Jurassic Park Period Part 2

Paleoclimate

Climate during the Jurassic was approximately 5-10 degrees C (41-50 degrees F) hotter than present time, with atmospheric carbon dioxide likely 4 times higher. It's likely that forests grew near the poles, where they experienced warm summers and cold, sometimes snowy winters. It is unlikely there were any ice sheets, as the high summer temperatures would have prevented the accumulation of snow, although there may have been mountain glaciers. The ocean depths were likely 8 degrees C (about 46 degrees F) warmer than present, and coral reefs grew further north and south by 10 degrees of latitude There were probably large areas of desert in the lower latitudes.

The beginning of the Jurassic was probably marked by a thermal spike corresponding to the eruption of the Central Atlantic magmatic province. This was followed by the Early Jurassic cool interval between 199 and 183 million years ago. ('Cool', of course, is a relative term.) Then came a spike in global temperatures of around 4-8 degrees C (39-46 degrees F) during the eruption of the Karoo-Ferrar large igneous provinces in southern Gondwana, which lasted from 183 million years ago until 174 million years ago.

During this long temperature spike, the ocean surface temperatures likely exceeded 30°C (86°F) and all the land mass between 30°N to 30°C were likely extremely arid, with temperatures in the interior in excess of 40°C (104°F).

There was an episode of widespread oceanic anoxia that is often attributed to the eruption of the Karoo-Ferrar large igneous provinces and the associated increase of carbon dioxide concentration in the atmosphere. This event had significant impact on marine invertebrates, but little effect on marine reptiles. During this time, the Sichuan Basin (of southwestern China) was transformed into a giant lake, 3 times the size of Lake Superior. Seawater pH dropped to its lowest point around the middle of this event.

This was followed by a (relatively) cool period between 174 and 164 million years ago, which was followed by a warm interval between 164 and 150 million years ago. During this warm interval, the land mass interior had less severe seasonal swings than before because the expansion of the Central Atlantic and the western Indian Oceans provided new sources of moisture to moderate the temperature. The end of the Jurassic was marked by another cool interval, which began 150 million years ago and continued beyond the end of the Jurassic.

I recently saw someone on social media poo-pooing concern over the climate changing. As they put it, the climate has been changing for millions of years. And they are right, it has been. What they fail to take into consideration is that mass extinction events have been happening for millions of years, AND the climate changes of the past have not occurred as rapidly as this one. If we want to survive this climate change, we need to use the brains we have.

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

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 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)

Carboniferous Period

 The Carboniferous Period spanned 358.9 million years ago to 298.9 million years ago. On a time table, it sits behind the Devonian Period and before the Permian Period.

In the Early Carboniferous Period, average global temperatures were approximately 68 F (20 C). During the Middle Carboniferous, they dropped to about 54 F (12 C). Carbon dioxide levels fell during the period from roughly 8 times today's level at the beginning to about the same as today's level at the end. Lack of growth rings of fossilized trees suggest a lack of seasons, or a tropical climate. Glaciations in Gondwana were triggered by its southward movement, and continued beyond this time period.

Also, there was mountain building as continents collided to form Pangaea. There was a minor extinction event at the end of the period, caused by climate change.

Now, the last we heard, pieces of Gondwana had broken off and were sitting at the equator or slightly north, while the rest of Gondwana drifted south to the south pole.

During the Carboniferous Period, the land was covered by vast forests, which would eventually become the coal beds characteristic of this period's stratigraphy. Some of the Early Carboniferous land plants were very similar to those of the Late Devonian, but new groups also appeared. The main plants of the early period were horse-tails, scrambling plants, club mosses, scale trees, and ferns. The club mosses of this period are cousins to today's tiny club-moss, but not ancestors; and they had trunks 30 meters high and up to 1.5 meter in diameter. Another type of large tree was ancestor of today's ferns. These continued throughout the period, but late in the period, they were joined by cycads (a new form of 'seed fern') and plants related to conifers.

At least one tall plant (6 to over 30 meters tall) was related to cycads (often mistaken for palm trees) and conifers and are thought to have lived in swamps. True conifer trees appeared later in the period and preferred higher, drier ground.

