Hawaii Volcano Blog

Volcano Watch: Geologists Rock!

February 6, 2020, 1:35 PM HST
* Updated February 6, 1:11 PM

A USGS Hawaiian Volcano Observatory geologist measures the height of the growing tephra cone around fissure 8 during Kīlauea Volcano’s 2018 lower East Rift Zone eruption. USGS photo by A. Klesh, June 17, 2018.

Continuing with the Volcano Awareness Month theme of people and their work at the USGS Hawaiian Volcano Observatory, we move on to another role at HVO — that of “geologist.”

A geologist studies the Earth. This includes the study of rocks and the ways in which they form. Specifically, HVO geologists specialize in the numerous forms of volcanic rocks — liquid and solid lava flows and explosive deposits, such as ash.

As lava cools and solidifies, it can take the form of ʻaʻā or pāhoehoe — Hawaiian words used worldwide by volcanologists. Solid volcanic rock can also occur as particles, ranging from fine ash and Pele’s hair to vehicle-sized lava bombs and blocks. In between, there are Pele’s tears (droplets of volcanic glass), scoria and reticulite (forms of basaltic pumice), and spatter (clots of molten lava).

Geologists also try to understand the past to better anticipate the future. As liquid lava turns to solid volcanic rock, it records the processes that formed the rock. Through field observations and petrologic and petrographic analyses, physical and chemical information can be found in the rock at various scales, from micro-sized crystals to lava flows that are kilometers (miles) long.

The HVO geology team studies how volcanic rocks form, how lava erupts and solidifies, and how explosions are triggered. We study how and when the surface of a volcano is created and how and why disturbances such as faulting and collapses happen. We also assess the hazards of eruptions and rock breakage.


The general approach to using geologic data on a volcano is to reconstruct how the volcano formed. We then use this information to model or forecast how the volcano could behave in the future.


Maintaining HVO’s camera network is one of the geology team’s critical jobs. HVO’s current network consists of 22 live web cameras and on time-lapse camera covering 45% of the Kīlauea lava-flow hazard zone 1 area and 36% of the Mauna Loa lava-flow hazard zone 1 area. The camera network provides real-time monitoring of areas that cannot be staffed 24/7. This allows us to track changes in critical areas so that we always know what the volcano is doing.

HVO’s geology group is responsible for the camera network, but it takes many others to keep the network running. HVO engineers help build the camera systems and provide the power systems that keep them running. HVO IT staff ensure that our cameras can transmit images to the website.

Cameras cannot, however, replace “boots on the ground” observations by geologists in the field. How much time we spend in the field depends on volcanic activity. During this relatively quiet time on Kīlauea, we’re in the field one or two days per month. During the 2018 eruption, HVO geologists were in the field seven days per week.


During an active eruption, our field work tasks include collecting lava samples, tracking a lava flow’s growth and advance rate, and assessing if hazards in the affected area have increased or decreased. In both eruptive and non-eruptive times, we also examine older deposits in a continuing study of the island’s volcanic history.

There is no “typical” field day for HVO geologists—our work is determined by what information is needed. For instance, prior to 2018, we tracked Pu‘u ‘Ō‘ō lava flows, as well as the growth of lava deltas, looking for signs of impending collapses or potential explosions. During the 2018 lower East Rift Zone eruption, we measured how fast lava flowed through the fissure 8 channel and checked the boundaries of the lava channel to assess their stability.

Our field work produces many detailed measurements, enabling us to accurately assess volcanic hazards. Examples include monitoring how heat is progressing away from the 2018 dike in lower Puna and measuring the rise of water in the Halema’uma’u crater lake with a laser rangefinder.

HVO geologists also spend time in the office. That’s when we analyze and interpret data collected in the field and write reports that are ultimately published. To help interpret geologic data, we use several computer programs, some of which help us create the maps posted on HVO’s public website. Otherprograms help us create 3-dimensional models of volcanic features, or help us calculate and model lava flow behavior, explosion behavior, and collapse processes.

There’s rarely a dull moment for HVO’s geology team, which is why we enjoy our work. The job of a geologist definitely rocks!

This is the final article about HVO people and jobs in the Volcano Awareness Month 2020 series, but additional HVO teams may write about their work in future Volcano Watch articles.

Volcano Activity Updates

Kīlauea Volcano is not erupting. Its USGS Volcano Alert level remains at NORMAL. Updates for Kīlauea are now issued monthly.

Kīlauea monitoring data over the past month showed no significant changes. Rates of seismicity were variable but within long-term values. Sulfur dioxide emission rates were low at the summit and below detection limits at Puʻu ʻŌʻō and the lower East Rift Zone. The water lake at the bottom of Halema‘uma‘u continued to slowly expand and deepen.

Areas of elevated ground temperatures and minor gas release are still found in the vicinity of the 2018 lower East Rift Zone fissures. Gases include steam (water) and small amounts of hydrogen sulfide and carbon dioxide. These conditions are expected to be long-term. Similar conditions after the 1955 eruption continued for years to decades.

Mauna Loa is not erupting. Its USGS Volcano Alert level remains at ADVISORY. This alert level does not mean that an eruption is imminent or that progression to an eruption is certain.

This past week, 134 small-magnitude earthquakes were recorded beneath the upper elevations of Mauna Loa. The strongest was a M2.4 on Feb. 3, 2020. Deformation indicates continued slow summit inflation. Fumarole temperature and gas concentrations on the Southwest Rift Zone remain stable.

Mauna Loa updates are issued weekly. For more information, go online.

Four earthquakes with three or more felt reports occurred in the Hawaiian Islands this past week: a magnitude-3.3 quake two miles southeast of Fern Acres at a 24-mile depth on Feb. 5 at 8:32 p.m. HST, a magnitude-2.8 quake five miles northeast of Pāhala at a 20-mile depth on Feb. 4 at 8:37 p.m. HST, a magnitude-4.2 quake four miles south of Volcano at a five-mile depth on Feb. 2 at 8:37 p.m. HST, and a magnitude-3.0 quake 12 miles southeast of Volcano at a four-mile depth on Jan. 30 at 1:51 a.m. HST.

HVO continues to closely monitor both Kīlauea and Mauna Loa for any signs of increased activity.


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