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

Triassic Period Part 1

 The Triassic Period spans 50.6 million years, from 251.9 million years ago to 201.4 million years ago. It is the first and shortest period of the Mesozoic Era. It both started and ended with a major extinction event.

The Permian–Triassic extinction devastated terrestrial life. Diverse communities with complex food-web structures took 30 million years to reestablish.

The Triassic period ended with a mass extinction which was particularly severe in the oceans. All the marine reptiles disappeared except for the ichthyosaurs and plesiosaurs. Invertebrates like molluscs were severely affected. In the oceans, 22% of marine families and possibly half of marine genera went missing.

The vast supercontinent of Pangaea continued until the mid-Triassic, after which it began to gradually split into two separate landmasses, Laurasia to the north and Gondwana to the south.

During this time period, almost all the Earth's land mass was concentrated into a single supercontinent centered more or less on the equator and spanning from pole to pole. The Tethys Sea penetrated the east side of this continent for a good distance along the equator. There was an older branch of the ocean (called the Paleo-Tethys Ocean) north of the Tethys Sea that was now closed off by a group of moving islands that became a strip of land.

During the mid-Triassic, a similar sea penetrated along the equator from the west coast. This sea was not named in the article I read. All the rest of Pangaea's shores were surrounded by the world-ocean known as Panthalassa. Although it was not stated, my guess is that these 2 long seas coming from the east and the west along the equator finally met, and Pangaea was no more.

The sea level was consistently low compared to the other geological periods. The beginning of the Triassic saw the sea level at around present sea level, rising to about 10-20 m (30-60 ft) above sea level during the Early and Middle Triassic. Then the sea level began to rise, with it reaching up to 50 metres (150 ft) above the present sea level. It then began to decline, reaching a low of 50 metres below the present sea level, which continued into the next time period.

The global climate during the Triassic was mostly hot and dry, with deserts spanning much of Pangaea's interior. There is no evidence of glaciation at or near either pole. In fact, the polar regions were apparently moist and temperate, providing a climate suitable for forests and vertebrates, including reptiles. Pangaea's large size limited the moderating effect of the global ocean; it's continental climate was highly seasonal, with very hot summers and cold winters. The strong contrast between Pangea and the global ocean triggered intense monsoons.

The climate shifted and became more humid as Pangaea began to split apart. The Triassic may have mostly been a dry period, but evidence exists that it was punctuated by several episodes of increased rainfall in tropical and subtropical latitudes of the Tethys Sea and its surrounding land. It may be that volcanic activity helped trigger climate change during this period.

Next we'll take a look at the inhabitants of Earth during the Triassic Period.

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

Mesozoic Era

 Okay, we're going to take a quick overview look at the Mesozoic Era, also known as the Age of Reptiles. It lasted from 252 to 66 million years ago. It has 3 Periods nestled within it; the Triassic, Jurassic and Cretaceous periods. It was characterized by dinosaurs, conifers and ferns, a hot greenhouse climate, and the tectonic break-up of Pangaea.

The Mesozoic began just after the largest well-documented mass extinction in Earth's history, and it ended with another extinction event.

During this era, the supercontinent Pangaea broke into separate landmasses that would eventually move into their current positions during the following era. There was not much mountain building during this era, but what little did occur took place around what is now known as the Arctic Ocean. In contrast, the supercontinent Pangaea gradually split into a northern continent, Laurasia, and a southern continent, Gondwana. (Seems like this name has been used before.) By the end of the era, the continents had split up and some had rejoined into their present forms, though not their present positions. Laurasia became North America and Eurasia, while Gondwana split into South America, Africa, Australia, Antarctica and the Indian subcontinent, which would eventually slam into Asia, giving rise to the Himalayas, but not during this Era.

The climate varied, alternating between warm and cool periods. Overall, the Earth was hotter than it is today. The Triassic (first) Period was generally dry and highly seasonal, especially in Pangaea's interior. Low sea levels would have exacerbated temperature extremes. Pangaea's interior probably included expansive deserts.

