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Plates and Gates
ELF Activity: Geosphere 2A
http://andrill.org/education/elf/activities/2A
The Current Location of Continents on the Earth Today
If these were pieces to a puzzle, can you see how they would fit together?
The Continents and the Plates They are Riding On
Notice that some plates are only ocean, while others have areas of ocean and land
masses. Which plate do you live on?
The land masses on Earth were not always in
the same position as they are now.
This is how the continents were
positioned 250 million years ago
(mya). The supercontinent was
called Pangaea.
Approximate location of the Equator
Predict which regions were
warmer 250 mya based on their
location. Which ones were
colder?
Pangaea
It took approximately 180 million years for the plates to
move from their position in Map 1 to Map 2.
1
2
Notice how Antarctica has broken away
from South America and all the other
continents, then moved south and become
isolated.
How the Movement of the Earth’s
Plates Affected Life in the Oceans?
How the Movement of the Earth’s
Plates Affected Life in the Oceans?
There are over 300 species of octopuses and their
range is worldwide. One question researchers ask is:
How are octopus species related?
We have seen that continental drift caused Antarctica to be separated from South America about 34 mya.
The Drake Passage was formed, creating a cold oxygen-rich deep water environment. The fossil record
shows new species of deep water octopus evolved about the same time. When similar species of octopus
were found in deep waters in the Northern Hemisphere, researchers wondered where they came from.
The activity explores where these deep water octopus originated and how they spread worldwide.
Close-up map of the Drake Passage showing the
bathymetry (shape of the ocean floor) in this region.
When the lines are very close, it indicates a steep drop.
When the ‘gate’ opened up between Antarctica and
South America, the waters from the Pacific could mix
with the Atlantic. Species that were previously only in
one ocean were now found in both.
Here you can see how the ocean current going around Antarctica keeps the water
cold. Notice the swift drop in water temperature at the Polar Front. South of the
Polar Front there is very little mixing of water from warmer latitudes; this is one
reason Antarctica is so cold.
South
North
About 33-34 mya, Antarctica split
off from South America, forming
this deep cold channel. As the
water became colder, it could hold
more oxygen so organisms
migrated deeper and deeper.
As Antarctica became more isolated
from the other continents, it became
colder. The Antarctic Circumpolar
Current surrounded the continent so
the mixing with warmer waters from
the north no longer occurred. As a
result, ice sheets began to form. The
plants could no longer live there and
the animals either left, adapted to
food from the sea, or became extinct.
The black line shows how much
oxygen can be dissolved in water as
the temperature increases. Notice
that as the water gets warmer, the
less oxygen it will hold. This means
that the colder the water, the more
oxygen it will hold.
As the colder waters around Antarctica began to hold more oxygen,
octopus species began to migrate to the deeper levels and developed
new species that could only live in the deeper regions.
As the colder waters around
Antarctica began to hold more
oxygen, octopus species began to
migrate to the deeper levels and
developed new species that could
only live in the deeper regions.
(b) Example of deep water species
that evolved about 34 mya as the
Drake Passage was opening. The
deep water species have a small,
non-functioning ink sac.
Shallow water species (a, c, d) found
in various places around Antarctica
contain a large, functioning ink sac.
Recently, Antarctic deep water octopus species were
found to be related to similar deep water species in
the Northern Hemisphere. How did they get there?
Blue = deep cold water
Red = warmer surface water
www.oceanservice.noaa.gov/education
As the continents moved to their current position, ocean currents began to form. Cold, deep water
from Antarctica is moved along the bottom of the ocean and surfaces near areas where warm
water is being cooled. Follow the arrows in the map below to see where warm water near the
Arctic is cooled, sinks, and forms a large conveyor belt of water throughout the Earth’s oceans.
With the development of the deep ocean conveyor belt, which picks up cold water in Antarctica,
deep water octopus species were able to migrate to the Northern Hemisphere.
This map shows the deep cold water species of octopuses that developed AFTER the Drake
Passage opened and the waters became deep, cold, and oxygen-rich. The blue lines show
the flow of deep cold water and you can see how they were able to migrate to other deep
water areas around the world.
Cousins of the deep water octopus species which evolved
in Antarctica are found in these areas. They are carried by
this cold, deep ocean current.
Meet the scientist who gathered data and put
this story together. Jan Strugnell with one of her
octopus species. Want to read more about her?
Go to:
http://www.antarctica.gov.au/science/meet-ourscientists/dr-jan-strugnell
This material is based on work supported by an Environmental Literacy Grant from
the National Oceanic and Atmospheric Administration’s Office of Education
(NA09SEC4690009) and prior work supported by the National Science Foundation
under Grants ANT-0342484 and ESI-0632175. Any opinions, findings, and
conclusions or recommendations expressed in these materials are those of the
authors and do not necessarily reflect the views of the National Oceanic and
Atmospheric Administration or the National Science Foundation.
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