Monitoring & Predicting
by Jared Lubben & Matt Rogers
View of Mauna Loa from Mauna Kea
For decades, geoscientists have been using new and interesting ways to monitor volcanic activity to not only help predict an eruption, but to determine the intensity of eruptions. This web page will focus on three main methods that are used most by volcanologists to monitor and predict volcanic activity. These three main methods include monitoring volcanic gasses, seismic waves and the use of tiltmeters.
Monitoring Volcanic Gasses
Scientists have long recognized that gasses dissolved in magma are the driving forces of volcanic eruptions. Gasses such as sulfur dioxide and water vapor escape when magma rises toward the surface, and when the magma cools and crystallizes below ground.
The primary objective for scientists is to determine changes in the release of certain gasses from the volcano. This is very difficult to do, direct sampling of the gas requires a visit to an active vent, usually high on the volcano's flank.
Three main methods are used to monitor volcanic gas
Emission of gasses from Kilauea Iki
Monitoring Seismic Activity
Moving magma and other volcanic fluids trigger
earthquakes below the surface. When magma rises, pressure is exerted
causing the volcano to swell. This increase in pressure causes
rocks to break, triggering earthquakes. Seismic activity almost
always increases before an eruption. Scientists work to detect
subtle and significant variations in the magnitude of the activity
to determine an eruption. Networks of seismometers, an instrument
that measures ground vibrations caused by earthquakes, are needed
to precisely monitor seismic activity. Presently, computers and
technology have enabled scientists to locate earthquakes faster
and more accurately.
This seismograph, found at the observatory,
monitors the seismic activity at
three different volcanoes. (From left, Mauna Loa, Kilauea Iki, Pu'u O'o)
Diagram of the water-tube tiltmeter
When a volcanic eruption is imminent, the magma and gasses
below the surface cause the volcano to swell. After the eruption,
when the magma below the surface moves back down, the volcano
will subside. Both of these movements are measured by geologists
with a tiltmeter. When the volcano is swelling, the tiltmeter
can measure exactly how much the slope of the volcano is tilting
away from the center of uplift. Usually the movement of this swelling
amounts to a fraction of a degree.
This is the most widely used instrument for measuring the ground
movement of the volcano. A tiltmeter, much like a level, has a
small container with conductivity fluid. In this fluid there is
a bubble that measures a change in slope. Electrodes within the
fluid and the bubble determine the bubble's position. As the bubble
moves, voltage output from electrodes changes in a way that correlates
to the amount of tilt picked up by the tiltmeter. The tilt is
measured in microradians (0.00006 degrees). Different tiltmeters
are also used depending upon the type of volcano, as well as the
expected degree of tilt.
These three methods of predicting eruptions are the most common. However, geologists also use GPS (Global Positioning System), Satellites, and remote sensing data in the prediction of volcanic eruptions.
Highlights from the Trip
View of lava entering the ocean
View of lava entering the ocean
View of the illuminated steam cloud after nightfall
This web page has been brought to you by Jared (left) and Matt