Mixing the Paste: In a medium bowl, combine 2 cups of baking soda, 2 tablespoons of corn starch, and 2 tablespoons of water.
Divide and Color: Separate the mixture into three bowls. Add several drops of blue, green, and brown food coloring to each bowl, respectively, and mix until you achieve a paste consistency. Adjust with more water or baking soda as needed.
Creating the Earth: In your sensory bin, use rocks to outline a circle. Spoon the blue paste inside for water, and add the green and brown pastes around it to represent land and mountains. Arrange your animal toys accordingly.
Start the Fizz: Pour some vinegar into a bowl and hand your little one an eye dropper and invite them to squeeze the vinegar onto the earth. It will create a really cool fizzing sound and action as the vinegar reacts with baking soda.