The weathering of the mountains pulled carbon dioxide (CO2) from the atmosphere, causing the opposite of a greenhouse effect -- an "icehouse" effect.
Scientists have suspected that our current ice age, which began 40 million years ago, was caused by the rise of the Himalayas. This new study links a much earlier major ice age --one that occurred during the Ordovician period -- to the uplift of the early Appalachians .
It also reinforces the notion that CO2 levels in the atmosphere are a major driver of Earth's climate.
Seth Young, a doctoral student in earth sciences at Ohio State, reported the new study October 25 at the Geological Society of America meeting in Philadelphia.
Because we are currently living in an ice age -- or, more precisely, in a slightly warmer interglacial period within an ice age -- CO2 levels worldwide would ordinarily be low; but scientists believe that humans have raised CO2 levels by burning fossil fuels.
Matthew Saltzman, professor of geological sciences and Young's advisor, looks for evidence of ancient climate change to help scientists gain perspective on the climate change of today. He believes the geologic record can help solve current debates.
One such debate is whether atmospheric carbon dioxide truly drives Earth's climate. The planet has shifted between greenhouse conditions and icehouse conditions throughout its history, and research from Saltzman's team strongly suggests that carbon dioxide levels are a key cause.
"In this study, we're seeing remarkable evidence that suggests atmospheric CO2 levels were in fact dropping at the same time that the planet was getting colder. So this significantly reinforces the idea that CO2 is a major driver of climate," Saltzman said.
This study builds on work the same team published in 2005, when they used quartz sandstone deposits in Nevada and two sites in Europe to determine when the Ordovician ice age began -- approximately 450 million years ago.
They've now analyzed the same set of rock samples in a different way, comparing the ratio of two isotopes of the element strontium, strontium-87 and strontium-86.
They found that, immediately prior to the time that the Ordovician ice age began, the strontium ratio dropped dramatically. The likely cause: a vast amount of volcanic rock was being eroded away, and the resulting sediment was being deposited in the world oceans.
"We observed a major shift in the geochemical record, which tells us something must have changed in the oceans," Young said.
The timing of the strontium ratio decline matches the rise of the Appalachian Mountains . The crustal plate underneath what is now the Atlantic Ocean pushed against the eastern side of North America, lifting ancient volcanic rock up from the seafloor and onto the continent.
This kind of silicate rock weathers quickly, Young explained. It reacts with CO2 and water, and the rock disintegrates. Carbon from the CO2 is trapped in the resulting sediment.
The chemical reaction that weathered away part of the Appalachians would have consumed large amounts of CO2 from the atmosphere –- right around the time that the Ordovician ice age began.
The Ordovician period started out warm, with high sea levels worldwide. It ended cold, with low sea levels as glaciers covered the poles and portions of the continents. According to the Ohio State study, most of the Appalachian weathering took place over 7 or 8 million years -- a very short time, by geological standards -- as the climate moved from one extreme to the next.
The crossover between greenhouse and icehouse conditions set the stage for mass extinctions around the planet at the end of the Ordovician.
"We are seeing a mechanism that changed a greenhouse state to an icehouse state, and it's linked to the weathering of these unique volcanic rocks," Young said.
This kind of rock is often called "island arc" rock, because it forms curved chains of volcanic islands such as Indonesia and Japan.
"Those rocks are around today, where you have ocean crust being subducted under a crustal plate," Young explained. "What's unusual about the Ordovician period is that those island arcs were being uplifted onto a continent. The ones in the Pacific Ocean now are mostly underwater, so they're not weathering away like the Appalachian rock did."
The rise and subsequent weathering of the Himalayas may have caused our current ice age, the one that began 40 million years ago.
"In the Himalayas, the process would have been the same -- silicate rocks are exposed to the atmosphere, weathering sucks CO2 out of the atmosphere and chills the planet," Saltzman said.
"This may be the only effective way to bring CO2 levels down to a threshold that's cool enough for ice to start building up."
Coauthors on the study included Kenneth Foland, a professor, and Jeff Linder, a research associate, both in earth sciences at Ohio State. The National Science Foundation funded this research.
Matthew Saltzman | EurekAlert!
Greenland ice flow likely to speed up: New data assert glaciers move over sediment, which gets more slippery as it gets wetter
17.08.2017 | Swansea University
Climate change: In their old age, trees still accumulate large quantities of carbon
17.08.2017 | Universität Hamburg
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
17.08.2017 | Physics and Astronomy
17.08.2017 | Earth Sciences
17.08.2017 | Physics and Astronomy