The focus of this activity is on interpreting geologic history through volcano formation and excavation. Baking soda, vinegar and play dough are used to model fluid lava flows. Various colors of play dough identify different eruption events. Students will:
- Construct a model of a volcano
- Produce lava flows
- Observe, draw, record, and interpret the history and stratigraphy of a volcano produced by other students
- Make the connection between the life cycle of a volcano and why they see these features on Earth and Mars
- This activity is best utilized when students have already learned a bit about volcanoes.
- Either commercially available or homemade play dough (download recipe) may be used. Homemade is more economical.
- Each group of 2-4 students will need at least 3, preferably 4-6, different colors of play dough – one for each lava flow.
- If using only 3 colors of play dough (which yields 3 lava flows), initially limit students to making 1 stream cut and taking 3 core samples (see Procedures, Part 2, Step 7).
- Depending on the length of the class period, students can create volcanoes one day and investigate student-created volcanoes the next day. If doing the activity over two days:
- Collect the maps/answer keys and file them in a manner that they can be reconnected to the associated volcano
- Cover volcanoes with plastic wrap to keep play dough pliable
Part 1: Creating a Volcano
- Cut the top of the small paper cup so that the cup is 2.5 cm high.
- Place the small paper cup in the center of each piece of graph paper and trace around it with a pencil.
- Secure the small paper cup (right-side up) onto the cardboard using a small loop of tape on the bottom of the cup. This short cup is your eruption source (eventual caldera) and the cardboard is the original land surface.
- Mark north, south, east, and west on the edges of the cardboard and the graph paper, orienting them similarly on the table.
- Fill about half of a large paper cup with baking soda.
- Place one heaping spoonful of baking soda in the short cup.
- Pour some vinegar into a second large paper cup.
- You are now ready to create an eruption. Slowly pour a small amount of vinegar into the small, source cup and watch the eruption of simulated lava.
- When the lava stops, quickly draw around the flow edge with a pencil.
- Dab up the fluid with paper towels.
- As best you can, use a thin layer of play dough to cover the entire area where lava flowed.
- On one piece of graph paper, use a colored pencil that matches the play dough color to draw an outline representing the edge of the play dough, being sure to maintain the cardinal orientation (north, south, east, west) of the paper with the orientation of the volcano. Shade in this lava flow drawing. Make a note on the graph paper regarding the order of eruptions (which color came first).
- Repeat steps 6 - 12 for each color of play dough available. Four to six flows show a good example of a shield volcano, but three flows will be adequate for a simple shield volcano model. Notes: The source cup may be cleaned out as needed. Be sure to mark the entire area of each lava flow – over previous flows and on the cardboard. On subsequent flows, you will need to dig into the underlying play dough with your pencil to mark the flow area. The result will resemble a strange layer cake with new flows overlapping old ones.
- If time is short, cover each volcano with plastic wrap and return to the activity the following day.
Part 2: Investigating a Volcano
In this portion of the lesson, students will simulate a mapping and field-geology exercise. This is very similar to the first steps that geologists employ when they map and interpret the geologic history of an area. Geologists use images acquired by planes and spacecraft to interpret the history of a planet’s surface. If they can examine the surface in person, they do field work by making maps and collecting samples. To determine the history of a feature, exposed strata are examined and core samples are extracted.
When it comes to studying other planets, such as Mars, geologists use images taken from Mars orbit and data gathered by rovers on the surface to interpret the history of the planet’s surface. NASA aims to eventually send humans to Mars to do field work.
This portion of the lesson is designed to promote the use of higher-order thinking skills and encourages the questioning, predicting, testing, and interpreting sequence that is important to scientific inquiry.
- Have teams trade volcanoes so that they can investigate and map a volcano with an unknown history. They may give the volcano a name if desired.
- Explain to students that they are to act like planetary geologists who have just come upon this volcano and must determine its history and create an accurate map representing its formation.
- Have students orient and label their blank piece of graph paper to match the cardinal (north, south, east, west) directions of their volcano.
- Have students draw the visible layer(s) of the volcano to scale on the graph paper using a ruler and colored pencils.
- Discuss that there is much detail that can't be seen from the surface.
- Answer the questions on the student worksheet. Note: Some volcanoes may be more complex than others. Each will be different! There may be flows that are completely covered, some flows that have two separate lobes, and some flows for which the sequential relationship cannot be determined at the surface.
- Lead the students to question what they cannot see below the surface. Where do the flows extend under the exposed surface? Ask students to hypothesize how geologists investigate such hidden details. Then discuss various subsurface exposure techniques including core sampling, erosion cuts, road cuts, earthquakes, surface-penetrating radar, etc.
- Have groups make a plan that shows on their map where they want to investigate the layers of their volcano using using the subsurface exposure techniques discussed above. They should indicate how the proposed cores and cuts will maximize the information they might gain from excavations. Limit the number of exposures each group may use, e.g., five drill cores and one road cut and one river erosion.
- To make the cuts or cores on the volcano models:
- Remove a core sample by pushing a straw vertically into the play dough until encountering the cardboard surface, twisting if necessary, and withdrawing the straw. The various layers of play dough will be visible in the core sample inside the straw. Lay the straw containing the core sample next to the hole from which it was taken.
- River valleys may be made by cutting and removing a V-shape in the side of the volcano (open part of the "V" facing down slope).
- To make road cuts, use a plastic knife or dental floss to cut and remove a strip about 1-cm wide and as deep as you want from any part of the volcano.
- To make earthquake exposures, make a single cut and lift or drop one side of the fault line. Some support will be necessary.
- What could groups have done differently to improve the accuracy of their maps?
- In what ways are these model volcanoes similar to real volcanoes?
- In what ways are these model volcanoes different from real volcanoes?
- The results of Part 1 of the lesson may be assessed by monitoring group performance and the finished product. Were all group members equally involved in the process of creating the volcano and the map?
- The results of Part 2 of the lesson may be assessed by the accuracy of the map, the strategies employed in deciding where to take core samples and place cuts, and the reflection on how a more accurate map might be created.
- Allow students to make more cuts or cores (within specified reasons) to see if they are able to better refine their maps.
- Have students compute the surface area covered by each flow.
- Have students compute the volume of each flow.
- Examine images and read stories of real volcanoes by searching NASA's Earth Observatory.
- Learn about the largest volcano in the solar system, Mars' Olympus Mons.
- Explore all the volcanoes in our solar system using the Space Volcano Explorer.
- Search the Aster Volcano Archive, the world's largest specialty archive of volcano data.
- Download a Volcano Field Trip Guide for US volcanic regions and go on a field trip!
- Download 30 Cool Facts About Mount St. Helens.
- Download Eruptions in the Cascade Range During the Past 4,000 Years.
- Read about Earth's largest volcano!
- Watch a planetary scientist talk about how we study volcanoes on Earth, the moon, and Mars.