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Surprising Geological Discovery: Ancient Rocks Emit as Much CO2 as All World’s Volcanoes
Sedimentary formations along Canada’s Mackenzie River, a prominent river basin where rock erosion contributes to CO2 emissions. Image Credit: Robert Hilton
A recent study conducted by the University of Oxford has uncovered that rock weathering can serve as a substantial source of CO2, comparable to emissions from volcanic activity. This revelation holds significant importance for future predictions regarding carbon budgets.
New research has challenged the conventional belief that natural rock weathering functions as a CO2 absorber, removing carbon dioxide from the atmosphere. Instead, it has been revealed that this process can also release considerable amounts of CO2, rivaling the emissions of volcanoes.
These findings have far-reaching implications for the modeling of climate change scenarios. Notably, the current climate models do not account for CO2 emissions from rock weathering.
Future research will explore whether human activities might be amplifying CO2 release through rock weathering and examine potential management strategies.
A Shift in Our Understanding of the Carbon Cycle
A recent study led by the University of Oxford has overturned the conventional perspective that natural rock weathering acts as a CO2 sink, suggesting instead that it can be a substantial source of CO2 emissions, comparable to volcanic activity. These findings, published in the journal Nature on October 4, have significant implications for climate change modeling.
Rocks and Their Role in the Carbon Cycle
Rocks house vast quantities of carbon in the ancient remnants of plants and animals that existed millions of years ago. Consequently, the “geological carbon cycle” functions as a thermostat, helping to regulate the Earth’s temperature. For instance, during chemical weathering, rocks can absorb CO2 when specific minerals react with the weak acid present in rainwater. This process counterbalances the continuous CO2 emissions from volcanoes worldwide and forms a crucial part of Earth’s natural carbon cycle, which has sustained a habitable environment for billions of years.
The Discovery of a New CO2 Emission Mechanism
However, this new study has, for the first time, quantified an additional natural process by which rocks release CO2 into the atmosphere, demonstrating that it is as significant as the CO2 emissions from volcanoes worldwide. Strikingly, this process remains absent from most models of the natural carbon cycle.
This process occurs when rocks formed on ancient seafloors, where the remains of plants and animals were buried in sediment, are thrust back to the Earth’s surface, often during the formation of mountains such as the Himalayas or the Andes. This exposure brings the organic carbon within the rocks into contact with oxygen in the air and water, leading to chemical reactions that release CO2. Consequently, weathering rocks can act as a source of CO2, challenging the previously held belief that they exclusively serve as sinks.
Methodology and Findings
Measuring the release of CO2 from weathering organic carbon in rocks has historically posed challenges. In this new study, researchers employed a tracer element, rhenium, which is released into water when rock organic carbon reacts with oxygen. By analyzing rhenium levels in river water, it became possible to quantify CO2 emissions. Nevertheless, achieving a global estimate by sampling all river water proved to be a formidable task.
To expand their findings globally, researchers conducted two crucial steps. First, they determined the amount of organic carbon present in surface rocks. Second, they identified regions where these rocks were being exposed rapidly due to erosion, often occurring in steep, mountainous areas.
Dr. Jesse Zondervan, the lead researcher from the Department of Earth Sciences at the University of Oxford, explained, “The challenge was then how to combine these global maps with the river data, while considering uncertainties. We fed all of our data into a supercomputer at Oxford, simulating the complex interplay of physical, chemical, and hydrological processes. By piecing together this vast planetary jigsaw, we could finally estimate the total carbon dioxide emitted as these rocks weather and exhale their ancient carbon into the air.”
This estimate was then compared to the amount of CO2 that could be absorbed through natural rock weathering of silicate minerals. The results indicated numerous regions where weathering acted as a source of CO2, reshaping our understanding of its role in the carbon cycle. Notably, CO2 emissions hotspots were concentrated in areas with high rates of uplift, such as the eastern Himalayas, the Rocky Mountains, and the Andes. The global CO2 emissions from weathering of rock organic carbon were calculated to be 68 megatons of carbon per year.
Professor Robert Hilton, who leads the ROC-CO2 research project at the University of Oxford, stated, “This is about 100 times less than the current human CO2 emissions from fossil fuel combustion, but it is comparable to the CO2 emissions from volcanoes worldwide, signifying its importance in Earth’s natural carbon cycle.”
Implications and Future Directions
It is possible that these fluxes have varied throughout Earth’s history. For instance, during periods of mountain formation, when large quantities of rocks containing organic matter are exposed, CO2 emissions may have been more substantial, exerting an influence on global climate in the past.
Ongoing and future research will explore how alterations in erosion due to human activities, coupled with the increasing warming of rocks attributed to anthropogenic climate changes, could amplify this natural carbon release. A key question researchers are now addressing is whether this natural CO2 emission will increase in the coming century. Hilton concludes, “Currently we don’t know—our methods allow us to provide a robust global estimate, but not yet assess how it could change.”
While the release of carbon dioxide from rock weathering is comparatively minor in comparison to contemporary human emissions, a better understanding of these natural processes will enhance our ability to predict and manage our carbon budget, as emphasized by Dr. Zondervan.
Table of Contents
Frequently Asked Questions (FAQs) about Carbon Cycle Discovery
Q: What is the main discovery of the University of Oxford study discussed in this text?
A: The University of Oxford study reveals that natural rock weathering can be a significant source of CO2 emissions, challenging the conventional belief that it primarily acts as a CO2 sink. This discovery implies that rock weathering releases CO2 into the atmosphere, on par with emissions from volcanoes.
Q: How does the geological carbon cycle impact Earth’s climate?
A: The geological carbon cycle, involving the release and absorption of carbon by rocks, plays a vital role in regulating Earth’s temperature. During chemical weathering, rocks absorb CO2 when specific minerals react with rainwater’s weak acid. This process counterbalances the continuous CO2 emissions from volcanoes, contributing to Earth’s habitability.
Q: What is the significance of the CO2 release from rock weathering not being included in climate models?
A: The omission of CO2 release from rock weathering in climate models means that our understanding of the carbon cycle and its impact on climate change is incomplete. Including this process is essential for more accurate climate change predictions and carbon budget calculations.
Q: How did researchers measure the CO2 release from weathering organic carbon in rocks?
A: Researchers used a tracer element, rhenium, which is released into water when rock organic carbon reacts with oxygen. By analyzing rhenium levels in river water, they quantified CO2 emissions. This method allowed them to estimate the total CO2 emitted as rocks weather and release ancient carbon into the air.
Q: Where were the hotspots of CO2 release from rock weathering identified?
A: The study identified hotspots of CO2 release in regions with high uplift rates, including the eastern Himalayas, the Rocky Mountains, and the Andes. These areas have sedimentary rocks exposed due to erosion, contributing significantly to CO2 emissions.
Q: How does this discovery relate to climate change and human activities?
A: Ongoing research is investigating whether human activities and increased warming of rocks due to anthropogenic climate changes could amplify the natural carbon release observed in this study. Understanding these factors is crucial for assessing their impact on future CO2 emissions.
Q: Is the CO2 release from rock weathering significant compared to human emissions from fossil fuels?
A: The CO2 release from rock weathering, estimated at 68 megatons of carbon per year, is about 100 times less than current human emissions from fossil fuel combustion. However, it is comparable to the CO2 emissions from volcanoes worldwide, indicating its importance in Earth’s natural carbon cycle.
