Journeying to the Center of the Earth Using iPads and Smart Phones
SHEILA ALFSEN (firstname.lastname@example.org), teaches geoscience at the Yamhill Valley campus of Chemeketa Community College in McMinnville, Oregon, and DANA HOUSTON JACKSON (email@example.com), is a masters of education information technology student at Western Oregon University, Monmouth, Oregon.
One of the most difficult concepts for beginning geology students is understanding how seismic waves are used to determine the physical properties of Earth's interior. As geologists know, the solid and liquid states of the inner and outer core have been determined by the travel of P and S waves as they propagate through the Earth during an earthquake. Getting this idea across to students is difficult because it has been determined by a form of remote sensing and is therefore abstract. One simple way to communicate how remote sensing works is by using the analogy of knocking on a wall to find the studs inside.
An innovative lab exercise that combines the use of iPads and a seismogram app can help students understand even better how geophysicists have determined the structure and composition of Earth's interior. This activity makes use of current application technology and the hands-on manipulation of simple materials (water, sand, gel) to help visualize the transmission of seismic waves through Earth materials in different states of matter. The iPads (see Figure 1) are equipped with a seismometer app called iSeismometer. These devices record a seismic signal when tapped directly. When positioned on top of certain Earth materials that are tapped, they can also record seismic waves as they travel through them. When the exercise is completed, the devices' concrete visual displays make it easy to distinguish the type of material (liquid, solid, semi-solid) through which the signal was transmitted. The exercise is inexpensive to implement and conduct: the application for the iPad, tablet or smart phone can be easily downloaded and currently is available for free.
Prior Learning Required
Students must understand certain concepts before this lab will be useful. They should know what P and S waves are, as well as how their propagation is affected by the materials through which they travel. Students should also understand the basic workings of a seismograph and how to read a seismogram.
2-quart freezer bags
Sand (enough to fill a 2-quart bag and still create a flat surface for the device to sit on)
Water (enough for a 2-quart bag)
Cold pack gel — large (the type sold in pharmacies to put in a freezer)
Three iPads, tablets or smart phones with the "iSeismometer" App by ObjectGraph LLC. Available free on iTunes.
Small wooden "hammers" for tapping (a wooden ball with a dowel inserted works well)
Setting Up the Exercise
This recommended set-up bypasses one of the pitfalls that often are associated with geoscience and technology blends: the significant time investment for the initial setup (Wallace and Witus, 2013).
Prior to the start of class, fill one bag with sand and another with water — the gel pack will come ready to go. Double-bag each sample to reduce the risk of leakage, making sure that the bag openings are on opposite sides. The sand bags can be reused, but use new bags for the water containment. Take care to remove all excess air; it is important that the signal is transmitted only through the material being tested.
For extra protection against water damage, put the iPads or tablets in clear, sealed plastic bags. Place one device on top of each bag of material.
Executing the Exercise
Students should tap rhythmically on the bag to produce waves through the material. It is important that they tap only the material and not the iPad or device itself. To reduce the variable of inconsistent timing, have them use a metronome or another source that produces a consistent rhythm.
The seismic waves will travel through the material and the iPad will record the shaking (see Figure 4, next page). When a consistent signal is achieved, have the students pause the recording and replicate it on the worksheet. Have the students perform the procedure with all three materials.
Learning Performance and Informal Assessment
Once the exercise is completed, students can compare the results that they have copied down from the devices. Ask them to verbalize the differences they see between the materials and make a generalized statement regarding the use of seismic waves to determine the composition of the layers inside the Earth. It should be very easy for them to see that there is a difference in the propagation of seismic waves through each type of material.
You can help students affirm their new-found skill by conducting a follow-up exercise that utilizes the media equipment that may be in the classroom — either an overhead projector or a document camera that can project images on a screen (see Figure 5). Take one of the material bags used in the exercise (water, sand, gel) and place it on the overhead projector (making sure that students don't see what type of material has been selected). Put the iPad on top of it and tap rhythmically as students did. Students should readily identify the anonymous material based on the wave projection they see on the screen.
Learning Models Used
Higher education holds the pragmatic view that learning requires students to apply knowledge, complete meaningful tasks, and solve problems (Lyman & Varian, 2003). This exercise helps to promote learner ability to apply knowledge and solve problems and thus aligns with task-centered learning (Merrill, 2002, 2007) and problem-based learning (Barrows, 1996; Hung, Jonassen & Liu, 2008). "Instead of focusing on learning through lecture, [task-centered learning] centers learning on tasks or activities that require learners to apply knowledge in a specific domain by completing real-world tasks." (Francom, Gardner, 2013). The use of the metronome to produce a consistent rhythm is also beneficial to learning: "Rhythms have been found to be beneficial in improving overall brain function as well as heightening learning and sensory processing" (J. Strong, taken from Ostrander, 1994).
Student response to this activity was overwhelmingly positive despite the initial challenges. The first time we attempted this exercise, solid colored containers were used to hold the materials in order to conceal their contents. These gave false results— the students were getting a vibration from the solid container rather than from the medium used. Although anonymity of the material was sacrificed (it was included in the follow-up exercise), we overcame this difficulty by using plastic 2-quart bags, which doubled as protection for the devices. The second challenge we faced was avoiding water leakage. Double bagging worked most of the time to achieve this; using new bags protected against tiny punctures. We found the bags of sand could be used and reused with no negative effects.
The students were impressed by the sensitivity of the iPad, which captured even the slightest vibrations. Most of them expressed that the activity was fun. Their enjoyment of the activity was evident by watching them perform the exercise and by their verbal and worksheet comments. This element of "fun" promotes effective education. "The highest-level executive thinking, making of connections, and 'aha' moments are more likely to occur in an atmosphere of 'exuberant discovery,' where students of all ages retain that kindergarten enthusiasm" (Willis, 2006). There is no doubt to the benefit of "hands-on" experiences in the classroom. One student said that even though he had been exposed earlier in school to the idea that Earth's interior was interpreted by seismic waves, the idea had still always seemed abstract. After performing the exercise, he enthusiastically commented: "It's so easy to understand when you actually do it!"
In contrast to the distractions that electronic devices can pose in educational settings, this exercise puts technology to constructive use in the classroom. Easy implementation and cost effectiveness aside, the effect on student engagement and retention are beneficial and the exercise is in accordance with the Department of Education's national educational technology plan. Students are familiar with and comfortable using the devices, and they enjoy finding another use for them in the education setting.
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