During this period, animals and bacteria had great difficulty processing the lignin and cellulose that made up the gigantic trees. After the trees died, they piled up on the ground, occasionally becoming part of long-running wildfires after a lightning strike. Others very slowly degraded into coal. White rot fungus was the first living creature that could process these trees and break them down.

Animal life was well established by now. Amphibians were diverse and common by the middle of the period, the dominant type of land vertebrates. Some were as long as 6 meters, but most were probably about 6 in (15 cm) in length. Some were aquatic and lived in rivers, while others may have been semi-aquatic. One branch of amphibians would eventually evolve into the first solely terrestrial vertebrates. The cooling climate slowed the evolution of amphibians, who could not survive as well in the new conditions.

Insects, spiders, crustaceans, and others were also very common, and many were much larger than those of today. The atmospheric content of oxygen reached its highest level in Earth's history—35% compared to today's 21%—which allowed the land invertebrates to get so large. There was a millipede-like creature that grew to 8.5 ft (2.6 m) long. Startling to come across, but if you could kill it, there should be some meat on all those legs. This was the largest known land invertebrate of all time. Among the insects, there were the griffinflies, which included a dragonfly-like insect with a wingspan of 30 in (75 cm). This was the largest flying insect ever to roam the planet. Many other insects flew and crawled about, including cockroach ancestors.

Reptiles, however, prospered due to specific adaptations, such as the amniote egg, which allowed the laying of eggs in a dry environment. Some of the small lizard-like animals gave rise to many descendants, including reptiles, birds and mammals.

I wanted to include a statement about the marine animals of the time, but that section of the article was mostly full of names and little else. I did gather than sponges were fairly prolific and diverse. Also sharks evolved into a multitude of shapes and sizes. Although sharks were mostly sea creatures, there was one type that would sometimes visit swamps. At least one marine fish explored river outlets, and fresh-water fish were common in rivers.

During the latter half of this period, there were glaciations, which meant low sea levels. The cooling and drying of the climate led to a minor extinction event at the end of the period. The tropical rainforest fragmented and then was devastated by climate change.

 

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

Silurian Period

After the Ordovician Period came the Silurian Period, lasting 24.6 million years, from 443.8 million years ago to 419.8 million years ago. It began approximately the same time as the major series of extinction events mentioned at the end of the Ordovician Period, when a large number of marine fauna were wiped out.

The Silurian saw wide-spread diversification of jawed fish as well as bony fish. Multi-cellular life also appeared on land as small plants similar to liverworts, hornworts, and mosses, which grew besides lakes, streams and coastlines. Invertebrate animals with an exoskeleton also found land during this time period. This includes insects, spiders and crustaceans. However, terrestrial life would not greatly diversify until later.

With the supercontinent Gondwana still covering much of the southern hemisphere, a large ocean occupied most of the northern half of the globe. High sea levels and relatively flat land (there were few significant mountain belts) produced a number of island chains, meaning there was a rich diversity of environmental settings.

What was left of Gondwana remained intact and continued to drift south, but there is evidence that the icecaps were less extensive than those of the late-Ordovician time period. The smaller continents of Avalonia, Baltica, and Laurentia drift together near the equator, starting the formation of a second supercontinent known as Euramerica.

When proto-Europe (Baltica) collided with proto-North America (Laurentia), the collision folded coastal areas from modern New York State through Europe and Greenland to Norway. At the end of the Silurian Period, sea levels dropped again, and the new mountain ranges were rapidly eroded.

The Silurian period enjoyed relatively stable and warm temperatures, in contrast with the extreme glaciations of the period before it, and the extreme heat that would follow it. Sea levels rose during the first half of this period, and fell during the second half.

Climate was warm because high CO₂ levels and warm shallow seas produced a greenhouse phase. Glaciers at the South Pole nearly disappeared entirely. There is strong evidence of a climate dominated by violent storms generated by warm sea surfaces.

The Silurian was the first period to have megafossils in the form of moss-like miniature forests along lakes and streams. The first fossil records of vascular plants (land plants with tissues that carry water and food) appeared in the second half of the Silurian period.

Fish reached considerable diversity. A diverse fauna of sea scorpions (some of them several meters in length) prowled the shallow Silurian seas of North America. Leeches made their appearance.

