1 In recent years, the U.S. has seen a number of winter storms that have caused surprisâ¦. 2  The Periodic Table of Elements Life is sustained by a number of chemical elements. 3  They are responsible for the birth of planets and the evolution of cells to complex organisms.
Water distribution on Earth - Distribution of saline and fresh water. 1  The total volume of water on Earth is estimated at 1.386 billion kmÂ³ (333 million cubic miles), with 97.5% being salt water and 2.5% being fresh water. 2  The total volume of water in rivers is estimated at 2,120 kmÂ³ (510 cubic miles), or 2% of the surface fresh water on Earth.
The saltwater in Earth's oceans has an average salinity of 3.5 percent, and freshwater in Earth's lakes and streams has less than 0.5 percent. Freshwater is a basic need for all animals, including humans, which makes the discussion of water one of the most important in this course.