The Hawai'ian Islands are of volcanic origin. There are almost no karst caves on the island, but a huge amount of lava tubes.
Hawai'i is sometimes called the highest mountain on Earth, as this shield volcano reaches from the ocean floor 4,000m below sea level to the top of Mauna Kea with 4,200m above sea level, which is more than 8,200m. This huge montain is very flat, just about 4% slope, and the lava tends to calmly flow down this slope. An ideal situatation for the formation of lava tubes.
The lava tubes on Hawai'i have been used as living place and religious centres. Many of them are holy places, on private property or in a National Park. This makes it rather difficult, to go caving on Hawai'i. Some private owned caves can be visited.