Module 1, Investigation 1: Volcanic Hazards
Introduction
Welcome!
In this module, you will assume the role of a volcanologist. In this investigation, you will travel
across the globe, visiting a series of volcanoes. As you observe each volcano, examine the
information provided in the placemarks, make observations using the navigation features (pan,
zoom, tilt, rotate) and measuring tools, and record your findings in your field notebook.
If you are not sure when to record your findings, look for this symbol as a reminder:
You will use your data to compare volcanic behavior and impacts. Your challenge is to identify
the unique behavior of each volcano you visit. Knowing the history of a volcano can help you
predict when it will erupt, and how much damage it might cause. After all, the ultimate goal of
most volcanologists is to save lives.
There are many new words you will encounter in your Google Earth travels. Vocabulary words
have a dotted line under them. If you hover over the words a definition will pop up.
Folder 1: Mount Vesuvius, Italy
Volcanic Ash and Pyroclastic Flows
People living in the Roman communities of Pompeii and
Herculaneum desperately tried to survive the deadly blast of Mount
Vesuvius in 79 CE. The ash and rock ejected from Mount Vesuvius
rained down over a large area near the volcano, burying Pompeii in
three meters of tephra. Pyroclastic flows (see video) swept down the
volcano’s sides, engulfing nearby towns, igniting buildings, and
asphyxiating inhabitants.
The volcanic eruption of Mount Vesuvius destroyed both cities,
killing between 10,000 and 25,000 people. The eruption lasted
almost 19 hours and released approximately 4 cubic kilometers (I
cubic mile) of ash and rock into the air.
How much is 1 cubic mile of ash? Using soda pop as a unit of measurement it would be the
equivalent of drinking 32,178,765,952 cans every day for a year!
In Pompeii, 38% of the victims were found buried in ash; 62% were found beneath pyroclastic
flow deposits. Cloth, frescos (paintings), and skeletons were found intact.
Although Herculaneum was closer to Mount Vesuvius than Pompeii was, it did not receive
significant ash fallout. However, it was buried under 23 meters of pyroclastic flow deposits. In
contrast to Pompeii, skeletons and wood fragments found in Herculaneum were severely
charred. Turn on the Ancient Cities Folder and use the ruler tool to determine where Pompeii
and Herculaneum were located relative to the volcano.
Make the observations prompted in your field notebook and interpret that evidence to answer
the questions posed.
[Pyroclastic Flow video]
Folder 2: Nevado del Ruiz, Colombia
Lahars
Nevado del Ruiz has been “active” (erupting occasionally) for
about two million years. Its most recent eruptive period began
about 150,000 years ago. The eruptions produce massive
mud flows called “lahars”. Lahars typically flow down river
valleys and can reach speeds exceeding 160 kilometers per
hour (see video). In 1985, a relatively small eruption caused a
gigantic lahar that buried the town of Armero under several
meters of mud and debris. Approximately 28,700 people died,
making this event the deadliest lahar ever recorded.
The Nevado del Ruiz volcano is steep sided with slopes of 20 to
30 degrees, and is covered by large glaciers approximately 50
meters thick. The 1985 eruption destroyed about 10% of the ice
cover at the summit. Since then an additional 50% of the
volcano’s ice cover has melted as a result of atmospheric
warming. Approximately 500,000 people live within reach of the
volcano’s lahars today. Turn on the Armero placemark to see
where the city of Armero is located relative to the volcano.
Make the observations prompted in your field notebook to help guide future development
near Nevado del Ruiz.
[Lahar video]
Folder 3: Laki, Iceland
Convective Eruption Columns
Can volcanic eruptions affect people in countries far-removed
from the site of the blast? Some scholars think
the eruption of Laki triggered the French Revolution, which
began in 1789 and resulted in hundreds of thousands of deaths.
Laki is part of a large volcanic system on the island nation of
Iceland. During an 8-month period in 1783 and 1784, Laki and
an adjoining volcano erupted, pouring out an estimated 14
cubic kilometers (3.4 cubic miles) of lava, which flowed
from lava fountains rising several thousands of feet high. In
Great Britain, Laki’s volcanic ash fell throughout the summer,
significantly affecting farming.
The volcanoes also spewed forth clouds of gases, including an
estimated 8 million tons of hydrogen fluoride (HF) and 120
million tons of sulfur dioxide (SO2). On Iceland, fluorine
poisoning, which damages bones and joints, killed 50% of the
livestock. This caused a famine, which killed 25% of Iceland’s
residents.
The gases rose in a convective eruption column (see video) to
heights of over 16 km (10 miles). The gases built up in the
stratosphere, creating hazy weather conditions across Europe.
An estimated 23,000 people in Great Britain died from inhaling the sulfur dioxide, which causes
internal tissues to swell, asphyxiating its victims. Europe experienced an extremely cold winter
in 1784, which killed an additional 8,000 people. Even in North America, the winter of 1784 was
the longest and coldest on record; ice formed in the Gulf of Mexico!
Using the ruler tool, make the observations prompted in your field notebook to help identify
factors that can result in a volcano's global impact.
[Convective Eruption Column video]
Summary
Let's Reflect!
You have now toured a few of the deadliest volcanoes on Earth. Let’s see how these travels
have informed your thinking about volcano behavior. Which of the volcanoes you visited do you
think poses the greatest threat today?
Consider the questions posed in your field notebook and record your thoughts.