The BGS have revealed the "Secrets of an ancient supervolcano uncovered that change our understanding of England's geological past"

The origin of the Kinnekulle tephra, a huge volcanic ash layer spread across Norway, Sweden, the Baltic region, Belarus and Poland, has long been a mystery but new evidence may have uncovered the source of the ash for the first time.

Scientists at the British Geological Survey (BGS) and the University of Oslo have studied tiny crystals, smaller than the diameter of a human hair, extracted from boreholes 65 km apart in Lincolnshire and Norfolk. The analysis uncovered evidence of a 454 million year old supervolcano, now concealed beneath The Wash on the east coast of England.

Volcanic rocks of comparable age comprise the rugged topography of Eryri (Snowdonia) and the Lake District. A belt of arc volcanism extended from the Lake District towards Belgium in late Ordovician times, when England was separated from Scandinavia by an oceanic basin. The geography was probably comparable to the West Pacific region (Korea–Japan–Indonesia) today.

From the referenced paper:

The Wash Igneous Complex of eastern England: A candidate Avalonian source for Sandbian tephra in Baltoscandia and implications for closure of the Tornquist Sea

Tim C. Pharaoh; Jeremy Rushton; Dan Condon; Simon Chenery; Matt Horstwood; Diana Sahy; Chris Thomas; Elliott Hamilton; Charles J.B. Gowing; Jonathan Busby; Richard Haslam; Trond H. Torsvik

Author and Article Information

GSA Bulletin (2026)

https://doi.org/10.1130/B38831.1

The Wash Igneous Complex (WIC) is a component of a Sandbian (Late Ordovician) calc-alkaline magmatic arc that extends from the Lake District in northern England to the Brabant Massif of Belgium, associated with fast subduction of Tornquist ocean crust separating Avalonia (upper plate) and Baltica (lower plate). Buried beneath the East Midlands and The Wash of eastern England, the WIC is likely to comprise an extensive nested caldera system, underlain by a granite batholith, inferred from geophysical data. New whole-rock geochemical data confirm the calc-alkaline character of the WIC and elucidate relationships with other calc-alkaline magmatic complexes in eastern England. Detailed petrographic and geophysical data indicate that the WIC had the capacity to generate super-eruptions. Evidence for ultraplinian volcanism comes from contemporary, regionally distributed and thick metabentonite tephra in Baltoscandia. New, high-precision U-Pb isotopic (chemical abrasion−isotope dilution−thermal ionization mass spectrometry; CA-ID-TIMS) ages of 454.45 ± 0.13/0.23/0.54 Ma and 454.40 ± 0.11/0.22/0.53 Ma (2σ, Sandbian, Late Ordovician) are reported for zircons from a heterolithic dacitic tuff-breccia and a subvolcanic microgranite respectively, recovered from two deep boreholes that intersect the WIC. These dates are identical, within their analytical uncertainties, with equivalently high-precision U-Pb zircon dates for the Kinnekulle Metabentonite (KKMB; Baltoscandia). A population of younger grains from the breccia yielding a CA-ID-TIMS age of 453.70 ± 0.17/0.26/0.55 Ma (2σ) may correlate with the Lower Grimstorp Metabentonite. The matching U-Pb dates and closely comparable apatite microphenocryst chemistry from WIC rocks and the Baltoscandian tephra suggest the WIC as a primary candidate for much of the composite KKMB.

Thank you for drawing our attention to this.

+1

The rather later SW granite batholith has left no evidence of vulcanism.

The vulcanism in eastern Scotland (Perth) is just a little bit younger than this and Edinburgh slightly younger still.

Edited August 29Aug 29 by studiot

I always thought the British isles were pretty stable geologically.
I once read that Northwestern Scotland has exposed rock formations dating back 2.5 Billion years.
( Archaean rock formations )

Then again, I come from a region in Southern Europe with active volcanoes and earthquake zones due to the African plate pushing up into the Eurasian plate.

