原题
Ancient Air in Glaciers
Glaciers, repositories of ancient ice, serve as frozen libraries of Earth's climatic history. As snow accumulates and compresses over centuries, it traps air bubbles that create tiny atmospheric snapshots. These bubbles are crucial for understanding climate evolution. By analyzing the gases within the bubbles, researchers are able to reconstruct past concentrations of greenhouse gases like carbon dioxide and methane, revealing both natural climate cycles and the escalating impact of human activity.
Though many glaciers are retreating due to rising temperatures, surviving ones offer a window into the past. Scientists drill deep into the ice to extract cylindrical cores, whose layers, much like tree rings, correspond to distinct time periods. These layers contain more than just gases: They hold chemical and physical markers of past environmental events. Ice cores can reveal data about volcanic eruptions via ash and sulfate layers, solar activity via isotopic changes, and forest fires via trapped particulates and black carbon.
Recent studies underscore the precarious future of these icy archives. As glaciers melt, they contribute to rising sea levels, and the risk that invaluable climate data will be lost increases. The urgency to study and preserve these records grows. While scientists race against time, the question remains: what secrets do these frozen giants still hold?
Why does the author mention "tree rings"?
ATo compare the usefulness of trees and ice cores for studying past climates
BTo highlight the extreme age of some layers of ice cores
CTo illustrate the layering that exists in ice cores
DTo contrast the physical markers present in tree rings with the chemical markers found in ice cores
正确答案：C
解题思路
老师暂未填写解题思路。