Sea levels began to rise during the Jurassic (second) Period, most likely caused by seafloor spreading. The sea levels could have risen as much as 656 ft (200 m) above today's sea level. This would have flooded coastal area. In addition, the breaking up of Gondwana into smaller continents created new shorelines. Temperatures continued to increase for a time, then began to stabilize. With the proximity of water, humidity also increased, and the deserts retreated.

The climate of the Cretaceous (third) Period is more widely disputed. Probably, higher levels of carbon dioxide in the atmosphere could have almost eliminated the north-south temperature gradient, meaning that temperatures were about the same across the planet, about 10 degrees Centigrade higher than today.

Dinosaurs first appeared mid-way through the first period, and became the dominant terrestrial vertebrates by early in the second period, then died out at the end of the third period. Archaic birds appeared during the 2nd period (Jurassic), evolving from a branch of dinosaurs. True birds appeared in the third period. Mammals also appeared during this era, but they remained small (less than 33 lb) until the third period. Flowering plants appeared early in the third period and rapidly diversified, replacing conifers and other gymnosperms as the dominant group of plants. But we'll take a closer look at flora and fauna as we get to those periods.

 

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

Permian Period Part 2

 Mammals and reptiles could cope with the desert conditions better than amphibians, and so rose to dominate the Permian. Such dry conditions favored plants with seeds enclosed in a protective cover, rather than plants like ferns, that disperse spores. Modern trees like conifers, ginkgos and cycads appeared in the Permian.

On land, life included diverse plants and fungi. At first, a lot of the Carboniferous flora still flourished. But around the middle of the period, a massive desert covered the interior of Pangaea, and there are indications that the desert was devoid of vegetation. Even in areas where it wasn't such a stark desert, more advanced seed ferns and early conifers moved in. A number of types of plants and animals died out or became marginal elements. By the end of the Permian, swamps reminiscent of the Carboniferous survived only on a series of equatorial islands east of Pangaea that would later become South China.

The Permian saw the diversification of many important conifer groups, including ancestors of many present-day families. Rich forests were present in many area, with a diverse mix of plants. Southern Pangaea saw extensive seed fern forest, and oxygen levels were probably high there. The ginkgos and cycads also appeared.

Insects were very prevalent during the Permian, especially considering that 90% of the insects at the start of this period were cockroach-like insects. Primitive forms of dragonflies were the dominant aerial predators. Several insect groups appeared or flourished during this time, including beetles, true bugs and others.

Larger 'more advanced' types of animal life included reptiles and amphibians. A number of the reptiles seemed to be what I call the 'sail-backed' lizards, where they have bone ridges protruding from their spine and covered in skin. Some of these were herbivore and some were carnivore. I didn't find any indication of how large they might have gotten.

At some point, amphibians declined, and at least one family of the 'sail-backed' lizards was replaced with more advanced animals, including mammals and mammal-like animals. Towards the very end of the period, the first archosauriforms appeared. These were reptiles that possibly rose from the crocodile family and would go on in the next period to produce dinosaurs and pterosaurs. There were no flying vertebrates, although there was a family of gliding reptiles by the end of the period.

Also appearing late in the Permian were the first synodonts, which would evolve into mammals during the next period. Permian synapsids (the group that would later include mammals) thrived and included some large members, such as Dimetrodon. Their special adaptations enabled them to flourish in the drier climate, and they grew to dominate the vertebrates.

In the Permian sea, life was everywhere. You might have found mollusks, starfish, sea dollars, sea urchins and sea cucumbers if you went swimming, or animals very much like these modern versions. But as stated earlier, most of the marine life went extinct during the last days of this period. Nothing was said about the sharks or fish that were so prevalent in the previous period.

Could we live here? Plenty of plants are growing, at least, where it wasn't a desert, so maybe we could grow crops. Could we domesticate some of the herbivore sail-backed lizards? Would we want to? They're lizards, so they wouldn't give any milk. I have no idea how big their eggs might be, so that might be a reason to domesticate them. Okay, we'll leave some of us here to colonize the Permian, and the rest of us will go on to see what comes next.

