Tag Archives: carboniferous

Frozen Earth.

Coal formation sucked so much CO2 out of the atmosphere that Earth nearly froze over 300 million years ago

A new paper showcases the massive effect CO2 levels in the atmosphere have on Earth’s climate, describing its link to the great cooling period in the Carboniferous and Permian ages.

Frozen Earth.

Image credits Kevin Gill / Flickr.

We call it a ‘greenhouse’ gas for a reason. Today, it’s most widely known for the part it plays in climate change — but 300 million years ago, CO2 was involved in one of the most severe cooling events in Earth’s history. Using a large ensemble of computer simulations, Georg Feulner from the Potsdam Institute for Climate Impact Research was able to model how coal formation in the late Paleozoic came inches away of locking Earth into a ‘snowball state’.

A leaky greenhouse

In the very distant geological past, Earth was a much warmer place. Overall, it had a more uniform, tropical, humid climate than exists today, and plant life was going rampant. Vegetation resembled what you’d expect to see in a jungle setting today, but even more bountiful. Trees especially (they were still recent-ish technology at the time) were turbocharged by warm temperatures and swampy environments, growing to huge sizes. They lacked tree-rings, suggesting they could sustain growth throughout the year. All off this eventually led to Pangea (the only continent at the time) becoming plastered with immense quantities of biomatter. Some 300 million years ago,

Swampy, plant-infested areas are prime breeding spots for coal. Since that was basically all of the dry land at the time, most of the quality coal we’ve ever mined formed in this period. So much so that geologists know one subdivision of this time as the Carboniferous, which translates to ‘the coal-bearer’.

One unexpected side-effect of all this coal being formed, however, was that CO2 in the atmosphere was increasingly sequestered underground. Because of this, the Earth began to rapidly cool down. By the end of the Carboniferous, a full-fledged Ice Age had developed, one which came very close to lock our planet in a permanently frozen state.

“This illustrates the enormous dimension of the coal issue,” Feulner says. “The amount of CO2 stored in Earth’s coal reserves was once big enough to push our climate out of balance. When released by burning the coal, the CO2 is again destabilizing the Earth system.”

His research shows that some of the changes in temperature at the time can be attributed to other planetary factors, such as the axis tilt and the planet’s orbit. However, it also shows that CO2 concentrations in the atmosphere played the prime role in shaping the climate during the Carboniferous. Estimates drawn from samples of ancient soils and leaves show that CO2 levels fluctuated widely during this period, at one point dipping to about 100 parts per million (ppm) in the atmosphere — which is extremely low. Feulner’s models show that when atmospheric CO2 levels dip under 40 ppm, global glaciation is virtually guaranteed.

The flipside of Feulner’s findings is that burning coal today releases the CO2 captured over 300 million years ago. Today, we’re past the 400 ppm mark, which is above the 350 ppm deemed safe by the ICCP, but still under 450 ppm — a point where our chances of stabilizing the climate before planetary-scale irreversible damage is done are basically 50-50.

That’s because CO2 traps incoming heat in the Earth’s atmosphere, warming up the planet. Higher concentrations mean a higher percentage of incoming energy is trapped.

“It is quite an irony that forming the coal that today is a major factor for dangerous global warming once almost lead to global glaciation,” Feulner adds. “We should definitely keep CO2 levels in the atmosphere below 450 parts per million to keep our climate stable, and ideally much lower than that. Raising the amount of greenhouse gases beyond that limit means pushing ourselves out of the safe operating space of Earth.”

“Earth’s past teaches us that periods of rapid warming were often associated with mass extinction events. This shows that a stable climate is something to appreciate and protect.”

The paper “Formation of most of our coal brought Earth close to global glaciation” has been published in the journal PNAS.


How coal is formed

Most coal formed approximately 300 million years ago from the remains of trees and other vegetation. These remains were trapped on the bottom of swamps, accumulating layer after layer and creating a dense material called peat. As this peat was buried more and more underground, the high temperatures and pressure transformed it into coal.

Coal Formation

how is coal formed

Image via Pixabay.

Coal is still the largest source of energy for the generation of electricity worldwide, though it’s being phased out in many parts of the world due to its impact on the climate. But if we want to understand the origins of coal, we have to look back much further — to a period called the Carboniferous.

The Carboniferous (after the Latin name of coal) took place approximately 360 to 300 million years ago. Amphibians were the dominant land vertebrates and vast swaths of huge trees covered the singular mega-continent Pangaea. The atmospheric content of oxygen was at its highest level in history: 35%, compared with 21% today; all the conditions were ripe for the formation of massive coal beds.

Coal never formed before the Carboniferous, and very rarely formed after it. Two conditions are regarded as crucial for this event:

  • the emergence of wooden trees with bark; a large quantity of wood was buried in this period because mushrooms and microorganisms hadn’t yet figured out how to decompose trees. After they did, coal formations became much rarer.
  • the lower sea levels; the decrease of the sea level created many swampy environments in what is today North America and Europe. These swamps were vital for coal formation.
coal formation

Coal formation. Image via Kentucky Geological Survey.

