Trudy Myers's Blog, page 22
February 18, 2021
Paleozoic Era
The Paleozoic Era is the earliest era of the Phanerozoic Eon. It is the longest of the Pahnerozoic eras, lasting from 541 to 251.902 million years ago. (I am left wondering why such an odd date for an ending? Why not 252 million years ago? I hope they offer an explanation.)
The Paleozoic was a dramatic time, incorporating geological, climatic and evolutionary changes. There was an explosion of variety in lifeforms, in which almost all modern families appeared. This began in the ocean, but eventually transitioned onto land. Great forests of primitive plants covered the continents, and towards the end of the Paleozoic, the first modern plants (conifers) appeared.
The Paleozoic Era also saw the largest extinction event in the history of Earth. This catastrophe was so devastating that it took life on land 30 million years into the next era to recover. Life in the sea may have recovered much faster.
During the early part of this era, the climate was probably moderate, becoming warmer as the second-greatest sea level rise of the era occurred, where the sea level was 200 meters above today's levels. Gondwana moved south until West Gondwana (Africa and South America) lay directly over the South Pole, while most of the parts that now reside in the northern hemisphere remained in the tropical zone, and China and Australia lay in a temperate zone. This warm period ended rather abruptly with a short but severe ice age that caused the second-greatest mass extinction of the Phanerozoic time. This ice age was only 30 million years long, and occurred 445 million years ago.
Sea levels dropped, of course, during the ice age, but slowly recovered over the middle of the Paleozoic. Bits and pieces of Gondwana moved northward, which created numerous new regions of warm, shallow sea floor. As plants took hold on the continental edges, oxygen level increased and carbon dioxide dropped. The far southern parts of Antarctica and West Gondwana became less barren.
Then a spike in atmospheric oxygen (while carbon dioxide plummeted) destabilized the climate and led to one or perhaps two ice ages. These were even more severe than the brief one already mentioned, but the effects on the world biota were mostly inconsequential. The oxygen and carbon dioxide level returned to more normal levels, but the assembly of Pangaea created huge inland areas that were subject to temperature extremes. The end of the era saw a huge mass extinction event.
While macroscopic plant life possibly appeared before this era began, plants mostly remained aquatic until about 420 million years ago, when they began to explore dry land. They reached a point where towering lycopsid (a type of plant that includes clubmosses, firmosses and quillworts) rainforests dominated the tropical belt of Euramerica. Climate change caused this rainforest to collapse, fragmenting this habitat and diminishing the diversity of plant life.
Nearly all of the invertebrate animal phyla appeared in great abundance at the beginning of this era. The first vertebrates were primitive fish, which lost no time in diversifying. Some fish had lung and powerful bony fins that allowed them to crawl onto land about 367.5 million years ago. Their fins evolved into legs about 390 million years ago. Amphibians were dominant for a time, until the climate change that reduced the rainforests also greatly reduced the amphibian diversity. Then reptiles prospered and increased in number and variety by the end of the era.
I'm sure we'll get even more details when we study each period of this era.
February 14, 2021
Hank's Wife
Wanda lost her husband Hank in a terrible Chicago traffic accident caused by a snow storm. She couldn't afford their apartment without getting some kind of a job, and that would play havoc with her writing career, which was just starting to take off. So when she found a deed to a house in Hank's tiny home town in Nebraska, she rather rashly decided to move there, to save on rent. She did get some survivor's benefits from his job, so what could go wrong?
What Hank had never told her was that there were 3 other men living in Belgrade who looked a lot like him. And 2 of them were still bachelors.
Tentatively set for a July release!
February 5, 2021
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!
January 28, 2021
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#....
https://en.wikipedia.org/wiki/Evoluti...
https://en.wikipedia.org/wiki/Cryogen....
https://en.wikipedia.org/wiki/Ediacaran
January 22, 2021
Mercury
I’m sure we all remember Mercury from our school days. It’s the closest planet to the sun, traveling around our local star once every 88 days. Now, I learned—way back when—that Mercury was tidally locked to the sun, meaning that one side was always facing the sun, while the opposite side was forever dark. But such is not the case. It turns out that Mercury spins completely around roughly every 59 Earth days. But because it is also moving around the sun, a day/night cycle is about 176 days long. So it has long days, and short years.
