The Earth's magnetic field surrounds us every second of the day, everywhere on Earth. Anyone who has picked up a pocket compass and watched the magnetic needles quickly align has seen this ever-present invisible field at work. But can we use magnetic fields to predict volcanic activity? Emerging techniques in the field of “quantum” science may help.
On a large scale, the Earth's structure is divided into four main layers: the crust, the mantle, the inner core, and the outer core. The outer core begins at about 1,800 miles (2,900 km) beneath its feet, extends further to 1,400 miles (2,260 km), and is composed primarily of iron and nickel. At these depths, the temperature (about 9,000 degrees Fahrenheit or 5,000 degrees Celsius) keeps the outer core fluid and constantly in motion. This move sets up a process similar to the generator you are familiar with. In other words, the movement of a metallic fluid generates an electric current. These currents generate the Earth's magnetic field. This is the same one you use to point your compass north.
In volcanoes, fluctuations in the magnetic field result from four main sources. These are long-term changes related to changes in the motion of the Earth's outer core, external currents, space weather phenomena (such as solar flares), and changes in the magnetic properties of rocks. Caused by volcanic activity. In general, the changes caused by the first three sources of variation can be considered to be relatively uniform over small areas, and measurements at remote but “local” and “magnetically quiet” reference locations can be used to correct them.
The rapid magnetic changes associated with volcanic activity are typically very small, on the order of 1 to 10 nanoteslas (nT). For comparison, the magnetic field strength of a refrigerator magnet is approximately 5 million nT. The sensitivity of magnetic measuring instruments (“magnetometers”) determines whether they can detect volcanic changes amid the considerable noise generated by other non-volcanic electromagnetic fluctuations. These volcanic fluctuations can arise from changes in rock magnetization caused by stress redistribution or changes in the thermodynamic state of the volcanic edifice.
Italy's National Institute of Geophysics and Volcanology (INGV) has been building a magnetic monitoring network on Mount Etna for more than 20 years. This network consists of his eight observation points on the volcano and one reference station. All stations measure the sum of the local magnetic field every 5 seconds, and the network is designed to easily distinguish between sources of deep and superficial changes.
INGV has shown from long-term time series data that observed magnetic field fluctuations are often due to shallow magma intrusions (when magma moves to new areas below the surface but fails to erupt). Ta. These intrusions cause permanent magnetic anomalies, which, along with observed earthquake swarms and ground deformation, generally precede and accompany the movement of magma toward the surface. For example, INGV observed pre- and post-eruption magnetic anomalies during Etna's 2001, 2002, and 2008 eruptions.
At Kilauea, measuring changes in the magnetic field to monitor the volcano has only been studied for a short period of time. Initial investigations were conducted by geologist Gordon McDonald of the USGS Hawaii Volcano Observatory (HVO) in his 1950-1951 years. Mr. MacDonald recognized that the conditions were not ideal, but he did his best given available time, staffing, and the current state of technology.
Twenty years later, in 1973, HVO geologist Paul Davis determined that daily averages of records from three synchronous magnetometers on Kilauea showed that the local magnetic field change during the ongoing eruption of Mauna Ulu was 1.5 nT. revealed something. A few years later, USGS volcano geodesist Dan Dzurisin operated a small magnetometer network, but the results were never published.
Newly available quantum-based sensors, as well as recent instrumental advances in measuring the absolute acceleration of gravity, have opened the door to traditional magnetic monitoring challenges. These new quantum magnetometers offer sensitivity and data rates comparable to traditional technologies, but require significantly less power and are easier to install. The new sensor is dramatically smaller, about the size of your thumb.
Although HVO does not currently operate a quantum-based magnetometer, the observatory is constantly testing the potential of new technologies for volcano monitoring. The questions we ask about volcanoes – when and where do they erupt – fundamentally remain the same, and our ability to answer them only improves as technology advances. Will magnetic monitoring be the future of monitoring Kilauea Volcano, as HVO scientists hoped 70 years ago? I don't know yet, but I'll let you know when I find out!
Latest information on volcanic activity
Kilauea has not erupted. The USGS Volcano Alert Level is ADVISORY.
Over the past week, the rate of seismic activity beneath the summit has increased but remains low compared to periods prior to recent intrusions or eruptions. Approximately 365 events were detected, nearly double the number from the previous week. Inclinometers near Sand Hill continued to record inflationary trends. Ongoing ground deformation patterns in the southwest rift indicate that magma continues to move down the rift in this region. No unusual activity has been observed along the East Rift Zone.
Mauna Loa is not erupting. The USGS Volcano Alert Level is NORMAL.
The webcam shows no signs of activity on Mauna Loa. Seismic activity at the summit has remained at low levels for the past month. Ground deformation indicates continued slow expansion as magma replenishes the reservoir system after the 2022 eruption. SO2 emission rates are at background levels.
Two earthquakes were reported in the Hawaiian Islands in the past week. One was a M3.2 earthquake that occurred 5 km (3 miles) south of Pahala at a depth of 32 km (20 miles) on April 15 at 8:16 a.m. PST, and the other was a M2.8 earthquake. . The earthquake occurred at 6:31 a.m. Pacific time on April 15, 5 kilometers (3 miles) south of Pahala and at a depth of 32 kilometers (20 miles).
HVO continues to closely monitor Kilauea and Mauna Loa.
Visit the HVO website for past Volcano Watch articles, updates on Kilauea and Mauna Loa, volcano photos, maps, recent earthquake information, and more. Please email your questions to askHVO@usgs.gov.
