GEOGRAPHY [Social Studies] * PLATE TECTONICS [EaS] * EXTREME ENVIRONMENTS [EaS]
Objectives
After viewing the video and participating in one or more of the Hands-On and/or Online Activities, students will be able to:
• describe how and why researchers use sound waves to study the mile-deep and otherwise inaccessible rock-ice boundary
• relate Earth's internal heat and volcanic activity to the motions of ice streams and glaciers
• compare and contrast how 2 researchers use fossils and the rock record to argue for two different climate histories of Antarctica
• list and discuss evidence presented by both sides in this debate about climate, and appreciate their ongoing debate as a case study for how science works
Program Description
It was the Greek natural philosopher, Heraclitus, who said that the only thing that's constant is change. Yet on geological time scales, over millions of years, gradual change is sometimes hard to see. This video provides informative and intriguing examples of how both innovative technology and good, old-fashioned pick and shovel field work can help us understand how Antarctica and the Earth have changed over time. In addition to seeing inherently fascinating phenomena such as volcanoes, ice caves and ice streams, this program provides an intriguing case study in the scientific method, relating to Science Standard 15 "Understands the nature of scientific inquiry," (Project 2061 Benchmarks for Science Literacy, page 9).
• "Ice in Motion" (04:51) Could Antarctica's huge repository of ice melt and change global sea levels? This segment begins by showing how and why NSF and the U.S. Geological Survey reposition the marker for Earth's geographic South Pole each year to compensate for the annual 10 meters the ice sheet moves over the underlying surface. Out in the middle of the vast Central West Antarctic ice sheet (CWA), geologist Sridhar Anandakrishnan (now at the University of Alabama) shows us how his team uses seismic charges to document the movement of fast-moving streams of ice by imaging the mile-deep rock-ice boundary. Some of these streams (seen in NASA computer animation based on space radar imaging) flow up to 2,000 ft per year which is, as Sridhar says, an "enormous" speed for a glacier. Supporting the CWA experiment takes a little village out on the ice, a team of drillers from PICO, the Polar Ice Coring Office, and lots of good, hot food! Anandakrishnan's work helps wire the continent to make it a kind of early warning system to show us the rate and direction of global climate change.
• "Fire Down Below!" (02:10) One possible reason for the rapid motion of the ice streams may be Earth's geothermal heat. Location footage and animation shows Earth's internal structure, and what happens when Mount Erebus pokes up through Earth's crust as our planet's southernmost active volcano. On the rim of the volcano, Nelia Dunbar shows us the volcano out-gassing some of the constituents of our atmosphere. Farther down the flanks of the 13,000 foot mountain, her colleague from the New Mexico Institute of Mining and Technology, Bill McIntosh, takes us inside one of the beautiful ice caves, carved by the volcano's heat. Could this be, he wonders, analogous to the processes which make the ice streams slip over the West Antarctic rocks?
• "Reading the Rocks" (06:11) This segment shows 2 geologists attempting to document Antarctica's past climate, in part, to provide a baseline upon which to understand what might happen in the future. Dramatic scenes of remote field camps and extreme conditions (note the ice encrusting Dave Marchant's beard!) make the tale of the "Two Daves" a compelling example of how science uses hard (in this case, rock) evidence to illuminate important but difficult questions. The Daves fundamentally disagree. David Harwood: "One view that we hold is that the ice sheet has been very dynamic: growing ice sheets, shrinking ice sheets, growing ice sheets, shrinking ice sheets, through time." Dave Marchant: "The volcanic ash story has told us that Antarctica has been a cold desert for 15 million years, and it's a frozen landscape." Students will see the two researchers marshal some of the evidence which lies behind and below their strongly held opinions. Harwood points out how layers in the rock contain evidence of what's older and what's younger, and shows us fossils of the diatoms and leaves he thinks prove Antarctica was much warmer and wetter just a few million years ago. At a still more remote 2-person field site, Marchant, by contrast, shows us volcanic ash trapped in distinctive cracks which he believes could only have been made if Antarctica has been locked in a perennial deep freeze for at least 13 and-maybe-30 million years. As Harwood concludes, in something that is the credo of true scientists everywhere: "The only way we're going to resolve these two different views, one a 'stablist' view, one a dynamic view, of the ice sheet, is by collecting more information. By working on these rocks that are here around us, by discussing the various bits of evidence, finding the weak points, posing the new questions."
