Date:

Yellowstone spawned twin super-eruptions that altered global climate

A new geological record of the Yellowstone supervolcano’s last catastrophic eruption is rewriting the story of what happened 630,000 years ago and how it affected Earth’s climate. This eruption formed the vast Yellowstone caldera observed today, the second largest on Earth.

Two layers of volcanic ash bearing the unique chemical fingerprint of Yellowstone’s most recent super-eruption have been found in seafloor sediments in the Santa Barbara Basin, off the coast of Southern California. These layers of ash, or tephra, are sandwiched among sediments that contain a remarkably detailed record of ocean and climate change. Together, both the ash and sediments reveal that the last eruption was not a single event, but two closely spaced eruptions that tapped the brakes on a natural global-warming trend that eventually led the planet out of a major ice age.

- Advertisement -

“We discovered here that there are two ash-forming super-eruptions 170 years apart and each cooled the ocean by about 3 degrees Celsius,” said U.C. Santa Barbara geologist Jim Kennett, who will be presenting a poster about the work on Wednesday, 25 Oct., at the annual meeting of the Geological Society of America in Seattle. Attaining the resolution to detect the separate eruptions and their climate effects is due to several special conditions found in the Santa Barbara Basin, Kennett said.

One condition is the steady supply of sediment to the basin from land — about one millimeter per year. Then there is the highly productive ocean in the area, fed by upwelling nutrients from the deep ocean. This produced abundant tiny shells of foraminifera that sank to the seafloor where they were buried and preserved in the sediment. These shells contain temperature-dependent oxygen isotopes that reveal the sea surface temperatures in which they lived.

But none of this would be much use, said Kennett, if it not for the fact that oxygen levels at the seafloor in the basin are so low as to preclude burrowing marine animals that mix the sediments and degrade details of the climate record. As a result, Kennett and his colleagues can resolve the climate with decadal resolution.

By comparing the volcanic ash record with the foraminifera climate record, it’s quite clear, he said, that both of these eruptions caused separate volcanic winters — which is when ash and volcanic sulfur dioxide emissions reduce that amount of sunlight reaching Earth’s surface and cause temporary cooling. These cooling events occurred at an especially sensitive time when the global climate was warming out of an ice age and easily disrupted by such events.

- Advertisement -

Kennett and colleagues discovered that the onset of the global cooling events was abrupt and coincided precisely with the timing of the supervolcanic eruptions, the first such observation of its kind.

But each time, the cooling lasted longer than it should have, according to simple climate models, he said. “We see planetary cooling of sufficient magnitude and duration that there had to be other feedbacks involved.” These feedbacks might include increased sunlight-reflecting sea ice and snow cover or a change in ocean circulation that would cool the planet for a longer time.

“It was a fickle, but fortunate time,” Kennett said of the timing of the eruptions. “If these eruptions had happened during another climate state we may not have detected the climatic consequences because the cooling episodes would not have lasted so long.”

GEOLOGICAL SOCIETY OF AMERICA

- Advertisement -

Stay Updated: Follow us on iOS, Android, Google News, Facebook, Instagram, Twitter, Threads, TikTok, LinkedIn, and our newsletter

spot_img
Mark Milligan
Mark Milligan
Mark Milligan is a multi-award-winning journalist and the Managing Editor at HeritageDaily. His background is in archaeology and computer science, having written over 8,000 articles across several online publications. Mark is a member of the Association of British Science Writers (ABSW), the World Federation of Science Journalists, and in 2023 was the recipient of the British Citizen Award for Education, the BCA Medal of Honour, and the UK Prime Minister's Points of Light Award.
spot_img
spot_img

Mobile Application

spot_img

Related Articles

Significant multi-period discoveries in Delbrück-Bentfeld

An archaeological excavation in Delbrück-Bentfeld, a town in the east of North Rhine-Westphalia, Germany, has unearthed nearly 400 features of archaeological interest that span several centuries.

Excavation confirms the origin of Sheffield Castle

Archaeologists excavating the former site of Sheffield Castle site have confirmed that an artificial mound within the castle interior is a motte dating back to the earliest phase of the castle’s construction.

WWII bunker unexpectedly discovered during forest clearance works

A WWII bunker has been discovered during forest clearance works for the S17 Piaski–Hrebenne expressway in eastern Poland.

Salvage project reveals 500 years of Veracruz history

An archaeological salvage project in Veracruz, Mexico, has uncovered more than five centuries of the city’s urban development and everyday life.

Aerial photographs indicate an enormous Avar-Era cemetery

An analysis of aerial photographs has led to the discovery of a previously unknown Avar-era cemetery on the outskirts of Tatabánya, Hungary.

Excavations reveal a vast Roman villa complex

Archaeologists from Inrap have revealed a vast Roman villa complex during excavations in Auxerre, France.

Unprecedented Roman discovery in Ireland

Archaeologists have made an unprecedented Roman discovery during excavations at Drumanagh in north Dublin.

Exquisite marble sarcophagus unearthed near Caesarea

Archaeologists from the Israel Antiquities Authority (IAA), working on behalf of the Caesarea Development Corporation, have unearthed an exquisitely sculptured marble sarcophagus near the coastal city of Caesarea, Israel.