It is the smallest planet of our system... except for the dwarf planets. It is slightly larger than Earth’s moon at 9,525.1 miles around its equator. By the way, Mercury has no tilt to it, so it has no seasons except whatever small differences might occur because its orbit is elliptical and not round. The gravity at its surface is roughly 3/8 that of Earth. So a person weighing 100 pounds on Earth would weigh about 37.5 pounds on Mercury.
Like all the ‘inner’ planets, Mercury is a rocky planet. It’s surface is quite cratered, much like our moon.
It is only 39 million miles from the sun. If you were standing on Mercury, the sun would look 3 times larger than it does on Earth. It would also feel 7 times hotter. The daylight temperature can climb to 800 degrees Fahrenheit. At night, that temperature would plummet to -290 degrees Fahrenheit. Therefore, it is not likely that life as we know it would be able to exist there.
That is particularly true because of the atmosphere, what there is of it. It consists of oxygen, sodium, hydrogen, helium and potassium. These are atoms that are thrown up by blasts of the solar winds as well as micrometeor strikes.
The article stated quite bluntly that Mercury has no moons. How lonely it must be. I also wonder, what if it does? In that case, it would need to be very small, or it would have been found by now. But what if there were a pea-sized moon zipping around Mercury? And let’s suppose we eventually sent a manned mission there, to land on the dark side (since the light side is so hot) to bring back Mercury samples. How many spacemen would be killed by that moon zipping through their space suit (and maybe them) before they figured out what was happening? Or would punching through their space suit slow it down enough that it would fall to Mercury’s surface, and they might never figure it out?
Well, I’d have to stop and figure out the physics. And I’m not sure where my physics book is anymore.
January 15, 2021
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.
January 8, 2021
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
January 1, 2021
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!
December 25, 2020
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 supercontinentColumbiahad 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/Orosiri....
https://en.wikipedia.org/wiki/Vredefo...
https://en.wikipedia.org/wiki/Sudbury...
https://en.wikipedia.org/wiki/Statherian
December 17, 2020
Siderian & Rhyacian Periods
Siderian Period
There are 4 periods in the Paleoproterozoic Era, the first being the Siderian Period. This period lasted from 2,500 to 2,300 million years ago.
Early in this period is when banded iron formations peaked. As I explained before, cyanobacteria produced waste oxygen, which initially combined with iron that was in the sea, forming magnetite (Fe3O4), an iron oxide, in a crystal structure rock. This process removed iron from the oceans, presumably turning the greenish water clear.
Then, with no remaining iron in the sea to serve as an oxygen sink, the oxygen escaped the ocean and built up the oxygen level in the atmosphere. This led to the oxygen catastrophe, wherein a great deal of the life then existing on the Earth was wiped out because they could not tolerate such high levels of oxygen.
Some geologists believe the high level of oxygen also triggered the Huronian glaciation. This glaciation started in mid-Siderian (2,400 million years ago) and extended into the next period, lasting until 2,100 million years ago. It was apparently caused when free oxygen combined with the methane in the atmosphere to form carbon dioxide and water, which do not retain heat as well as methane does. With far less of this greenhouse gas in the atmosphere, a great chilling took place, also known as the Huronian glaciation. I don’t know if the entire planet froze, and the article stated that this glaciation caused a mass extinction. I’m waiting for a geologist I know to clarify whether there were 2 mass extinctions so close together, or just one, with both the presence of oxygen and the cooling temperatures to blame.
Rhyacian Period
The Rhyacian Period is the 2nd geologic period in the Paleoproterozoic era. It lasted from 2,300 to 2,050 million years ago. And that is just about all the wikipedia article had to say on the subject. Oh, there were a bunch of rock formations created, and the Huronian glaciation lasted 100 million years, but that still leaves 150 million years at the end of the period during which, apparently, absolutely nothing of note happened.
Oof! What was the tipping point that caused the end of the glaciation? For that matter, did it cover the entire Earth? Was there an explosion of new species afterwards?
Maybe they don’t know. What about theories? Doesn’t anybody have any theories? Well, without sitting my geologist friend down and picking his brain clean, I guess that’s as far as I can go with this period. Maybe the next 2 period of the Paleoproterozoic Era will have more meat to them.
