Part 5—View and Interpret an ANDRILL Core

Step 1 – Locate the Drill Sites MIS on the Map

In earlier parts of the chapter you viewed an online animation, and created a sample sediment core as you manipulated Earth's temperature. In Antarctica, the ANDRILL project team uses a specialized drill to recover a series of sediment cores from the seafloor under the ice shelf. The core you will view in this part was brought up from between 200-212 meters below the ocean floor. It was drilled from an area of ocean which has been covered for several thousand years by an ice shelf. The sediment cores that are recovered by the drill took many millions of years to form. During this time period Earth went through several warming and cooling cycles. In this step you will be viewing a section of that core which was over 200 meters below the ocean floor was around 2.5 million years old. Look at the map below and locate the drill site on the Ross Ice Shelf. It is marked with "MIS" for McMurdo Ice Shelf.

Step 2 – View the Core Images

1. After looking at the map, above, view the core image here. Note: Once the image loads, it appears on the left side of your screen as a narrow line. You may need to click directly on the image to see the image in full size.
2. Next, go to the website gallery and view the core section. Move the slider on the left-hand side up and down to view the entire interval.
3. Examine the different layers of the core and use your sediment cards from Part 1 to find places on the core which represent the 4 sediment types on both the rotating and split core.

Sample of core 201-212 from gallery website.


4. Now, examine a graphic model of the core you have just viewed which looks like the image below.

201-212 m core with graphic interpretation. Click on image for a larger view.


Click here for a downloadable PDF of this image, with caption. Fig 16 Handout PDF (Acrobat (PDF) 550kB Sep8 10)
5. Examine the picture and model drawn with PSICAT. Identify the various layers. Notice that there are missing segments in the graphic where the sediment type is continuous between the numbers indicated. Record the lengths, in meters, of each sediment type. Compare the graphic model with the photograph and find the event boundaries, which is where the layers change.
Consider the following questions:
• Is the graphic model a good representation of the core, based on your observations of the picture?
• What changes would you make?
• Record your thoughts about this core in your journal.

Step 3 – Interpret the Core

1. Review the different climate events represented by the core pictured above. Write a short paragraph telling the climate change story contained in the core layers. Remember, the most recent (youngest) layer is on the top of the core (near the 201 mark).
2. Optional: Share your description and story. How does your description and story differ from others? Record your thoughts in your journal.
3. Observe the different lengths of each sediment type in the core. They are not the same. Which climate event do you think was the longest in duration? Hint: look at the different sediment rates on your cards from Part 1. Give a reason for your decision. Different scientists looking at these cores will come up with different answers; no one knows the answer for sure.

Step 4 – Make a Prediction

Based on what you have seen so far, how do you think cores from several different drill sites would compare to each other?

1. Look at the map above. Imagine that in the second season of the ANDRILL project, imagine the drill site was moved to location #2 on the map above. This location is closer to the shore than the first, "MIS", site. Now, pretend that at the second site, a core was recovered representing the same time period as the one you just examined. Think about how the sediment layers might differ.
   
   Use the questions below to guide your examination:
   • What differences in the kind of sediment would you expect to see for the same time period if the drill site was at point '#2'?
     Show me the answer
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     Answer: The types of sediments would be the same.
   • What difference in the length (thickness or thinness) of each sediment type would you expect to see for the same time period if the drill site were at point '#2'?
     Show me the answer
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     Answer: The thickness of the layers will be different. The advancing layer will be thicker because it started earlier, and the retreating layer will be thicker because it lasted longer. An open water layer will be thinner because the ocean was uncovered a shorter amount of time.
2. Record your thoughts in your journal.
Show me a hint to help with this analysis
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Refer to the animation if you need help with this step. In the animation, the drill site doesn't move. You'll need to use your imagination to add a second drill site closer to the left hand side of the animation. This represents a location closer to the shore in the diagram and similar to drill site #2 on the map. Run the animation and see how the sediment layers are different at the new location than at the original drill site, which does not change in the animation. You can compare them as the animation runs.

Step 5 – Explore Further

The ANDRILL scientists have asked you to come up with a way to determine how many years are represented in the section of the core 201-212. What information do you need to make this calculation? Propose a mathematical formula to determine the span of years represented by this core. The correct answer is an ongoing debate by the scientists who have analyzed this core section.