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Friday, January 27, 2012

Radiometric Dating Resources

Since I teach in Montana, I use "bison kill sites" as a context for introducing students to radiometric dating. I have developed an assignment that has students use certain web sites to figure out answers. CLICK HERE to print a copy. First, I explain some of the background as we work through Part A of the worksheet together. Next, I help them get started on the graph (Part B). CLICK HERE to see what the graph should look like when they are finished. Finally, students finish Parts B and C on their own as homework.

As they are working at home, the worksheet instructs them to go to where they find links to sites such as Virtual Dating and others needed to finish the worksheet. I haven't provided a key because I want you to work through it before having your students do it. Even if it's not something you're interested in, take a look at the "Virtual Dating" site. . . No, it's not that kind of dating!

Photo courtesy of Montana Historical Society: The diorama, which depicts the First Peoples Buffalo Jump west of Great Falls, is on display in the society's museum in Helena, Montana.

Reminder: Watch NOVA on Wednesday, February 1 on PBS. The title this week is Ice Age Death Trap.

Friday, January 20, 2012

Geologic Time Scale Organizes Earth's History

Many students don't understand what the "geologic time scale" is. The time scale is a way to show the various time periods of Earth's history in chronological order. Basically it's an outline that facilitates communications between geologists and paleontologists, etc. by making it easier for them to determine relationships between rock formations and fossils, and describe the timing of past events. CLICK HERE to see an interactive version of the time scale, courtesy of the University of California Museum of Paleontology. Another, printable (pdf) version, is provided by the Geologic Society of America: CLICK HERE to open it.

The time scale was established in the 1800s, using principles of relative dating (fossils, super-position, cross-cutting relationships, etc.). In the 20th century radiometric dating allowed dates to be added. Earth's history was divided into major time periods called "eons", and then sub-divided into even smaller spans of time (eras, periods, epochs).

Students may wonder why one period ended and another began. Each period was different from than those before and after it; different organisms, different climate, etc. . . and one of the challenges of geology is figuring out what caused these changes. In some cases the ends of time periods coincided with mass extinction events. For example, most scientists believe the extinction event that abruptly ended the Mesozoic Era was caused by an asteroid impact. Unfortunately, not all transitions are so well-understood.

And the resource is . . .
To strengthen your understanding of Earth's history, read Why Geology Matters (2011) by Doug Macdougall. Macdougall explains significant events in Earth's history and provides a perspective that brings together oceanography, meteorology, astronomy, and geology. Macdougall also wrote "Frozen Earth: The Story of Once and Future Ice Ages"; another one of my favorites.

Friday, January 13, 2012

Moon Phase Interactive Tutorial

Check out this fun tutorial/review of moon phases provided by the ASPIRE Lab in conjunction with the University of Utah. The moon phase tutorial includes 3 interactive activities for students to check their understanding. CLICK HERE to access the tutorial. The interactive windows will open up when you select the boxes titled "Activity 1", etc. This is a great review tool for those students who are having a hard time understanding moon phases.

The ASPIRE Lab offers several other activities created by teachers for teachers, many of them related to Earth Science.

Friday, January 6, 2012

Hands-On Watershed Activity

In order to understand many important water-related issues, students need to understand the existence and dynamics of watersheds (a.k.a. drainage basins). This "Island Watershed Activity" will help them realize how an abandoned mine can cause the presence of dissolved metals in a stream many miles from the mine site, and how farming practices in the Midwest can contribute to a "dead zone" in the Gulf of Mexico. CLICK HERE to read about the details and print a student handout. The activity takes the better part of three class periods to complete (50-minute periods).