The peak of Kilauea is capable of tossing molten rock over a hundred meters (more than a hundred and fifty feet) in the air, and episode 41 was no different: lava fountains were erupting up to 460-480 meters (1,500-1,575 feet) into the air through two vents within Halema`uma. The show remained in Hawai`i Volcanoes National Park but the aftermath was elsewhere.
The engineering issue of this episode, once at the ground level, was delivery: how the material thrown off a crater gets on highways, overlooks, rooftops, water tanks and in the air that people breathe. Surface layer weak winds with stronger winds aloft, where a column of dense eruption and fine tephra as well as the hair of Pele was carried across the eastern Hawai Island. Downwind communities did report fallout up to Hilo and coastal Puna (over 40 kilometers (25 miles) downwind of the vents).
Draped up close, the stuff was far otherwise coarse. On Highway 11, and in the places of popular view, near Volcano Village, coarser volcanic rocks were dropping in the afternoon, and some of them were reported to be as large as 30 centimeters (approximately 1 foot). Small-to-large fragments were reported in various visitor areas in the park, a reminder that ashfall can consist of hot, dense projectiles around the source- not just of a powdery coating.
The Hawaiian Volcano Observatory at the U.S. Geological Survey reported Tephra in such communities as Volcano Village, Mauna Loa Estates, Ohia Estates, Mountain View, Fern Acres, Kurtistown, Ainaloa Estates, Hilo, Hawaiian Paradise Parks, Hawaiian Beaches and Pahoa.
The same bulletin increased: Fine-grained ash and Pele hair fall in more distant communities (Mountain View, Fern Acres, Kurtistown, Ainaloa Estates, Hilo, Hawaiian Paradise Parks, Hawaiian Beaches, and Pahoa) are fine-grained ash and will continue to fall as the plume spreads out further downwind in a general easterly direction. The falling tephra could be a health risk and can pollute the catchment water sources.
These strands-hair of Pele are not an aesthetic element. They are volcanic glass that has been drawn into a fibre in the active fountaining light enough to travel over long distances and unbearable to the skin and eyes. The risk is chronic since after it settles it may be re-suspended again by subsequent winds, with exposure not to one burst but to a clean-up and health-of-the-population problem that is more protracted.
The charge of pressure which accompanied the display was recorded on instruments in the crater. Uekahuna tiltmeter registered deflation to a matter of a few dozen microradians during the event, which was in accord with magma moving out of storage into the emissions of the eruption. It was also estimated by reference measurements to have had a peak output of approximately 800 cubic meters per second and an erupted volume of approximately 11 million cubic meters of lava or enough to cover most of the floor of Halemaumauma.
Episode 41 also points out the reason why Kilauea can be located at WATCH/ORANGE and yet have a far-reaching impact. The alert level is based on the hazards of people and infrastructure on the ground whereas the color code is based on the aviation risk of ash. Here, the action was limited to the crater and airport business operations resumed, despite localized actions and visibility concerns that trailed the tephra fall along some major park MPassages and Highway 11.
The episode was cut off at about 8 hours and 20 minutes with fountaining ceasing almost at the same time on both the vents. Settlement of ash was slow, the engineering fact of downwind settlement was not an end time, but an oily film of fine particles and glass fibers which can be re-moved at a subsequent change of wind.
