Wednesday, October 17, 2012

Understanding the Bering Strait Land Bridge

How did thousands upon thousands of people migrate to North America and South America from Asia? And how did this land bridge disappear?

In class this week, we created a simulation of the Bering Strait Land Bridge and how it disappeared after the last Ice Age. Even though many students had already heard about the land bridge and were familiar with the concept, they weren't visualizing exactly how the land bridge ceased to exist after the last Ice Age. Some thought it washed away, others thought it sunk, and yet others were still picturing a "bridge" in their minds.

To prepare for this project, I borrowed a bunch of cookie sheets from another department of the school and sketched a map in color of the Beringia area. There were several maps available on the web, but I wanted something a little more specific to our needs. I scanned the sketch into the computer, then printed color copies as needed. I laminated the maps so that they would hold up to the clay that would be applied later.

On the first day of the assignment, students were given a lump of air-dry clay, the laminated map, a few popsicle sticks and a cookie sheet to create their model. I instructed them to make the green areas of the map thicker and the brown areas thinner. They used the sticks to contour the edges of the land..

I always have students maintain record sheets of their labs, demonstrations and projects so that they may look back at them later. With any leftover time after completing the models, they began sketching their work on the record sheet and reading the accompanying information.

We stacked the cookie sheets to dry overnight so they would be ready for the next day's simulation. To prepare for day two, I filled one bucket with some warm water and another bucket with some ice. We are fortunate enough to have an ice machine in our fitness room and cafeteria, but you can also purchase bagged ice if necessary. You may also want another empty bucket available for disposal of water and ice after the demonstration.

Students poured "ocean" water onto their models until water surrounded all landmasses, but did not cover the land bridge. We then placed piles of ice to model glaciers in the Arctic region. We placed the trays in the warmest part of the room near the heater, an area the kids dubbed the "climate change zone." Students completed some of their record sheets while I circulated the room and left the "glaciers" to melt over the heater.

While filling in the record sheets, students periodically checked on their models and watched as the water slowly encroached on the land bridge, eventually submerging it completely. The ice did not fully melt, but we discussed that this was accurate, since there are still large amounts of water locked in ancient glaciers to this day.

The project might have gotten a little messy, but there is just no substitute for kinesthetically feeling and seeing the process take place. With just a few minutes of cleanup and a table wipe-down, our classroom was back to its neat-and-orderly self and we had a better understanding of how the world's landscape could change due to a slight change in temperature.