Ka‘ū News Briefs, Saturday, November 28, 2020

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WATCH FOR NUISANCE COASTAL FLOODING, as a northwest swell and high tides affect Kaʻū shores and shores all over Hawaiʻi Island, through at least Wednesday. The National Weather Service issued a Special Weather Statement Saturday that advises, "Impacts may include flooding of beaches that are normally dry, some minor coastal erosion, and salt water inundation of typically vulnerable low-lying roads, docks, boat ramps and other coastal infrastructure. Additional impacts will be felt as a large incoming northwest swell is expected to produce warning level surf which will coincide with high tide."

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Aerial photograph showing the distal western branch of the Thanksgiving  Eve Breakout. This flow was active on the western side of the TEB flow  field, near the top of the Royal Gardens subdivision and east of Puʻu ʻŌʻō.  The Puʻu ʻŌʻō cone and gas plume are visible in the upper left of the image  and the TEB vent plume is visible in the upper center. Mauna Kea is  visible in the background. USGS photo taken on January 19, 2010.

THIS WEEK'S VOLCANO WATCH, written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates, tales a look back at the Thanksgiving Eve Breakout from 2007:
    Recall this lava flow crisis from years ago: lava breaks out of the normal confines of the long-lived Puʻu ʻŌʻō eruption, with flows advancing relentlessly towards residential areas downslope. Over several months, USGS HVO and County of Hawai‘i Civil Defense Agency monitor the hazards closely in lower Puna as the situation evolves.
    While this scenario describes the highly destructive 2018 eruption on the lower East Rift Zone of Kīlauea, it also pertains to an earlier event on the East Rift Zone: the Thanksgiving Eve Breakout lava flow in 2007.
    Although the TEB flow was much less destructive than the 2018 LERZ eruption, it nevertheless threatened homes in lower Puna for months. The TEB episode also bore important lessons on lava flow hazards that are worth considering in any future rift zone eruption in Hawaiʻi.
    By late 2007, the Puʻu ʻŌʻō eruption, on the middle East Rift Zone of Kīlauea Volcano, was already 24 years old and showed no signs of slowing down. A new vent had formed in July just east of Puʻu ʻŌʻō cone, with lava heading north of the rift zone, forming a large perched lava channel during September through November.
    Early on Nov. 21, the day before Thanksgiving, lava broke out of the vent area on the south flank of the elevated lava channel, and the slope of the channel levees helped direct lava towards the south.
    The new TEB flow slowly advanced downslope towards the south, with the pāhoehoe lava forming a lava tube as it moved. The flow cut through the remains of Royal Gardens subdivision on its course to the ocean.
    The TEB flow reached the coastline, just west of Kalapana, in March 2008. Its lava tube remained active for three years, supplying lava to ocean entries (including the long-lived Waikupanaha entry). The consistent supply through the tube allowed the flow to gradually widen on the low slopes of the coastal plain.
    In mid-2010 the eastward expansion of the flow began threatening Kalapana Gardens subdivision. The subdivision had been covered by lava flows in 1990, with subsequent rebuilding in later years. Between July 2010 and January 2011, a slow-motion lava flow crisis destroyed three homes, while threatening many more.

Puʻu ʻŌʻō flows from 1983 through 2008, episodes 1 through 58. USGS map

    Eventually, a backup of magma in the system near Puʻu ʻŌʻō drove rising pressure, which then caused an intrusion and new vents to form west of Puʻu ʻŌʻō in March 2011. Within weeks, however, activity shifted back to Puʻu ʻŌʻō, and it continued with its eruptive activity from new vents for another 7 years.
    What can we learn from the TEB episode 13 years ago? The main takeaway is that a minor shift in vent position on the rift zone can cause a major change in lava flow direction and the resulting hazard.
    When the TEB breakout started, it moved the vent location by just a stone's throw, and yet it shifted the entire thrust of the flow from north to south. The precise location of a vent relative to the axis of the rift zone, which forms a subtle ridge, can determine which side of the ridge the flows descend. This was also a factor in why lava flows headed northeast during the 2014–2015 Pāhoa lava flow crisis.
    The TEB flow also shows how an eruption can build new features on the rift zone, like lava channels and lava shields, that can influence subsequent flow direction. More recently, during the 2018 LERZ eruption, lava from early fissures built up new topography that contributed to the destructive fissure 8 flow focused northeast towards Kapoho subdivisions. The early lava kept the fissure 8 flow from moving southeast towards less populated areas.
    These examples illustrate why the opening hours or days of a rift zone eruption are so consequential for hazards, both for Kīlauea and Mauna Loa. When an eruption starts, geologists must keep a close eye on the position of fissures relative to the rift zone axis. And they must be on the lookout for growing features like lava channels or shields that may shunt subsequent lava in a new direction.
    The 2007 TEB episode of the Puʻu ʻŌʻō eruption, and rift zone events since then, are a reminder that big changes in hazards can hinge on small changes at the vent. 

