Local weather regulation has modified with the proliferation of marine animals and land vegetation – Watts Up With That?
Geoscientific study follows the carbon-silicon cycle over three billion years using lithium isotope values
JOHANNES GUTENBERG UNIVERSITY OF MAINZ
Research news
PICTURE: BORIANA KALDERON-ASAEL COLLECTION 450 MILLION YEAR OLD ROCK SAMPLES IN PENNSYLVANIA, USA MORE CREDIT: PHOTO / ©: ASHLEIGH HOOD
The earth’s climate was relatively stable over a long period of time. For three billion years, temperatures were mostly warm and carbon dioxide levels high – until a shift occurred around 400 million years ago. A new study suggests that the change at this point was accompanied by a fundamental change in the carbon-silicon cycle. “This transformation from what was a consistent status quo in the Precambrian era into the more unstable climate we see today was likely due to the emergence and spread of new forms of life,” said Professor Philip Pogge von Strandmann, geoscientist at Johannes Gutenberg -University of Mainz (JGU). Together with researchers from Yale University, in particular Boriana Kalderon-Asael and Professor Noah Planavsky, he followed the long-term development of the carbon-silicon cycle with the help of lithium isotopes in marine sediments. This cycle is considered to be a key mechanism for the earth’s climate, as it regulates the carbon dioxide content and thus the temperature. The researchers’ results were recently published in Nature.
The carbon-silicon cycle is the key regulator of the climate
The carbon-silicon cycle kept the earth’s climate stable for long periods of time, despite strong fluctuations in the sun’s brightness, the oxygen concentrations in the atmosphere and the composition of the earth’s crust. Such a stable climate created the prerequisites for a long-term settlement of the earth by life and gave rise to initially simple and later complex life forms over billions of years. The carbon-silicon cycle contributes to this by regulating the carbon dioxide content of the atmosphere. Through weathering and sedimentation, silicate rock is converted into carbonate rock, carbonate rock is converted back into silicate rock, among other things through volcanism. When silicate rock is converted into carbonate rock, carbon dioxide is removed from the atmosphere, while the reverse process releases carbon dioxide again. “We consider this to be the main mechanism by which the earth’s climate is stabilized in the long term,” explains Pogge von Strandmann.
In order to trace long-term carbon-silicon cycles back in time and to better understand the exact interrelationships of the earth’s climate, the research team investigated the ratio of lithium isotopes in marine carbonates. Lithium occurs only in silicate rocks and their silicate and carbonate weathering products. The research team analyzed more than 600 samples deposited as sediments in shallow prehistoric ocean waters and obtained from more than 100 different rock layers from around the world, including Canada, Africa and China. “With these samples we have created a new database that covers the last three billion years,” emphasized Pogge von Strandmann.
These data show that the ratio of lithium-7 to lithium-6 isotopes in the oceans was low from three billion years ago to 400 million years ago and then suddenly increased. It was precisely at this time that land plants were developing, while marine animals with skeletons made of silicon, such as sponges and radiolarians, were spreading in the oceans. “Both played a role, but we don’t yet know exactly how the processes are linked,” adds Professor Philip Pogge from Strandmann.
The relocation of “clay factories” to the countryside affects the carbon-silicon cycle
Research suggests that the extent to which clay, a secondary silicate rock composed of very fine particles, has changed massively in the Earth’s past – possibly due to an increase in clay formation on land and a decrease in the oceans. Clay formation is a crucial component of the carbon-silicon cycle and influences the ratio of lithium isotopes. On land, it arises from the extensive weathering of silicate rocks, but various processes are involved in the oceans. It is believed that increased continental clay formation has reduced carbon dioxide levels in the atmosphere. In contrast, ocean clay formation known as “reverse weathering” releases CO2, so its decline also lowers atmospheric carbon dioxide levels.
According to the authors of the Nature paper, this suggests that the type of climate regulation on earth, as well as the primary location in which this process takes place, has changed dramatically over time: “The transition from a Precambrian Earth state to the modern state can probably be “attributed to great biological innovations – radiation from sponges, radiolarians, diatoms and terrestrial plants.” The result of this change in climate regulation has since been reflected in the frequent alternation between cold ice ages on the one hand and warmer periods on the other. However, this climatic instability in turn helps to accelerate evolution.
###
From EurekAlert!
Like this:
Loading…
Comments are closed.