Are volcanoes a source of atmospheric carbon dioxide? This question is a point of
controversy concerning the greenhouse effect and its potential impact on global
warming. In this activity you will learn how volcanic eruptions contribute to atmospheric
carbon dioxide, the greenhouse effect, as well as global temperatures. Initially, when a
volcano erupts, it ejects many different types of material into the air including a variety
of gasses and ash (small particles of dust). Among these gasses ejected into the
atmosphere are gasses such as water vapor and carbon dioxide. Both of these gasses
are greenhouse gasses and can contribute to the greenhouse effect. Carbon dioxide
levels in the atmosphere have been increasing—now scientists are studying whether
volcanoes are playing a significant role in the greenhouse effect.
- Which contributes more carbon dioxide per year to the atmosphere: volcanic
eruptions or human activity? - Does a volcanic eruption cause a warming or cooling effect?
Large volcanic eruptions deposit water vapor (H2O), carbon dioxide
(CO2), sulfur dioxide (SO2), and other gasses into the environment.
Volcanoes can also put great amounts of ash (small particles of dust)
into the air. As you have learned, carbon dioxide and water vapor are
greenhouse gasses and can contribute to global warming. Water can
combine with other volcanic gasses such as hydrochloric acid (HCl)
and hydrofluoric acid (HF) to fall as acid rain. Volcanoes also emit
sulfur dioxide (SO2) which converts to a fine mist of particulates that
migrate high into the atmosphere. These sulfur dioxide particulates are called sulfate
aerosols, and they reflect sunlight back into space. Sulfate aerosols encourage the
formation of high clouds which also reflects sunlight back into space. Therefore
Explore and Explain
Engage Your Thinking
Activities for Conceptualizing Climate and Climate Change 3
Copyright © 2008, Revised 2014 Purdue University
MIDLATITUDE CYCLONES AND CLIMATE CHANGES LESSON 1
Volcanoes and Global Warming
aerosols and clouds reduce the amount of warming and cause the atmosphere to cool.
Sulfate aerosols tend to stay in the upper atmosphere for long periods of time (months
or even years) until they finally are brought to earth in the form of sulfuric acid. The
volcanic ash in the atmosphere also blocks sunlight from reaching the surface of the
earth causing the air to cool. (The ash eventually falls to the ground.) - What greenhouse gasses are added to the atmosphere during a volcanic
eruption? - Explain how a volcanic eruption cools the atmosphere.
Other factors need to be considered in the study of volcanic eruptions and their impact
on the atmosphere. All volcanoes are not the same. The type of eruption is dependent
on the circumstances that cause the volcanic activity. Volcanoes created by hotspots in
the ocean are rarely explosive and do not eject much ash. Eruptions taking place at
geographic plate boundaries, however, can be very explosive with much ash. Also, the
types and amounts of gasses ejected by each type of volcano differ. Table 1 shows
gasses ejected by three different volcanoes situated at three different geographic
locations. Make a bar graph that shows the amount of H2O, CO2, and SO2 emitted by
the three different volcanoes.
Table 1. Examples of Volcanic Gas Compositions. Source: USGS
Volcano
Tectonic Style
Temperature
Kilauea Summit
Hot Spot
1170°C
Erta` Ale
Divergent Plate
1130°C
Momotombo
Convergent Plate
820°C
H20 37.1 % 77.2 % 97.1 %
C02 48.9 % 11.3% 1.44%
S02 11.8% 8.34% 0.50% - In general, volcanoes eject which gas the most?
Activities for Conceptualizing Climate and Climate Change 4
Copyright © 2008, Revised 2014 Purdue University
MIDLATITUDE CYCLONES AND CLIMATE CHANGES LESSON 1
Volcanoes and Global Warming - Which volcano ejected the greatest percentage of carbon dioxide?
Many people argue that volcanic eruptions are a major cause of carbon dioxide levels in
our atmosphere. In reality, volcanic eruptions contribute very little to the atmosphere’s
carbon dioxide levels. Below are the USGS carbon dioxide emission estimates for
volcanic and human activity (Table 2).
Table 2. Yearly Average Carbon Dioxide Emissions
From Volcanoes: 145 – 225 million tons of CO2
From human activity: 30 billion tons of CO2
Let’s express the volcano amount as about 200,000,000 or 2.0 X 108
tons
The human activity amount is 30,000,000,000 or 3.0 X 1010 tons
Imagine that you will make a bar graph to compare the carbon dioxide contribution of
volcanoes and human activities. (You will not actually make the graph.)
Using a scale with one centimeter representing 1.0 X 108
tons, your bar graph will
represent the carbon dioxide contributed by volcanoes with a bar 2 cm. high.
Volcanoes emit 2.0 X 108
tons of CO2 per year which gives you a bar that is 2 cm. high. - Calculate the height of the bar representing carbon dioxide from human activity.
- How important are volcanoes in adding carbon dioxide to the atmosphere?
Mount Pinatubo is a volcano that lies near a divergent plate boundary in the Philippines.
In June of 1991, Mount Pinatubo violently erupted, and this eruption is now on record as
the second largest volcanic eruption of the twentieth century. The eruption had ten
times the explosive power of the 1980 eruption of Mt. St. Helens in the state of
Washington. Within two hours of the major Pinatubo eruption, gasses and ash reached
high into the atmosphere. During the following two weeks, the sulfate aerosols created
by the blast circled the globe and at the end of a year, the entire atmosphere of the
earth was filled with a layer of sulfate aerosols ejected from the eruption.
Extend Your Thinking
Activities for Conceptualizing Climate and Climate Change 5
Copyright © 2008, Revised 2014 Purdue University
MIDLATITUDE CYCLONES AND CLIMATE CHANGES LESSON 1
Volcanoes and Global Warming
The sulfur aerosols created by the Pinatubo blast reflecting solar energy (heat and light)
back into space and decreased temperatures around the world in 1992 and 1993. In
spite of rising amounts of greenhouse gasses and the presence of an El Nino event
(factors that should warm the atmosphere), the sulfate aerosols reduced global
temperatures in 1992 and 1993 by about 0.4 to 0.5ºC—a global cooling effect. The
United States experienced its third-coldest summer in seventy-seven years.
The 1815 eruption of theTambora Volcano in Indonesia created an even larger global
cooling effect. Global temperatures were lowered by as much as 3ºC. The year 1816
was known as the year without summer in many parts of Europe and North America.
Many Midwest states experienced snowfall in June and frost in July. - What effect do the sulfate aerosols formed by volcanoes have on global
temperatures?
Draw an erupting volcano. In your drawing, draw and label the materials that are ejected by the volcano. Under your drawing, explain what effect each material might
have on the temperature of the atmosphere.
Apply What You Have Learned
Activities for Conceptualizing Climate and Climate Change 6
Copyright © 2008, Revised 2014 Purdue University
MIDLATITUDE CYCLONES AND CLIMATE CHANGES LESSON 1
Volcanoes and Global Warming
10.Which contributes more carbon dioxide per year to the atmosphere: volcanic eruptions or human activity?
11.Does a volcanic eruption cause a warming or cooling effect?
12.What is the major cause of cooling after a volcanic eruption?
13.Please explain how your ideas and thinking about greenhouse gases has
changed.