Ice cores are pretty amazing. > Cores are drilled with hand augers (for shallow holes) or powered drills; they can reach depths of over 3.2 km, and contain ic

Ice cores are pretty amazing. > Cores are drilled with hand augers (for shallow holes) or powered drills; they can reach depths of over 3.2 km, and contain ice up to 800,000 years old. > The physical properties of the ice and of material trapped in it can be used to reconstruct the climate over the age range of the core. The proportions of different oxygen and hydrogen isotopes provide information about ancient temperatures, and the air trapped in tiny bubbles can be analysed to determine the level of atmospheric gases such as carbon dioxide. https://en.wikipedia.org/wiki/Ice_core https://en.wikipedia.org/wiki/Ice_core (edited for SI units preference)