One student filled three-fourths of a flask with water and closed its mouth with a rubber stopper. He put a glass tube through the hole in the rubber stopper. The flask was heated on a Bunsen burner. After some time the boiling water was forced up through the glass tube as shown below. (1 point) Image of a flask sitting on a Bunsen burner, the flask is 3/4 filled with water, the flask is closed with a rubber stopper that has a glass tube through it, water is rising to approximately 1/3 of the glass tube.

The student's experiment demonstrates the formation of
wells
caves
geysers
sinkholes