Kenorland

Not to be confused with Kennerland, a theme park (based on a toy company) I just made up when I stumbled across the name of this supercontinent.

Kenorland was one of the earliest supercontinents, having formed about 2.72 billion years ago. It accreted some cratons that already existed, but also found some new continental crust to merge with. Pieces of it would later become Laurentia (most of North America and Greenland), Baltica (todays’ Scandinavia and Baltic regions), Yilgarn (Western Australia), and Kalaharia (large portions of South America and Africa).

It is known that Kenorland sat in low latitudes until great underground magma surges started to cause tearing of the crust about 2.48 billion years ago. At about that time, Baltica straddled the equator and was connected to Laurentia (Canadian Shield), Kola and Karelia (2 pieces that have since rejoined with Baltica).

It is thought that the breakup of Kenorland may have been when the Earth shifted from tearing caused by magma plumes to the modern plate tectonics we know today. However, the discovery of an earlier continent and a supercontinent may indicate this transition occurred even earlier.

By 2.45 billion years ago, Yilgarn (Western Australia) was no longer connected to the other cratons, and Kola and Karelia cratons were also drifting away. Therefore, there was longer a supercontinent, and this was about the same time as the Huronian glaciation, which lasted up to 60 million years. Indications are that atmospheric oxygen rose from 0.1% to 1%. This increase in oxygen caused the virtual disappearance of the gas methane, which was oxidized into carbon dioxide and water.

Furthermore, the breakup of Kenorland generally increased continental rainfall, reducing the other greenhouse gas, carbon dioxide. Also, the solar output at that time was less than 85% of its current power, and all these circumstances together produced a runaway “Snowball Earth”, where average temperatures planet-wide fell to below freezing.

Wow, that’s a pretty drastic response to a supercontinent not being able to hold itself together.

https://en.wikipedia.org/wiki/Kenorland

Everybody’s Heard of Gondwana

Gondwana existed from about 550 million years ago until 180 million years ago. It is one of the most well known super-continents, in the sense that more people have at least heard of it, rather than individual cratons like Avalonia or Baltica.

If I’m reading the information correctly, Gondwana existed both before and after Pangaea. Before Pangaea, it came into being when several cratons stuck together, beginning about 800 million years ago with the formation of the East African Orogeny, which involved the collision of India and Madagascar with East Africa. Between 600 to 530 million years ago, this group added South America, Australia and Antarctica, in that order. Thus Gondwana was born.

Eventually, it merged with Laurasia and became Pangaea, sometime around 335 million years ago. But it wasn’t an easy relationship, you might say. Pieces of what had formerly been Gondwana kept breaking off, drifting north to join the former Laurasia section, such as bits of China and Indo-China. The western edge of Pangaea was beginning to break up while the eastern edge was trying to collect itself together.

Meanwhile, the formation of Pangaea and its mountains greatly impacted sea levels and global climate, producing glaciers and continent-wide sedimentation.

But what about Gondwana? About 175 million years ago, it had had enough and broke away. But it didn’t come out of it unscathed. Besides the bits that had already drifted to ‘the other side’, Florida, southern Georgia and Alabama stayed attached to North America.

Once it separated from its partner, Gondwana just kept falling apart. About 132 million years ago, Antarctica, Australia, India and Madagascar broke off and then broke up, going their separate ways. South America slowly broke away from Africa, starting in the south and going north, but the exact timing is uncertain. It could have started as early as 190 million years, and finally finished around 85 million years ago.

So, if you’ve been paying attention, you’ll realize that most of the cratons that formed Gondwana now inhabit the southern hemisphere. Its remnants account for about 2/3 of today’s continental area, including Africa, Antarctica, Arabia, Australia, Indian Subcontinent and South America.

If I were a paleo-geologist, I might have made more sense out of the wiki articles I consulted on this subject. The writer of these articles - particularly the one on Gondwana - seemed to think that anybody who was looking up this subject must be a student, for he/she/it kept using names and terms that I - as a lay person - did not know, leading to much confusion on my part. It seemed far more detailed than I felt I could fit into a blog, anyway, so I skipped lightly through most of it, looking for the important details without bogging down the blog.

Paleo-geology was going to be an elective of mine in college, but I didn’t get that far. Hmm, anybody got a good used textbook on the subject?

https://en.wikipedia.org/wiki/Gondwana

https://en.wikipedia.org/wiki/Pangaea