An ice core is a cylindrical sample of ice drilled from glaciers or ice sheets, such as those found in Antarctica and Greenland. These cores contain layers of ice that have built up over thousands of years, preserving information about past climate conditions, atmospheric composition, and volcanic activity. Scientists analyze ice cores to study climate change and understand how Earth's climate has varied over time. Each layer of ice represents a year or season, allowing researchers to reconstruct historical climate data and gain insights into the effects of greenhouse gases and other environmental changes.