Celebrating Hawai`i's own unusual trees

This is the season when the aroma of pine and fir greets KTA supermarket shoppers as they arrive to buy their fish and poi. Although more than 60,000 trees are imported for the Christmas season, Hawai`i is also home to some trees of its own that deserve hearty celebration.

Adventurers poking around the Big Island will find the spirit of trees past in the form of lava trees and tree molds. These volcanic features are created when fluid lava surrounds a tree and a coating of solid lava forms around the trunk. It might seem that 2,000°F lava would cause a tree to burst into flame and burn away. But when hot lava touches the moist, cool tree, the layer of lava next to the trunk chills and solidifies, insulating the tree from the heat of the oncoming flow. Eventually, the tree does burn to ash or, if the temperature and airflow are right, “bakes” into charcoal. But if the lava flow that encased the tree drains away through a nearby crack or to a lower area, a pillar of lava, or lava tree, remains, rising above the ground’s surface where the tree once stood.

Lava trees are often picturesque, taking on forms ranging from Stonehenge-like obelisks to those resembling Roman coliseums. The top of a lava tree, which can be several meters high, represents the former height of the flow.

When a tree is encased by lava that does not drain away, a cylindrical mold of the tree is formed that appears as a hole in the ground. These holes are often as deep as the tree was tall and an observer can peer downward through the hole to the base of the lava flow.

Some tree molds preserve the original surface texture of a tree so that the bark structure is still visible. Alert observers can find horizontal tree-molds on the surface of lava flows from downed trees, or even within the upright lava trees themselves. Tree molds are most common in pahoehoe flows but are occasionally found in `a`a flows, as well.

Lava trees and molds can be viewed at a number of places within Hawai`i Volcanoes National Park, including around 700-year-old subterranean specimens that can be seen at the Tree Molds area off Mauna Loa strip road. The flows containing these remnants originated from a long-gone shield at the summit of Kilauea.

The above-ground variety can be viewed along the trail to Pu`u Huluhulu, where the eruption of Mauna Ulu, which ended in 1974, left a legacy of spectacular lava trees. Lava Trees State Monument, off of Highway 132 on the lower east rift zone of Kilauea, is home to lava trees and molds left behind from the 1790 eruption. The rift zones and flanks of Mauna Loa are also scattered with examples, as is Haleakala Volcano on Maui.

World travelers can also see lava trees and molds at Craters of the Moon National Monument in Idaho, Newberry Volcanic Park in central Oregon, and at Mount St. Helens National Monument. At Mount Fuji in Japan, a person can traverse a tunnel created from the overlap of upright and horizontal tree molds for over 200 meters.

Lava trees and molds can offer volcanologist clues to the past. By observing the structure of a lava tree, lava flow speed, direction and thickness can be deduced from eruptions that had no human observers. Also, lava trees and molds are a good place to look for tree remnants in the form of charcoal, which can be used for dating flows.

So although in Hawai`i we can seasonally experience the beauty of imported pine and fir trees, those who wish to see lava trees and tree molds will have to visit a volcanic area for a first-hand experience. And one distinct advantage to lava trees is that they don’t have needles to lose.

Activity Update

Eruptive activity of Kilauea Volcano continued unabated at the Pu`u `O`o vent during the past week. Lava flows through a tube system from the vent to the sea. Lava continues to enter the ocean at the Wilipe`a and West Highcastle lava deltas. A new ocean entry from the east arm of the Mother’s Day flow developed on December 9 in the area between Highcastle and Lae’apuki. Numerous surface breakouts are observed in the coastal flats from the base of Paliuli to the coast. The public is reminded that the ocean entry areas are extremely hazardous, with explosions accompanying sudden collapses of the new land. The steam clouds are highly acidic and laced with glass particles. The National Park Service has erected a rope barricade to delineate the edge of the restricted area. Do not venture beyond this rope boundary and onto the lava deltas and benches.

There were no felt earthquakes in the week ending on December 12.

Mauna Loa is not erupting. The summit region continues to inflate. The earthquake activity is low with only 2 earthquakes located in the summit area during the last seven days.

This article was written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory and is republished by HawaiiNews.com with permission.

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