Hawaii's Amazing Lava Fossils

by Donnie MacGowan

With minor local exceptions, the rocks of the Big Island of Hawaii are made up almost entirely of eruptive volcanic effluent—lava and ash, and sediment derived from eroding and weathering lava and ash. As such, it doesn't seem a likely place to hunt fossils. After all, the lava pours from the vents on Hawaii's volcanoes at between 1100° and 1130° C and even the hardened crust on the top of an active flow can be as hot as 600°C. It seems like the advancing lava ought incinerate everything in its path and leave no trace of organic matter behind as fossils.

Palm Frond Fossil in Basalt From 30-Year Old Lava Flow, Kalapana, Hawaii: Photo by Donald B. MacGowan

Or would it? Sometimes things in nature don't always act the way we expect them to.

Lava Mold of a Palm Tree in a 2000 Year Old Flow, Honaunau, Hawaii: Photo by Donald B. MacGowan

As a child, my mind, when not actually occupied with thoughts of dinosaurs, was chiefly occupied with thoughts of volcanoes or thoughts of fossils. It's scarcely surprising, then, that I grew up to be a geologist, but when I eventually washed-up on the shores of the Big Island, I thought I'd landed in heaven—five volcanoes, three of them active! But as I explored my new home I found more and more examples of where Hawaii's volcanoes had preserved fossils of plant and animal life.

To be sure, owing the the extreme temperatures of the lava, these fossils tend to be molds or casts, but they are abundant and fascinating. More delicate fossils are contained in ash deposits, but so far, these have been only marginally explored.

Let's take a quick tour around the island of Hawaii and look at some of the remarkable, amazing, lava fossils of Hawaii.

Lava Tree State Monument

Lava Tree Mold at Lava Trees State Monument, Big Island, Hawaii: Photo by Donald B. MacGowan

Let's start down in Puna District, just a few miles south of Pahoa Town. At Lava Trees State Monument fingers of lava poke vertically at the sky, remnants of a flow that that passed through a wet ohi'a tree forest in 1790. The flowing lava enveloped the wet ohi'a trees, cooling and congealing around them. As the lava flow drained away down nearby cracks, the fingers of cooling lava were left behind. The remnants of the trees were burned and rotted away, so today these stubby towers are hollow.

Towers of Lava Tree Molds at Lava Trees State Monument, Big Island, Hawaii: Photo by Donnie MacGowan

Mauna Loa Tree Molds, Hawaii Volcanoes National Park

But what happens if the lava doesn't drain away and leave the fingers behind, but rather cools in place around the trees? An example of this can be found along the Mauna Loa Road, in the part of Hawaii Volcanoes National Park that is north of Highway 11. Here, large acacia koa trees (the same kind of trees that are currently growing around the parking area) were buried 10-30 feet deep in lava erupted by Kilauea some 700-800 years ago.

Tree Molds on Mauna Loa in 700-800 Year Old Basalt, Hawaii Volcanoes National Park, Hawaii: Photo by Donnie MacGowan

The wet trees chilled and cooled the lava as it surrounded them and thus they were insulated from the intense heat of the surrounding flow. The cooling was rapid enough to preserve the shape, even the texture of the bark, of the trees, though the trees themselves burned away.

Tree Molds on Mauna Loa in 700-800 Year Old Basalt, Hawaii Volcanoes National Park, Hawaii: Photo by Donnie MacGowan

Kalapana-Waikupanaha

But tree trunks are not the only casts and molds that are preserved in molten lava. Sometimes even quite small items, such as coconuts and fruits are preserved with incredibly finely-detailed impressions. Down in the Kalapana-Waikupanaha area of Puna, up against the eastern border of Hawaii Volcanoes National Park, the lava surface is between 30 years and 30 minutes old.

Lava Mold of a Coconut in Basalt from a Very Recent Flow Near Kalapana, Hawaii: Photo by Donald B. MacGowan

Trails leading out to both Kaimu Black Sand Beach and the Waikupanaha Ocean Entry Lava Viewing Area are literally punctuated with preserved palm fronds, pandanus fruit, coconuts and other vegetation debris. The hiker has only to keep his eyes sharp to find hundreds of examples of where the lava has preserved, sometimes in astonishing detail, the forest it flowed through.

Mold of Pandanus Fruit in Basalt from Flow Less Than 10 Years Old, Waikupanaha, Hawaii: Photo by Donnie MacGowan

Devastation Trail, Hawaii Volcanoes National Park

As I mentioned earlier, however, sometimes other volcanic processes also preserve fossils. Along Devastation Trail in Hawaii Volcanoes National Park are some well-preserved tree molds—some with the dead tree still standing in them—from hot ash and cinder erupted from the Pu'u Pua'i vent on Kilauea Iki in 1959.

Dead Tree Standing in Future Tree Mold in Ashfall from Pu'u Pua'i, Hawaii Volcanoes National Park: Photo by Donnie MacGowan

This eruption produced fire-fountains some 1900 feet tall, showering the downwind region with hot ash and cinders. Some of the pieces of volcanic material were so hot they welded together after landing, others were so cool the trees they buried didn't burn. Many trees were completely buried or burned away, but you can still see some, standing above the level of the ground, in what will be tree molds when the trees eventually rot away. There are also numerous examples of already empty tree molds along the trail.

