MidOcean Ridges and Plate Tectonics: The Formation of an Island

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Mid-Ocean Ridges and Plate TectonicsThe
Formation of an Island

• Amanda Greenhalgh
• Gena Renninger
• Tom Sabbatelli
• Joe Swearman

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Presentation
The following topics will be covered in depth
Mid-ocean ridges
Tectonic plate interactions
Island formation and examples
- Surtsey (Iceland)
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What is a Mid-Ocean Ridge?
Formed by two divergent tectonic plates,
spreading Earths crust apart, creating new ocean
floor
Magma wells to the ocean floor, forming
underwater mountain ridges, valleys, and volcanoes
Process of forming new sea floor known as
sea-floor spreading
New ocean floor constantly becoming renewed and
created by plate spreading
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Types of Mid-Ocean Ridges
Ridges shaped differently according to spreading
speed and volcanic activity
Faster ridges hotter because more magma and
more fluid, easier spreading
Slower ridges crack and break when pulled apart
enough, breaking into ridges and valleys
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Tectonic Plate Interactions
There are three types of tectonic plate
interactions based on the relative movement of
the plates, two of which can eventually form
islands
Transform Motion
Two tectonic plates simply slide past one another
Offsets active spreading plates, creating zig-zag
plate margins
Characterized by subtle underwater earthquakes
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Tectonic Plate Interactions
Convergent Plate Interactions (Subduction)
Two plates collide, forcing one plate to descend
under the other
Buckles the earths crust up, creating an oceanic
ridge
In subduction, descending plate melts when
reaching a hot depth
The molten crust spews back towards the surface,
creating underwater mountains, volcanoes, and
perhaps even islands
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Convergent Plate Interactions
Diagram of convergent plate interactions
(http//www.windows.ucar.edu)
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Tectonic Plate Interactions
Divergent Plate Interaction (Hot Spots)
Tectonic plates separate, causing magma and
molten rock to spew upward
Magma cools and hardens, forming new crust and
ridges
Solidified rock/magma piles up to form seamounts,
then islands
Mid-Atlantic Ridge a prime example of divergent
interactions
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Island Formation
Examples of islands formed by mid-ocean ridges
and tectonic interactions include Hawaii, the
Galapagos chain, the Azores, and Iceland
Every year new islands continue to be formed
Seamount christened Kick em Jenny only 492
feet under the sea, could break ocean surface
within a year
Most famous recent island formation was Surtsey,
off Iceland
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The Mid-Atlantic Ridge
Slow-spreading mid-ocean ridge branch that runs
up the middle of Atlantic Ocean, from Iceland to
Antarctica
Longest mountain range on Earth
Separates the North American and Eurasian plates
in the North Atlantic
Separates the South American and African plates
in the South Atlantic
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Surtsey
Formed between 1963 and 1967 after a series of
episodic volcanic explosions
Icelandic island located just off southern coast
of the country
Current elevation of 174 meters
Named after Surtur, a fire-possessing giant in
Norse folklore
Surtsey (http//volcano.und.nodak.edu)
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Surtseys Formation
First explosions occur November 1963
Lava flowed continually through May 1965,
solidifying into hard shell
Massive submarine eruption in an active fissure
in the Mid-Atlantic Ridge
Eruptions ended in 1967
After the final eruption, Surtsey measured 170
meters above sea level with an area of 2.7 km²
Molten lava as hot as 1150C spewed upward from a
depth of 130 meters
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Surtseys Formation
Images of Surtsey (http//www.icelandicgeographic.
is)
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Surtseys Value
Volcanic island manifests tornados, hail,
waterspouts, and lightning on its own
One of the few valuable opportunities modern
scientists have to study formation of new land
and a new ecosystem
Species of animal, plant, insect, and sealife
have all developed in past 40 years
Salix, one of the many plants growing on Surtsey
(http//www.vulkaner.no)
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Surtseys Value
Example of Surtseys influence on weather
phenomena (http//www.vulkaner.no)
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Conclusion
Why should you care? What makes this relevant?
The spreading of mid-ocean ridges and tectonic
plate interactions are still ongoing processes
Mid-ocean ridges separate several inches per
year, on average
New islands continue to form year after year
Within a year, Kick em Jenny could become the
worlds newest island and ecological resort