Drilling Uncovers Ancient Eruptions That May Have Caused Global Warming

November 05, 1997

By David Williamson
UNC-CH News Services

(Embargoed) CHAPEL HILL -- Drilling into the sea floor south of Haiti has uncovered conclusive ashy evidence that multiple massive volcanic eruptions occurred roughly 55 million years ago in the Caribbean Basin.

Those cataclysmic events appear to have caused abrupt inversion of ocean waters, triggering one of the most dramatic climatic changes ever, according to a geologist on the team that discovered the eruptions.

The inversion caused release of massive amounts of sea floor methane into the atmosphere, leading to global warming and possibly speeding evolution of countless new plant and animal species, including many primates and carnivores, the scientist believes. At the same time, close to half of all deep-sea animals went extinct, asphyxiated in the suddenly warmer and stagnant deep waters.

"We found multiple very distinct blue, green and occasionally red volcanic ash layers that were very different from whitish-gray sediments above and below them in the core samples," said Dr. Timothy Bralower, associate professor of geology at the University of North Carolina at Chapel Hill. "The time those ash layers -- direct evidence of volcanic eruption -- were deposited corresponds to the beginning of a known period of rapid warming of the Earth. This is the first evidence for a major volcanic episode at that time in the Caribbean."

A report on the discovery appears in the November issue of the journal Geology.

Core sampling to about 3,000 feet took place aboard the 470-foot JOIDES Resolution, the world's largest scientific drill ship, in late 1995 and early 1996.

"Many geologists are interested in this interval 55 million years ago because we don't know of any other geologic period when warming occurred so precipitously, and warmth covered the globe like this," Bralower said. "The million-dollar question is what triggered the sudden burp of methane. A dramatic climatic change had to have occurred first."

The new work shows a huge Caribbean volcanic eruption occurred just as the warming began, Bralower said.

"That's a microsecond of geologic time, and the chances that the events are just coincidence is minute," he said.

The geologists speculate that like most explosive volcanism, the Caribbean eruptions first led to minor cooling of the atmosphere and that the cooling was most severe near volcanoes in the tropics. They believe that temperature drop caused the tropical ocean waters to become denser and to sink, replacing the usual cold polar waters in the deep ocean and fomenting an oceanographic change of titanic proportion.

"Sudden warming of the deep ocean would cause methane trapped in sediments under the sea floor to become unstable and rapidly rise into the ocean and atmosphere," Bralower said. "That would fuel further warming and instigate the dramatic environmental and evolutionary changes."

Scientists already know that comparable volcanic activity occurred in the North Atlantic Ocean beginning some 61 million years ago, the geologist said. The new discovery suggests the Caribbean volcanism may have been even more important for the Earth and somehow acted in tandem with the earlier known eruptions farther north.

Understanding major warming events in the past is one of the best ways of determining the possible effects of global warming, he said. "The giant Caribbean eruption provides a worst-case scenario of what could happen to Earth in the future."

Co-authors of Bralower's paper are UNC-CH geology graduate student Debbie Thomas and faculty members at the universities of California at Santa Cruz, Rhode Island and Minnesota, Bremen University in Germany and Wesleyan University in Connecticut. The National Science Foundation and the Texas A&M University-based Ocean Drilling Program supported the research.


- 30 -


Note: Bralower can be reached at (919) 962-0704 (w) or 933-6090 (h). Contact: David Williamson

University of North Carolina at Chapel Hill

Related Global Warming Articles from Brightsurf:

The ocean has become more stratified with global warming
A new study found that the global ocean has become more layered and resistant to vertical mixing as warming from the surface creates increasing stratification.

Containing methane and its contribution to global warming
Methane is a gas that deserves more attention in the climate debate as it contributes to almost half of human-made global warming in the short-term.

Global warming and extinction risk
How can fossils predict the consequences of climate change? A German research team from Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), the Museum of Natural History Berlin and the Alfred Wegener Institute compared data from fossil and marine organisms living today to predict which groups of animals are most at risk from climate change.

Intensified global monsoon extreme rainfall signals global warming -- A study
A new study reveals significant associations between global warming and the observed intensification of extreme rainfall over the global monsoon region and its several subregions, including the southern part of South Africa, India, North America and the eastern part of the South America.

Global warming's impact on undernourishment
Global warming may increase undernutrition through the effects of heat exposure on people, according to a new study published this week in PLOS Medicine by Yuming Guo of Monash University, Australia, and colleagues.

Global warming will accelerate water cycle over global land monsoon regions
A new study provides a broader understanding on the redistribution of freshwater resources across the globe induced by future changes in the monsoon system.

Comparison of global climatologies confirms warming of the global ocean
A report describes the main features of the recently published World Ocean Experiment-Argo Global Hydrographic Climatology.

Six feet under, a new approach to global warming
A Washington State University researcher has found that one-fourth of the carbon held by soil is bound to minerals as far as six feet below the surface.

Can we limit global warming to 1.5 °C?
Efforts to combat climate change tend to focus on supply-side changes, such as shifting to renewable or cleaner energy.

Global warming: Worrying lessons from the past
56 million years ago, the Earth experienced an exceptional episode of global warming.

Read More: Global Warming News and Global Warming Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.