Remote Sensing Used in Monitoring Active Volcanoes
Cara Haas
ES 771 Remote Sensing Fall 2007
Image taken from:nai.arc.nasa.gov/.../images/volcano_small.jpg
Volcanic eruptions are spectacular events and studying
these natural phenomena can be an unbelievable journey. But the dangers
and constraints of ground observations left a gap for scientist to fill
in regards to observing active volcanoes. Remote sensing has increased
throughout the last decades and has became a popular tool for observing
active volcanoes throughout the world. Remote sensing is the
measurement or analysis of properties of the Earth's surface from a
location not in physical contact with the objects in view (USGS 2006).
There are numerous active volcanoes on planet Earth, monitoring all of
these volcanoes can be a task, therefore numerous techniques of remote
sensing contributes to accurately collecting data and observations.
New
developments in remote-sensing techniques have expanded the capability
of scientists worldwide to monitor volcanoes using satellite. Two types
of satellites are used for monitoring active volcanoes. One is known as
"geostationary" while the other satellite is known as "low Earth
orbit". Satellites are used for six main objectives in regards to
volcanic eruptions: 1) Rapid detection of an eruption plume, 2)
monitoring thermal energy emitted from the volcano, 3) large area
mapping of surface deformation of a volcano, 4) measurment of volcano
topography and topographic change, 5) illustrating spatial distibution
of ash, gases and aerosols produced by eruptions, and 6) referencing a
data set for each volcano for quantifying of future changes (Johnson
et. al 2000). One of the objectives is to illustrate the spatial
distribution of the eruption cloud. This can be carried out through the
use of satellite imagery. When a volcano erupts it emits a massive
amount of gases into the atmosphere immediately heating the air above
the opening of the volcano. With time, the eruption cloud is moved by
wind patterns and spreads out over an area. The movement of volcanic
emissions can have short-lived impacts or can have effects that last
for several years. This process can have impacts on weather and climate
over local or global areas affecting overall climate variability.
| The image to the left shows the eruption cloud approximately
1.5 hours after the actual eruption occurred. The blue color portrays
warm temperatures whereas the red color illustrates colder
temperatures.
|
Image taken from:http://volcanoes.usgs.gov/About/What/Monitor/RemoteSensing/WXTRsatellites.html
| The image to the left was taken approximately 3 hours after
the actual eruption. Notice the size of the eruption cloud compared to
the size of the cloud in the image above. Again, the blue color
represents warm temperatures and the red color illustrates colder
temperatures. |
Image taken from:http://volcanoes.usgs.gov/About/What/Monitor/RemoteSensing/WXTRsatellites.html
Volcanic
processes can occur far below the Earth's surface, therefore not being
visible to the naked eye. Thus, radar provides a new tool to help study
and understand the structure of a volcano. Radar interferometry is used
for two main reasons: 1) to examine the topography of a volcano and 2)
to map surface changes such as lava flows or deformations. This helps
in providing a safe enviornement as well decreasing the amount of
on-site information needed. This allows researchers to study volcanoes
in all types of enviornments. Interferograms are the result of two
radar images combined, differentiated only by time. These images can
locate magma flow by mapping surface deformations, which assist in
monitoring and analyzing subsurface activity. Radar is more widely used
because there are fewer restrictions on the actual image taking
process. Radar is able to penetrate clouds, therefore there are fewer
limitations on the time of day or altitude that the radar process is
carried out. Monitoring hotspots is an example of how radar is used in
monitoring volcanic activity. Impacts of volcanic eruptions can affect
homes, populations, agriculture use, etc. Thus, predictions of
potential volcanic activity can be produced in a timely fashion,
essential for hazard alertness. Radar interferomtery provides complete
spatial coverage from space therefore can provide forecast and
predictions of volcanic activity before the eruption occurs.
| The image to the left illustrates a monitoring image of a
hotspot. The red color portrays an area where deformation is occuring.
