Answer:Ice that formed thousands of years ago is often found to contain tiny bubbles of gas. This gas came from the ATMOSPHERE.
Step-by-step explanation:
Atmospheric gases which consists of carbondioxide, nitrogen oxides and rare gases can be trapped inside the water body as bubbles. If these bubbles are surrounded by ice when they form, they get trapped and remain in the ice cube. A typical example of ice that contains bubbles of gases includes glacier ice. These are mass of ice that moves slowly over the land. It preserve bits of atmosphere from thousands of years ago in tiny air bubbles, or, deeper within the core, trapped within the ice itself. This is one way scientists know that there have been several Ice Ages.