Lost Continent

We’ve all heard of Atlantis, which was a ‘continent’ or at least a city that reportedly sank into the ocean due to some natural disaster. Every few years, there is some report in the news of the latest theory about where that continent or city was located.

When I was considerably younger, I read at least one book about the lost continent of Lemuria. I keep wanting to say the book I read was written by Lin Carter, who did write about Lemuria (before it sank into oblivion), but it was so long ago that the name of the continent is all I remember. Nowadays, Wikipedia says that a lost continent called Lemuria was proposed in 1864 by zoologist Philip Sclater, who theorized it was located in the Indian Ocean. The idea was debunked in the 20^th century once scientists understood plate tectonics and continental drift.

But a team of scientists really have discovered a lost continent now, which they are calling Zealandia. Most of it is underwater, but New Zealand and some other islands stand up far enough to be above the ocean. Zealandia is more than half the size of Australia, and it extends northwest and southeast of the New Zealand islands.

It was a part of Gondwana when that supercontinent existed, but when it started to break apart, Zealandia was one of the parts, breaking away around 81 million years ago. Then 95% of that part, Zealandia, sank beneath the waves.

The scientists have finished mapping Zealandia recently after 20 years of work, and they state that it contains a vast array of diverse rocks that proves it is made of continental crust, so it is not just a section of seafloor.

Zealandia is sometimes referred to as Earth’s 8^th continent.

 

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

https://www.msn.com/en-us/news/technology/scientists-finally-finished-mapping-earth-s-8th-continent-zealandia-helping-them-solve-the-lost-continent-s-mysterious-history/ar-AA1hu1QE?ocid=mailsignout&pc=U591&cvid=71bd9ad3ca8b4b63b9e2633f4f699f75&ei=36#image=AA1bYYe9|1

Jurassic Park Period Part 1

 

Paleogeography

Everybody knows about dinosaurs, right? And thanks to the Jurassic Park series of movies, we all know the dinosaurs lived during the Jurassic Period. But what else is noteworthy about this geologic period? I'll try to uncover something other than various dinosaurs to study.

However, I am just as fascinated with dinosaurs as any little kid, so I'll spend some time studying some of our favorites while I'm at it.

The Jurassic Period started 201.3 million years ago and ended approximately 145 million years ago. There was, as seems so common with these geological periods, an extinction event at the dividing point between the Triassic and Jurassic Periods.

The Triassic/Jurassic extinction event seemed to be caused by the Central Atlantic Magmatic Province, which, as best I can figure out, means a lot of magma and lava was moving around in the areas currently known as northwestern Africa, southwestern Europe, southeastern North America and Northeastern South America.

The articles I read seemed to indicate that this was not just a matter of volcanic activity, that some of it could have been caused by the action of diverging plate tectonics. We are aware of the Atlantic rift, where two tectonic plates are moving away from each, allowing a large volume of magma to flow, but this is not considered a volcano. This magma movement began about 201 million years ago, and continued for about 600,000 years. It was the largest activity of this type known to man, covering roughly 11 million km².

By the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses: Laurasia to the north and Gondwana to the south. The rifting between North America and Africa was the first to happen, in conjunction with the Central Atlantic Magmatic Province

By the beginning of the Jurassic, there was flooding in most parts of central and western Europe, transforming it into an archipelago of islands surrounded by shallow sea. Beginning in the Early Jurassic, the proto-Atlantic was expanded by the "Viking Corridor" (or Transcontinental Laurasian Seaway) which stretched between the Baltic Shield and Greenland, and was several hundred kilometers wide. All during the Jurassic, the North Atlantic Ocean remained relatively narrow, while the South Atlantic did not open until later.

At the beginning of the Jurassic, North and South America remained connected, but at some point, they rifted apart to form the Caribbean Seaway, which connected the north Atlantic Ocean with what is now called the Pacific Ocean, although it was much larger back then, taking up over half the globe and was called the Panthalass Ocean.

About 183 million year ago, another magmatic event started, the Karoo-Ferrar event, this one in South Africa and Antarctica. This triggered another extinction event by causing widespread oceanic anoxia, ocean acidification and elevated temperatures. I am uncertain if these types of conditions were responsible for the Triassic/Jurassic extinction event.

Madagascar and Antarctica rifted away from Africa in association with the eruption of the Karoo-Ferrar large igneous provinces, which opened the western Indian Ocean and began the fragmentation of Gondwana.

