Andes Volcanoes, Whales, and Algae: How Ancient Eruptions Shaped Earth’s Climate

When researchers at the University of Arizona connected volcanic ash from the Andes to ancient whale fossils in Chile’s Atacama Desert, it wasn’t just a paleontological curiosity—it revealed a planetary feedback loop where earth, ocean, and life intertwined across millions of years. That same mechanism, where nutrient-rich eruptions fueled algae blooms that cooled the planet by drawing down carbon dioxide, feels unexpectedly relevant today as coastal communities from Maine to Miami grapple with shifting ocean chemistry and harmful algal blooms. Here in the Chesapeake Bay watershed, where the Susquehanna River meets the Atlantic near Annapolis, Maryland, scientists are watching eerily similar nutrient dynamics play out—not from volcanoes, but from agricultural runoff and wastewater—and wondering what lessons deep time holds for our modern estuaries.

The study published this month in Nature Geoscience builds on years of fieldwork at Cerro Ballena, the “Whale Hill” fossil site uncovered during Panama Highway expansion in 2010. There, researchers found more than 40 marine mammal fossils dating to the late Miocene epoch, approximately 6 to 9 million years ago. What struck paleontologists wasn’t just the concentration of whales, porpoises, and dolphins, but how rapidly they appeared to have died—suggesting a sudden, localized catastrophe rather than gradual decline. Geochemical analysis pointed to volcanic aerosols from the Altiplano-Puna Volcanic Complex, Earth’s largest active silicic magma system, which had been erupting intensely as the Andes mountains rose. Those eruptions lofted ash rich in iron, phosphorus, and silicon into the atmosphere, where winds carried it thousands of miles to the Southern Ocean.

Once deposited, those nutrients acted like a hyper-concentrated fertilizer for phytoplankton, particularly silica-loving diatoms. The resulting algal blooms were so massive they pulled significant amounts of carbon dioxide out of the atmosphere through photosynthesis, sequestering it when the organisms died and sank to the seafloor. This biological pump, amplified by volcanic fertilization, likely contributed to a global cooling trend between 5.4 and 7 million years ago—a period when sea surface temperatures dropped and ice sheets began expanding. Yet the same blooms that cooled the planet also produced deadly consequences in localized hotspots: certain algae species generated neurotoxins that accumulated in the food chain, ultimately lethal to marine mammals feeding in affected zones. It’s a stark reminder that even planetary-scale cooling mechanisms can have tragic, immediate costs for ocean life.

Fast forward to today, and while we don’t have Andean volcanoes fertilizing the Chesapeake, we are inadvertently creating analogous nutrient overloads. The Susquehanna River, which provides about half the Bay’s freshwater inflow, carries nitrogen and phosphorus from farms in Pennsylvania and New York, as well as effluent from wastewater treatment plants. Every spring, this nutrient surge fuels algal growth that can deplete oxygen when the blooms die and decompose, creating dead zones where fish and shellfish struggle to survive. In recent years, toxic strains like Microcystis and Karlodinium have appeared in Bay tributaries, prompting swimming advisories and fish kills—echoes, in miniature, of the ancient Miocene mortality events. Researchers at the University of Maryland Center for Environmental Science (UMCES) Horn Point Lab have been tracking these patterns for decades, using sediment cores to reconstruct how nutrient loading has changed since colonial deforestation intensified erosion.

What makes the Andes-Chile connection so powerful as an analog is its demonstration of Earth’s self-regulating feedback loops—how geological forces can inadvertently trigger biological responses that alter climate. It also highlights the dual nature of nutrient enrichment: essential for life at moderate levels, but catastrophic in excess. For coastal managers in the Mid-Atlantic, this deep-time perspective reinforces why reducing nutrient inputs isn’t just about clearer water or better fishing—it’s about preventing the kind of systemic imbalance that, millions of years ago, could turn a thriving marine ecosystem into a lethal trap. Institutions like the Chesapeake Bay Program, a federal-state partnership led by the Environmental Protection Agency (EPA), and the Smithsonian Environmental Research Center (SERC) in Edgewater, are using paleoceanographic insights to refine models that predict how warming waters might exacerbate today’s blooms.

Given my background in environmental systems journalism, if this trend impacts you in the Annapolis area, here are the three types of local professionals you need to understand the evolving relationship between land use, water quality, and public health:

• Watershed Scientists and Restoration Ecologists: Look for professionals affiliated with UMCES, the Severn River Association, or the Chesapeake Bay Foundation who specialize in nutrient trading programs, living shoreline projects, or submerged aquatic vegetation (SAV) monitoring. They should demonstrate expertise in interpreting Maryland’s Phase III Watershed Implementation Plan (WIP) and have experience designing bioswales or regenerative stormwater conveyance systems tailored to the Coastal Plain’s sandy soils.
• Environmental Health Specialists Focused on Harmful Algal Blooms (HABs): Seek experts certified by the National Environmental Health Association (NEHA) who collaborate with the Maryland Department of the Environment (MDE) on recreational water monitoring. Key criteria include experience with ELISA testing for microcystin toxins, familiarity with NOAA’s HAB forecasting system for the Bay, and a track record of advising local governments on beach closure protocols during bloom events.
• Sustainable Agriculture Consultants for the Delmarva Peninsula: Prioritize advisors who work with University of Maryland Extension’s Nutrient Management Program and understand the specifics of Maryland’s Phosphorus Management Tool (PMT). Ideal candidates will have practical knowledge of cover cropping strategies for corn-soybean rotations, phosphorus saturation index (PSI) testing for Eastern Shore soils, and experience helping farmers access cost-share programs through the Maryland Agricultural Water Quality Cost-Share (MACS) program.

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