November 4, 2013
Environmental Changes Following Pangea Integration May Have Caused Mass Extinction Event
redOrbit Staff & Wire Reports - Your Universe Online
The integration of Pangea that began during the early Permian period may have caused the environment to deteriorate, playing a role in the mass extinction event that occurred 250 million years ago, according to research appearing in the most recent edition of the journal Science China Earth Sciences.
In the study, co-authors, professor Yin Hongfu and Dr. Song Haijun of the State Key Laboratory of Geobiology and Environmental Geology at the China University of Geosciences, reported that Pangea integration reached its peak sometime during the Late Permian or Early Triassic period, and during its formation, the world’s scattered continents joined together in one enormous landmass.
This supercontinent had an approximate area of 200 million km2, and the average thickness of this massive continent’s lithosphere would have been far greater than that of each individual continent. Based on equilibrium principle, the thicker this outermost shell of the landmass, the higher its portion over the equilibrium level. This means that the average altitude of Pangea should have been much higher than each of the individual modern continents, Hongfu and Dr. Haijun explained in their study.
At this same time, the oceans gathered to form one massive body of water known as the Panthalassa, which was likely far deeper than the separated oceans of today. Thus, during their peak, Pangea and Panthalassa would have marked an era of high continents and deep oceans, the researchers added. This should have induced tremendous regression and influenced several parts of the planet’s surface systems, especially global climate.
Also during this time, the Tunguss Trap of Siberia, the Emeishan Basalt erupted, and this large-scale volcanic event should be evoked by mantle plumes and related to Pangea integration, the study authors said. Those types of volcanic activities could cause a series of extinction events, including the emission of large volumes of carbon dioxide, methane, nitric oxide and cyanides. The release of those gases would have caused greenhouse effects, followed by poisonous gases, damage to the ozone layer and an increase in UV radiation.
Increases in greenhouse gas concentration would have resulted in global warming, oxygen depletion and carbon-cycle anomalies, and other atmospheric changes. Furthermore, physical and chemical anomalies in the oceans – including euxinia (restricted hydrologic circulation), acidification, and low sulfate concentration – would have resulted in marine extinction due to unadaptable environments, selective death and increased CO2 levels in the blood.
Meanwhile, tropical rain forests and other terrestrial land vegetation would have been devastated by wildfires, continental aridity and the disappearance of the monsoon system, Hongfu and Dr. Haijun explained. These planetary changes and mass extinction events were probably the result of the interaction among the lithosphere, the atmosphere, the hydrosphere, and the biosphere (including the process of evolution in living creatures). In particular, the scientists cite relationships between the biosphere and the geospheres as a key piece of the puzzle.
“The event sequence at the Permian-Triassic boundary (PTB) reveals two-episodic pattern of rapidly deteriorating global changes and biotic mass extinction and the intimate relationship between them. The severe global changes coupling multiple geospheres may have affected the Pangea integration on the Earth's surface spheres,” the study authors wrote.
They added that “mantle convection may have caused the process of the Pangea integration,” and that “subduction, delamination, and accumulation of the earth's cool lithospheric material… started mantle plume by heat compensation and disturbed the outer core thermo-convection, and the latter in turn would generate the mid-Permian geomagnetic reversal. These core and mantle perturbations may have caused the Pangea integration… and probably finally the mass extinction at the PTB.”