May, the crater with a lava lake about 200 feet below the surface was emitting a plume of gas and ash. At night, the crater was taking on a bright glow. "You have to wait for dark, but it becomes more and more orange," Ellwood Johnson says.

The park contains two active volcanoes: Mauna Loa, the most massive mountain in the world, which last erupted in 1987, and Kilauea, which has offered "pretty much non-stop action in modern history," according to park spokeswoman Jessica Ferracane.

The Halemaumau crater can be seen from an overlook platform about half a mile away at the Thomas A. Jaggar Museum. Though it requires a long, difficult hike in winter gear, visitors also can see lava from the Puu Oo vent on a coastal plain in the volcano's east rift zone. There is no way to tell how long the eruptions will last, Ferracane says, though Puu Oo has been erupting since 1983 and Halemaumau since 2008.

Hawai'i Volcanoes is home to a variety of wildlife and plants, including some species found nowhere but the Hawaiian islands or the park itself. The park contains six endangered native bird species, including the nene (Hawaiian goose) and the io (Hawaiian hawk). The park's coastline holds nesting areas of the endangered hawksbill sea turtle.

Slightly above the coastline area, visitors can use a boardwalk to view petroglyphs carved into lava rock.

Walkers and hikers will find more than 150 miles of trails from easy to those that traverse wilderness areas, while bikers can use the park's roads and some trails.

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About the park

Size: 333,086 acres

Visitors: 1,352,123 in 2011

Established: 1916

History: Native Hawaiians lived for over five centuries in the area that would became Hawai'i Volcanoes National Park. The park was named an International Biosphere Reserve in 1980. Since 2008, when the Halemaumau crater began erupting, Hawai'i Volcanoes was seeing two simultaneous eruptions from the Kilauea volcano as of early May — a first-time occurrence since the park's establishment. The volcano's Puu Oo vent has been erupting since 1983.

When visiting: Headquarters and Kilauea Visitor Center at 1 Crater Rim Dr., Hawaii National Park, Hawaii 96718-0052. Visitor information: 808-985-6000.

Of note: The park contains two types of Hawaiian lava: pahoehoe is smooth and ropy, while a'a is crumbly and jagged.