The network of underground caves carved out by Hawaii's transformative lava is a mysterious island treasure that few tourists take the time to experience and understand. In fact, many visitors remain completely unaware that they are walking on top of a vast chain of crisscrossing lava tubes. This is especially the case on Hawaii Island, where the most recent volcanic activity can be observed more closely.
How Lave Tubes Are Formed
While the world's most famous tunnels and caves were carved slowly over time by natural acidic water, Hawaii’s lava tunnels—which can take anywhere from weeks to months to form—are the result of volatile volcanic eruptions.
When a volcano erupts, a deadly combination of molten rock and gas explodes from beneath the earth’s crust. While the lava flows, its exterior begins to slow, cool, and harden into a crust while its still-molten interior continues to move. Once the hot lava (upwards of 2,000 degrees Fahrenheit) has built up enough volume or reached a roadblock, it is pushed upwards and outwards to form a crack or opening—this becomes the entrance or exit to the tube.
With a texture unlike any other type of mineral cave, these volcanic tubes also range greatly in size: Some are too small for humans while others are larger than subway tunnels. Inside, ecosystems of animals that have adapted to live in the darkness thrive. If anything, the cold, dark temperatures inside a lava tube offer a welcome break from Hawaii's tropical heat.
How Native Hawaiians Used Lava Tubes
Lava-formed caves and tunnels were greatly important to native Hawaiians, who used them for both shelter and food storage. Precious drinking water from the earth could also be found dripping through the lava rock. These structures were also used as burial chambers and ceremonial areas, a reason why entry to many caves and tunnels on the Hawaiian Islands remain closed to tourists.
Kazumura Cave: Formed by the 500-year-old ‘Ailā‘au lava flow of Kīlauea Volcano and spanning more than 40 miles, the Kazumura lava tube system is believed to be the longest lava tube cave on Earth. To see it for yourself, you will need to book a tour of the Lava Falls, Pit Room, or Maze. The cave is open from 8 a.m. to 6 p.m. Monday through Thursday.
Thurston Lava Tube: Perhaps the most famous of Hawaii’s lava tubes is the Thurston Lava Tube (Nāhuku) inside Volcanoes National Park on the Big Island. The famous tube was closed for nearly 22 months following a series of powerful volcanic eruptions in 2018 that greatly affected surrounding sections of the island. The half-mile walk from the parking lot to the tube will take about 20 minutes; while it is open 24 hours a day, it’s only illuminated from 8 a.m. to 8 p.m.
Pua Po'o Lava Tube: While Pua Po'o is about the same size as Thurston, it requires a great deal more effort to discover. Hikers must first climb down a 15-foot ladder from the mouth of the tube, scrambling over rocks and uneven terrain with little light before continuing in a crouched position for about 25 feet under a four-foot-high ceiling. To exit and finish the five-mile trek, a moderate climb up a large pile of boulders is required. The Hawai’i Volcanoes Institute offers guided tours that include information about the surrounding area and photo opportunities; these are available on alternative Wednesdays and Sundays from 10 a.m. to 2 p.m.
Located on the southern coast of Kauai, the Spouting Horn Blowhole is a natural lava tube that runs to the ocean. When the surf is just right, the blowhole can spray water up to 50 feet in the air. You can access Spouting Horn Park very easily using its ample parking. Pro tip: The blowhole is especially beautiful during sunset.
The Hālona Point Blowhole can be found right off the Kalanianaole Highway on the east side of Oahu. Many choose to pull over to the scenic lookout on their way to one of many surfable beaches or on their way back from snorkeling at Hanauma Bay. You’ll be able to view Hālona Cove from the right side of the parking lot, and a short (though very rocky) hike down will bring you to the water. Towards the back of the cove, there is an entrance to a lava tube, which extends under the highway and into the mountain. Do not venture near the blowhole, however; the slippery rocks have been responsible for many injuries and even fatalities.
Waiʻānapanapa State Park: An easy-to-access tube located on the black sand beach at Waiʻānapanapa State Park, this unique spot offers some amazing photo opportunities. The combination of the black sand with the crashing blue water in the background is mesmerizing (just be sure to exercise caution when attempting to enter or view the cave during high surf).
Hana Lava Tube: One of the more popular stops along the famous Road to Hana, Ka’eleku Cave (Hana Lava Tube) is nothing short of a natural wonder. The tube runs about one-third of a mile past stalactites, stalagmites, and some spectacular rock formations once used as a fallout shelter during the Cold War era. Entrance to the tube costs $11.95 per person (children five and under are free) and includes use of handrails and flashlights.