Small Tree Mold Along Devastation Trail, Pu'u Pua'i, Hawaii Volcanoes National Park: Photo by Donald B. MacGowan

Warrior Footprints Trail, Hawaii Volcanoes National Park

Not all the fossils, molds and casts we find in ash and cinder deposits are from plants, either. Although the Hawaiian volcanoes have a reputation as being quiet and well-behaved, rarely violent in their eruptions, such is not always the case. There are quite thick and extensive ash deposits indicating episodes of intensely violent eruption. Called “phreatomagmatic“, these eruptions get their power and violence from ground water entering the magma chamber and flashing to steam, blowing ash high into the atmosphere. Many times the ash produced in these eruptions preserves the material it covers in quite fine detail. One such case can be visited along the Ka'u Desert/Warrior Footprints trail in Hawaii Volcanoes National Park.

Mold of Human Footprint in Ash from 1790 Phreatic Eruption of Kilauea, Hawaii Volcanoes National Park: Photo by Donnie MacGowan

In 1790, a party of warriors was passing by Kilauea on their way to make war on Kamehameha the Great. 400 men, women and children were caught in a giant phreatomagmatic eruption and suffocated where they stood. Another contingent of warriors, coming upon their companions bodies, momentarily thought them merely sleeping until they realized their comrades were all dead. Molds of the footprints left by this second set of warriors are preserved in the ash along the Warrior Footprint Trail; it's an an eerie hike to see them.

Place of Refuge, Pu'u Honua O Hounaunau

Small Bowl Carved into Surface of Basalt, Pu'u Honua O Honaunau National Historic Park, Hawaii: Photo by Donnie MacGowan

Sometimes we find things on the surface of lava flows which do not look like any kind of natural lava flow structure, but they are also not an obvious mold, cast or fossil. Some of these features are obvious human artifacts and not fossils at all. Hawaiians would spend days carving out bowl-shaped depressions into the surface of the rock—once made, they could be used for generations. In just such manner, salt pans for evaporating sea water to get salt were constructed. Larger carved depressions were for cooking. Hawaiians would build a fire in these larger depressions until the rock was quite hot. Scooping away the fire and ash, they would add water and food to cook, sometimes continuing to add hot pebbles to keep the water boiling. Although these features are ubiquitous on the Big Island, excellent examples of them can be found all the way along the beach fronting the temple complex at Pu'u Honua O Honaunau over to Two Step Beach on Honaunau Bay.

Tree Branch Fossil Preserved in Extremely Recent Lava Flow, Kaimu, Hawaii: Photo by Donald B. MacGowan

For more information on traveling to Hawaii in general and touring the Big Island in particular, please also visit www.tourguidehawaii.com and www.lovingthebigisland.wordpress.com. For information about the author, please go here.

All media copyright 2009 by Donald B. MacGowan; all rights reserved.

Eruption! Viewing lava at Hawaii Volcanoes National Park

Written directed and produced by Donald B. MacGowan; Narrated by Frank Burgess; Original Musical Score by Donald B. MacGowan

Can you believe this? It's absolutely outstanding and amazing! You can actually walk right up to flowing lava here; see a volcano erupt before your eyes and the molten rock pour into the sea. This has to be one of the four or five most exciting, amazing, wonderful, mystical experiences on earth...you must not miss this!

Mauna Loa is active but not currently erupting. The summit area is slowly inflating, filling with magma and the flanks are subject to frequent minor earthquakes, but no obvious activity is apparent to the visitor. Kilauea, the most active volcano on Earth, started its current eruptive phase in 1983, the longest eruption in history. Since then it has ejected almost 3 billion cubic meters of lava. Flowing from various vents in the rift, most notably Pu'u O'o, in streams and tubes at over 1000 degrees Celsius, much of the lava makes its way into the sea in fiery, steamy explosions or the incredible incongruity of glowing hot lava pouring directly into the sea with little more apparent than a mere bubbling of the water.

Although surface flows and breakouts are frequent and common, there is no guarantee that over any given trip to the Big Island they will be visible or easily accessible to the casual visitor. Since the flow of lava over the moonscape plains and into the roiling sea can be seen nowhere else on earth, it is certainly the most exciting, unique and moving highlight of any trip to Hawai'i. People stand at the edge of the flow and weep at the majesty and mystery of the earth remaking itself; it is wondrous, remarkable and unforgettable. Before planning a hike to see the lava, check with the Rangers at Hawaii Volcanoes National Park for information on the hike length and location of surface flows and a review of safety information.

The lava seems to glow with only a dull petulance during the day and may be less than inspiring until nightfall brings it alive and the madly glowing, fiery goddess within is revealed. Thus knowledgeable hikers plan their hike to commence in the afternoon, reaching their destination at dusk, and to hike back in the dark. The lava streams and tubes migrate back and forth from time to time over a pali and plain of about 8 miles breadth. Sometimes the hike is a few hundred meters, sometimes a few miles, but it is always over an uneven, rough surface, hot during the day even when it rains, cold at night and navigation can sometimes be counterintuitive. The trail at first is marked with cairns and reflectors, but after the viewpoint overlook at a few hundred meters, you are on your own to navigate the basalt wilderness. Take at least 3 quarts of water for each person and two working (check before you leave!) flashlights per person. It is further recommended that you carry sunscreen, snacks, a first aid kit (that rock is SHARP, cuts are common) and wear sturdy hiking boots and long pants. Remember that you are hiking on a highly active volcano, if flowing streams of lava strand you, no rescue is practical or possible; plan, take care and pay strict attention accordingly.

For more information on viewing the lava, visit www.tourguidehawaii.com and www.lovingthebigisland.wordpress.com.