The groups will examine each of the maps in turn for a few minutes and then move to the next map, until each group has observed each map. Each map probably will have more than one group examining it at a time. Researchers get information about the thickness of the ice sheet and depth to basement through cores - a data collection method similar to the way students collected topographic information in their mystery boxes. They also use other techniques, using sound waves and electromagnetic waves. The researchers using electromagnetic waves to image through the ice sheet use radio waves.
Scientists use devices to generate radio waves at the surface of an ice sheet.
The radio waves travel through the ice sheet. The scientists can figure out where the object is under the ice using the amount of time the wave traveled to the object and back. The students will look at GPR data from the ice sheet later in the activity. The time has to be divided in half because the time the scientist records includes the wave's trip to the object and the wave's trip back to the surface. Have each group work near a wall.