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Triassic
Triassic
The Triassic world represents the transition from the Late Palaeozoic icehouse to the later Mesozoic greenhouse, and was characterised by a relatively warm climate in which there were wide subtropical, dry desert belts and a monsoonal circulation. The Triassic began (252mya) with the largest mass extinction (EPE) in Earth history and ended with a series of substantial extinctions (201mya).
The name Triassic comes from Germany where it was originally named the Trias in 1834 by Friedrich August Von Alberti (1795-1878) because of a 3-part division of rock types in Germany.
Triassic Pangea
Pangea moved north and started to split, but remained whole during this period., but Laurasia and Gondwana evident
It was pretty hot throughout.
End of Triassic
Desertification
Desertification
Desertification was one of the significant factors that contributed to the collapse of terrestrial ecosystems during this Triassic period. However, it was not the only cause. Multiple environmental and climatic factors interacted to create widespread ecological instability.
Factors contributing to ecosystem collapse during the Triassic:
Factors contributing to ecosystem collapse during the Triassic:
Pangaea's configuration and aridification:
During the Triassic, the supercontinent Pangaea was fully assembled, creating a vast landmass that significantly influenced global climate patterns. The interior of Pangaea was far from the moderating effects of oceans, leading to extreme continental climates with seasonal temperature extremes and long periods of aridity.
Large regions of Pangaea experienced desertification, as vast swaths of land turned into deserts due to the lack of moisture, leading to the collapse of ecosystems dependent on more humid conditions.
Climate volatility:
There were extreme climatic fluctuations, including significant warming trends. Increased temperatures and a global greenhouse effect were likely driven by massive volcanic eruptions, particularly later, contributing to severe ecological stress.
These warming trends exacerbated desertification, increasing aridity in already dry regions, further stressing terrestrial life, especially plants and animals adapted to more temperate or moist environments.
Volcanism
One of the most significant volcanic events was the formation of the Central Atlantic Magmatic Province (CAMP), which occurred near the end of the period, that released vast quantities of carbon dioxide (CO2) and other greenhouse gases into the atmosphere, contributing to global warming and disrupting ecosystems through ocean acidification and changes in precipitation patterns.
Volcanic outgassing also played a major role in driving desertification in terrestrial regions, compounding the stress on ecosystems already struggling with a lack of moisture.
As ecosystems collapsed, many terrestrial organisms—especially reptiles, amphibians, and early mammal-like synapsids—were significantly affected by the increasing aridification, compounded by other environmental stresses.
Soil Survival
Soil Survival
The soil must have saved Earth. As plants took several million years to recover, they would have needed something to grow in. Presumably there was places where soil remained aerobic and alive despite the widespread desertification and ecosystem collapse.
On the ground, moss, liverwort, and ferns carpeted forests of conifers, ginkgoes, and palm-like cycads. Spiders, scorpions, millipedes, and centipedes thrived. Grasshoppers appeared and the main addition in soil was the invasion by insect larvae.
What was the role of soil in the resurrection of plants over several million years and animals over tens of millions of years? Many of the terrestrial (and 95% aquatic) creatures died out and took up to 30 million years to recover, yet most of the plants recovered within several million years, while the soil stayed resilient. Generally, we find organic-matter-poor sediments during the Triassic .
Soil survival must have been crucial, but has been largely ignored when describing the resurrection, which did not happen by magic. Processes to support plant life and then animals would have developed from those soil systems. The survival on land following the major End-Permian Extinction (EPE) would have relied on the soil, with a little help from lichens. Without the soil, particularly in dealing with excessive methane (below), volcanic halogens and ozone depletion, it is doubtful whether the earth would have survived. We will look at how soil dealt with halogen fixation and UV attenuation.
Climate
Climate
Climate was generally very dry over much of Pangaea with very hot summers and cold winters in the continental interior. A highly seasonal monsoon climate prevailed nearer to the coastal regions. Although the climate was more moderate farther from the equator, it was generally warmer than today with no polar ice cap
"The observed vertical progression (ie the way different soil types are stacked on top of each other in sediment layers, representing changes in the environment over time) in the major paleosol types from Vertsols to Gleysols and Oxisols implies a systematic change in the number of wet months, most probably in response to regional tectonics and long-term climate change. But it may have been a more exaggerated seasonality due to the size of Pangea." (Dawit, 2016).
Due to the dry climate, the interior of Pangaea was mostly desert. In higher latitudes, gymnosperms survived and conifer forests began to recover from the Permian Extinction. Mosses and ferns survived in coastal regions. Spiders, scorpions, millipedes and centipedes survived, as well as the newer groups of beetles. And the soil was still intact.
Change
Change
The globe warmed 8–11 °C caused by carbon dioxide from volcanic emissions. This triggered the release of much methane from permafrost and shelf sediment methane hydrates, which further accelerated global warming. The rapidity of the methane hydrate emission lasted from several years to thousands of years, but not before global warming had reached levels lethal to most life on land and in the oceans.