As mentioned before, these trees were not decomposed by anything and were preserved. In time, they were buried. As they went deeper and deeper, temperature and pressure started building up and started to transform the coal.

Types of coal

The geological process of changing something under the effect of temperature and pressure is called metamorphism. Coal is generally classified into types based on the grade of metamorphism — the higher the grade of metamorphism, the more energy they contain:

Types of coal. Image via CUNY.

  • peat is generally considered a precursor of coal, but it has been used as a fuel in some areas — most notably in Ireland and Finland. In its dehydrated form, it can help soak up oil spills.
  • lignite is the lowest quality and the first to be formed.
  • sub-bituminous coal is most often used as fuel for steam-electric power generation.
  • bituminous coal is a dense sedimentary rock, generally of a high-quality.
  • steam coal” is a transition type between bituminous and anthracite.
  • anthracite is the highest rank of coal. It’s a hard, glossy rock and highly valued for its properties.
  • graphite is not generally considered a type of coal because it cannot be used for heating. It is most often used in pencils or as a lubricant (when powdered).

Coal can be used in its natural form, or it can be either gasified, liquefied or refined. However, no matter the type of coal or how you use it, coal is a non-renewable resource. In realistic terms, no coal is being formed to restock the resources we are using.

The adverse effects of coal

Coal is one of the main contributors to global warming, and coal mining and its fueling of power stations cause major environmental damage.

Historically, coal mining has been very dangerous. The list of coal mine accidents is long, and even today, accidents are still surprisingly common. Many miners also suffer from coalworker’s pneumoconiosis, colloquially known as “black lung”. But the main problem with coal is its emissions.

In 2008 the World Health Organization (WHO) calculated that coal pollution alone is responsible for one million deaths annually across the world; other organizations have come up with similar figures. According to a US report published in 2004, coal-fired power plants shorten nearly 24,000 lives each year in the US (2,800 from lung cancer). In China, the situation is even more dire as smog is a common occurrence in many major Chinese cities.

Burning coal releases great quantities of carbon dioxide into the air and also releases methane a much more potent greenhouse gas. Methane accounts for 10.5% of greenhouse gas emissions created through human activity. Coal may have allowed the industrial revolution to take place, but if we want to build a sustainable future, we simply have to phase out coal and implement other sources of energy in its stead.

350-million-year-old former inhabitant of Gondwana found

A 350 million year old fossilized scorpion has become the world’s oldest known land animal to have ever walked the supercontinent Gondwana.

Ancient history

laurasia gondwana

It’s 350 million years ago – take a moment to ponder that. Take a long human lifespan of 100 years, and multiply it by 100, and again by 100 – now you have a million years. Multiply it again by 350, and you get to the life of this now fossilized scorpion! It blows my mind just to think about that; it was so long ago, that the face of the Earth looked nothing like it does now.

There were only two major continents back then, called Laurasia and Gondwana, separated by the Tethys sea. Gondwana included most of the landmasses in today’s Southern Hemisphere, including Antarctica, South America, Africa, Madagascar and the Australian continent, as well as the Arabian Peninsula and the Indian subcontinent, which are now a part of the Northern hemisphere.

Paleozoic Era

We’re in a period called Carboniferous – when amphibians were dominant land vertebrates and were almost starting to evolve into reptiles, arthropods are extremely common, and vast swaths of forest cover almost every inch of land; these forests will lie down and eventually become coal – thus giving the name of the period (Carboniferous = coal bearing).

The oldest land walking Gondwanese

scorpion gondwana

Ok, Gondwanese isn’t a real word, I just made it up. But this new species, Gondwanascorpio emzantsiensis is the oldest we know that walked on Gondwana. Its discovery brings some tantalizing clues about the development of life before Earth’s continents broke apart to form the continents as we see them today.

“There has been no evidence that Gondwana was inhabited by land living invertebrate animals at that time,” said Robert Gess who is based at the Evolutionary Studies Institute at Wits University.

Gess uncovered the scorpion fragments—with a pincer and a sting clearly showing in the rock in South Africa, near the Eastern Cape. The implications this finding has are quite significant.

“For the first time we know for certain that not just scorpions, but whatever they were preying on were already present in the Devonian,” added Gess.

“We now know that by the end the Devonian period Gondwana also, like Laurasia, had a complex terrestrial ecosystem, comprising invertebrates and plants which had all the elements to sustain terrestrial vertebrate life that emerged around this time or slightly later,” said Gess.

scorpion 2

The first real land vertebrates, from which ultimately even humans evolved appeared some 350 million years ago.

Journal reference: The earliest record of terrestrial animals in Gondwana: A scorpion from the Famennian (Late Devonian) Witpoort Formation of South Africa.

GeoPicture of the week: Giant Dragonfly fossil


This is a Cast of an original fossil of a Meganeuridae. If you’re scared of dragonflies, brace yourself for this: these extinct insects from the Carboniferous period measured up to 70 cm. They are the largest known species of flying insect.

Controversy has prevailed as to how insects of the Carboniferous period were able to grow so large, especially considering that there is a fixed upper limit placed on insects, based on the way oxygen is diffused through the insect’s body via its tracheal breathing system.

