Who’s on First? A Relative Dating Activity

Marsha Barber and Diana Scheidle Bartos
Type Category
Instructional Materials
Lesson/Lesson Plan
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.



Who’s on First? A Relative Dating Activity is a hands on exercise which introduces students to the concepts of sequencing and using fossils to establish relative dates for rock strata.  In the first part of the activity, students are asked to sequence cards by identifying and ordering overlapping letters found on the cards.  In the second part of the activity, students progress to dating rock layers by sequencing fossils found in the different strata. Using the results of these activities, teachers can then lead students in a discussion of the Law of Superposition and the identification and value of index fossils. It should be noted that teachers may have to edit the introductory materials provided to students, since the readings may be too difficult for younger middle school students. Both parts of the activity can be completed in one class period.

Intended Audience

Educational Level
  • Grade 8
  • Grade 7
  • Grade 6
  • Middle School
Access Restrictions

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

Performance Expectations

MS-ESS1-4 Construct a scientific explanation based on evidence from rock strata for how the geologic time scale is used to organize Earth's 4.6-billion-year-old history.

Clarification Statement: Emphasis is on how analyses of rock formations and the fossils they contain are used to establish relative ages of major events in Earth’s history. Examples of Earth’s major events could range from being very recent (such as the last Ice Age or the earliest fossils of homo sapiens) to very old (such as the formation of Earth or the earliest evidence of life). Examples can include the formation of mountain chains and ocean basins, the evolution or extinction of particular living organisms, or significant volcanic eruptions.

Assessment Boundary: Assessment does not include recalling the names of specific periods or epochs and events within them.

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

Comments about Including the Performance Expectation
Who’s on First? is a set of introductory activities in which students use a fossil record to assign relative dates to rock strata. Teachers should note that the stratigraphic information provided for the second part of the activity is purely hypothetical; however, this is still a valuable exercise since its successful completion will allow teachers to initiate a discussion on the Law of Superposition and index fossils without overwhelming students with too many details. In particular, these activities allow students to explore the portion of the Clarification Statement dealing with the evolution or extinction of particular living organisms by pinpointing when specific fossils appear and disappear in the strata record. These activities do not include any discussion of physical events or processes in Earth’s history.

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
In this activity, students are tasked with constructing a timeline using fossils. In order to align this activity more closely to this practice, teachers should require students to explain and justify each step of their timeline. For example, students should discuss which fossils are making their first appearance in a particular segment and which fossils have disappeared. In addition, students should discuss which, if any, of the fossils in a particular segment could be utilized as an index fossil. Once these answers are shared and evaluated, students would be prepared for a discussion of the Law of Superposition.

Disciplinary Core Ideas

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

Comments about Including the Disciplinary Core Idea
In this activity, students construct their fossil timeline simply by identifying overlapping fossils in the pieces; it is only after students construct their records that teachers are instructed to provide Figure 2-B which illustrates a hypothetical section of rocks with fossils. To bring this activity more in line with the Disciplinary Core Idea, teachers may wish to redesign the materials provided the students by cutting up FIgure 2-B and instructing students to organize these pieces instead. Because Figure 2-B shows the fossils already embedded in rock strata, the relationship between fossils and rock strata is strengthened. Note: teachers may wish to assign a different code to the various fossil pieces. In the current activity, the word “organism” is spelled out if the pieces are placed in correct order; brighter students may figure this out and align the pieces accordingly without giving thought to the actual exercise. To align more closely to the Disciplinary Core Idea, teachers may also want to incorporate the Relative Dating Activity (http://www2.mbusd.org/staff/pware/labs/RelativeDating.pdf) which tasks students to assign relative dates by specifically looking at rock strata.

Crosscutting Concepts

This resource appears to be designed to build towards this crosscutting concept, though the resource developer has not explicitly stated so.

Comments about Including the Crosscutting Concept
The success of this activity lies completely in a student’s ability to recognize patterns in the cards. Only one sequence is correct for each activity, but the answer is easily achievable if students can recognize the relationships detailed in the cards. The major difficulty that students may encounter is the concept that extinction is forever. Once a species disappears, it cannot make a comeback at a later date or, in this case, card.

This resource appears to be designed to build towards this crosscutting concept, though the resource developer has not explicitly stated so.

Comments about Including the Crosscutting Concept
After successfully completing the second part of this activity, students will have sufficient background information to begin relating the appearance and disappearance of various fossils to the relative age of the rock strata in which they’re found. Again, this exercise is only hypothetical but the experience provided to students can be transferred to actual rock data. Although students are only working with the relative ages of the rocks, they still will gain an appreciation for how this model represents a way to organize Earth’s history. The activity helps students to understand that long spans of geologic time can be broken down into more manageable segments by using relative ages. Teachers should not be concerned that this activity does not assign specific dates and/or titles to the various segments; its main purpose is to introduce a methodology to study the immense span of geologic time.

Resource Quality

  • Alignment to the Dimensions of the NGSS: Who’s on First? is a lesson plan that strongly incorporates all three dimensions of the NGSS. In order to achieve success, students must make sense of the evidence provided in the fossil strips and utilize scientific principles, such as the permanence of extinction, before assembling their timelines. By requiring students to provide an explanation for the individual steps in their timelines, teachers will ensure that students will be constructing explanations to complicated phenomena. The use of the fossil record to create this timeline closely mirrors the content of the Disciplinary Core Idea of Scale, Proportion and Quantity. Since the entire activity requires the recognition and analysis of fossil overlaps, Who’s On First? is closely aligned to the Crosscutting Concept of Patterns. In order to recognize and make sense of these patterns, students must use the Scientific Practice of Analyzing and Interpreting Data, especially in regards to temporal relationships.

  • Instructional Supports: The construction of the fossil timeline is an engaging activity that reflects how scientists work in the real world. Although there is no specific opportunity for students to discuss their ideas, it should be easy for teachers to make time for class presentation of models and general discussion. The activity uses scientifically accurate and grade-appropriate information in laying the groundwork for an examination of how fossils can be used to organize rock strata; however, no guidance is provided for differentiation. The introductory material that is provided will be above the reading level of some students but the actual activity can be completed by English language learners and those students with special needs.

  • Monitoring Student Progress: Who’s On First? provides two accessible and unbiased activities for students. No embedded formative assessments have been provided; teachers will only be able to determine student progress by inspecting individual fossil sequences and reviewing the answers to the interpretation questions. Aligned rubrics and scoring guidelines are not included but answers to the interpretive questions have been provided.

  • Quality of Technological Interactivity: Who’s on First? is a paper and pencil, hands on activity. There is no technological component.