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| An artist's idea of the Archean Image courtesy of: http://www.etsu.edu/physics/plntrm/dino/stromat.gif |
It is under debate when the first continents appeared. During the Archean, areas of land increased in size because of a more stable crust. In the Middle Archean, the first continent-sized land masses appeared. These protocontinents only exist as traces in cratons (which will be explained in more depth when reading about Geology) or resting on continental plates. While we are not sure exactly when, the Archean is the eon in which the continent first began, because it was the first time the Earth was stable enough for continents to exist.
There are two major theories about continents in the Archean:
- The first theory says that no large continents existed until late in the Archean, instead small "protocontinents" were the norm, prevented from growing until the late Archean because of huge amounts of tectonic activity. Eventually, these protocontinents would grow and band together in the late Archean to make larger continents that eventually led to Pangaea, and our seven continents today.
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| The darkest orange are the protocontinents. Image: http://media-2.web.britannica.com/eb-media/89/789-004-B50C80D0.gif |
The other theory follows the ideas of Richard Armstrong, who thought continents grew the way they did in the first 500 million years of Earth's history, and have stayed constant ever since- for most of history, the recycling of continental material keeping growth in check.
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| A map showing Richard Armstrong's theory. http://www.innovateus.net/science/what-archean-eon |
Either way, major continent formation existed during the Archean. An Archean supercontinent called Ur is well known for consisting of many cratons. It is thought to have survived for a long time, joining to create Rodina, and eventually Pangaea.
The Archean was colorful, skies were orange from methane and the oceans were green from dissolved iron compounds. As the crust stabilized continents' mass increased with stromatolites lining shorelines. The remnants of old protocontinents are on cratons.
ReplyDeleteDuring the Archean, it was very colorful. The sea's were green because of dissolved iron compounds and the skies were orange due to high methane in the atmosphere. There were tons of volcanoes, and the shoreline were full of stromatolites. Also, ares of land increased because there was a more stable crust.
ReplyDeleteDuring the Archean Eon, the sky was orange due to increased levels of CO2 and methane. The sea was green because of dissolved iron compounds. Stromatolites, or colonies of blue-green algae, monopolized the shores. The Earth underwent major crust formation during this time, and it eventually the protocontinents which formed here accreted to form Rodinia, and then Pangea.
ReplyDeleteThe Archean period was colorful because of what the earth and atmosphere were made up of such as the sky was orange because of methane and sea green because of iron compounds that had been dissolved. As the crust stabalized protocontinents were formed , because there was to much techtonic activity for much larger. As well as a slit up of Ur that created Rodina and later Pangea.
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