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

A Brief Study of Euramerica

Sometimes it’s called Euramerica, sometimes it’s known as Laurussia (not to be confused with Laurasia). It’s called a minor supercontinent because it consisted of several (3) cratons, which are pieces of crust that include land.

About 410 million years ago, the Laurentian (most of North America), the Baltica (Baltic states) and Avalonia cratons all slammed together to form Euramerica. Avalonia was the smallest of the 3; a microcontinent that was long and skinny and sat along the southern border. Euramerica appears to have sat pretty squarely on the equator and was mostly covered with tropical rainforests.

Around 300 million years ago, the climate changed rather abruptly. Many of the lycopsids - such as clubmosses - were replaced by ferns. There was a great loss of diversity in amphibians while the reptiles diversified.

Later, Euramerica became part of the major supercontinent Pangaea. When Pangaea broke into two continents - Gondwana and Laurasia - Euramerica was a part of Laurasia.

Eventually, Laurasia split into the continents of North America and Eurasia. The Laurentian craton became a big portion of North America. Baltica became part of Eurasia. Avalonia ceased to be a long skinny microcontinent as bits of it became some of the east coast of North America, and bits became parts of Ireland, England and other areas of southern Europe.

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

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

Poor Science or Poor Writing

The other day, my husband and I watched a movie we’d never heard of. The setting of the story was that Earth had been in winter for the past 300 years, and it would continue for thousands of years. The only humans that still existed lived 10 kilometers under the surface, where they used geothermal energy as their power source. They had created a race of ‘humans’ to do their work for them, including sex workers, but nobody ever indicated what type of work this ‘inferior’ race did, except for the one sex worker.

Hubby had difficulty with Arizona being covered in snow and ice, with daytime temperatures of -60° F. In the latest ice age, the glaciers never reached the sw states. To me, that said the the earth was not just in an ice age, but had entered a ‘snowball earth’ ice age, where the entire globe is frozen.

How did the ice age winter begin? The characters gave 2 theories, but didn’t know which was right. The first theory was that an asteroid had struck the earth, throwing up so much dust and debris into the atmosphere that most of the sunlight couldn’t get to the ground. The second theory was that it was a bomb that threw up all that dust and debris.

Okay, yes, a lot of dust and debris in the atmosphere can reflect enough sunlight to produce some very chilly results. Large volcanos can produce enough dust to chill the entire globe as the dust rides through the atmosphere. BUT, such dust doesn’t stay in the atmosphere for hundreds or thousands of years.

What about the asteroid that ‘killed the dinosaurs’? you may ask. Yes, that threw up a lot of dust and debris. But what killed so much of the flora and fauna was the firestorm produced by the heat released when the asteroid hit. Think of it as a huge explosion, so hot the heat wave raced around the globe, burning almost everything it touched. There may have been a long winter afterwards, but all that dust and stuff did settle out in a fairly short amount of time.

The plot was that a squad of ‘normal’ military-type humans had to go out into the world to track down a renegade ‘inferior’ made human. The squad's DNA was changed to allow them to survive in the far-below-zero temperatures, but that would only last for 48 hours. I had a little trouble accepting that, but... okay, let’s see what they do with it.

The scene that got me was right after they arrived on the surface. It had been stated that ‘all the animals’ were gone. But what they see right after they arrive on the surface was a man fishing. He had chopped a hole in the top of a small rivulet of water racing over the snow/ice, and had actually caught a fish, but seeing that he was going to be interrupted, he put the fish back.

I really couldn’t accept that. If all the animals had died, where did this fish come from? Okay, maybe they were mistaken. But at the temperatures they were talking about, I would expect that little rivulet to be frozen solid, and the fish with it.

It didn’t help that long after the main character had been on the surface for 48 hours, the main character was still chasing the renegade, with his head bare and no gloves. Frostbite was completely ignored.

It was not a good movie. If you are going to change the rules of life (daytime temperatures of -60F), then you (the writer) have to follow those new rules. And it is easy to have characters who don’t know what happened to end the civilization we (the audience) are familiar with. It’s easy for the writer, but it’s not satisfying to the audience.