How volcanic hotspots are all connected to Earth's interior mantle

Many of us, when thinking about volcanic eruptions or lava streams, envision Earth’s mantle as a mysterious source feeding these fiery displays.

Often, we associate volcanic hotspots with distinct characteristics and varied compositions, influenced by their unique locations.

However, recent findings published in Nature Geoscience suggest that this belief may not align with the actual processes occurring deep within the Earth.

In a dynamic shift from conventional thinking, the research reveals that hotspot lavas, despite their surface differences, may all originate from a relatively uniform reservoir in the mantle.

The implications of this discovery? The mantle may be far more chemically homogeneous than scientists ever contemplated, reshaping our understanding of its role in volcanic activity.

Homogeneous volcanic origins: Global mantle reservoir

Lavas from these hotspots — whether erupting in Hawaii, Samoa, or Iceland — may all originate from a relatively uniform reservoir in Earth’s mantle. 

This is according to a study led by Dr. Matthijs Smit, associate professor and Canada Research Chair at the University of British Columbia, which challenges the traditional view that the mantle contains distinct, isolated reservoirs.

“The discovery literally turns our view of hotspot lavas and the mantle upside down,” Dr. Smit explained.

“In a way, Earth’s lavas are much like humankind itself — a beautifully diverse population with a common ancestor, which developed differently wherever it went.”

Lava’s unique chemical ‘flavours’

So, how do we reconcile the stark differences between these lavas? According to the research, lavas acquire their unique chemical ‘flavors’ as they journey from the mantle to the surface, interacting with various rocks along the way.

“By looking at a specific set of elements, we were able to discern the chemical effects of various processes that act on magma melts on their way to the surface to discover that all hotspot lavas actually share the same starting composition,” said Dr. Smit.

“The lavas only come out differently because the magmas interact with different types of rocks as they ascend.”

Study mantle and volcanic hotspots

Studying Earth’s mantle is no easy task, as it cannot be sampled directly. 

Scientists, including Dr. Smit and co-author Dr. Kooijman from the Swedish Museum of Natural History, have to rely on trace-element and isotope analysis of erupted lavas. 

These methods have led to the previous belief that the mantle contains distinct reservoirs of different ages, formed by unique processes. However, this new research turns that assumption on its head.

“The discovery is a game-changer when it comes to models for Earth’s chemical evolution and how we look at global element cycles,” Dr. Smit added. 

“Not only is the mantle much more homogeneous than previously thought, it likely also no longer contains ‘primordial reservoirs’ — entities that were once needed to explain the data, but could never really be reconciled with the concept of mantle convection.”

Implications for geological models

The revelation of a chemically uniform mantle reservoir necessitates a re-evaluation of existing geological and geochemical models.

Conventional theories posited that variations in erupted lava compositions were indicative of a heterogeneous mantle, with distinct refractory processes involved.

However, with the understanding that surface diversity arises during magma transit rather than at its origin, models of mantle convection and differentiation must be reimagined.

This has broader implications for our comprehension of tectonic plate dynamics, the formation of the Earth’s crust, and the driving forces behind seismic activity.

By refining these models, scientists can enhance predictive capabilities regarding volcanic eruptions and improve the safety and preparedness for populations living in volcanic regions of mantle.

Environment and science policy

The discovery of a homogeneous mantle reservoir also extends beyond the academic world, influencing policy and decision-making in environmental science.

This research underscores the importance of international collaboration in advancing our comprehension of volcanic processes and the Earth’s internal chemistry.

By promoting collaborative research initiatives and sharing data, scientists can collectively deepen our understanding, influencing not only academic discourse but also informing policies related to disaster preparedness and mitigation.

As we attempt to address climate-related challenges, a refined understanding of the Earth’s mantle provides a crucial foundation for developing informed strategies that can mitigate the impact of natural events on societies worldwide.

Implications for plate tectonics

The newfound understanding of a chemically homogenous mantle not only reshapes how scientists view volcanic activity but also opens new avenues in the study of plate tectonics and mantle convection. 

Traditionally, geologists believed that distinct reservoirs within the mantle were responsible for driving the movement of tectonic plates, influencing volcanic and seismic activity in different regions.

However, the discovery of a uniform mantle suggests that the processes driving these tectonic shifts may be more interconnected and global than previously thought. 

This insight could prompt further investigation into how mantle material circulates and how chemical interactions between the mantle and crust contribute to volcanic diversity.

This new perspective may lead to refined models of mantle convection and magma transport, potentially influencing how scientists predict volcanic activity in geologically active areas, such as the Pacific Ring of Fire. 

Additionally, it could offer a more comprehensive understanding of how Earth’s internal heat and material movements shape surface processes like earthquakes and mountain formation over millions of years.

The full study was published in the journal Nature Geoscience.

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