This could mean volcanic activity is occuring beneath the Earth's
surface such as a magma chamber shift. The yellow dot represents the
actual hotspot.
|
Image taken from:http://goes.higp.hawaii.edu/bigisland/lasthot.png
Ultraviolet Remote
Sensing is used to produce measurements and data of volcanic emissions
during the actual eruption. Thus, Ultraviolet remote sensing can be
used to monitor the emissions of sulfur dioxide and ash contents
emitted into the atmosphere as volcanic clouds. This technqiue for
monitoring eruptions provides a safe environnment to view and model
volcanic clouds. Ultraviolet remote sensing maps atmosphere components
rather than just photographs an active volcano. Data collected from
this type of Remote Sensing helps in calculating sulfur budgets,
tracking volcanic clouds and can estimate the volcanic eruptions
impacts on the earth's atmosphere. The instrument used during
Ultraviolet processes is known as the Total Ozone Mapping Spectrometer
or TOMS. This instrument is a ultraviolet spectrometer that monitors
the ozone and fluctuating trends of the atmosphere by measuring
reflectance and scattering using six different wavelength bands. This
is done by measuring temperature variations. Most of the impacts close
to the eruption itself such as lava flows, landslides, etc. can be
observed by photographs, but the gases emitted from an active volcano
can have impacts on the climate and weather long after the actual
eruption occurs. Here TOMS is used to observe the amount of emissions
and their impacts on the Earth's atmosphere. An example of this process
is the conversion of sulfur dioxide into sulfate aerosols once emitted
into the atmosphere. This type of volcanic aerosol can impact the
atmosphere's chemistry and global climate by increasing atmospheric
albedo, the reflection of solar radiation or modification of greenhouse
gases. The Total Ozone Mapping Spectrometer can observe these impacts
and also help predict future climate and weather fluctuations. The
first time TOMS was used to accurately detect sulfur dioxide in the
atmosphere was after the eruption of El Chichon, Mexico in 1982.
| The image to the left is of the sulfur dioxide cloud emitted
from the 1982 eruption of El Chichon, Mexico. The image is portraying
the drift of the aerosols four days after the actual eruption. |
Image taken from:"Remote Sensing of Active Volcanism".
Volcanoes differ from other
natural hazards because they are located in fixed-areas. This is an
advantage for the use and accuracy of remote sensing applications with
regards to active volcanoes. Remote sensing is able to monitor
volcanoes in the most isolated areas without extensive manpower.
Without the need for personnel to perform on-site obervations the
endangerment to human life has been minimized. Though remote sensing
has helped in many aspects of data collecting, the ability to gather
data directly from a satellite has improved the timely fashion of
studying volcanic eruptions. Before the use of remote sensing in active
volcanism, scientists had to gather on-site data and process the data;
eventually producing images and models. Now, with the snap of image
from a satellite instrument, the events taking place internally and
externally of a volcano can be observed in a matter of minutes. As this
website discusses, remote sensing has had a major impact in
contributing to the understanding and predicting the life of active
volcanoes. This will not only save time, lives and resources but can
also help in predicting the future of our planet.
If interested in the active volcanoes of today's world click on the following website:
http://www.geocodezip.com/v2_activeVolcanos.asp?lat=20.149&lon=163.535&type=map&zoom=1
Hawaii Institute of Geophysics and Planetology. "About our GOES 9/10/12 Image Products". URL:
http://images.google.com/imgres?imgurl=http://goes.higp.hawaii.edu/bigisland/lasthot.png&imgrefurl=http://goes.higp.hawaii.edu/about.html&h=468&w=440&sz=130&hl=en&start=10&tbnid=YrXIjT6KvNgpaM:&tbnh=128&tbnw=120&prev=
Mouginis-Mark, Peter J., Joy A. Crisp, Jonathan H. Fink. 2000. "Remote
Sensing of Active Volcanism". American Geophysical Union. pgs. 272.
Robock, Alan and Clive Oppenheimer. 2003. "Volcanism and the Earth's Atmosphere". American Geophysical Union. pgs 360.
USGS. 2000. "Monitoring Volcanic Gases: the driving force of eruptions". URL: http://volcanoes.usgs.gov/About/What/Monitor/Gas/GasMonitor.html
USGS. 2001. "Detecting Eruption Clouds with Weather Satellites".
URL: http://volcanoes.usgs.gov/About/What/Monitor/RemoteSensing/WXTRsatellites.html