During the Middle to Late Jurassic, the Sundance Seaway, a shallow inland sea, covered much of northwest North America.

The sea level rose and fell many times during the Jurassic, peaking at one point as high as 140 meters (462 feet) above the present level.

Wow! So much happening! And that's just the geography! This makes me wonder what else was going on!

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

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

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

Ordovician Period

When I first started reading the article on the Ordovician Period, I got to the mention of Gondwana, which made me stop and wonder, "Wait, haven't we been through this breakup before?" And the answer is yes, we have, in the blog I wrote about the Paleozoic Era, which the Ordovician Period is part of. I had to remind myself that this is not really déjà vue, that the Paleozoic Era has 6 periods to it, and my blog on the Era would have been like an overview, while the blogs on the periods would have more details. So, some of the big events, like the breakup of Gondwana, will be mentioned in both posts.

The Ordovician Period spans 41.6 million years, from the end on the Cambrian Period some 485.4 million years ago to 443.6 million years ago.

Life continued to flourish during the Ordovician Period, although there was an extinction event at the end of the period. The Ordovician Period is known for its biodiversification event, which considerably increased the diversity of life. Invertebrates, namely molluscs and arthropods, dominated the oceans, although fish, the world's first true vertebrates, continued to evolve, and fish with jaws may have first appeared late in the period. Life on land had yet to diversify.

However many meteorites strike the Earth in a year today, there were 100 times that many hitting the Earth per year during this period.

The southern continents were collected into Gondwana, which started the period in equatorial latitudes but then drifted toward the South Pole. Meanwhile, other continents, Laurentia (part of North American), Siberia, and Baltica (northern Europe), were drifting north, and Baltica started moving towards Laurentia later in the period. Another small continent, Avalonia, separated from Gondwana and began moving north towards Baltica and Laurentia.

Temperatures were mild in the early and middle Ordovician Period, but from 460-450 million years ago, volcanoes along one of the oceans spewed massive amounts of carbon dioxide (a greenhouse gas) into the atmosphere, turning the planet into a hothouse. These volcanic island arcs eventually collided with proto-North America and formed the Appalachian Mountains. [At last! I've been waiting for billions of years for the Appalachians to appear!]

Initially, sea levels were high, but as Gondwana moved south, ice accumulated into glaciers and the sea levels dropped. At first, low-lying sea beds increased diversity, but later glaciation led to mass extinctions as the seas drained and continental shelves became dry land. By the end of the period, the volcanic emissions had stopped. By then, Gondwana had neared the South Pole and was largely glaciated.

Reef-forming corals first appeared early in this period. Land plants probably evolved from green algae, first appearing in a form resembling liverworts. Fungi was also an early adopter of living on land, and facilitated the colonization of land by making mineral nutrients available to plant cells.

This period closed with a series of extinction events that are generally regarded as one major event, in which 49% of all fauna died. It is generally agreed that this event or series of events were caused by an ice age. That ice age had several pulses of increasing/decreasing glaciation. Each time the glaciation increased, the sea level dropped, killing many of the fauna that inhabited the shallow seas. When the sea levels rose during the next decrease of glaciation, there were entire families of fauna that had not survived to re-establish themselves in the shallow seas. This may have happened several times, producing a series of extinction events.

Well, now we're starting to get some place. Plants (of sorts) on land, starting to make the soil arable. Not sure about the carbon dioxide level in the atmosphere, but the meteor showers would be beautiful, as long as they didn't land too close. Hunting probably wouldn't do much good yet, but, hey, there's fish! Too bad I can't stand fish.

Maybe the next period will be even more amenable?

 

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

Orosirian & Statherian Periods

 Orosirian Period

The 3rd geologic period in the Paleoproterozoic Era is the Orosirian Period, which loosely means ‘mountain range’. This period lasted from 2,050 to 1,800 million years ago.

The latter half of the period involved intense orogeny on virtually all continents. Orogeny is when 2 continental plates slam into each other and one is shoved down, while the other is shoved up, producing mountain ranges.

Other important events include 2 of the largest known impact events. At about 2,023 million years ago, a large asteroid collision created the Vredefort impact structure, located in what is now South Africa. Although most of the crater has eroded away, the impact dome at the center is still visible.

