Drainage Patterns
Drainages tend to develop along zones where rock type and structure are most easily eroded. Thus various types of drainage patterns develop in a region and these drainage patterns reflect the structure of the rock. Continental Divides - Continents can be divided into large drainage basins that empty into different ocean basins.
For example:
In Eastern Australia a coastal mountain range creates the Great Divide; rivers to the east flow into the Coral Sea and rivers to the west flow inland to the site of a sea that no longer exists or to the Gulf of Carpenteria.
In North America can be divided into several basins west of the Rocky Mountains that empty into the Pacific Ocean. Streams in the northern part of North America empty into the Arctic Ocean, and streams East of the Rocky Mountains empty into the Atlantic Ocean or Gulf of Mexico. Lines separating these major drainage basins are termed Continental Divides.
Such divides usually run along high mountain crests that formed recently enough that they have not been eroded. Thus major continental divides and the drainage patterns in the major basins reflect the recent geologic history of the continents.
