Continuing the Discussion:
“Have you ever observed someone picking up something they shouldn’t?”
“Do you think ancient tools belong where they were left or in a museum?”
“What do you think you should you do if you find an ancient tool?”
Extent of glaciation in North America. Solid white areas represent where glaciers existed during the last ice age. Dotted white line indicates maximum extent of older Quaternary glaciations. Copyright 2013 Colorado Plateau Geosystems Inc.
Earth has changed over time. This lesson focuses on a period called the Late Pleistocene (~129,000 to 11,700 years ago), and in particular, the time following the Last Ice Age ~16,000 to 11,700 years ago). At the time when glaciers were at their peak in North America, global average temperatures were 5 to 10 degrees Celsius (9 to 18 degrees Fahrenheit) below today’s average temperatures. Modeling of past climates tells us that when glaciers were present, the jet stream across North America was south of where it is now. This brought more moisture from the Pacific into the desert areas of the southwestern United States, creating more precipitation and more cloud cover than we have today. Because temperatures were also colder, there was less evaporation of that moisture and many of the basins filled with lakes.
People first arrived in the Americas near the end of the Last Ice Age when the Great Basin was a land full of lakes.
The Importance of Context
View the YouTube video here with Dr. Wriston discussing how the location of artifacts, or their context, helps archaeologists interpret what they were used for and what activities happened at a site.
During the Late Pleistocene, people spread throughout the world. Scientists continue to debate when and how people first arrived in the Americas, but all agree that they were here by 14,000 years ago when large mammals called megafauna still roamed the Great Basin. Within southeastern Nevada, we have fossil evidence of mammoth, mastodon, and other extinct ice age mammals. We also have fragmented tools that people left behind that are over 12,000 years old.
Late Pleistocene age fluted spear point base fragment from Lincoln County
Take a look at the resources videos to consider what archaeologists look for and find as evidence of people's activity. Use the videos to collect data to complete the Artifact Table in your Field Journal.
Artifacts in the Great Salt Lake Desert in Utah
Coastal artifacts in North America
Artifacts in Ancient Coal Valley in Nevada
In the last section, we learned about artifacts and fragments of artifacts that archaeologists have found all over the American West. But, do these artifacts represent everything the first Americans used to survive?
In the next activity, you will explore materials that may have been used or consumed during the Late Pleistocene. You will use the images and materials in your Green Box to form a hypothesis about which materials would remain intact for archaeologists to discover tens of thousands of years after they were used. Then, you will test your hypothesis.
Laminated images of artifacts and materials
Artifact Box
Stone pieces (sandstone, limestone, obsidian, basalt)
Shell pieces
Wood pieces
Plant material
Seeds
Clay
Feathers
Weathering Box
Sandpaper
Plastic tubs
Spray bottles
Vinegar
Hair Dryer
Students should be in groups of 3 or 4.
Each group starts with collection of laminated images.
Hypothesize which artifacts and materials would have survived in the Great Basin for thousands of years for archeologists to find. Sort the cards into 3 piles: SURVIVE, WOULD NOT SURVIVE, and UNSURE/MIGHT SURVIVE.
Once groups have formed their hypotheses, a spokesperson for each group will share their hypotheses with the whole class. What is in each category? Why led to their decisions?
Teachers collect grouping data on the board. Guide a whole-class debrief with questions like:
What common ideas emerged?
Where did groups differ in their assessment?
What materials created the most uncertainty?
First, watch this video on Wind and Water Weathering processes.
2. Now, take a look in your Artifact Box. Match the materials in your box to some of the artifacts in your image sort. Which of the materials in your box do you predict will survive weathering and erosion and which would not? Sort your materials the same way you sorted the images. Use your Field Journal to create an argument for each item:
Claim: Will it survive the test of time or not?
Evidence: What information do you have from the real world or from the video above that gives you a reason to classify the item?
Reason: This is your "why?" Connect your Evidence to your Claim with a rationale.
Example:
Plant material will not survive the weathering process.
When I go to a museum, I see artifacts made of stone, shell, and bone.
If plant material artifacts survived the weathering process, I would see plant material in a museum that houses artifacts in the real world.
3. Now open your Weathering Box. In your small groups, and using the materials and tools in your Weathering Box, as well as classroom tools and ideas, devise a process for weathering the materials in your materials box. Consider wind, water, chemical, and pressure weathering processes. Use your Field Journal to describe your tests. Things to consider:
You might want to test the same weathering process on each artifact to be consistent in your testing.
Each group in the class might take on one weathering process. For example, one group might only use sand paper, while another uses water.
4. Systematically test your weathering processes on each of the materials in your box. You can divide and conquer, test as a whole class, or each group can test each material. Ask your teacher for guidance in deciding which tests to run. Some tests may have some processing time (i.e. soaking, wind exposure), so it is okay to "weather" your materials over night.
5. Use your Field Journal to record your results. You will record the material, the test description, the type of weathering or erosion it simulates, the duration of the test, and the result. Did the material remain intact, did it get damaged, but was still recognizable, or did it completely disintegrate? Finally, record any additional notes or insights. For example, do you think that simulated weathering worked as the real process would?
6. Discuss your finding as a whole class, designating a speaker for your group.
Use your Field Journal to describe the kinds of artifacts you would look for in the Great Basin Desert as evidence of the first Nevadans. Use evidence from your exploration in this section. What tools and artifacts were used and left behind? Which of them would still be detectible, present day?
In your journal, you will name the type of artifact or material, why you think you will find it, and what people activities it would tell us about.