Name:
Homeroom:
Volcanoes: Explosive and Effusive
Background Knowledge: Volcanic eruptions may be explosive (violent) or effusive (passive), depending
on the lava chemistry (amounts of silica and dissolved gases). Silica is a mineral found in nature as sand
or quartz. High levels of silica mean very viscous (thick) lava, and low levels mean more fluid lava.
Dissolved gases like sulfur dioxide, water vapor, and carbon dioxide build up inside the volcano, similar
to how carbon dioxide builds up inside a can of soda that has been shaken. The higher the level of gas,
the more pressure that builds – and the more violent an explosion. The combination of silica and
dissolved gas levels determine the type of eruption and shape of the volcano. Volcanoes are classified
by their shape and lava chemistry.
My Notes of the Background Information:
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Lava Viscosity:
Not all volcanoes have the same type of lava. Some volcanoes are viscous, meaning that they
are thick and sticky, while other volcanoes have thin, runny lava.
We will test out the viscosity of various substances and see how they relate to lava flow.
Procedure:
1) Stack 3 books on top of the lab station. Place one end of a cardboard on it so it slopes into the
aluminum pan.
2) Mark a “Start” line and a “Finish” line.
3) Pour substances down the ramp and time how long it takes to get to the Finish line. Record the
data below.
Modified From:
Issue 9: Earth’s Changing Surface (December 2008)
Copyright 2008: Ohio State University. Funded by the National Science Foundation.
http://static.ehe.osu.edu/sites/beyond/penguins/downloads/misc/explosive-or-effusive.pdf
Re-modified Mr. Shutes 2014
Name:
Homeroom:
Volcanoes: Explosive and Effusive
Substance
Time
Viscosity is… because…
Mt. St. Helens is a volcano that has explosive eruptions, while Hawaii has volcano eruptions that are not
explosive. Which substances are similar to the lava chemistry (viscosity) of Mt. St. Helens and which
ones are similar to Hawaii? Explain using data from your experiment.
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Modified From:
Issue 9: Earth’s Changing Surface (December 2008)
Copyright 2008: Ohio State University. Funded by the National Science Foundation.
http://static.ehe.osu.edu/sites/beyond/penguins/downloads/misc/explosive-or-effusive.pdf
Re-modified Mr. Shutes 2014
Name:
Homeroom:
Volcanoes: Explosive and Effusive
Dissolved Gases:
Gases trapped inside magma build up pressure inside the magma chamber, much like shaking a
container of soda or other carbonated beverage. Some volcanoes have more gas in their magma than
other volcanoes. Which amount do you think would yield an explosive volcano, more or less dissolved
gas? (Think back to shaking a carbonated beverage.)
Prediction:
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The Upcoming Simulation Requires Safety Glasses:
1) You will be given two alka seltzer tablets. Break one in half. Set one half off to the side. Break
the other half in half. You should now have one full tablet, ½ tablet, and two ¼ tablets.
2) With your film canister, pour 20mL of water in.
3) MR. SHUTES IS SERIOUS ABOUT WEARING SAFETY GOGGLES.
4) Drop one of the ¼ alka seltzer pieces into the canister and close the cap immediately.
5) Let it sit for more than 2 minutes. Observe the canister. (Are bubbles forming? Is the cap
beginning to swell up?)
6) Empty the contents of the canister. Pour 20mL of water in. Place ½ tablet and close the cap off
immediately. Observe the canister.
7) Empty the contents. We will now see what happens when the top of a volcano allows for some
degassing. We will do this by leaving the cap partially off when we conduct this portion of the
experiment.
8) Pour 20mL of water in the canister. Place ¼ of a tablet in to the canister and place the lid on
partially. Observe what happens.
9) With the remainder of the alka seltzer, come up with other variables to test to see how
explosive volcanoes can be.
Modified From:
Issue 9: Earth’s Changing Surface (December 2008)
Copyright 2008: Ohio State University. Funded by the National Science Foundation.
http://static.ehe.osu.edu/sites/beyond/penguins/downloads/misc/explosive-or-effusive.pdf
Re-modified Mr. Shutes 2014
Name:
Homeroom:
Volcanoes: Explosive and Effusive
Data Collection:
Amount of Alka Seltzer
Observation
1/4
½
¼ with lid partially off
What Do You Think?
How would you rank the explosivity of these four combinations:
1) High viscosity with a lot of dissolved gas
2) High viscosity with a small amount of dissolved gas
3) Low viscosity with a lot of dissolved gas
4) Low viscosity with a small amount of dissolved gas.
Modified From:
Issue 9: Earth’s Changing Surface (December 2008)
Copyright 2008: Ohio State University. Funded by the National Science Foundation.
http://static.ehe.osu.edu/sites/beyond/penguins/downloads/misc/explosive-or-effusive.pdf
Re-modified Mr. Shutes 2014
Name:
Homeroom:
Volcanoes: Explosive and Effusive
(Please answer with the most explosive and then to the most effusive. Answers should include a claim,
evidence from your lab data, as well as reasoning from real world examples like Mt. St. Helens and
Hawaii.)
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Modified From:
Issue 9: Earth’s Changing Surface (December 2008)
Copyright 2008: Ohio State University. Funded by the National Science Foundation.
http://static.ehe.osu.edu/sites/beyond/penguins/downloads/misc/explosive-or-effusive.pdf
Re-modified Mr. Shutes 2014