Towards the end of the period, about 1,850 million years ago, the Sudbury Basin was created by the impact of another asteroid in what is now Ontario Canada. I’m not sure if the article was saying the basin is in the city of Greater Sudbury, or the city is in the basin. It did state that the locals merely refer to it as ‘the valley’.

So, the Orosirian Period saw much happening to Earth’s crust, from holes being punched into it (craters) to mountains climbing towards the sky. I couldn’t find anything on life forms or what the environment was like, which is a bummer. I assume the lifeforms that existed at the beginning of this period mostly managed to survive, and possibly evolved.

 

Statherian Period

The final period in the Paleoproterozoic Era is the Stratherian Period, which roughly means ‘stable, firm’. It started at 1,800 million years ago and lasted to 1,600 million years ago.

This period was characterized by erosion and folding. Folding, as I understood the article was when the forces that created mountain ranges continued to deform the land around the mountains, forming foothills. In other places, erosion took place, sending sediment to a lower level, which formed new platforms of land extending out from what land already existed.

The oldest known eukaryotic fossil organism was found in Statherian beds in India, so life was carrying on. At that time, the oxygen level was 10-20% of our current level.

By the beginning of the Statherian Period, the supercontinent Columbia had assembled.

So there we have all the important highlights of the back half of the Paleoproterozoid Era. It almost sound like a livable place. Well, except the oxygen level would be a problem. And I’m not sure we have any earthworms yet to help fertilize the soil. Well, at least we’re getting closer to a livable planet!

 

https://en.wikipedia.org/wiki/Orosirian#:~:text=The%20Orosirian%20Period%20(%20%2F%CB%8C%C9%92r,these%20dates%20are%20defined%20chronometrically.

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

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

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

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

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

The Paleoproterozoic Era

 Next up is the Paleoproterozoic Era, which spans from 2,500 to 1,600 million years ago. It is the first of 3 sub-divisions (era) of the Proterozoic Eon. It is the longest era of the Earth’s geological history, and is divided into 4 periods, which we will look at later. During this era, the continents first stabilized.

Paleontological evidence suggests that the Earth rotated during this era at a speed that produced days that were 20 hours long, which would have meant a year would have about 450 days long.

It was during this era that the atmosphere and shallow seas saw a great increase in free oxygen, thanks to all that cyanobacteria that had been pumping out oxygen as a waste product for so long. Before that, almost all existing lifeforms were anaerobic, meaning they did not require oxygen. In fact, free oxygen in large amounts is toxic to most anaerobic organism. Therefore, the majority of the anaerobic lifeforms died when the atmospheric free-oxygen levels soared. This was the first major and possibly the most significant mass extinction event, and is called the Great Oxidation Event.

But this was not just a time of death. Many eukaryotes lineages have been approximately dated to the Paleoproterozoic era. Eukaryotes consist of cells that have a nucleus enclosed within a nuclear envelope. To the best that I can remember my high school biology, that would mean that most plants and animals are eukaryotes. It is currently accepted that there are 3 domains of life on Earth, and the eukaryotes are one of them. Bacteria and Archaea are the other two. Neither of these types of life have cells with a nucleus within a nuclear envelope, and I think neither one of them gets large enough to be seen with the naked eye.

During this era, a number of continents collided, creating mountain belts and basins. This happened so often that it led to the assembly of the supercontinent named Columbia (or Nuna, depending on who you talk to).

Now, in doing my research about the Paleoproterozoic Era, I chanced upon a phrase called The Boring Billion. Believe it or not, that sounded interesting, so I did a little more digging (so to speak) and found that it referred to the time period between 1.8 and 0.8 billion years ago, which spans the middle of the Proterozoic eon. It would have just been starting when this era was ending, but I’ll mention it here and hope it comes up again when we get to the next era, so I can study it in more detail.

The Boring Billion section of time was characterized by a fair amount of tectonic stability, climatic stasis, and stalled biological evolution. Supposedly, it was bordered by 2 different oxygenation and glacial events, but the Boring Billion itself had very low oxygen levels and no evidence of glaciation.

Well, no doubt about it, the world is really beginning to shape up into the Earth we know. But I’m not quite ready to move in.

 

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

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

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

Ur...

Okay, not a lot of information on this subject. Only to be expected, I suppose, since Ur is the name given to the very first super continent, which came into being about 3.1 billion years ago. At that time, the only life on Earth was single-celled, and some of it knew how to photosynthesize. And it’s called a super continent, though it was probably smaller than modern Australia.