 

The Thanksgiving Eve Breakout lava flow in 2007 created a lava tube that helped supply the long-lived Waikupahana entry. USGS photo

    Volcano Activity Updates
    Kīlauea Volcano is not erupting. Its USGS Volcano Alert level remains at NORMAL (https://www.usgs.gov/natural-hazards/volcano-hazards/about-alert-levels). Kīlauea updates are issued monthly.
    Kīlauea monitoring data for the past month show variable but typical rates of seismicity and ground deformation, low rates of sulfur dioxide emissions, and only minor geologic changes since the end of eruptive activity in September 2018. The water lake at the bottom of Halema‘uma‘u continues to slowly expand and deepen. For the most current information on the lake, see https://www.usgs.gov/volcanoes/kilauea/k-lauea-summit-water-resources.
    Mauna Loa is not erupting and remains at Volcano Alert Level ADVISORY. This alert level does not mean that an eruption is imminent or that progression to eruption from current level of unrest is certain. Mauna Loa updates are issued weekly.
    This past week, about 89 small-magnitude earthquakes were recorded beneath the upper-elevations of Mauna Loa; most of these occurred at shallow depths of less than 8 kilometers (about 5 miles). Global Positioning System measurements show long-term slowly increasing summit inflation, consistent with magma supply to the volcano's shallow storage system. Gas concentrations and fumarole temperatures as measured at both Sulphur Cone and the summit remain stable. Webcams show no changes to the landscape. For more information on current monitoring of Mauna Loa Volcano, see usgs.gov/volcanoes/mauna-loa/monitoring.
    There were two events with three or more felt reports in the Hawaiian Islands during the past week: a M2.3 earthquake 17 km (10 mi) S of Volcano at 4 km (3 mi) depth on Nov. 25 at 7:38 a.m. and a M3.1 earthquake 8 km (4 mi) ENE of Pāhala at 31 km (19 mi) depth on Nov. 21 at 6:26 a.m.
    HVO continues to closely monitor both Kīlauea and Mauna Loa for any signs of increased activity.
    Visit HVO's website for past Volcano Watch articles, Kīlauea and Mauna Loa updates, volcano photos, maps, recent earthquake info, and more. Email questions to askHVO@usgs.gov.

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Onset of COVID-19 cases in the last 14 days, by zip code. Gray areas have populations less than 1,000. White is zero cases. Yellow is one to 10 cases. Light orange is 11-50 cases. Dark orange is 51-200 cases. Department of Health map

HAWAIʻI ISLAND REPORTS SEVENTEEN NEW COVID case today. There are two people hospitalized on Hawaiʻi Island with the virus. The average daily case rate for Hawaiʻi Island is nine over the last two weeks.
    New cases reported statewide today total 76, with 48 on Oʻahu, nine on Maui, one on Kauaʻi, and one residents diagnosed out-of-state. The average daily case rate for the state is 94 over the last two weeks.
    Since the pandemic began, 49 deaths have been reported on Hawaiʻi Island. At least 240 people have died in the state, according to state records, none reported today.
    Since the pandemic began, there have been 17,784 total COVID cases in the state. Oʻahu has reported 15,218 total cases, Hawaiʻi 1,591, Maui 530, Lanaʻi 106, Molokaʻi 17, and Kauaʻi 111. Residents diagnosed while out-of-state, 211. Statewide, 1,287 people have been hospitalized since the pandemic began.
    No new cases have been reported in the last 14 days for Volcano zip code 96718 and Kaʻū zip code 96777.
    In the last 14 days, less than ten active cases have been reported in zip code 96704, which includes Miloliʻi; zip code 96772, which includes Nāʻālehu, Waiʻōhinu, and Discovery Harbour; zip code 96737, which includes Ocean View; and Volcano zip code 96785.
    In the last 14 days, 15 cases have been reported in Hilo zip code 96720, 49 in Kona zip code 96740.
    See the Hawaiʻi County COVID-19 webpage. Report violators of COVID-19 safety protocols or quarantine to non-emergency at 935-3311. Hawaiʻi Island police continue enforcement of preventative policies.
    COVID-19 case count in the U.S. is more than 13,227,195 – about 20.9 percent of worldwide cases. The death toll is more than 265,973 – about 18.5 percent of worldwide deaths. Worldwide, there are more than 62 million COVID-19 cases. The death toll is more than 1,449,642.