The examples below are condensed to portray a brief overview of several paleocontinents. The time scales are on the order of
millions of years ago (mya).
Gondwana Location Gondwana was located in the Southern Hemisphere, with the land mass that makes up what is now the part of
Antarctica that is closest to the
South Pole. The continent reached from just above the
equator to the South Pole. In modern times,
South America and
Africa are the closest continents to the equator, and
Northern Africa crooses it.
Time period 600-180
mya, Precambrian - Jurassic Period.
Formation Gondwana was made of present-day South America, Africa, Arabia, India, Antarctica, Australia, and Madagascar. The continent had become fully formed by the late Precambrian period, 600 million years ago. It was an amalgamation of all of today's continents in the Southern Hemisphere. Gondwana lasted in many different time periods and was a part of other supercontinents like
Pangea.
Demise Gondwana broke up in distinct stages. The continent started to split during the
Jurassic Period around 180 million years ago. The first event was the separation of the western half of Gondwana, which includes Africa and South America, from its eastern half, which includes Antarctica, Australia, Madagascar, and India. Next, 40 million years later, South America and Africa began to split, which began to open up the Atlantic Ocean. Also around then, India and Madagascar began to detach from Australia and Antarctica. The separation created the Indian Ocean. Lastly, during the Cretaceous, India and Madagascar began to split, and Australia and Antarctica began to detach from each other. Also, vertebrates started to make an appearance in the fossil record. Terrestrial species started to become more prominent in the Silurian, but during the
Devonian, modern fish and shark species began to diversify, and terrestrial vegetation begun colonizing the continent, as organic soil accumulation can be detected.
Amniotic eggs started to evolve, as more terrestrial land became available with the rising land masses and lowering sea levels. During the Permian extinction, almost all marine species were lost, along with some terrestrial species. This event gave rise to terrestrial species, such as reptiles, dinosaurs, and small mammals. During the time of the
supercontinent Gondwana, Laurentia was smashed in between Eastern and Western Gondwana, but when Gondwana attached to Laurussia to form Pangea, Laurentia moved and became closer to Northern Africa.
Time period 4 bya-present day, Precambrian-Quaternary.
Formation Laurentia is the North American craton. It is one of the largest and oldest cratons dating back to Precambrian times. The craton itself includes the Canadian and Greenland shields, as well as the interior basin of North America, and the craton can also include the Cordilleran foreland of the Southwestern United States. The
craton itself formed in
deep time, the early Proterozoic age of the Earth and has stayed coherent since then. It formed through many different
orogenies and the suture zones that they create. The smaller land masses were made of
Archean crust and belts of Early Proterozoic island arcs. Laurentia has been a part of many supercontinents throughout its time. The formation of Laurentia is similar to the formation of Eurasia.
Demise Laurentia is presently still coherent and still a continental craton and now goes by the name North America. The craton can be found stretching from Alberta, Canada to the eastern coast of both Canada and the United States. The craton stretches from the Southeastern United States to Greenland. The western border of Laurentia can be found on the eastern side of the Rocky Mountains.
Life The sea level rose in the
Cambrian period, which gave rise to marine invertebrates, which flourished.
Climate Laurentia experienced a variety of climates, as it has been a land mass for billions of years. The craton experienced an ice age during the late Proterozoic and another during the Ordivician period. The Cambria had no ice age and was slightly warmer, as most continents avoided the poles, which gave the land a milder climate.
Time period 299–272 mya to 200 mya, Early Permian-Early Jurassic.
Formation Pangea was created by the continent of Gondwanaland and the continent of
Laurussia. During the
Carboniferous period the two continents came together to form the supercontinent of Pangea. The mountain building events that happened at this time created the
Appalachian Mountains and the Variscan Belt of Central Europe. However, not all landmasses on Earth had attached themselves onto Pangea. It took until the late Permian until the Siberian land mass collided with Pangea. The only land mass that was not be part of Pangea was the former North and South China plates, which created a much smaller land mass in the ocean. There was a massive ocean that encompassed the world; it is called
Panthalassa because most of the continental crust was sutured together into one giant continent, which had a giant ocean to match.
Demise Pangea broke apart after 70 million years. The supercontinent was torn apart through fragmentation, when parts of the main landmass would break off in stages. Two main events that led to the dispersal of Pangea. The first was a passive rifting event that occurred in the
Triassic period. The rifting event caused the
Atlantic Ocean to form. The other event was an active rifting event. It happened in the
Lower Jurassic and caused the opening of the Indian Ocean. The break-up took 17 million years to complete.
Life Pangea formed roughly 20 million years before the Permian Extinction, when over 95% of all marine species and 70% of terrestrial species were lost. The Triassic period of Pangea became a time of recovery from the Permian Extinction. The recovery included the rise of sea levels, which created extensive shallow oceanic shelves for large marine reptiles. The recovery period had terrestrial animals flourish and land reptiles diversify and flourish, along with the appearance of dinosaurs. The dinosaurs would become what would characterize the life during the Jurassic and the Cretaceous periods. At the end of the Triassic and the beginning of the Jurassic periods, small shrew-like mammals first appearedm which came from reptiles.
Climate The main characteristic of Pangea's climate was that its position on Earth helped start a cycle of megamonsoonal circulation. The monsoons reached their maximum strength during the Triassic period of the Mesozoic. During the late Carboniferous, peat was formed in what is currently Europe and the eastern areas of North America. The wetter, swamp-like conditions necessary to form peat were contrasted with the dry conditions on the Colorado Plateau. Near the end of the Carboniferous, the region of Pangea centered on the equator became drier. In the Permian, the dryness contrasted with seasonal rainfall, and that type of climate became more normal and widespread on the continent. However, during the Triassic, the Colorado Plateau started to regain some moisture, and there was a shift in wind direction. Around the same time, parts of what is now Australia were at higher latitudes and much drier and seasonal in character. At the start of the Jurassic, the megamonsoon started to fall apart, as drying started in Gondwana and the southern portion of
Laurasia.
Rodinia Location Rodinia was centered on the Equator and reached from 60° N to 60° S.
Time period 1.2-1 bya to 800-850 mya,
Proterozoic Eon - end of
Precambrian.
Formation It was the first supercontinent to form on Earth, when all of the continental crust on Earth came together and formed one giant land mass. The land mass was surrounded by an even larger ocean, known as Mirovia. There were about four smaller continents, which collided and came together to form Rodinia. The event is called the
Grenville Orogeny. Mountains were built along the places the ofwere continents collided. The continental crust was not very dense and so neither continent would sink or subduct. That caused the formation of
fold and thrust belts, similar to the Himalayas today. Also, the atmosphere had little oxygen because Rodinia's land surface was too harsh of an environment for land plants to flourishé The atmosphere was devoid of oxygen, and the ozone layer was much less extensive, which is attributed to the harsh land environment. ==See also==