 

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

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

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

Permian Period Part 1

 The Permian Period is the last period of the Paleozoic Era, and it spans the 47 million years from 298.9 million years ago to 251.9 million years ago.

The Permian witnessed the diversification of two groups, the mammals (and all creatures more closely related to mammals than to reptiles and birds) and the reptiles. But I'm going to look at the conditions existing on the Earth at the time before I consider the animals that populated it.

At the time, the world was dominated by the supercontinent Pangaea, which formed when Euramerica and what was left of Gondwana collided during the Carboniferous. There was a smaller continent that lay to the northeast of Pangaea called Angara. There were also some small islands east of Pangaea called Cathaysia. Of course, with most of the land mass gathered into one supercontinent, the rest of the globe was ocean. The superocean of the time was the Panthalassa. Pangaea straddled the equator and reached for the poles (but didn't necessarily get there). This, of course, had an effect on the ocean currents of the time.

Early in this time period, Cimmeria—a string of microcontinental islands—tore off from the Gondwana area in the Southern Hemisphere and during the course of the period, moved up to join the Eurasian part of Pangaea in the Northern Hemisphere. Cimmeria included parts of today's Turkey, Iran, Afghanistan, Tibet and the Malay Peninsula. The Central Pangean Mountains, which began forming due to the collision of Laurasia and Gondwana during the Carboniferous Period, reached their maximum height shortly after the beginning of the Permian, and would have been comparable to the present Himalayas.

The Carboniferous rainforest collapse left behind vast regions of desert stretching over the continental interior. From approximately 262 million years ago to 259 million years ago, a series of volcanic erruptions in what is now China (was then part of Pangaea) led the way to an extinction event. This was compounded when a similar series of volcanic activity over a wide swath of Siberia (then located in Angara) continued to change the atmosphere. This mass extinction event ended the Permian Period, and started the next period. It was the largest mass extinction in Earth's history, with nearly 81% of marine species and 70% of terrestrial species dying. On land, it took 30 million years into the next time period for the ecosystems to recover.

Sea levels were mostly stable during the Permian, at several tens of meters (yards) above the present level. There was a sharp drop at one point, producing the lowest sea level of the entire Palaeozoic Era, roughly the same as today's level.

At the start of the Permian, the Earth was still in an icehouse. Around 323 million years ago, glaciers began to form around the South Pole, which would eventually cover a vast area of the southern Amazon Basin, Southern Africa, Australia and Antarctica. The coldest period was around 293 million years ago. By 285 million years ago, temperatures warmed, and a great deal of the ice retreated, although some glaciers remained. The Permian was cool compared to other time periods, at least until those volcanoes started pouring CO2 (a greenhouse gas) into the atmosphere.

It sounds like the Permian had a lot of diverse climates and ecosystems, right? So as long as we stayed away from that awful desert, we should be able to find a nice place to live. So let's take a look at the neighbors we'd have in the next blog.

 

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

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

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

Phanerozoic Eon

 The current geologic eon of Earth is the Phanerozoic Eon. It started 541 million years ago and continues today. It is the only eon during which abundant animal and plant life has existed. It began at about the same time that animals first developed hard shells, as preserved in the fossil record.

During the early stages of the Phanerozoic Eon, a number of animal types came into existence and evolved into diverse forms, and complex plants emerged and developed. In addition, fish, insects and tetrapods (which includes all living and extinct species of amphibians, reptiles, birds and mammals) also emerged and evolved. Plant life appeared on land early in the eon.

Pangaea was the most recent supercontinent during the early days of this eon, but tectonic forces broke it up into the current continental landmasses, and then proceeded to move them around into their current configuration.

The Phanerozoic Eon consists of 3 eras, which are broken up into 12 periods. Now that plants and animals have shown up in earnest, I expect there will be plenty of information about what was going on during each segment.

In fact, the article I found for this eon actually had paragraphs (or more) for each period, but I skipped over them because I didn't want to get ahead of myself. I hope I remember to check back to this article if I have trouble finding information on the eras and periods that comprise this eon.