25 minutes ago, MigL said:

I always thought the British isles were pretty stable geologically.
I once read that Northwestern Scotland has exposed rock formations dating back 2.5 Billion years.
( Archaean rock formations )

Then again, I come from a region in Southern Europe with active volcanoes and earthquake zones due to the African plate pushing up into the Eurasian plate.

What do you mean ?

NW Scotland was once part of North America and SE England is still under construction.

😀

16 hours ago, sethoflagos said:

Detailed petrographic and geophysical data indicate that the WIC had the capacity to generate super-eruptions. Evidence for ultraplinian volcanism comes from contemporary, regionally distributed and thick metabentonite tephra in Baltoscandia

The supervolcano under Yellowstone we live 360-400 miles east of (prevailing westerlies would bring us ejecta) reportedly still has the capacity for super-eruptions. Ashfall fossil beds are found at our present distance or greater, produced by ultraplinian events from Yellowstone. In NE Nebraska, 400 miles farther east, ashfall was a foot deep on average but more concentrated in depressions, up to ten feet. As we are closer, and between a couple of ridges in a scoop-like neighborhood, I would see us as lucky if our chimney opening (about 26 feet above grade) remained above the ashfall and allowed us some air exchange. I suspect ash would undermine the power grid quickly, so if eruption seemed imminent I'd want to keep battery powered sabre saws charged, in case we needed to cut our way out of the attic to leave, and help neighbors also escape.

N95 masks, snowshoes, and emergency backpacks fully stocked.

Or the house collapses and we join a future fossil-rich tephra layer with anomalous inclusions of aluminum and lithium. 🌋

Not for another million years, I hope.

1 hour ago, MigL said:

I always thought the British isles were pretty stable geologically.

The OP refers to the British Isles being at the epicentre of the multiple continental collisions that led to the creation of Pangaea, when almost all of earth's landmass was welded into a single supercontinent - the biggest pile up in the last billion years (see Avalonia, Caledonian Orogeny, Pangaea).

That lasted until the magmatic plume currently marked by Iceland broke through the Pangaean crust in a part of East Greenland that was to become the Scottish Western Isles creating the huge basaltic outpourings of the North Atlantic Igneous Province leading to the opening of the North Atlantic and most likely the sudden 5^o - 8^o C global temperature excursion of the Palaeocene-Eocene Thermal Maximum.

If that's what you call "geologically stable" God alone knows what you make of your Laurentian Shield over that same period.

39 minutes ago, TheVat said:

Not for another million years, I hope.

I hope so too, dear friend.

By-the-by, a bit of light side research threw up the fascinating Astronomically forced cyclicity in the Upper Ordovician and U–Pb ages of interlayered tephra, Oslo Region, Norway

Highlights

• •

  We present radiometric datings of two bentonites in the Upper Ordovician of Norway.

• •

  We show a magnetic susceptibility curve for the section containing the bentonites.

• •

  The susceptibility data are studied with spectral and wavelet analysis.

• •

  The data can be interpreted as showing Milankovitch cyclicity.

Abstract

The Late Ordovician world experienced a series of huge volcanic eruptions, recorded as the big Deicke, Millbrig and Kinnekulle bentonites, together with numerous thinner beds. The Kinnekulle event can be traced across northwestern Europe. U–Pb zircon ages are here presented of both the Kinnekulle K-bentonite and the uppermost recorded tephra layer in the Upper Ordovician of the Oslo Region, Norway. The tephras are located in the upper part of the Arnestad Formation (Sandbian) south of Oslo and gave ages of 454.52 ± 0.50 Ma (the Kinnekulle K-bentonite) and 453.91 ± 0.37 Ma (the upper Grimstorp K-bentonite). The dated tephras are separated by a 7 m thick shale succession with subordinate nodular limestone beds. Although the two U–Pb ages overlap within errors, statistical considerations indicate a most likely time interval of about 600 kyr between the tephras. High-resolution magnetic susceptibility logging in the same section shows cycles that likely represent changes in sediment supply in response to astronomical forcing. Spectral analysis shows the presence of long (400 kyr) and short (100 kyr) eccentricity bands, and obliquity components in the 30 kyr band. Precessional cycles are not detected. Based on this method, it is possible to estimate a time interval of 766 kyr between the two tephra events, and the radiometric dating therefore does not exclude a Milankovitch interpretation of the cycles. This opens new possibilities for understanding the evolution of one of the world's best preserved Ordovician marine systems.