About the middle of the Silurian, the earliest-known animals fully adapted to terrestrial conditions appeared, including a millipede. There is also some evidence of predatory spiders and millipedes and centipedes. Predatory invertebrates indicate that simple food webs were in place that included prey animals. These may have included those who grazed on micro-organisms.

Yes, we are getting closer and closer modern Earth. That is what happens when you start at the beginning and work your way towards today. I'm still not seeing any fauna that would be worth hunting. Although a millipede several meters in length might have enough meat to make a stew. Is the ground fertile enough to grow carrots and potatoes to put in that stew? And just how bad did those storms get? Maybe I'll keep going before I try to colonize.

 

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

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 

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

Tonian, Cryogenian, and Ediacaran Periods

Tonian Period

The first section of the Neoproterozoic Era is the Tonian Period. It lasted from 1,000 million years ago to 720 million years ago. The breakup of supercontinent Rodinia began around 900-850 million years ago.

The first large evolutionary radiation of organic microfossils occurred during the Tonian Period. This means a huge increase in diversity caused by a large rate of specialization. None of the examples in this article of evolutionary radiation were from the Tonian period, however, probably since it involved microfossils, which most lay people are not terribly familiar with.

So, Rodinia started breaking up, and microorganisms multiplied and diversified. It still sounds like a pretty barren place to me.

Cryogenian Period

The second geologic period of the Neoproterozoic Era was the Cryogenian Period, lasting from 720 to 635 million years ago. There were 2 ice ages during this period, the Sturtian and Marinoan Glaciations, which are said to be the greatest ice ages known on Earth. There is much debate over whether these glaciations covered the entire planet (Snowball Earth) or a band of open sea survived near the equator (Slushball Earth).

In any case, the Sturtian Glaciation lasted from 720 to 660 million years ago, while the Marinoan Glaciation ended at approximately 635 million years ago, although there was no indication when it began. Whenever it began, it was relatively short-lived when compared to the Sturtian.

Fossils of hard-shelled amoeba first appear during this period, as well as the oldest known fossils of sponges. Debate about how much the glaciation might have impacted biology rages on, with some suggesting that several species began during this period.

Me, I much prefer warmer climes.

Ediacaran Period

The end of the Era is marked by the Ediacaran Period, which lasted from 635 million years ago to 541 million years ago.

Fossils from the Ediacaran are sparse, as not a lot of hard-shelled animals had yet evolved. But there were multicellular organisms with specialized tissues. The most common types resemble segmented worms, fronds, disks, or immobile bags. Although Ediacara biota bear little resemblance to modern lifeforms, more than 100 genera have been described.

During this period, the moon was considerably closer, making the tides stronger and more rapid than they currently are. A day was about 21.9 hours long, meaning there were about 13.1 months per year, and approximately 400 days/year.

Okay, now we're getting somewhere. The place had worms and fronds, or at least lifeforms that looked like them. I was particularly pleased with the information about the days being shorter and the moon being closer. How long do you suppose it would take human colonists to get used to a 22-hour day instead of a 24-hour day?

 

https://en.wikipedia.org/wiki/Tonian#:~:text=The%20Tonian%20(from%20Greek%20%CF%84%CF%8C%CE%BD%CE%BF%CF%82,Mya%20(million%20years%20ago).&text=The%20Tonian%20is%20preceded%20by,and%20followed%20by%20the%20Cryogenian.

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

https://en.wikipedia.org/wiki/Cryogenian#:~:text=The%20Cryogenian%20(%20%2Fkra%C9%AA,and%20followed%20by%20the%20Ediacaran.

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

  

Neoproterozoic Era

 The next Era is the Neoproterozoic Era, which lasted from 1,000 to 541 million years ago. It is divided into 3 Periods, which we will probably take a closer look at, given the chance.

This article says the most severe glaciation occurred in the middle of this era, when ice sheets reached the equator and formed a ‘snowball earth’. I seem to remember reading somewhere that may not have been a hard freeze at the equator, it may have been slushy in the lowest latitudes.

This severe glaciation may have occurred because of the supercontinent Rodinia, which straddled the equator. It broke up into a number of individual land masses during the first period of this era. Somehow, the low-latitude position of most continent pieces caused the large-scale glacial events. We’ll see if this is explained when we look at the individual periods.

Fossils of the earliest complex multicellular lifeforms have been found dating from the last period of this era. These organisms include the oldest definitive animals in the fossil record.