Ancient Fossilized Sea Creatures Yield Oldest Biomolecules Isolated Directly from a Fossil

Paleontologists have long believed that complex organic molecules couldn’t survive fossilization; but to contradict this long standing belief, some 350-million-year-old remains of aquatic sea creatures uncovered in Ohio, feature exactly that type of molecules.


The animals icrinoidsn case are called crinoids, but are probably better known today as “sea lilies”; they are absolutely remarkable creatures, able to survive from shallow waters to depths of up to 6.000 meters. The earliest group of crinoids lived in the Ordovician – some 460 million years ago. The Crinoids found by Ohio State University geologists are a little younger, dating from the Carboniferous – the period when North America was covered with vast inland seas. Typically, these creatures disintegrate fast, even in a few hours, but in some cases, like this one, they are buried quickly and covered with sediment which keeps them together. They are isolated from the water above by a sedimentary layer and their porous skeletons are gradually filled with minerals. What makes this discovery absolutely special is the fact that some of the pores containing organic molecules were sealed intact.

That’s what researchers concluded, at least. William Ausich, professor in the School of Earth Sciences at Ohio State and co-author of the paper, explained why the organic molecules are special:

“There are lots of fragmented biological molecules — we call them biomarkers — scattered in the rock everywhere. They’re the remains of ancient plant and animal life, all broken up and mixed together,” he said. “But this is the oldest example where anyone has found biomarkers inside a particular complete fossil. We can say with confidence that these organic molecules came from the individual animals whose remains we tested.”

Part of why the crinoids are so well preserved also has a lot to do with the location and the structure of their skeletons. In the flat American Midwest, the rocks weren’t pushed up into mountain chains or heated by volcanism – they are pretty much orogenically pristine. Conditions that preserve crinoids over such long periods of time are quite rare due to their skeletal structure.

“We think that rock fills in the skeleton according to how the crystals are oriented. So it’s possible to find large crystals filled in such a way that they have organic matter still trapped inside,” Ausich said.

This opens up a whole new area of paleontological research – directly analyzing organic material. Of course, this is not DNA, and it will never be as good as DNA, but it’s definitely important, and could mark a turning point.

“These molecules are not DNA, and they’ll never be as good as DNA as a means to define evolutionary relationships, but they could still be useful,” Ausich said. “We suspect that there’s some kind of biological signal there — we just need to figure out how specific it is before we can use it as a means to track different species.”

Via Ohio State University

300 million year insects pictured in 3D

Researchers managed to construct a three dimensional (3D) portrait of two nymphs that inhabited our planet 305 million years ago by scanning their fossils with X-Rays.

Old insects

At the moment, they are by far the most detailed pictures of juvenile insects that inhabited that period; nymphs are the immature form of some invertebrates, particularly insects, which undergo gradual metamorphosis until they reach their adult stage. Aside from being downright incredible in itself, this achievement is also quite useful for future research, especially as one of the insects belongs to an unknown species and even genus.

This specimen is characterized by sharp spines on its body and head; scientists have named it Anebos phrixos, which is Greek for “young and bristling”, while the other one is quite similar to a modern cockroach. However, the classification is very difficult because their adult stage could have been significantly different from their nymph form.

X-ray tomography

Roach-like insect

The technique used in this case is called X-ray microtomography and it is used to obtain cross-sections of the fossils, each about 2 centimetres long, both found in France, in Montceau-les-Mines Lagerstätte. Then, using these sections, scientists were able to construct accurate 3D models of the insects.

“Fossils of juvenile insects become very uncommon when you go back as far as the Palaeozoic,” says Russell Garwood, a palaeontologist at the University of Manchester, UK, and co-author of the paper. “We hope these images will help scientists to better understand the evolution of insects’ life cycle.”

For now, this provided valuable insight about the lifestyle of these younger insects; the roach-like insect for example has well-preserved mouth parts which suggest it fed off of rotting matter on the bottom of the forest.

“The spikes of Anebos phrixos may be interpreted as an evolutionary strategy to avoid being eaten by early amphibians’ ancestors, which had arrived on land about 70 million years before this insect was born,” adds Garwood.

However, as this method is developed and perfected, we can move on to more complicated matters, and extract even more information – something definitely worth keeping an eye out for.

The world, 305 million years ago

The year is 305 million BC. How does the world look like? We’re nearing the end of the Carboniferous period, the period in which the most coal beds were formed (hence the name). Life, both aquatic and terrestrial is pretty much settled in this period – amphibians rule the land mass, and some of them already start evolving into reptiles. Arthropods are very common, but they are generally much larger than the ones we see today.

However, by now, the Carboniferous Rainforest Collapse (CRC) already took place, as a result of changing climate, from hot and humid to cold and arid – but don’t worry, this will change back a hundred million years from now. In fact, it is this move which will hit deep into the amphibian biodiversity, favoring early reptiles which were much more adaptable, and which will someday go on and become dinosaurs.

Scientific article: Tomographic Reconstruction of Neopterous Carboniferous Insect Nymphs (PLoS One)