Introduction

Several studies suggest that Milankovitch-band cyclicity is recorded in sedimentary successions from the Ordovician. For instance, meter-scale shallowing-upward cycles (parasequences) have been observed in North America (Smith et al., 1993) and Asia (Meng and Ge, 1996, Kim and Lee, 1998). These cycles can be interpreted as induced by short eccentricity cycles in the 100 ka band (e.g. Kim and Lee, 1998). On the other hand, Holland et al. (1997) reported on irregular meter-scale cycles in the Upper Ordovician of Kentucky that cannot easily be interpreted in terms of astronomical forcing. Even regular cycles can alternatively be explained by dynamics internal to the sedimentary system (autocycles), although this is less likely for subtidal cycles on a stable platform (e.g. Goldhammer et al., 1993). Astronomical forcing is more convincingly demonstrated if spectral analysis shows several periodicities (eccentricity, obliquity, precession) in the expected frequency ratios. Examples include the Upper Ordovician in Australia (Williams, 1991) and the Middle Ordovician in Siberia (Rodionov et al., 2003). Astronomical forcing of the marine sedimentary system can lead to notable changes in both influx and deposition of material triggered by sea level and climatic changes. In addition to the lithological changes mentioned above, a number of proxies are used to identify Milankovitch cyclicity, for instance Ba and Fe concentration and bulk rock magnetic susceptibility. In recent years, the study of Milankovitch cycles has moved way beyond the Quaternary, with important implications for chronostratigraphy and dating of short-lived climatic perturbations like the Toarcian carbon isotope excursion and the PETM (e.g., Suan et al., 2008, Westerhold et al., 2008). Combined with absolute dating of tephra layers, sedimentary sequences and boundaries can now be dated with a great accuracy provided there was stable and continuous sedimentation in the studied sections.

Magnetic susceptibility is a fast, low-cost log parameter frequently used in petroleum exploration. The main element contributing to susceptibility in most sediments is iron, which may be found in e.g. clay minerals (chlorite), in siderite and in iron sulphides in shale. Magnetic susceptibility is used frequently for cyclostratigraphic studies (e.g. Rodionov et al., 2003), reflecting periodic changes in sediment supply presumably driven by climate-induced variation in weathering, erosion and sea level.

This study combines tephra dating and magnetic susceptibility logging in the Sandbian of the Ordovician succession in the Oslo Region. Several tephra layers, including the major Kinnekulle K-bentonite, are present within the Arnestad Formation in Asker (Vollen/Arnestad), south of Oslo (Hagemann and Spjeldnæs, 1955, Bergström et al., 1995). The tephra layers preserved in the Oslo Region have, however, never been dated using radiometric methods. Moreover, the published ages on the Kinnekulle K-bentonite in Sweden and Estonia were hampered by large error bars (e.g. Huff, 2008). New high precision data on the Ordovician tephras have now been published by Sell et al. (2013), including the Kinnekulle K-bentonite from a locality on Bornholm in Denmark.

This study provides the first zircon ages of the Kinnekulle K-bentonite and the upper Grimstorp tephra in the Oslo Region and combines the ages with cyclostratigraphic measurements. The Arnestad Formation is a bioturbated, dark gray mudstone with thin carbonate beds and nodular horizons (Hansen and Harper, 2008) that are ideal to test the presence of Milankovitch cycles. Following Hansen and Harper (2008), the formation is informally divided into a lower and an upper part, separated by the base of the Kinnekulle K-bentonite. According to Nielsen (2004), this horizon marks the base of the Keila East Baltic Stage.