Originally, the fossil remains of multicellular life such as trilobites and archeocyathid sponges were used to designate the beginning of Cambrian Period. Early in the 20th century, other complex fauna started to be found that pre-dated these fossils, so there were multicellular lifeforms during the Neoproterozoic Era, possibly arising in the last period, after the world-dominating glaciers subsided. Some of these early creatures may or may not be ancestors of modern animals. Even the scientists don’t agree on that or on which ancient lifeform may have produced which modern animal.

Another milestone attributed to this era is that this is when the most continental crust was formed.

Well, I managed to boil that entire article down to less than 300 words. I could have included more, but it would have come out sounding more like a thesis, rather than a blog.

Here’s what I look forward to finding out in looking up the 3 periods for the era:

* Anything that happened in the first period, because this article seemed to have glossed right over those years.

* How Rodinia’s ‘children’ all sitting near the equator created such massive glaciers when Robinia itself, sitting on the equator, did not.

* What finally caused the glaciers to retreat? I’ve heard it might have been volcanoes in Siberia (which wasn’t sitting anywhere near where it is today).

* More information about these lifeforms and their supposed modern descendents.

 

https://en.wikipedia.org/wiki/Neoproterozoic#:~:text=The%20Neoproterozoic%20Era%20is%20the,%2C%20Cryogenian%2C%20and%20Ediacaran%20Periods.

Calymmian, Ectasian & Stenian Periods

 

Calymmian Period

There are 3 periods in the Mesoproterozoic Era. However, the article on the first of these periods, the Calymmian Period, was less than 100 words long. The Calymmian Period lasted from 1600 to 1400 million years ago. During this time, the continents expanded by adding sedimentary flatlands. Right in the middle of the period, the supercontinent Columbia started to break up.

 

Ectasian Period

The 2nd period is the Ectasian Period, which in Greek means “extension”. It lasted from 1400 to 1200 million years ago. The name refers to the continued expansion of sedimentary flatlands.

Fossils have been found dating from this period that provide the first evidence of sexual reproduction. This allowed and was necessary for complex multicellularity, in which certain cells of the organism are specialized to perform different functions.

 

Stenian Period

The Stenian Period is the final segment of the Mesoproterozoic Era, lasting from 1200 to 1000 million years ago. The supercontinent Rodinia assembled during the Stenian.

And the Keweenawan Rift formed at about 1100 million years. This rift (tear) occurred in the middle of the North American continent. I had never heard of this rift before. One wonders if North American was much skinnier before the rift occurred and the rift has been filled in since then. If that were the case, the rift could have been as small as the Mississippi River valley, or it could have stretched from the Rocky Mountain foothills to the Appalachian foothills, if those existed at that time. What would have happened if the rift had grown and deepened. Would we have 2 continents where we only have 1?

A closer look at the map provided showed it to be a lop-sided horse-shoe-shaped rift. The 2 ‘arms’ meet at Lake Superior, which defines the northern arc of the rift. The eastern arm trends south into lower Michigan, and possibly as far south as Alabama. The western arm runs southwest into Kansas and possibly as far as Oklahoma. A northern arm, which was not shown on the map, ran up into Ontario and formed another lake, but didn’t go any further.

So, let’s see, if that 3-armed rift had actually grown and spread, we might have had 3 continents where we now only have 1. That would certainly change things up. Now I have alternate histories running rampant through my mind. What do you think about that? Eastern North America, Western North America and a Mexico that reaches Lake Superior.

 

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

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

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

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

Mesoproterozoic Era

The Mesoproterozoic Era is still part of the Proterozoic Eon. It lasted from 1,600 to 1,000 million years ago. This is the first period of Earth’s history which has a fairly definitive geological record. The continental masses of this era were more or less the same ones that exist today, but not necessarily in the same forms.

During this era, the Columbia supercontinent broke up, the Rodinia supercontinent formed, and, oh yeah, sexual reproduction evolved, which greatly increased the complexity of life to come.

Further development of continental plates and plate tectonics took place. This era saw the first large-scale mountain building episode, the Grenville Orogeny. From the maps I’ve see of this mountain range, it could be what produced the Appalachian Mountains and the Ozark Mountains, but it continued down along what is now the Texas Gulf Coast and into northeastern Mexico.

