How Andean Volcanism Triggered Global Cooling in the Late Miocene
New research is reshaping our understanding of Earth’s paleoclimate, revealing a surprising link between volcanic activity in South America and a planetary cooling trend millions of years ago. A study led by Mark Clementz, a professor at the University of Wyoming Department of Geology and Geophysics, suggests that massive eruptions in the Andes during the Late Miocene Epoch played a pivotal role in lowering global temperatures.
- Timeframe: The cooling occurred approximately 5.4 to 7 million years ago.
- Mechanism: Volcanic ash acted as a fertilizer for the Southern Ocean.
- Outcome: Increased carbon sequestration in the deep ocean contributed to global cooling.
- Publication: Findings were published in Communications Earth & Environment.
The “Fertilization” Effect: From Ash to Ocean
While we often associate volcanoes with short-term cooling via ash clouds blocking sunlight, this study highlights a more enduring biogeochemical process. The Andes, the world’s longest active volcanic arc, delivered nutrient-rich ash to the surrounding oceans through atmospheric transport.
During the Late Miocene, episodic and massive explosive eruptions generated significant ash fluxes. This ash supplied critical limiting nutrients—specifically iron, phosphorus, and silicon—to the Humboldt Current and the Southern Ocean. These nutrients are essential for biological productivity in marine environments.
Stimulating Primary Productivity
The influx of these nutrients acted as a catalyst for marine life. By fertilizing the Southern Ocean, the volcanic ash stimulated primary productivity, which increased the amount of carbon being captured by marine organisms. This process enhanced carbon export, effectively pumping atmospheric carbon dioxide into the deep ocean for long-term sequestration.
Impact on the Global Climate
The correlation between heightened volcanic activity and a cooling trend is evident in the geological and paleoecological records. By combining geochemical analyses with global ash dispersion modeling and Earth system simulations, researchers determined that this sustained nutrient supply contributed to a cooling of the Earth between 5.4 and 7 million years ago.
This discovery underscores the complex interaction between tectonics and climate. It shows that geological processes on a regional scale—such as the activity of the Andean volcanic arc—can have profound implications for the global carbon cycle and planetary temperature.
Frequently Asked Questions
Did the volcanoes cool the Earth directly?
While volcanic aerosols can cause immediate cooling, the primary driver identified in this study is indirect. The ash fertilized the ocean, which increased the absorption of CO2 from the atmosphere, leading to long-term cooling.
Which oceans were most affected?
The Southern Ocean and the Humboldt Current were the primary beneficiaries of the nutrient-rich ash, making them critical zones for carbon drawdown during this period.
When did this occur?
The study focuses on the Late Miocene Epoch, specifically the window between 5.4 and 7 million years ago.
Looking Ahead
The findings presented in phys.org and other scientific outlets highlight the underappreciated role of volcanic nutrient delivery in reshaping marine ecosystems. As scientists continue to analyze the interactions between the geosphere and the atmosphere, this research provides a vital blueprint for understanding how natural carbon sequestration mechanisms have operated throughout Earth’s history.