It qualifies as a super continent because it incorporated all or nearly all pieces of land then in existence. More recently, scientists have started calling Ur and other small ‘super’ continents by the term super-cratons. The best I can figure is that a craton is a piece of land considered too small to be a continent.

Other scientists have postulated the existence of another super-craton at about the same time, which they have called Vaalbara, but apparently, the ideas of these two early cratonic assemblages are incompatible.

About 1,300–1,071 million years ago, Ur joined the continents Nena and Atlantica to form the supercontinent Rodinia. In one proposal, Ur remained the nucleus of East Gondwana until that supercontinent broke up. But in other proposals, India and East Antarctica did not collide until Rodinia formed 1,071 Million years ago. However, during that time period, the Earth’s mantle was 200 degrees C hotter than today, making many characteristics of modern tectonics rare or non-existent. This would preclude Roger’s 3 billion years ago supercontinent of Ur.

The proposal for the super-craton Vaalbara places two cratons, Kaapvall of southern Africa and Pilbara of western Australia, next to each other based on stratigraphic similarities. In Roger’s configuration of Ur, these two cratons were placed far apart during Gondwana, which is contradicted by widespread collisional events between Australia and Africa.

Yet another possible supercraton, Zimgarn, was proposed by Smirnov in 2013. Unfortunately, I didn’t understand the paragraph dealing with it, so I’m mostly ignoring it. After all, I’m supposed to be studying Ur.

Geological similarities in parts of India (Singhbhum and Dharwar), western Australia (Kilbaran and Pilbara), and southern Africa (Kaapvall and Zimbabwe) indicate these area were close together in the Mid-Archaean Era. Ur was named for the german prefix meaning “original” by Rogers because in his proposal, it was the first continent. Other Archaean continental assemblages are considerably younger. In some reconstructions, the various pieces of Ur stayed near each other until the break-up of Gondwana.

So, was there really an Ur, as proposed by Rogers? Should it really be called Vaalbara or Zimgarn? Or something else entirely? I didn’t find any indication of where it was located, and given how long it supposedly existed, it could have drifted quite a ways from its original location, but still, I would have liked to see some of that type of information.

How many planets do you suppose are out there with only single-celled life and 1 large island? With such a small land mass, would it be worth it to colonize it?

 

https://en.wikipedia.org/wiki/Ur_(continent)

https://simple.wikipedia.org/wiki/Ur_(supercontinent)

Hadean Eon

Unless you have a degree in geology or paleontology or something similar, you are probably as confused by the various Ages, Eons and Periods that get named when you look anything up about the History of Earth. I decided to take a look at one of them, and see if I could get it figured out as to when it happened, what major events happened during it... that sort of thing.

So, I had a list of these names, and I picked one at random: the Hadean Eon.

Turns out, I had picked the very first of Earth’s Eons; it started with the formation of Earth about 4.6 billion years ago and ended approximately 4 billion years ago. Other names for it are the Priscoan Period and the Pre-Archean Eon.

Obviously, since we are looking at the very first half billion years of the world, we won’t be talking about dinosaurs or super continents. What could there possibly be to discuss? Well, let’s dig in and see what turns up.

First, there’s the name, which gives us a clue about what was going on. ‘Hadean’ comes from Hades, the Greek god of the underworld. And that describes the conditions of what Earth was going through: The planet had just formed and it was very hot due to a number of factors, including frequent collisions with other Solar System bodies.

One important collision happened about 4.5 billion years ago, when a Mars-sized planetoid smashed into the infant Earth. The collision sent quite a lot of material into orbit around Earth, while the planetoid and the rest of Earth merged and tried to settle down. The orbiting material probably took less than a century to form the moon.

The big collision didn’t melt all of the Earth, but a fair fraction of material was vaporized, which created a rock vapor atmosphere around the young planet. But that rock vapor would have condensed out within 2,000 years, and left behind an atmosphere heavy in CO2 with some hydrogen and water vapor.

Apparently, there was a sizable quantity of water in the material that formed the Earth. After the moon was formed, the surface temperature was about 230C (446F), but even so, oceans of liquid water existed. That’s because the atmospheric pressure was over 27 times what it is today, because of the heavy CO2 atmosphere. As cooling continued, most of the CO2 was removed from the atmosphere by subduction and dissolving in ocean water, but the levels oscillated wildly.