Coal Gap
Coal Gap
There was no coal in the early Triassic. There have been many explanations for this ‘coal gap’, one is due to the lack of appropriate plants. "The Early Triassic coal gap began with extinction of peat-forming plants at the end of the Permian (ca. 250 Ma), with no coal known anywhere until Middle Triassic (243 Ma). Permian levels of plant diversity and peat thickness were not recovered until Late Triassic (230 Ma). Tectonic and climatic explanations for the coal gap fail because deposits of fluctuating sea levels and sedimentary facies and paleosols commonly found in coal-bearing sequences are present also in Early Triassic rocks" (Retallack, Veevers, and Morante, 1996)
Why no plants
Why no plants
It may be that sharp drops in sea level at the time of the Permian Triassic boundary, acid rain from the Siberian eruptions, that overwhelmed acidic swamps. This may have gone along with evolution of fungi or herbivores that destroyed wetlands (Retallack, Veevers, and Morante, 1996), the extinction of all plants adapted to peat swamps, or soil anoxia as oxygen levels plummeted due to the methane.
There may have been weather processes. Climate shift to a greenhouse climate that was too hot and dry for peat accumulation with decreased rainfall and increased input of rock chunks have also been put forward. However, the lack of coal may simply reflect the scarcity of all known sediments from the Early Triassic, having moved to areas with no sedimentary record (McElwain and Punyasena, 2007).
Methane Burp
Methane Burp
There were several ‘methane burps’. The release of methane (80X more effective warming gas than carbon dioxide) from permafrost and shelf sediment methane hydrate is deemed the ultimate source and cause for the dramatic life-changing global warming. Global warming triggered by the massive release of carbon dioxide may be catastrophic, but the release of methane from hydrate may be apocalyptic. The scale of this calamity to end the Triassic, made the one that doomed the dinosaurs 65mya - a six-mile-wide asteroid smacking the planet - seem like a picnic by comparison.
Microbe spewed methane into atmosphere
Microbe spewed methane into atmosphere
Causes are debated as to why there was such high amounts of methane in the air. But it seems while volcanoes increased acid rain and temperatures it was the release of methane hydrates that really did increase the temperature.
There is one theory that it was a microbe that spewed humongous amounts of methane into Earth's atmosphere triggering the global catastrophe 252 million years ago.. “Methanosarcina (an anaerobic methanogen)… would have been unable to proliferate so wildly without proper mineral nutrients. The researchers found that cataclysmic volcanic eruptions that occurred at that time in Siberia drove up ocean concentrations of nickel, a metallic element that just happens to facilitate this microbe's growth. Fournier called volcanism a catalyst instead of a cause of mass extinction - "the detonator rather than the bomb itself."
Methane & Soil
Methane & Soil
Methane would have bumped off most life above ground devoid of oxygen. Yet, oxygen is twice as heavy as methane (Oxygen O2 masses 32. Methane CH4 only 16 ). It may be that some oxygen would have circulated round, near and into the ground, depending on all sorts of kinetics, like warm air currents , diffusion, Brownian motion etc. Life underground must have survived.
"Aerobic soils consume atmospheric CH4 but their activities are very low and the micro-organisms involved are largely unknown". (Le Mer & Roger 2001)
Bacteria
Bacteria
We have seen the bacteria can adapt to life without oxygen by utilising other compounds – like nitrates. Were there methane-utilising bacteria? There are certainly many now, and we do not know when they first appeared. They’d probably been around a long time but came into their own at this period. These methane-oxidizing bacteria (methanotrophs) are a unique group of aerobic, gram-negative bacteria that use methane as their sole source of energy.
Methane Munchers
Methane Munchers
Methanotrophs are ubiquitous in nature and, now being studied much more as they are the major biological sink for the greenhouse gas methane, so involved in the mitigation of global warming (Horz et al., 2005).
They are very diverse, and can be aerobic or anaerobic. They live in a diverse range of environments like swamps and wetlands, and hence have various biochemistry and structural characteristics. They all have two challenges: “They must obtain energy in the form of ATP and NAD(P)H by oxidation of their unusual substrates, and they must have special pathways for carbon assimilation, as all their carbon-carbon bonds must be made de novo.”Basically, methanotrophs like Methylococcus bacteria have enzymes which transform methane into methanol and then via their cytoplasm into carbon dioxide. So plants can grow.
Yellow = volcanic activity between land masses moving apart
End Triassic Extinction (ETE)
End Triassic Extinction (ETE)
The main soil characters, the springtails, mites and nematodes, survived the great extinction (EPE), and this ETE, along with the systems of providing nutrients and support to plants. Soil continued to break down the debris, although there was less of it, and so recycle the water and nutrients.
This Triassic period was bought to an end by another mass extinction, not quite as bad as the previous one (EPE), but still responsible for getting rid of more marine creatures.
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