J Collins, Toowoomba, Qld
We were driving past Boyce Gardens in Toowoomba on a rainy day, and saw this line of trees dripping in foam. The foam puddled on the ground and took some time to dissolve. Can you explain what causes this?
Elizabeth Swane says
This is an interesting natural phenomenon. When it rains, water running down the trunk of the tree dissolves chemicals from the bark. A change in surface tension occurs, air is introduced to the water and a foam is formed. This is similar to the foam you sometimes see in a creek or on the ocean shore, when phosphates combine with water and air. A foaming tree, often a eucalypt, after rain is nothing to worry about. Enjoy nature at work!