One theory posits that between 4.4 and 4.1 billion years ago, the Earth’s climate was relatively cool, allowing for liquid water to be present at least that long. It was even suggested that the Earth may have been pretty much like it is today, except for the absence of flora and fauna.

One of the articles implied that life may have been getting started by the end of the Hadean Eon. But that was almost like a throw-away at the end of the last paragraph, so I’m thinking , one celled organisms? Maybe?

So as far as stories go, what if a spaceship gets too close to a forming star system and gets clobbered by tiny planetoids until it is forced to crash land on the nearest planet, which just happens to be vaguely Earth-like, but the only life it has are some quasi-amoebas swimming in the oceans. Maybe they have plants or seeds aboard, so they can grow some food. What about the stuff they don’t realize they’re carrying? Cockroaches, mice, fungal spores... What would those things evolve into, once there was enough food on the planet for them to successfully venture off the ship? There would be a whole lot of niches in the food chain for them to fill!

https://en.wikipedia.org/wiki/Giant-impact_hypothesis

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

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

Thoughts About Laurentia

Okay, Laurentia is not a super-continent, although it has been involved in those. It is today known as the North American Craton, because it is a bit of crust that makes up about the eastern 2/3 of North America. Originally, this craton included Greenland and a piece of Scotland, but those have split off.

The base of Laurentia is composed of metamorphic and igneous rocks formed 1.5 to 1 billion years ago. Above that are younger sedimentary rocks that were deposited when most of the craton was covered by a shallow (with a depth of no more than 200 feet) tropical sea where much marine life lived and died, settled to the bottom and eventually became rock such as limestone and dolomites.

During the Cretaceous Period, this type of sea - known as the Western Interior Seaway - ran from today’s Gulf of Mexico to the Arctic Ocean, diving North American into eastern and western land masses

The southwestern area of Laurentia has been deformed by continental collisions and has been stretched up to 100% of its original width. This area has experienced numerous large volcanic eruptions.

Laurentia sat on the equator some 458-444 million years ago.

About 1.82 billion years ago, Laurentia was part of the supercontinent Columbia. But by 1.35-1.3 billion years ago, Laurentia was an independent continent.

1.3 billion years ago, Laurentia joined other bits to form the supercontinent Protorodinia, and by 1.07 billion years ago, enough bits had joined to become the supercontinent Rodinia. This article didn’t mention when Rodinia broke apart.

750 million years ago, Laurentia had again joined others to form Protolaurasia, but Laurentia very nearly drifted away from the others. Still, it stuck around at least until 600 million years ago, when they formed the supercontinent Pannotia. (I’ve already written about that.)

419.2 to 358.9 million years, Laurentia and Baltica collided, forming Euramerica.

298.9 to 252.1 million years ago, all the ‘big boys’ got together to form the supercontinent Pangaea. That lasted until 201.3 to 145 million years ago, when Pangea broke into 2 supercontinents: Laurasia and Gondwana. Laurentia was part of Laurasia.

145 to 66 million years ago, Laurentia was again an independent continent. And about 23 million years ago, North America (Laurentia) crashed against South America, forming the minor supercontinent America.

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

Baltica

Despite my confusion over the location of ‘the Baltic States’, they are right where normal people would expect them; along the Baltic Sea. Somehow, over the years, my mind had decided that the otherwise-un-named Baltic states were located immediately north and northwest of Greece. However, I looked them up (for the sake of this blog), and boy, was I wrong. I had put these states in Eastern Europe, but way too far south.

The Baltic States (Estonia, Latvia, and Lithuania) are in Eastern Europe, snuggled up east of the Baltic Sea and west of the Ural Mountains of Asia. And that places them right on the protocontinent of Baltica!

So, yes, this is kind of related to the Supercontinents blogs, but I’m only going to explore this one little piece of crust. Sometimes it roamed around on its own. At other times, it gathered together with other pieces of crust. Right now, it is smooshed between NorthEastern Europe and NorthWestern Asia. Will it succumb and eventually be pushed under these larger plates, or will it somehow break free again? I don’t know. But let’s see what is known about it.

The thick core of Baltica is also known as the East European Craton and is more than 3 billion years old.

About 2 billion years ago, small pieces of crust started colliding. These included Sarmatia (which was the Ukrainian Shield and Voronezh Massif*) and Volgo-Uralia. That seemed to work pretty well, so about 1.8 billion years ago, they added Fennoscandia, which included the Baltic Shield.

