It is not uncommon to see a working model of a volcano at a science fair. Usually the model is activated by mixing vinegar and baking soda. Although this is a decent rendering of a volcano, you can create other forms of volcanoes. Underwater volcanoes are easy to make with two glass containers, yarn, water and food colouring, and making an underwater volcano will be a pleasant change from the baking soda volcanoes.
Cut a 2-foot length of yarn with a pair of scissors. Tie a knot around the neck of a salt shaker with one end of the yarn. Double-knot it to ensure the knot is secure. Repeat this process with the other end of the yarn, resulting in a handle to lower your shaker. Trim the yarn before tying the ends if it seems too long. The length of yarn may vary based on the size of the salt shaker and your larger jar.
Empty and clean a large jar, such as a large pickle jar. Fill the clean jar about three-fourths full with cold water.
Fill the salt shaker with hot water---as hot as you can get from your faucet---to just below the neck. Add three to four drops of red food colouring.
Hold your salt shaker over the mouth of the pickle jar by the yarn handle. Slowly lower the salt shaker into the pickle jar until the shaker is completely submerged and resting upright on the bottom of the jar. Observe how the coloured water erupts from the shaker into the cold water.
Try different colours of food colouring if you desire. Your salt shaker and pickle jar can be replaced with any kind of glass container. The important thing is that the smaller one will fit easily inside the larger jar. Use very cold water and very hot water for best results.