Question 1

Supercontinents

Accepted Answer

Over cycles of 250 - 300 million years, continental masses come together and separate. While landmasses are nowadays fragmented, our planet has been through several phases where these would merge into a « supercontinent » : a single mass aggregating most - if not all - of the emerged lands. The most recent of these, Pangea, was named by Alfred Wegener, who devised the continental drift theory. Pangea broke up 200 million years ago into two major chunks  – Gondwana to the south and Laurasia to the north – with the latter having a part in the formation of Eurasia and North America. Other supercontinents existed prior to Pangea, such as Ur, Columbia, Rodinia or Pannotia. Their formations and breakups resulted in geological and climatic disruptions, as it was the case for  Rodinia,  the  fragmentation of which is thought to be connected to the Snowball Earth episode.

Question 2

Funfact | Not a piece of cake

Accepted Answer

Reconstructing the lost continents is just like trying remaking a cake that was baked, cut, squashed and glued back not in the correct order while some  parts are missing or misshapen.

Question 3

Funfact | Superoceans

Accepted Answer

When continents aggregated into  supercontinents, they were surrounded by vast oceans - or superoceans - such as Mirovia around Rodinia or Panthalassa around  Pangea.  The Tethys ocean separated the continents 200 million years ago.

Question 4

Snowball Earth : the big freeze step by step

Accepted Answer

About 800 million years BP, the  continents were joined together in a supercontinent : Rodinia.When Rodinia broke up, new oceans and marine inlets opened up, releasing thus more water vapour in the atmosphere. Precipitations increased, capturing CO₂ from the atmosphere  that got trapped in the ocean in the form of carbonates.Concurrently, the continents were covered by massive flows  of basaltic lava. Basalt can absorb CO₂ eight times more efficiently than granite.Less CO₂ meant a reduction in greenhouse effect : the climate got colder. To cap it all, a younger and less luminous Sun   (6 % less radiation than present day).Ice reached the  tropics, which increased the planet's albedo : more sunlight was reflected , aggravating thus the global cooling .This process results in a global glaciation also known as Snowball Earth, about which a mystery persists  : was there still a free oceanic band near the equator ? Science has not decided yet… Snowball Earth :the deep freeze step by step.

Snowball Earth

720 million years ago, the Earth began to cool and all the oceans began to freeze: this was the beginning of a long and cryogenic period, the Sturtian glaciation.

The temperature was about -50 °C in the coldest areas, whereas the equator could boast -20 °C. Almost the entire planet was covered by glaciers. In spite of extreme cold, life would still hold on fast : microscopic organisms managed to survive under the ice sheets.

Informations complémentaires

Supercontinents

Funfact | Not a piece of cake

Funfact | Superoceans

Snowball Earth : the big freeze step by step

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