This was the high point of the Stromatolites before they started to decline. Stromatolites are a type of sedimentary rocks created by photosynthetic cyanobacteria when they exuded adhesives, gluing sand and dirt into mats, which eventually bonded together to form rock formations.

During this era, the chemistry of the sea changed, as did the sediments of the earth and the composition of the air. Oxygen levels continued to rise.

I believe this Era has 3 subdivisions, which I will probably study further, just to try to get a sense of what happened when. The problem with using Wikipedia is that the different articles are or can be written by different people, and then don’t always agree. For instance, is this the 2nd time the Grenville Orogeny is said to have happened? I seem to remember it having been mentioned before, because I remember looking at the map of how far it extended.

Another example is that this article said atmospheric oxygen was at 1% of today’s level at the beginning of this era, while another article said it reached 1-2% of today’s levels during a previous period. I suppose that’s not a huge difference, but it does tend to confuse people who are looking for absolute answers. It’s why I only stated that the oxygen levels continued to rise.

Still not ready for colonization, but we’re getting closer!

 

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

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

Proterozoic Eon

 Now to move on to the next eon, the Proterozoic Eon. This eon spans the time from the appearance of oxygen in Earth’s atmosphere to just before the proliferation of complex life such as trilobites or corals. It started at 2,500 million years ago to 541 million years ago, so very nearly 2 billion years. It is divided into 3 eras; the Paleoproterozoic, the Mesoproterozoic, and the Neoproterozoic. We may or may not take a look at each of these in more detail.

The geologic record of the Proterozoic Eon is more complete than for the Archean Eon, which preceded it. The Proterozoic features rock strata that were laid down in extensive shallow inland seas. Studies of these rocks show that the eon had massive continental accretion, including the first definitive supercontinent cycle, and modern mountain building activity.

There is also evidence of glaciations taking place during the Proterozoic. The first began shortly after the beginning of the Proterozoic, with at least four others near the end of the eon. These may have climaxed with the hypothesized Snowball Earth, an idea I am thoroughly fascinated by.

One of the most important events of this eon was the accumulation of oxygen in the atmosphere. Although oxygen was probably released by photosynthesis during the Archeon Eon, it first combined with sulfur and iron in the oceans. Until roughly 2.3 billion years ago, oxygen was only 1-2% of its current level. It is stated that about 1.9 billion years ago, all the iron in the oceans had all been oxidized.

The Proterozoic Eon was tectonically active. The early part of the eon experienced a period of increasing crustal recycling, which suggests subduction. This is where one piece of crust gets shoved under another piece of crust. The bottom crust is eventually melted, while the upper crust buckles into mountains. The melting crust eventually reformed, making the upper bits of crust thick enough to endure. It is believed that 43% of the modern continental crust was formed in the Proterozoic Eon, 39% during the Archean Eon, and only 18% in the current geological eon.

It is commonly accepted that during the Precambrian SuperEon--of which the Proterozoic Eon is a part--the Earth went through several supercontinent breakup and rebuilding cycles.

The supercontinent Columbia was dominant in the early-mid Proterozoic. The article did not say much about Columbia, so we shall skip ahead to Rodinia (1,000-750 Million years ago) of the late Proterozoic. It was created when a series of continents attached to a central craton called Laurentia, which today forms the core of the North American Continent. During its construction, the mountain building processes created the Grenville orogeny located in Eastern North America, from Labrador down through Mexico. From the map, it looks like the Appalachian Mountains could be part of the mountain range that was formed.

The first advanced single celled (eukaryotes) and multi-cellular life roughly coincides with the start of the accumulation of free oxygen. This may have been due to an increase in the oxidized nitrates, which is what eukaryotes use. But the rise of eukaryotes did not preclude the expansion of cyanobacteria. In fact, stromatolites (microbial mats) reached their greatest abundance and diversity, peaking roughly 1,200 million years ago.

The earliest fossils of something like fungi date to 2,400 million years ago. These organisms lived in the deepest areas of water, and had filamentous structures capable of forming branches.

Wow, sounds like Earth was getting busy, doesn’t it? But I still don’t think we could colonize, not with the crops we grow now. There’s too many forms of other life that our crops count on to help them get the nutrients they need from the soil. Plus, I’m not sure what the climate was like, with such a low amount of free oxygen in the atmosphere. Put me back in my pod and let me sleep another million years or so, and then we’ll see.

