Thurston Lava Tube

Thurston Lava Tube, also called Nahuku, is located in the rain forest ecological zone. The abundant rainfall contributes to the lush growth of the forest canopy trees and the understorey vegetation.

The visit here consists of a short walk down a paved trail as it descends into a pit crater (the sides of which are hard to distinguish because they are covered with vegetation).  The trail then goes through a short section of a lava tube.  Finally, the trail loops back to the starting point.

You'll see the general structure of a Hawaiian rain forest here and become reminded of the evolutionary importance of the underground ecosystems.



This area was fenced and pigs were removed in 1984 (Stone & Pratt 1994).  You will notice cattle guards along the road in this area; these are to keep out feral pigs. 

This particular guard, however, no longer appears to be needed.


Getting There

The Crater Rim Road takes you to this site.

This is a popular visitor stop and the small parking lot is often crowded with cars and buses.

GPS Location: N 19.4136, W 155.23900


Thurston Lava Tube parking lot


This is an easy site to visit although the trail is steep in places and there are several sets of stairs.  The underground portion is well lit.  If you do have a flashlight, you can visit a fenced-off section of the lava tube.

The trail enter from the parking lot and then splits just a few feet from the entrance.

You may want to visit the restroom located nearby to the left of this point.

Before descending into the pit crater, look at the abundant vegetation from this starting point.  There is a good overlook where the trail branches.  The canopy trees are Metrosideros polymorpha (Hawaiian: `ohi`a).  There is a dense understory layer of tree ferns (Cibotium glaucum; Hawaiian: hapu`u).

We'll take the right branch of the trail. It descends soon (below right) along a wide-paved trail.

Trail branch near entrance

Metrosideros - Cibotium rain forest

Down the trail to the right
You soon go down a short set of stairs.

At the bottom, look at the wall of the pit crater on your left.

Look for some large Metrosideros polymorpha (Hawaiian: `ohi`a) roots growing through cracks in the layers of basalt.

You'll see that this ability of Metrosideros to penetrate deep into the substrate will become important when you enter the lava tube.

Metrosideros roots penetrate the surface
There are several alien weeds that you'll see along the trail.

Fuchsia paniculata is a recently naturalized plant, with the first collection being made in 1966 (Wagner et al. 1990: 997).

Knotweed (Polygonum capitatum) (below) is found as a naturalized plant in wet forests, open lava fields and on the sides of the road.  It was first collected in 1960 and appears to be restricted to the Big Island (Wagner et al. 1990: 1063).  You'll see it here along the rock walls and trail margins.

The hybrid iris montbretia (Crocosmia x crocosmiiflora) (below right) has showy orange flowers.

Fuchsia paniculata

Polygonum capitatum

Crocosmia x crocosmiiflora
You soon reach a bridge leading into the lava tube.

Look at the wide variety of ferns on the walls.

There is even a Peperomia spp. clinging to this last area reached by sunlight.

Bridge enters the lava tube
Ferns at the entrance Peperomia spp.
Lava tubes are a common feature of the creation of the volcanic landscape. As molten lava flows down the side of the mountain, the surface cools. The lava then flows underground, through these self-made tubes. The distances that the lava travels are extended since the tube's roof effectively insulates the molten lava, keeping it fluid for a longer time. When the eruption stops, lava drains from the tube, leaving it an open chamber.  The often thin roof may collapse in time.

The picture on the right is looking back at the entrance from part way down the lava tube trail.

Lava tube
The ability of Metrosideros polymorpha (Hawaiian: `ohi`a) to penetrate cracks in the lava means that sometimes they extend down into the lava tube.

Here they serve as a food source for animals living in the lava tube.

Very unique ecosystems have developed in isolated lava tubes.

Metrosideros roots growing into the lava tube
Stairs lead you back to the surface.

As you continue following the trail, look again at the structure of the rain forest.

Cibotium tree ferns form a dense understory with Metrosideros growing through to form a closed canopy.

Stairs leading out of the lava tube
Cibotium glaucum under Metrosideros canopy Cibotium glaucum under a Metrosideros canopy

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Last Updated: 11/17/00

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