Geologic Time and Stratigraphy
Overview of PDA Series
Geologic time spans from the beginning of written history to the end of Earth’s physical formation as a
separate planetary body. Stratigraphy is the science of rock strata and the focus here is original
succession and age relations of rock strata. The geologic time scale is created using relative and
chronometric dating. Relative dating tells us that one thing is older or younger than another.
Chronometric dating assigns a numeric age.
The primary four topics for this PDA are Relative Age Dating and Geologic Time, Radioactive
(chronometric) Dating and Stratigraphy, Stratigraphy, and Fossils. The remainder of this document refers
to a one day PDA covering the topic of Relative Age Dating and Geologic Time.
Overview of One Day PDA on Relative Age Dating and Geologic Time
Earth scientists use the structure, sequence and properties of rocks, sediments and fossils to reconstruct
events in Earth’s history. Stratigraphic principles are used to place events in a relative order. The
succession of fossils in a specific order vertically allows for strata to be identified and dated in a relative
order. Paleomagnetic dating is based on major periodic changes in the Earth’s magnetic field from north
to south throughout geologic history and places events in a relative order.
Descriptors
Target Audience - High School Science Teachers
Workshop Objectives - The teachers will be able to conduct grade level appropriate investigations so
that students will be able to analyze and evaluate relative dating methods using original horizontality,
rock superposition, lateral continuity, cross-cutting relationships, unconformities, index fossils, and
biozones based on fossil succession to determine chronological order.
Workshop topics/themes - Relative Dating Methods (original horizontality, rock superposition, lateral
continuity, cross-cutting relationship, unconformities, index fossils, and biozones based on fossil
succession to determine chronological order), Stratigraphy, and Geologic Time.
Workshop Materials
Cayuga Basin Activity For each participant: Photocopy of the activity.
For each group of four: A copy of the outcrop page, scissors, transparent tape, manila file folder, glue,
colored pencils.
Guest Speaker –
For guest speaker: Computer, projector, screen, and honorarium
For participants: Computer with internet access and Google Earth installed. This could be through a
computer cart or a computer lab.
Speaker topics could include an overview of stratigraphy, using Google earth to examine stratigraphy,
and relevant applications of why we need to know stratigraphy – industrial mining, energy, and climate.
Using Fossils to Tell Deep Time For each participant: Photocopies of the activity
For each group: One laminated set of cards/group and transparent tape.
PBS Video Computer, screen, projector, wi-fi, cables, sound system
Science Literacy Article –
For each participant: photocopy of article, copy of anticipation literacy guide, jigsaw plan
What’s Up: A Relative Age Dating Activity –
For each participant: photocopy of the activity, including student pages
For group – photocopy of student pages
Evaluation Form –
For each participant: photocopy of evaluation forms
What Teachers Need to Bring Teachers should bring themselves with a good attitude, computer with long Ethernet cable and/or wi-fi
capability.
What Teachers Can Expect to Gain
They will walk out with instructional materials, networking experience, continued support for the
classroom, ongoing professional development opportunities, Continuing Professional Education credit,
leadership development.