Determining and Measuring Earth's Layered Interior

Contributor
Incorporated Research Institutions for Seismology (IRIS)
Type Category
Instructional Materials
Types
Lesson/Lesson Plan
Note
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be “fully aligned,” the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.

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Most Recent Review

4 My students and I both learned.

Reviewed by: Janet G on 9/5/2019 3:38:00 PM

This activity was not too difficult for Freshmen. They were able to do tasks as long as they had a capable leader. We did this before learning about Earth's structure to waylay the question, "How do they even know what the Earth is like inside?" I used it as a lesson that we know things because someone collected empirical evidence not because someone guessed.

Description

In this lesson, students examine seismic evidence to determine that the Earth must have a layered internal structure and to estimate the size of Earth’s core. Students are divided into two teams (theoreticians and seismologists) to test the simplest hypothesis for what is inside of the Earth: that the Earth is homogeneous throughout. The theoretician group uses a scale model of a homogeneous Earth combined with average seismic wave velocity to make predictions about when seismic waves should arrive at various points around Earth (predicted). The seismologist group interprets seismic data from a recent earthquake to determine when seismic waves actually arrive at various points around Earth (observations). Students then compare and discuss the fit of the predicted and observed data and then use a second scale model to further interpret these results. The students then measure the Earth’s outer core based on their data.

Intended Audience

Educator and learner
Educational Level
  • High School
Language
English
Access Restrictions

Free access - The right to view and/or download material without financial, registration, or excessive advertising barriers.

Performance Expectations

HS-ESS2-3 Develop a model based on evidence of Earth’s interior to describe the cycling of matter by thermal convection.

Clarification Statement: Emphasis is on both a one-dimensional model of Earth, with radial layers determined by density, and a three-dimensional model, which is controlled by mantle convection and the resulting plate tectonics. Examples of evidence include maps of Earth’s three-dimensional structure obtained from seismic waves, records of the rate of change of Earth’s magnetic field (as constraints on convection in the outer core), and identification of the composition of Earth’s layers from high-pressure laboratory experiments.

Assessment Boundary: none

This resource is explicitly designed to build towards this performance expectation.

Comments about Including the Performance Expectation
This lesson allows the students to compare actual data to a simple theoretical model of Earth’s interior in order to develop an evidence based model of Earth’s interior. To fully address the Performance Expectation, students would need to look at other examples of the Earth’s three-dimensional structure (such as seismic tomography maps, seismic wave reflection through Earth’s core, tectonic plate motion, depth of earthquakes at tectonic plate boundaries, records of Earth’s magnetic field flipping in sea floor rocks, etc).

Science and Engineering Practices

This resource is explicitly designed to build towards this science and engineering practice.

Comments about Including the Science and Engineering Practice
Students can explore the seismic wave arrival times data set to see that seismic waves do not arrival at the times predicted by the simple model of a homogeneous Earth. The difference in arrival times of the seismic waves will inform development of the student’s model of Earth’s interior. Students analyze data using tools (rulers, protractors) to mark the paths of the seismic waves through the Earth; technologies (Microsoft Excel and the computer) to access the seismic wave travel time data; and models (theoretical and actual data) in order to make valid and reliable scientific claims. The actual seismic data should lead the students to propose a model in which the Earth's core is different than its outer structure. Student analysis of the actual data should show them that the theoretical model of a homogeneous interior for the Earth is too simple.

Disciplinary Core Ideas

This resource is explicitly designed to build towards this disciplinary core idea.

Comments about Including the Disciplinary Core Idea
The seismic wave arrival times data set allows students to begin to develop a model of the interior of Earth. By comparing the actual seismic wave arrival times to the theoretical seismic wave arrival times, students will notice that the actual data does not match the theoretical data. The theoretical data assumes a homogeneous interior for the Earth. This is too simple of a model for the Earth's interior. The actual data will lead students to a model of the Earth's interior with a liquid core. The model developed in the lesson is not detailed enough to determine that the Earth has a solid inner core. The seismic wave arrival times data set does not provide an easy way for students to model the hot solid inner core, solid mantle or crust. The lesson does not address the last part of this Core Idea: Motions of the mantle and its plates occur primarily through thermal convection, which involves the cycling of matter due to the outward flow of energy from Earth's interior and gravitational movement of denser materials toward the interior.

Crosscutting Concepts

This resource is explicitly designed to build towards this crosscutting concept.

Comments about Including the Crosscutting Concept
The interior of the Earth is too large for any one individual to see at one time, thus we have to study the interior of the Earth indirectly using seismic waves. As seismic waves travel through the Earth they will speed up or slow down depending on the density of the material through which they are traveling. They will also reflect off of boundaries between materials of significantly different densities (such as a solid/liquid material boundary). Also the interior of the Earth is impossible to explore directly using current technology. The temperature of the Earth's interior rises dramatically with depth, eventually reaching a temperature where all materials will melt. The difference in the arrival times of the seismic wave data from the predicted arrival times in a homogeneous Earth (the effect) can be explained by the Earth having a core (cause).

Resource Quality

  • Alignment to the Dimensions of the NGSS: The Science and Engineering Practice (Analyze data using tools, technologies, and/or models (e.g., computational, mathematical) in order to make valid and reliable scientific claims or determine an optimal design solution) is significantly addressed. Students use tools (rulers, protractors), technologies (Microsoft Excel, computer), and models (theoretical, actual data) to determine that the Earth has a liquid outer core. The disciplinary core idea is significantly addressed. The lesson allows students to use actual data to begin to develop a model of Earth’s interior. The crosscutting concept of cause and effect is explicit in the analysis of the data performed by the students during the lesson. Given an effect (differences in arrival times between predicted and actual data) students model a cause (core of Earth) that explains the effect. The graphing of the actual data shows a discrepancy between the actual data and the theoretical data. This requires the students to develop an explanation for this difference in the data.

  • Instructional Supports: The lesson engages students in a scenario that reflects the interconnected nature of science as it is practiced and experienced in the real world. Students analyze real data, compare that to a theoretical model and devise an explanation for the differences between the two. The lesson uses scientifically accurate materials (actual seismic data) which is presented at an appropriate level for student understanding. The lesson expects students to express, justify, interpret, and represent their ideas for the model of the Earth's interior structure that matches the actual seismic data which is analyzed. This lesson does not provide differentiation of instruction for differing student needs; no connections to the students' home or culture; no reading, writing, or speaking modifications; no extras support for students struggling to achieve the performance expectations; nor does it provide extensions for students with high interest or who have achieved the performance expectations. Lesson provides all student handouts and work sheets, seismic wave data set, teacher’s guide, PowerPoint and spreadsheet.

  • Monitoring Student Progress: The lesson provides a flow chart that teachers can use to monitor student progress along the lesson. This lesson does not include guidance on using formative assessment to provide feedback to students and inform instruction. This could be added by asking the students questions that would probe student understanding and encourage discussion at various points along the activity.

  • Quality of Technological Interactivity: This lesson has the students using Microsoft Excel to plot actual seismic data and theoretical seismic data to compare and arrive at an explanation for noticeable differences between the two. Students learn how to graph data in Excel.