Difference between radiometric radiocarbon dating
These data can be combined to find the climate model that best fits all the available data. Coastal areas are more likely to include material of marine origin, such as sea salt ions.
Greenland ice cores contain layers of wind-blown dust that correlate with cold, dry periods in the past, when cold deserts were scoured by wind.
Ice cores are collected by cutting around a cylinder of ice in a way that enables it to be brought to the surface.
Early cores were often collected with hand augers and they are still used for short holes.
When the sun approaches its lowest point in the sky, the temperature drops and hoar frost forms on the top layer.Cores are drilled with hand augers (for shallow holes) or powered drills; they can reach depths of over two miles (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.Below this depth, electromechanical or thermal drills are used.The cutting apparatus of a drill is on the bottom end of a drill barrel, the tube that surrounds the core as the drill cuts downward.