Mapping Paleocurrents: Using the Past to Understand the Present
Summary
In this activity, students are given a series of world maps showing the different configurations of the continents through geologic history. Working back from the present, students reconstruct the location of past surface currents based on the location of the continents and global atmospheric circulation patterns. Students also need to consider the importance of oceanic gyres in global heat transport by identifying warm and cold currents, as well as, areas that in the past were isolated from hemisphere-scale gyres and as a result, experienced unusually cold or warm conditions.
Collapse
Context
Audience
This activity is used a 2-hour lab in an introductory-level physical oceanography class. The class is primarily taken by non-science majors.
Skills and concepts that students must have mastered
- Understand global atmospheric circulation.
- Understand relationship between atmospheric circulation and surface currents.
- Understand the Coriolis Effect, surface friction, and the formation of oceanic gyres.
How the activity is situated in the course
Used as a 2-hour lab but could be shortened for an in-class activity by doing only 2-3 maps.
Goals
Content/concepts goals for this activity
The primary goal of this activity is to help students understand the processes that produce surface currents (wind, Coriolis Effect, surface friction, and the configuration of the continents). A secondary goal is to illustrate the importance of gyres as means of oceanic heat transport and to get them to think about the climatic impacts of oceanic heat transport.
Higher order thinking skills goals for this activity
This activity requires critical and creative thinking. Students must think critically in order to predict unknown patterns based on known processes. In many cases, students are faced with ocean basins that are very different in size, shape, and geographic location from those of today and reconstructing surface currents takes a certain amount of creativity.
Other skills goals for this activity
Map reading (latitude and longitude).
Description and Teaching Materials
Paleogeographic Maps:
The maps I use for this lab were copied from a book a long time ago by David Westerman who originally designed this lab. He can't remember which book they are from and I am in the midst of trying to track down the reference and will give it here as soon as possible. I use maps from the following time periods: the present-day, 80 million years ago, 180 million years ago, 360 million years ago, and 480 million years ago. The maps are best in black and white and need to have latitude grid lines. There are beautiful, color paleogeographic maps available from multiple websites (see list below), however, for this exercise black and white is best and grid lines are essential so I continue to use the old school variety.
The maps I use for this lab were copied from a book a long time ago by David Westerman who originally designed this lab. He can't remember which book they are from and I am in the midst of trying to track down the reference and will give it here as soon as possible. I use maps from the following time periods: the present-day, 80 million years ago, 180 million years ago, 360 million years ago, and 480 million years ago. The maps are best in black and white and need to have latitude grid lines. There are beautiful, color paleogeographic maps available from multiple websites (see list below), however, for this exercise black and white is best and grid lines are essential so I continue to use the old school variety.
- The Paleogeographic Atlas Project from the University of Chicago; nice maps with latitude and longitude grid lines but only for early Permian to Lake Cretaceous.
https://www.uchicago.edu/research/center/paleogeographic_atlas_project/ - Library of Paleogeography by Ron Blakey; beautiful color images with grid lines for all time periods. Some work with these maps in Photoshop might be able to transform these into the simple black and white line drawings that work best for this activity.
- Paleomap Project by Christopher R. Scotese; very nice color maps for all time periods but without grid lines, also has nice paleoclimate maps.
http://www.scotese.com/earth.htm
Student Activity Instructions:
Student Instructions (Microsoft Word 2007 (.docx) 17kB May30 13) - This document contains information and instructions for students. The figures in the textbook that are referred to here are maps of global atmospheric circulation and ocean surface currents.
Teaching Notes and Tips
This lab involves a lot of arrows and maps can get messy and hard to read very quickly. I tell students to try to limit the number of arrows they have to show the Trade Winds, Westerlies, and Polar Easterlies. Also it is helpful for students to label the lines of latitude along the margins because the further back in time they go they are more likely to get disoriented. Finally, even though it says it on the instructions, some students will cut the Pacific Ocean in half and give it 4 gyres – can't hurt to mention this and take the opportunity to talk about issues involved with displaying a sphere onto a flat surface. Another map projection issue is that the north and south poles are distorted and in order to show wind or ocean currents around the poles you have to draw a line of straight arrows across the page.
Share your modifications and improvements to this activity through the Community Contribution Tool »
Assessment
When I grade these labs I am look for the following:
- Students properly located atmospheric circulation patterns
- Students understand the basic principles of gyre formation with the proper Coriolis deflection in each hemisphere and currents forming 45⁰ angle from the wind.
- Students were able to recreate a probable pattern of surface currents for the past.
- Students can show how warm and cold surface water is distributed between the equator and the poles and how this impacts the climate of certain regions.
- The maps are neat, legible and contain a legend