New study reveals how ancient volcanoes shaped our world

Scientists analyzed mercury levels from core samples from the Mochras Farm (Llanbedr) borehole in Wales to estimate how much and how rapidly carbon was released during ancient volcano events in Earth's history. Credit: Stephen Hesselbo.

Scientists have made a groundbreaking discovery that sheds new light on how ancient volcanoes have had a huge impact on Earth’s climate and possibly led to mass extinctions.

A team of international researchers, including experts from Penn State and the University of Oxford, have developed a new way to measure the carbon emissions from massive volcanic eruptions that happened millions of years ago.

Their findings, published in the journal Nature Geosciences, could change how we understand the relationship between volcanic activity and climate change.

Long ago, the Earth experienced volcanic events known as large igneous provinces (LIPs). These weren’t your ordinary eruptions – they lasted for millions of years and created vast flows of lava that could stretch for hundreds of miles.

Scientists believe these events are similar to human-caused climate change because they released enormous amounts of carbon dioxide into the atmosphere very quickly, in geological terms.

Isabel Fendley, an assistant research professor at Penn State and the lead author of the study, explains that understanding exactly how much carbon these ancient eruptions released has been a major challenge.

But their new research has started to solve this puzzle by looking at levels of mercury in rock samples from around 185 million years ago. Mercury is a key indicator because it’s released into the atmosphere during volcanic eruptions.

The team analyzed cores from the Mochras borehole in Wales, UK, which provided a detailed record of the early Jurassic period.

They noticed an increase in mercury levels linked to the activity of the Karoo-Ferrar LIP, a significant volcanic event, and the Toarcian Oceanic Anoxic Event, a time of major environmental changes.

Surprisingly, the amount of carbon emissions estimated from the mercury levels was lower than what scientists previously thought necessary to cause such drastic environmental shifts.

This led the researchers to conclude that the volcanoes might have triggered additional climate feedback loops – processes that could lead to more warming in response to the initial increase in temperatures.

This means the actual impact of the volcanic carbon emissions might be amplified by these feedbacks, something current models might underestimate.

The importance of this discovery goes beyond just understanding ancient climate changes. It’s also crucial for predicting future climate scenarios and the potential impact of releasing large amounts of carbon dioxide into the atmosphere.

Estimating carbon emissions from ancient LIPs has always been difficult. For example, the lava from the Karoo-Ferrar LIP, which occurred on the ancient supercontinent Gondwana, is now scattered across Southern Africa, Antarctica, and Tasmania.

By focusing on mercury – a substance that was rarely found in high concentrations before human industrial activity – the scientists could identify the extra mercury from volcanic eruptions.

Using the ratio of mercury to carbon emissions from modern volcanoes, they estimated the carbon released by these ancient giants. The core samples from Wales were key to this research, offering a rare glimpse into volcanic activity over millions of years.

This study, supported by the European Research Council and the Natural Environment Research Council, involved a team of scientists including Joost Frieling, Tamsin Mather, Hugh Jenkyns, Michael Ruhl, and Stephen Hesselbo.

Their work opens up new paths for understanding how volcanic eruptions can affect the Earth’s climate, helping us to prepare for the future by looking into the past.