Bethany Goodine and Brittany Hood
November 2010
Science
 What
is a continental drainage system?
- in North America, the continuous ridge of
mountain summits dividing the continent in
to two main drainage systems. On one side
rivers and streams go to the pacific and on
the other they go to Hudson’s Bay or the Gulf
of Mexico.
 What is an Ocean Basin?
- Ocean basins are deep wide depressions in
the Earth’s surface that contain the oceans.
 In
the late 60’s , J. Tuzo Wilson realized that
if continents rift apart to create ocean
basins, then other oceans must have been
closed in the process. This has happened in
Earth’s history and might be repeated in the
future.
 For example. The Iapetus ocean between
England & Scotland closed in the Caledonian
and later it opened as the Atlantic Ocean in
almost the exact same place.
 This process is called the Wilson cycle.
 According
to
http://www.le.ac.uk/geology/art/gl209/lect
ure3/lecture3.html, there are 4 steps in the
process:
 (1) Rifting of continents by mantle diapirism.
 (2) Continental drift, seafloor spreading &
formation of ocean basins.
 (3) Progressive closure of ocean basins by
subduction of ocean lithosphere.
 (4) Continental collision and final closure of
ocean basin.
 Ocean
basins are formed by tectonic forces
and processes.
 In history, tectonic plates moved and created
large basins which filled with water and now
hold the worlds oceans and seas.
Drainage Systems



These systems develop
so that water can
efficiently run off land.
Drainage Systems are
created so water from
small drainage basins
surrounded by land
empties into the ocean.
Drainage basins empty
into streams, which
empty into more
streams etc. until the
empty into the ocean.
http://www.tulane.edu/~sanelson/geol111/streams.htm
Theories of how Continental
Drainage Systems are formed.
 Plate
Tectonics.
-These are moving because of currents in
the magma and affects the drainage patterns
of the continents.
 Glaciers.
- They melt because of climate change and
the water has to flow out into the ocean and
creates paths that create new drainage
systems.
 Rift:
etc.
an opening made by splitting, cleaving,
 Streams
and drainage systems. (2010, November
15). Retrieved from
http://www.tulane.edu/~sanelson/geol111/strea
ms.htm
 http://www.edquest.ca/component/content
/article/122
 http://www.tulane.edu/~sanelson/geol111/s
treams.htm