for better research go to under NOAA - Climate.gov
This is a short paraphrased summary of the article about ice cores in that website.
Answer: Researchers in labs may melt or crush bits of the ice core a little at a time, each deeper layer shows the time in the Earth's climate history. Tiny pieces of pollution, metals, radoiactive fallout, pebbles, sea salt, volcanic ash and even air bubbles all present important information that researchers can look for to track changes in the atmosphere's composition and temperature.
I think it is c.polynesian
Tectonic plates is a theory that the lithosphere is separated into plates that move over the asthenosphere, the molten upper portion of the mantle. Oceanic and continental plates come together, spread apart, and interact at boundaries all over the planet.
Tectonic plates float on top of the molten rock and moving around the planet. The heat from radioactive processes within the planet's interior causes the plates to move, sometimes toward and sometimes away from each other. This movement is called plate motion, or tectonic shift.
