water systems

The very existence of floating islands seems counterintuitive.  Are there really chunks of earth solid enough to support our weight while drifting over the surface of a body of water?  Can these floating masses even support the weight of trees, animals or even human dwellings? The fact is that floating islands do exist on six of the seven continents and sometimes on the oceans between.  Some do have trees growing on them and do support the weight of humans (and even grazing cattle).  Some are, in fact, hundreds of feet across and are called "home" by their inhabitants.   These naturally occurring, waterborne vessels embody a fascinating subset of natural observation and are generally unknown - even though they