 

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

Mesoarchean & Neoarchean Eras

 Mesoarchean Era

We will continue studying the Archean Eon with a brief look at its 3rd part, the Mesoarchean Era. How brief a look? That will depend on how much I find.

The Mesoarchean Era lasted from 3,200 to 2,800 million years ago. There is no specific level in the rocks that designates this era, it is simply defined by the time period.

Fossils from Australia prove that stromatolites have been growing on Earth since the Mesoarchean Era. These sedimentary formations are created by photosynthetic cyanobacteria that produce adhesive compounds and cement sand and other rocky materials into mineral “microbial mats”. These multi-layered sheets of microorganisms, mainly bacteria, grow at interfaces between different types of material, mostly on submerged or moist surfaces. They have been known to colonize environments ranging in temperature from -40C to 120C (about -48F to 272F). The mats grow layer by layer and can grow to a meter or more. Although uncommon today, fossilized stromotalites record ancient life on Earth. The earliest reefs, probably formed by stromatolites, date from this era.

The article had a tantalizing statement about the Pongola glaciation occurring around 2,900 million years ago but a brief search couldn’t find any more information about it. Was it only at the poles, or was it world-wide?

At the end of this era, the first supercontinent broke up, right about 2,800 million years ago.

 

Neoarchean Era

That brings us to the 4th part of the Archean Eon, the Neoarchean Era,  from 2,800 to 2,500 million years ago. Again, this era is defined only by time, not to a specific rock level.

During this era, oxygenic photosynthesis released an abundance of oxygen, which first reacted with minerals and afterward was free to react with greenhouse gases of the atmosphere. By reacting with these greenhouse gases, the oxygen changed them into gases that trapped less heat in the Earth’s atmosphere, and the Earth began to cool off. Eventually.

Remember the microbial mats from the Mesoarchean Era? Did I mention these mats were created by cyanobacteria? Cyanobacteria give off oxygen as a waste product. We should celebrate the ancient existence of cyanobacteria as the provider of the oxygen that we need in order to live.

However, back then, what life existed could not use oxygen. In fact, it was poisonous to most forms of life of the time. So when O2 levels got too high, a lot of the existing life died off. But that happened later. The process that led to that problem was only beginning during the Neoarchean Era.

Also during the Neoarchean Era, at about 2,720 million years ago, the supercontinent Kenorland formed.

 

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

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

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

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

Columbia SuperContinent

 Columbia was a supercontinent thought to have existed about 2,500 to 1,500 million years ago in the Paleoproterozoic Era. It is also known as Nuna and Hudsonland. It consisted of proto-cratons known as the Amazonian Shield, Australia, Baltica, Laurentia, and the Ukrainian Shield. It may have possibly included Kalaharia, North China and Siberia as well.

Following its creation by combining most or all of the known bits and pieces of land, Columbia continued to grow by various areas of volcanic activity that created magma flows.

Columbia began to fragment about 1.5 to 1.35 billion years ago.

This is pretty much the sum total of what I learned from this article. I find it irritating when an article that is supposedly written for the average person presumes that the average person has taken a course or three in the specific subject covered by the article, and so it is filled with language and terms that actually mean very little to the average person. More and better pictures might have helped.

There was one graph that seemed to say that when Columbia began collecting its various pieces, single-cell life was strong, as was photosynthesis. Then a type of life known as eukaryotes began. This is a very broad type of life, where the cell nucleus containing the cell’s DNA is enclosed within a nuclear envelope. This is so broad a definition that these days, it includes all life except some or all types of bacteria.

At the very end of Columbia’s life, as it was beginning to break up, multi-cellular life was just beginning.

I don’t think I’d want to try to colonize a planet during this period of its life. I don’t think you could get crops to grow unless you brought along various soil denizens that would help make the soil and its potential nutrients usable by your plants. But then, I don’t have a degree in biology or agriculture, either, so maybe I’m way off base there.

I’d like to take a course in paleogeology, I just don’t know where I’d have to go to find one.

 

https://en.wikipedia.org/wiki/Columbia_(supercontinent)

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)

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?

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