This is a very short blog, not because I couldn't find much information, but because there was so much information, it needs to be broken into smaller time segments to get that information into manageable bites. But do stay tuned, because we are finally approaching Dinosaur Land!

 

https://en.wikipedia.org/wiki/Phanerozoic#:~:text=The%20Phanerozoic%20Eon%20is%20the,preserved%20in%20the%20fossil%20record.

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

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)

Rhynchosaurs

Imagine a reptilian pig with a hammerhead, no visible ears, and a parrot-like beak, and you'll have a pretty good mental picture of a rhynchosaur.

Rhynchosaurs were herbivores that in some fossil localities account for 40 to 60% of the specimens found, making them the most abundant plant eaters on land. They were reptiles with stocky bodies and a powerful beak.

Early forms were small, less than a meter long, and typically lizard-like in build. They had narrow, wedge-shaped skulls with a few small, blunt teeth for eating plants.

Later versions grew up to two meters in length. The skull in these later forms were short, broad and triangular, becoming much wider than long, giving them a somewhat hammer-head appearance, although the eyes were set close together, near the top of the beak. The broad skull accommodated powerful jaw muscles that enabled the rhynchosaurs to cut up tough plant material. The teeth were modified into broad tooth plates, and the lower jaw fit into a groove on the upper jaw, enabling the ‘cutting’ of plant fibers.

The hind feet were equipped with massive claws, presumably for digging up roots and tubers, although digging claws are usually found on the front feet. Like many animals of their time, they spread all across Pangea, and thus across the world.

And that seems to about all there is to say about the rhynchosaurs. They lived during the Triassic era (251 to 199 million years ago), dying out just before herbivore dinosaurs appeared.

I think I would have found rhynchosaurs terrifying, particularly the larger ones, even though they were basically reptilian cows or deer. Let’s face it, the larger ones were as long as a man is tall, and who’s to say they wouldn’t try munching on this new plant called human that invaded their space, even if it didn’t sit still like other plants?

What do you think? If you had a time machine, would you venture back to visit them up close and personal?

 

https://ucmp.berkeley.edu/taxa/verts/archosaurs/rhynchosauria.php

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

Dinosaurs

Like most kids, I had a steady interest in dinosaurs when I was young. I never truly outgrew that interest, and the science magazines I read don’t have much to report on them very often. How disappointing. I long to learn all the new stuff they’ve learned since I was a kid. Can you imagine my surprise a few decades ago when I discovered Fred Flintstone’s powerhouse Brontosaurus never actually existed? It was the result of a few bones that did not necessarily belong together and a scientist’s active imagination while trying to put them together.

One of my school science projects was on dinosaurs. I bought several giant bars of Ivory soap and tried to carve them into various dinosaurs. The T-Rex didn’t want to stand up, the stegasaurus’ back plates were difficult to carve without breaking them off. The easiest to carve was the brontosaurus, which way back then still had a place on the dinosaur family tree.

I can’t do justice to dinosaurs in a few hundred words. After all, they were around - in one form or another - for millions of years. So I plan to look around, pick some interesting versions and report on them over the course of several months.

What do you think you know about dinosaurs? Were they all cold-blooded? Covered in reptile scales or simply skin similar to our own? Did they do any parenting of their young, or simply lay their eggs and move on through the countryside? Did they really evolve into birds? How big did they get? What was their smallest representative? Are there any ‘dinosaurs’ alive today, or maybe animals that look very similar to their ancient ancestors?

I remember a story - I don’t remember if I saw it visually or read it - where a group of hadrosaurs (That’s what I remember their type being, but I may be completely wrong.) had left Earth in some fashion back in the Long Ago, and established a home on another planet in another system. And now their descendants were space travelers and meeting humans in the vastness of space.

Wouldn’t that be something?

Well, since we’re approaching that point where we may be space traveling in a few generations (meaning, outside our home system), maybe we should be considering what evolved dinosaurs might be like. And to do that, we should start by learning what dinosaurs were actually like.

Any suggestions you want me to look at?

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

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