Now, if I’m reading the articles right, about 750 million years ago, Baltica and Laurentia (most of North America) both rotated clockwise, bumped each other lightly and headed for the south pole. At some point (possibly 650 million years ago), it is postulated that Earth became completely covered in snow and ice. (Yes, Snowball Earth.)

It turns out that Siberia was located fairly close to the South Pole, too, and it apparently didn’t take long for Siberia to completely lose its cool. According to one theory, Siberia started having some severe volcanic eruptions, and the build-up of green house gases in the atmosphere from that source resulted in a complete melt-down of all that snow and ice in as little as 2,000 years.

Anyway, Laurentia beat feet and headed north, but Baltica remained in the south at least long enough to hang around Gondwanaland. After that, Baltica drifted north and approached Laurentia again. However, around 425 million years ago, Scotland-Greenland and Norway all collided together, forcing Baltica to look elsewhere for new continental buddies.

Just when you thought you’d found a friend. Poor Baltica.

* Now a piece of Central Russia

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

https://www.google.com/search?q=baltic+states&oq=Baltic+states&aqs=chrome.0.0l6.4638j1j7&sourceid=chrome&ie=UTF-8

Super Continent 2

As I stated before, Earth has experienced a number of super-continents, which is when all or most of the land masses are in the same place. Pannotia was one of those super-continents. It was fairly short lived, forming about 650 million years ago, and starting to break up 560 million years ago.

In this particular case, most of the land is south of the equator, centered around the south pole. There were a few ‘islands’ stretching towards the equator. Pannotia also included several seas trapped between batches of land, and one long skinny bay that looks like it might actually reach the south pole, according to the drawings.

Only South America and Africa - and possibly Australia - are recognizable land masses in the drawings. All the other continents are apparently unformed, bits and pieces scattered across the drawings. For instance, Siberia and Baltica have not yet joined with a lot more pieces of land to form Eurasia. Laurentia - which apparently will eventually become most of Canada - is a long piece of land located along (the current west coast of) South America. Most of the pieces of land on the drawings have no names attached to them at all.

I know we’re talking millions of years here, but how fast have these land masses been accumulating and then dissolving? And in between coming together, they just seem to zip all over the place, meeting up with other bits of land in new and different patterns.

Kind of makes me think of a kaleidoscope, where all the different pieces of colored crystals form new and intriguing patterns with every slight twist of the barrel.

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

Super Continents 1

In geology, a supercontinent is when all or most of the Earth’s continental blocks form a single landmass. But earth scientists may use a different definition; ‘a clustering of nearly all continents’, which leaves room for interpretation.

The land masses have conjoined and separated several times. The most recent mass that joined them all is called Pangaea. This conjoining began about 335 million years ago, and began to break up about 175 million years ago.

Pangaea looked more or less like a crescent or the letter ‘c’. The Eurasian continent sat at the top, with the area now forming southeast asia stretching south and east. To the southwest lay North America, and along the NA ‘east coast’ lay the west coast of the big hump of Africa, which was pushed clockwise a bit off its southern tip. The bump of Brazil of South America lay snuggled against North America and Africa. India and Antarctica rested along the southeast of Africa, from the ‘Red Sea’ area south. Australia nestled against India and Antarctica.

I used the words ‘lay’, ‘snuggled’ and ‘nestled’, but the drawing I looked at indicated all sorts of irregular-shaped bits and pieces scattered between all these known continents. I didn’t see anything that resembled the Arabian Peninsula, so I can’t say where that particular piece was hiding at the time of Pangaea.

Pangaea stretched from the south pole to within spitting distance of the north pole. It was a solid body of land that would not have allowed any ocean currents to go around the globe horizontally.

Pangaea began to break up about 175 million years ago. Once India broke away from its neighbors, it raced toward Eurasia at 6 inches a year. Is it any surprise that when they slammed together, they formed mountains like the Himalayas? India (as well as Australia) is still moving northeast at 2-3 inches per year. In a few million years, Australia could scoop up bits and pieces of Indonesia and then head for the northern Pacific. Will it?

I don’t know. Isn’t there a trench somewhere along Indonesia? Seems like a deep ditch would slow Australia down or something. Something else for me to look up and think about.

By the way, this is the first of probably several blogs on super-continents. How long they take me and how often other subjects insinuate themselves into the lineup of blogs remains to be seen. Thems the chances you take when you decide to read my blog.

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

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