Ka`u News Briefs Saturday, November 25, 2017

     All the Giving Tuesday and other donations "raised by our Foundation go directly to enhance the quality of care provided at Kāʻū Hospital and its rural health clinic by enabling the purchase of advanced medical equipment, resources to improve patient and resident care as well as staff training and scholarships," says the Foundation's website. Donations can be made to Kāʻū Hospital Charitable Foundation, P.O. Box 773, Pāhala, HI 96777 or online. For more information, contact
kauhcf@gmail. See more at Ka`u Hospital Charitable Foundation.

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WHAT IS NEW LAND CALLED AT KILAUEA VOLCANO'S OCEAN ENTRIES? That's the question answered by this week's Volcano Watch written by scientists a Hawaiian Volcano Observatory, operated by the U.S. Geological Survey:

An active delta earlier this year on the southeast coast of Kīlauea Volcano. USGS photo

     Those following Kīlauea Volcano's ongoing East Rift Zone eruption are likely aware that when lava enters the ocean, it often forms new land. But what is this new land called?
     A few years ago, "bench" was the term commonly used for the accumulation of lava at an ocean entry. But geologists have moved away from that word, because the geologic definition of a bench does not agree with the process by which new land forms when lava enters the sea.
     "Lava delta" is now the accepted geologic characterization. But, because the word "bench" was used for so long, it can be hard to transition to a different name for the new land formed at an ocean entry. As we all know, bad habits are hard to break.
     The purpose of this Volcano Watch is to help resolve any confusion about what new land at an active ocean entry should be called, and to describe the processes by which lava deltas form and evolve.
     So, why is "bench" the wrong word? First and foremost, to geologists, benches are erosional features, whereas deltas are depositional features, formed by the accumulation of new material.

This cross-section shows the structure of a lava delta and highlights the hazards of these unstable features. Despite layers of cooled, solid lava (brown) on the delta surface, the unstable foundation (white) often shifts along zones of weakness (dashed black line) within the delta. These weak zones are often expressed as large cracks parallel to the coastline on the delta surface. Even if the cracks are superficially covered by new flows, they continue to weaken the foundation, making the lava delta prone to collapse. USGS graphic by J. Johnson

     Coastal benches are nearly horizontal terrains commonly formed by wave erosion over long periods of time. These flat and narrow features form at the base of sea cliffs near the high tide mark. In Hawaiʻi, Hanauma Bay is an example of a bench that cut into the southeast wall of a tuff ring (low relief volcanic crater) next to Koko Head on the Island of Oʻahu.
     Referring to a lava delta as a "shelf" is another common, but misguided, term that's used to describe the ocean entry feature. A shelf is a nearly horizontal, shallow ledge of continental crust that extends below sea level off the coast of a land mass. Island shelves can be found off the coast of the Hawaiian Islands as well, but they are generally much larger than lava deltas.
    In contrast to the erosional origin of a bench, a lava delta is a depositional feature built by the accumulation of lava near the base of the sea cliff at an ocean entry. To understand this process, picture a river delta, like that of the Mississippi.

Lava flowing onto a lava delta, adding on land to the island, but unstable and capable of falling into the ocean. USGS photo

     River deltas are land areas that protrude from the surrounding coastline near the mouth of a river. They form when alluvium, such as silt and sand, is transported down the river and then deposited where the river enters a larger body of standing or slower-moving water, such as an ocean.
     Molten lava insulated in a tube is like a river. It is transported to the coast, where it enters the ocean.
     As the approximately 1140-degree Celsius (2080-degree Fahrenheit) lava flows into the ocean, it quickly cools, creating a potentially explosive interaction. Small explosions and surf action break the lava into smaller pieces of rubbly rock and sand, which are then deposited onto the sea floor beneath the ocean entry. The accumulation of this unconsolidated material produces the unstable foundation on which lava deltas are built.
     As a lava delta continues to grow, its front can begin to subside, because the increasing weight of the delta causes its rubbly foundation to shift. When a lava delta becomes too heavy, or is undercut downslope, it collapses, either partially or completely.
     When a lava delta collapses, it can trigger explosions that throw blocks of solid rock and fragments of molten lava both inland and seaward. Lava delta collapses can further undercut the older sea cliff, causing it to collapse as well. So, a seemingly stable sea cliff in the vicinity of an ocean entry is a hazardous area. Other hazards that accompany lava delta collapses include localized tsunami and large waves that can carry scalding seawater inland.
     Additional information about ocean entry hazards is posted on the USGS Hawaiian Volcano Observatory website athttps://volcanoes.usgs.gov/observatories/hvo/hawaii_ocean_entry.html.

   Names say a lot, and in this case the name describes the process by which a lava delta forms. Calling the feature by other names can be misleading. When enjoying the excitement of lava entering the ocean, remember to call the new land a lava delta.

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VOLCANO VILLAGE ARTISTS HUI'S 31ST ART STUDIO TOUR & SALE winds up on Sunday, Nov. 26, from 10 a.m. to 4 p.m., with the public invited to visit six artists' studios in Volcano Village. Meet artists, view and purchase wide variety of artwork from local artists. Special drawing held at sales end. For more call 987-3472. Find a map of the six participating artists studios at VolcanoVillageArtistsHui.com.

THE ANNUAL DECORATED COTTAGES HOLIDAY CHALLENGE at Kīlauea Military Camp within Hawai‘i Volcanoes National Park began this weekend and continues through Friday, Jan. 1. Open to authorized patrons and sponsored guests, the KMC Cottages are adorned with lighting and decorations for evening strolls. Park entrance fees apply. For more, call 967-8371 or visit kilaueamilitarycamp.com.

JOIN A GUIDED HIKE ALONG THE PALM TRAIL in the Kahuku Unit of Hawai‘i Volcanoes National Park on Sunday, Nov. 26, from 9:30 a.m. to 12:30 p.m. The hike will also be offered on Dec. 3 and Dec. 23.
     Palm Trail is a moderately difficult 2.6-mile loop traversing scenic pastures along an ancient cinder cone, with some of the best panoramic views Kahuku has to offer. Highlights include relics of the ranching era, sections of remnant native forest and amazing volcanic features from the 1868 eruptive fissures.
     For more, visit nps.gov/HAVO.

HOVE ROAD MAINTENANCE BOARD OF DIRECTORS meets Tuesday, Nov. 28, at10 a.m., in the HOVE Road Maintenance Corp. office. For more, call 929-9910.

KA‘Ū FOOD PANTRY offers free food to those in need on Tuesday, Nov. 28, from 11:30 a.m. to 1 p.m., at St. Jude’s Episcopal Church in Ocean View.

REGISTER KEIKI, GRADES K-8, BY TUESDAY, NOV. 28, FOR A FELT WINTER HANGING CRAFT class that takes place Wednesday, Nov. 29, from 3:30 p.m. to 5 p.m. at Pāhala Community Center. For more, call 928-3102 or visit hawaiicounty.gov/pr-recreation.

THE ART OF TAIKO COMES TO NĀ‘ĀLEHU PUBLIC LIBRARY on Thursday, Nov. 30, from 3:30 p.m. to 4:15 p.m. Master taiko drummer Kenny Endo and his Taiko Center of the Pacific ensemble will demonstrate and discuss taiko in group and festival drumming.
     Recommended for ages five and older. Young children must be accompanied by a parent or adult caregiver. For more information, contact 939-2442.
     For a schedule of other upcoming library programs visit librarieshawaii.org/events.