Volcano Watch: Thermal Cameras Keep a Cool Eye on Hot Lava
Thermal cameras have been used by volcanologists around the world for many years to study volcanic processes and search for signs of impending eruptions.
On Kīlauea, data from thermal cameras are used to track the level and movements of the summit lava lake within Halemaʻumaʻu. This helps us better understand lake behavior and the inner workings of the volcano. Insights gained from thermal images continue to teach us how molten lava erupts, degasses and, over geologic time, changes the landscape.
Thermal cameras work by measuring energy in the long-wave infrared part of the emitted light spectrum (8 to 14 micrometers). That energy is translated into a temperature value using principles of physics.
Included with this article are two recent thermal images of Kīlauea Volcano’s summit lava lake. Colors correspond to surface temperatures: darker colors indicate cooler surfaces and lighter colors represent molten and recently solidified lava.
The scale at right does not reflect true temperatures due to a variety of factors, including the obscuring effects of volcanic fume. Actual lava temperatures for the hottest areas in these images would be about 1150 degrees Celsius (2100 degrees Fahrenheit). But, relative temperatures are still correct. Hot is hot!
The field of view in each frame is roughly 660 feet across. In this view, the lake surface is about 410 feet below the camera.
In these images, captured at 4:05 p.m. (left) and 4:42 p.m. (right) local time on July 28, 2017, you can see a dramatic difference in lava lake surface characteristics. The difference resulted from a sudden collapse of lava veneer, the rocky coating left on the vent wall by spattering and previous higher stands of the lake.
The 4:05 p.m. image shows typical lake conditions, with spattering on the northeast lake margin. About a dozen different-sized plates of semi-solid crust on the lake surface slowly circulate. Jagged and straight cracks form as the plates pull apart, revealing molten lava beneath the crust. Bright areas, where the foundering of crustal plates churns up molten lava, are also visible.
At 4:28 p.m., a large patch of veneer—perhaps 165 feet wide and 100 feet high—cascaded into the lava lake, leaving behind a hot scar (circled in right image). The impact of this rocky debris falling into the lava lake caused agitation that persisted for tens of minutes. That disturbance broke the surface crust into dozens of microplates and possibly promoted new spattering along the lake margins.
HVO’s thermal camera at Halemaʻumaʻu has functioned well for over six years, sending data to us around the clock. The camera has a 53-degree-wide lens housed in a modified Pelican case for protection from weather, corrosive volcanic gas, and occasional bombardment by molten spatter. The box is mounted on a well-anchored, sturdy tripod. Images are transmitted by WiFi connection to HVO, where they are collected on computer servers for delivery to our public web site and to HVO staff for analysis.
HVO also maintains thermal cameras that look into the Pu‘u ‘Ō‘ō crater on Kīlauea’s East Rift Zone and Moku‘āweoweo caldera atop Mauna Loa. These cameras capture an image every 2–3 minutes. At Pu‘u ‘Ō‘ō, if a hot spot fills more than five percent of the camera images, a computer program sends a text message with an embedded image to HVO staff. Our Mauna Loa camera is similarly alarmed. If high temperature is detected, a text message is automatically sent to HVO staff. Upon receiving a text, we check other monitoring data (including more recent webcam images) to see if lava has suddenly appeared or if there is other cause for concern.
In the coming year, we hope to upgrade the Halemaʻumaʻu thermal camera to a new model that will acquire higher resolution images. Better images will allow even more detailed analyses and enhance tracking of lava levels.
An online interview with HVO geologist Matt Patrick tells more about how scientists use thermal cameras to study Kīlauea Volcano’s summit lava lake. He has also written a paper on the use of thermal cameras at Kīlauea and Mauna Loa, which is available at https://appliedvolc.springeropen.com/articles/10.1186/2191-5040-3-1.
Follow the changing lava lake activity, as seen through the eyes of a thermal camera, on HVO’s website.
Volcano Watch is a weekly article written by U.S. Geological Survey`s Hawaiian Volcano Observatory scientists and colleagues.