Analyses of glacial sedimentary rocks in Oman, published online today in Geology, have produced clear evidence of hot-cold cycles in the Cryogenian period, roughly 850-544 million years ago. The UK-Swiss team claims that this evidence undermines hypotheses of an ice age so severe that Earth's oceans completely froze over.
Using a technique known as the chemical index of alteration, the team examined the chemical and mineral composition of sedimentary rocks to search for evidence of any climatic changes. A high index of alteration would indicate high rates of chemical weathering of contemporary land surfaces, which causes rocks to quickly decompose and is enhanced by humid or warm conditions. Conversely, a low chemical index of alteration would indicate low rates of chemical weathering during cool, dry conditions.
The researchers found three intervals with evidence for extremely low rates of chemical weathering, indicating pulses of cold climate. However these intervals alternate with periods of high rates of chemical weathering, likely to represent interglacial periods with warmer climates.
These warmer periods mean that, despite the severe glaciation of this time in Earth history, the complete deep-freeze suggested by 'Snowball Earth' theories never took place, and that some areas of open, unfrozen ocean continued to exist. Leader of the study, Professor Philip Allen of Imperial College London's Department of Earth Science and Engineering, explains:
"If the Earth had become fully frozen for a long period of time, these climatic cycles could not exist – the Earth would have changed into a bleak world with almost no weather, since no evaporation from the oceans could take place, and little snowfall would be possible. In fact, once fully frozen, it is difficult to create the right conditions to cause a thaw, since much of the incoming solar radiation would be reflected back by the snow and ice. The evidence of climatic cycles is therefore hostile to the idea of ‘Snowball Earth’.”
Professor Allen adds that understanding how Earth's climate has changed in the past provides important data for current climate change models. He says:
"This isn't just curiosity about the past - we are living in a time of climate change and there is a huge debate going on over what the natural variability of the climate is. Knowledge of climate change in deep time provides clues to the way in which our climate system works under extreme conditions. But these extreme conditions were probably not a full global freeze. It is equally important to understand a picture of global climate retaining open ocean between the tropics.”
This challenge to the 'Snowball Earth' opens intriguing questions about how the Earth came so close to climate disaster but managed to avoid it, according to Professor Allen.
"This was the most severe glaciation experienced by the planet over the last billion years, and the big question is - how can ice get all the way to the tropics but not finish the job?" he says. "The total icy shutdown that we came so close to would have dealt a severe blow to early life and most likely would have resulted in a completely different evolutionary pathway. The reasons for Earth’s near-miss with global refrigeration remains an important scientific question to resolve."
The team's findings come from analyses of sedimentary rock from the Huqf Supergroup, Oman's oldest sedimentary sequence that spans around 200 million years of the Neoproterozoic era.
Abigail Smith | alfa
NASA examines newly formed Tropical Depression 3W in 3-D
26.04.2017 | NASA/Goddard Space Flight Center
Early organic carbon got deep burial in mantle
25.04.2017 | Rice University
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
26.04.2017 | Materials Sciences
26.04.2017 | Agricultural and Forestry Science
26.04.2017 | Physics and Astronomy