We walk along the edge of Kilauea Iki Crater to a 500-year-old lava tube in a temperate rainforest. It’s a real lava tunnel formed when molten lava once flowed beneath the surface during a volcanic eruption. Once the liquid lava drained away, it left behind a hollow tube you can walk through. The lava that carved out Nāhuku was over 2,000 °F (1,093 °C) while it flowed — crazy hot! ️ This lava tube is about 500 years old, geologically quite recent. The tunnel you walk through is roughly 600 feet long and in some places the ceiling soars 20 feet high or more. Rainforest Entrance The trail to get into the tube winds through a lush native rainforest, alive with native birdsong and big ferns. You’re literally going from jungle into the heart of what used to be a river of fire!

A July 1974 eruption partially filled in this crater as it oozed from vents nearby.

This area has a crater, but the most unusual feature of this area is the large thermal area that has killed trees and grass. The thermal area started around 1939, and it continues to slowly engulf the forest around it. We will have to wait and see what the future hold.

Mauna Ulu means “growing mountain” in Hawaiian — and the name is literal. It formed as a brand-new volcanic shield during a long-lasting eruption on Kīlauea’s East Rift Zone. It isn’t a single cone, but a broad lava shield, built layer by layer as lava repeatedly spilled out and spread gently across the land. A Historic Long-Lasting Eruption Eruption dates: 1969–1974 — nearly five years, making it one of the longest eruptions of Kīlauea in modern history. Over that time, Mauna Ulu erupted almost continuously, fundamentally reshaping the landscape along Chain of Craters Road.

Natural Sea Arch: Hōlei Sea Arch is a huge natural rock bridge formed by the relentless power of the Pacific Ocean eroding ancient lava cliffs. Waves slowly hollowed out softer and fractured parts of the basalt until an arch remained. Size: The arch reaches roughly 90 feet (27 m) high — taller than a 7-story building! Erosion at Work: The arch was carved from a lava flow that’s about 550 years old. Ocean waves pounded at cracks and weak spots between hard and soft lava layers — a process called differential erosion — gradually sculpting the arch you see today.

Pauahi comes from the Hawaiian words “pau” (finished/done) and “ahi” (fire), meaning “destroyed by fire” — a fitting name for a crater shaped by volcanic fire. It’s a large volcanic pit crater — a deep, steep-sided depression formed mostly by the collapse of the surface as magma moves underground, rather than by explosive bombardment. Pauahi is quite big: roughly 1,600–2,000 feet (about 500–610 m) long, up to about 300–500 feet (90–150 m) deep, and about 300 feet (90 m) wide. Eruptive History Pauahi has had multiple volcanic events in recent (geologic) history, making it more than just a static hole in the ground: May 1973: A fissure opened and erupted briefly on the crater floor. November 1973: A longer eruption (about 31 days) created lava flows and dramatic features on the crater floor. November 1979: The most recent eruption was brief (one day) and left the lava surface you see today.