# Document Id: 10_30_02_1

# Date Received: 2002-10-10 Date Revised:2002-11-27 Date Accepted: 2003-0109

# Curriculum Topic Benchmarks: S1.4.2, S1.4.3, S2.4.6

# Grade Level: High School \[9-12\]

# Subject Keywords: volcanoes, clouds, remote sensing, satellite images, gases, aviation hazards

# Rating: moderate

# 

# Volcanic Clouds and the Atmosphere

**By:** Lizzette A. Rodriguez, Department of Geology, Michigan
Technological University, Houghton, MI 49931 e-mail:larodrig@mtu.edu

# 

# From: The PUMAS Collection http://pumas.jpl.nasa.gov

# © 2002, California Institute of Technology. ALL RIGHTS RESERVED. Based on U.S. Gov\'t sponsored research. 

# 

## 

## Introduction

We frequently hear about volcanoes, eruptions, explosions, and probably
think these things will never affect us, that volcanoes only exist at
places far away. However, they should be a concern to everybody, since
more than 50 volcanoes scattered throughout the world are active every
year and their eruptions affect millions of people. Volcanic explosions
produce clouds, which the atmosphere transports. This means that
volcanic clouds can travel long distances and affect people that live
far from their sources. Volcanoes that have been active in the last 20
years include Mount St. Helens, Washington (1980); Kilauea volcano,
Hawaii (erupting since 1983); Mount Etna, Italy (2001); and Pinatubo,
Philippines (1991).

Volcanic clouds contain many components, such as volcanic gases, ash,
water, and aerosols. Eruptions carry large amounts of sulfur gas
species, as well as other particles, and what happens to them in the
atmosphere is not very well understood. In the stratosphere, sulfur
dioxide gas combines with water vapor to make tiny droplets of sulfuric
acid, which reflect solar radiation back to space, reducing the amount
of the sun's energy that reaches the surface, and affecting global
climate. Winds at the time of eruption and the volcano's latitude
determine the spreading of the cloud. Examples of eruptions that have
affected global climate are El Chichon in Mexico (1982; it produced
global cooling \~0.3-0.5 ^o^C) and Pinatubo in the Philippines (1991;
global cooling \~0.6 ^o^C). Such large eruptions occur about once every
decade.

**How do we study these phenomena?**

Along with traditional monitoring techniques (using ground-based
instruments and direct sampling), scientists are currently using data
obtained from satellite remote sensors, which have numerous applications
for volcano monitoring. Remote sensing is the detection by a
satellite\'s sensors of electromagnetic energy that is absorbed,
reflected, radiated, or scattered from the surface of a volcano or from
the plume of material it produces. A variety of sensors are used to
measure wavelengths of energy beyond the range of human vision, such as
ultraviolet, infrared, and microwave. Examples of web sites related to
remote sensing and volcanic clouds:

<http://www.geo.mtu.edu/volcanoes/>: Michigan Technological University's
Volcanoes Page -- particular links on /volcanoes/ are more relevant to
this example than others (i.e. Volcanic Clouds site and Remote Sensing
of Volcanoes site).

<http://volcanoes.usgs.gov/About/What/Monitor/RemoteSensing/WXTRsatellites.html>:
Detecting eruption clouds with weather satellites and images from Mt.
Spurr eruption

**Activity 1:** Why do we see things when using satellites?

1.  Turn off the lights in the room.

2.  Bang two erasers together, creating a cloud of dust.

3.  Ask the students if they can see the dust (if it is dark, they will
    not be able to see it).

4.  Shine a flashlight at the dust cloud, but not toward the students.

5.  The students can see the cloud now. Why? Because some of the light
    is scattered off the particles and back to their eyes.

6.  Leave them with a question: What takes the place of the flashlight
    for satellite sensors? After all, most satellites do not come
    equipped with searchlights that shine down on Earth.

Sunlight is scattered off of different materials, like volcanic ash, and
back to the satellite. This is why satellite data images, taken at
different times, can show the trajectory of volcanic clouds through the
atmosphere.

**Activity 2:**

Look at some examples of satellite images of volcanic clouds from the
Internet:

<http://www.geo.mtu.edu/volcanoes/research/diss/examples/images/>:
Examples of AVHRR (sensor used for volcanic ash studies) images. Links
for images of eruptions at Augustine volcano, Mt. Spurr, and Redoubt
volcanoes (Alaska) are found on /images/Augustine, /images/spur, and
/images/redoubt/, respectively.

<http://www.geo.mtu.edu/volcanoes/research/diss/examples/geostationary/ruapehu.html>:

Ruapehu Volcano, New Zealand satellite movies

**Activity 3:**

How far did the cloud travel? How might an aircraft be affected?

Atmospheric scientists use computer models to forecast the position of a
moving volcanic cloud for many hours into the future by using wind data
at various levels.

1\. Use the National Oceanic and Atmospheric Administration's (NOAA)
Volcanic Ash Forecast Transport and Dispersion (VAFTAD) model to create
and view the trajectory of a hypothetical volcanic cloud

2\. Go to VAFTAD's web site:
<http://www.arl.noaa.gov/ready/vaftadmenu.html>

3\. Go to **Run VAFTAD** model and click on **hypothetical**

4\. This page gives you a table with the names of different volcanoes
and the different modes and times after eruption that you can model.

5\. Choose a volcano, e.g. Augustine volcano, Alaska, with +12 & +24 hrs
and look at the trajectories the clouds would follow if they erupted
today.

Hazards to aviation are among the reasons that have stimulated research
on the satellite detection and tracking of volcanic clouds. If an
airplane flies through a volcanic cloud, its engine can suck in the ash,
and under these high temperatures it will start melting and adhering to
the engine. The aircraft might even ingest small rock projectiles, if
close to the volcano. There have been more the 80 incidents of jet
aircraft encountering volcanic clouds in the last two decades, some of
which resulted in the in-flight loss of engine power. Satellite images
provide critical information needed to keep commercial aircraft from
entering an eruption cloud downwind from the volcano.

<http://www.geo.mtu.edu/department/classes/ge404/gcmayber/>: Volcanic
Ash Clouds and Aircraft Safety. Links on this site lead to information
about aviation safety and descriptions of historic incidents.

<http://volcanoes.usgs.gov/About/What/Monitor/RemoteSensing/RemoteSensing.html>:

Composite satellite image showing the movement of an eruption cloud from
Mt. Spurr volcano, Alaska, through time (September 16, 1992). The cloud
disrupted air traffic in Canada and the US, as long as 5 days after the
eruption.