What Causes Floating Islands?
A floating island consists generally of a mass of earth held together by interlacing roots.
They occur on the Mississippi and other rivers, being portions of the banks detached by the force of the current and carried down the stream, often bearing trees. Sometimes such islands are large enough to serve as pasture grounds.
Artificial floating islands have been formed by placing lake mud on rafts of wicker-work covered with reeds. They were formerly used in the waters around Mexico, and may be seen in Persia, India, and on the borders of Tibet. On these the natives raise melons, cucumbers and other vegetables which need much water.