by US Geological Survey Hawaiian Volcano Observatory scientists and affiliates. This week’s nonfiction was written by National Science Foundation Postdoctoral Research Fellow Lis Gallant.

In the past fewer months, “Volcano Watch” articles person introduced respective probe projects funded by the Additional Supplemental Disaster Relief Act of 2019 (H.R. 2157). Each of these projects volition assistance scientists amended recognize however Kīlauea volcano works and however the 2018 little East Rift Zone eruption and illness of Kīlauea acme happened. 

Scientists from the USGS Hawaiian Volcano Observatory and collaborators from the University of South Florida had the unsocial accidental to get a peek astatine the layers inside Ahuʻailāʻau (the cone that formed around fissure 8) with crushed penetrating radar implicit the summer.  

GPR is simply a method that uses tiny radar pulses to observe objects and changes beneath the ground. When these pulses are transmitted into the ground, they brushwood things similar faults oregon the bound betwixt different lava layers. They deed these obstacles and bespeak backmost towards the surface, wherever they are captured by a receiving antenna. Unlike aesculapian X-rays, GPR uses low-frequency vigor waves nary much almighty oregon harmful than those picked up by household radios. Essentially, GPR allows america to “see” wrong of the cone successful a mode that does not harm it successful the long-term. 

The transmitter and receiver are attached to a sled and guided on the crushed aboveground and the information are collected successful lines. We usage antithetic enactment directions and orientations to necktie the lines unneurotic truthful we can get an idea of the layers beneath the aboveground successful 3D. 

You whitethorn beryllium wondering however heavy into the cone we are capable to see, and the reply to that question depends connected 2 main things. The archetypal is the wavelength of the vigor we transmit with the GPR—the longer the wavelength, the larger the antennae size, and the deeper we tin see. The 2nd is the benignant of crushed we tally the survey on—very bedewed clays and soils mostly marque for poorer survey conditions, whereas adust and hard layers are better. Luckily, things similar lava and tephra make for fantabulous survey conditions!  

We were capable to representation 50 feet (15 meters) into the cone for the Ahuʻailāʻau GPR survey utilizing 100 megahertz (MHz) antennas. The information collected from GPR surveys are plotted connected a “radargram.” Radargrams whitethorn look similar modern creation prints, but to the trained eye of a geophysicist these plots archer america a large woody astir what is lurking beneath the surface. 

The main intent of this GPR survey was to assistance HVO scientists amended recognize however cinder cones grow. The sanction “cinder cone” is simply a spot of a misnomer due to the fact that features like Ahuʻailāʻau are not built wholly retired of azygous piles of cinders. In fact, Ahuʻailāʻau is mostly basaltic pumice!  

Most cartoon drawings of cinder cones exemplify their insides similar a multi-layered barroom that slopes down and outwards from a cardinal precocious point. Some of these layers are made of cinders (the cake), portion others tin beryllium bits of lava that were inactive molten erstwhile they landed connected the sides of the cone (the icing). As things similar the fountain tallness and the upwind absorption change, truthful excessively bash the thickness and determination of the eruptive deposits.  

The pictured radargram shows that things are a small much analyzable and not astir arsenic delicious arsenic the elemental sloped barroom model. The precocious portion of the cone successful this country is made mostly of tephra (fragments of lava that question done the aerial earlier being deposited connected the ground). These layers are variably heavy and are not continuous down the flank of the cone. There is small spatter—globs of lava that instrumentality unneurotic erstwhile they land—present, arsenic well.

Essentially, we person a precise lumpy barroom that lacks good defined layers and contains lone a tiny magnitude of icing. The sections of the cone that bound the opening into the spillway incorporate a greater magnitude of spatter than the conception shown successful the radargram.

Combining our survey results with monitoring information and different geophysical surveys allows america to recognize however this salient diagnostic formed during the three-month-long eruption of Kīlauea’s little East Rift Zone successful 2018. We program to stock the results of this Ahuʻailāʻau survey aft we implicit the information processing.

Volcano Activity Updates

Kīlauea volcano is erupting. Its USGS Volcano Alert level is at WATCH.

Over the past week, lava has continued to erupt from the western vent within Halemaʻumaʻu crater successful Hawai‘i Volcanoes National Park. Sulfur dioxide emission rates stay elevated and were past measured at approximately 1,300 tonnes per time (t/d) connected September 7. Seismicity is elevated but stable, with fewer earthquakes and ongoing volcanic tremor. Over the past week, acme tiltmeters recorded 2 deflation-inflation (DI) events.

Mauna Loa is not erupting and remains astatine Volcano Alert Level ADVISORY. This alert level does not mean that an eruption is imminent oregon that progression to an eruption from the existent level of unrest is certain.    

This past week, astir 158 small-magnitude earthquakes were recorded beneath the acme and precocious elevation flanks of Mauna Loa—the bulk of these occurred astatine shallow depths little than 15 kilometers (9 miles) beneath oversea level. Global Positioning System (GPS) measurements amusement debased rates of ground deformation over the past week. Gas concentrations and fumarole temperatures astatine some the acme and astatine Sulphur Cone connected the Southwest Rift Zone person remained unchangeable implicit the past week. Webcams amusement nary changes to the landscape.

Two earthquakes were reported felt successful the Hawaiian Islands during the past week: a M3.2 earthquake 11 km (7 mi) ENE of Pāhala astatine 31 km (19 mi) extent connected September 14 astatine 4:20 a.m. HST and a M3.3 earthquake 18 km (11 mi)  WSW of Hilo astatine 38 km (24 mi) extent occurred connected September 13 astatine 1:39 a.m. HST.

HVO continues to intimately monitor Kīlauea’s ongoing eruption and Mauna Loa for immoderate signs of accrued activity.

Volcano Watch is a play nonfiction and enactment update written by US Geological Survey Hawaiian Volcano Observatory scientists and affiliates.