Evolution of the continents

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New York State Museum Teachers Workshop On
Evolution February 6, 2009
Evolution of the continents
Dr. William Kelly
New York State Geological Survey
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Continents large blocks of low-density rock
permanently removed
from crustal recycling process
Continent crust 2.7 SG Ocean crust 3.0 Mantle
- 3.2 to 4.1 Outer core 9.9 Inner core 12.7
Oldest rocks 4.28 Ga (?) oldest
mineral 4.404 Ga in rocks 3.8Ga
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How do we know?
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How do we know?
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Ancient continents
All smaller than continents today Ur
smaller than modern Australia
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Ur 3.0 Ga
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Evolution of Ur 3 Ga (Giga or billion years),
Ur formed as a rare continent on Earth 1 Ga, Ur
was part of the supercontinent Rodinia 300 Ma
(million years), Ur was part of the
supercontinent Pangea 208 Ma, Ur was torn into
parts of Laurasia and Gondwana 65 Ma, the
African part of Ur was torn apart as part of
India Currently, pieces of Ur are in Australia,
India, Africa and Madagascar
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Arctica 2.5 Ga
Nuvvuagittuq gneiss 4.28 Ga
Acasta gneiss 4.04 Ga
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Evolution of Arctica 2.5 Ga Arctica formed
from Siberian Canadian shields 1 Ga Arctica
became part of supercontinent Rhodinia 750 Ma
Arctica tore off Rhodinia becoming part of
ProtoLaurasia 320 Ma Arctica combined with
several smaller land masses Ultimately forming
part of Pangea 208 Ma Arctica was torn apart as
Pangea broke up Currently, pieces of Arctica are
in Canada and Siberia
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Atlantica 2.0 Ga
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Evolution of Atlantica 2 Ga, formed from rocks
now in South America and Africa 1.8 Ga become
part of supercontinent Columbia 1.1 Ga
Atlantica became part of Rodinia 500 Ma
Atlantica is part of Gondwana, then part of
Pangaea 208 Ma, Pangaea torn apart, splitting
Atlantica Currently, remains of Atlantica are in
Africa and South America
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Nena 1.8 Ga
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Evolution of Nena
1.8 Ga, formed from Arctica, Baltica and
Antarctica becomes part of supercontinent
Columbia
1.5 Ga, survives breakup of Columbia intact
1.1 Ga becomes part of Rodinia
750 Ma, survives breakup of Rodina mostly intact
600 Ma, becomes part of Pannotia
540 Ma, Pannotia rifted, Nena torn apart
Currently, the remains of Nena are in Canada,
northern Europe, Siberia and Antarctica
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Ancient supercontinents one large landmass
Supercontinent cycle ?quasi-periodic aggregation
and dispersal of crust ? continents are
constantly reconfigured as long as plate
tectonics works
Suggests a cycle of 750 Ma 500 Ma
assembly 250 Ma dispersal
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Columbia 1800 1500 Ma
Atlantica
Ur
Nena/Arctica
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Rodinia 1100 700 Ma
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Rodinia rifted into pieces that formed
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Congo, Proto-laurasia, -gondwana formed Pannotia
short lived, 60 Ma
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Pangaea 500 -160 Ma
Laurasia
260 m.y.
Gondwana
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Today..... But what about tomorrow?
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Pangaea Ultima
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