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
Novel method for investigating pore geometry in rocks
18.06.2018 | Kyushu University, I2CNER
Decades of satellite monitoring reveal Antarctic ice loss
14.06.2018 | University of Maryland
Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.
Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...
The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.
Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.
An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.
Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...
Light detection and control lies at the heart of many modern device applications, such as smartphone cameras. Using graphene as a light-sensitive material for...
Water molecules exist in two different forms with almost identical physical properties. For the first time, researchers have succeeded in separating the two forms to show that they can exhibit different chemical reactivities. These results were reported by researchers from the University of Basel and their colleagues in Hamburg in the scientific journal Nature Communications.
From a chemical perspective, water is a molecule in which a single oxygen atom is linked to two hydrogen atoms. It is less well known that water exists in two...
13.06.2018 | Event News
08.06.2018 | Event News
05.06.2018 | Event News
18.06.2018 | Earth Sciences
18.06.2018 | Process Engineering
18.06.2018 | Life Sciences