Apologies. Geology is not an area I'm comfortable, or proficient, in.

I had previously read that NW Scotland is home to some of the oldest rock formations in Europe, and assumed that meant a long period of geologic inactivity.
I don't recall where I originally read it, but Wiki seems to agree.

"The geologic history of Europe spans billions of years and reflects a complex interplay of tectonic processes. Archean rocks, over 2.5 billion years old, represent the oldest formations of the Precambrian era and are exposed in the northern Baltic Shield, Ukraine, and northwestern Scotland."

From Geology of Europe - Wikipedia

I guess 'old rocks' don't necessarily mean geologic inactivity.

26 minutes ago, MigL said:

I had previously read that NW Scotland is home to some of the oldest rock formations in Europe, and assumed that meant a long period of geologic inactivity.
I don't recall where I originally read it, but Wiki seems to agree.

You're referring to the Lewisian Complex of the Outer Hebrides (and parts of the adjacent mainland). They are typically 2.7-3.0 bya and derived from East Greenland so have much more in common with your Archaean shield geology than typical European units which are more Gondwanan in origin. Or rather, if you nip up from St Catherine's to Catherine Township in Northern Ontario, you'll be standing on a landscape of similar age and history. You got the gold though.

39 minutes ago, MigL said:

I guess 'old rocks' don't necessarily mean geologic inactivity.

They're the ancient roots of mountain chains significantly larger and higher than the Himalayas.

Btw I took my son to the top of Vesuvius when he was about 10. Inspired him to read Geography at University. I think it was the calzone restaurant half-way up that tilted the balance.

19 hours ago, MigL said:

Apologies. Geology is not an area I'm comfortable, or proficient, in.

I had previously read that NW Scotland is home to some of the oldest rock formations in Europe, and assumed that meant a long period of geologic inactivity.
I don't recall where I originally read it, but Wiki seems to agree.

"The geologic history of Europe spans billions of years and reflects a complex interplay of tectonic processes. Archean rocks, over 2.5 billion years old, represent the oldest formations of the Precambrian era and are exposed in the northern Baltic Shield, Ukraine, and northwestern Scotland."

From Geology of Europe - Wikipedia

I guess 'old rocks' don't necessarily mean geologic inactivity.

It is very common to show the skeleton outline of modern day continents and countries superimposed on maps of ancient continents.

It is important to realise that many parts of a modern country may not have existed, simply been under water at the bottom of a sea. at the time of the ancient map.

Watch this Gif animation of Britain and you will see what I mean.

Sorry it is not very large.

Green is land, brown are mountains/upland, blue is sea the outline is white and the white blob is icecap.

EDIT

Sorry various browns are used for different things, uplift, vulcanism, land generation from sediment deposition.

Edited August 30Aug 30 by studiot
Add useful information

On 8/29/2026 at 3:15 PM, MigL said:

I always thought the British isles were pretty stable geologically.
I once read that Northwestern Scotland has exposed rock formations dating back 2.5 Billion years.
( Archaean rock formations )

Then again, I come from a region in Southern Europe with active volcanoes and earthquake zones due to the African plate pushing up into the Eurasian plate.

The geology of the British Isles is like a Rubik’s Cube. It takes many twists and moves to unscramble it over geological time. The Tornquist Sea closed about half a billion years ago and there was plenty going on before that. Scotland is particularly nightmarishly complex.

21 hours ago, sethoflagos said:

Astronomical forcing of the marine sedimentary system can lead to notable changes in both influx and deposition of material triggered by sea level and climatic changes. In addition to the lithological changes mentioned above, a number of proxies are used to identify Milankovitch cyclicity, for instance Ba and Fe concentration and bulk rock magnetic susceptibility

Interesting stuff, with quite a complex snarl of possible causal chains between orbital eccentricities, axial tilt, and climatic effects. What I've gathered about Milankovich is that the main effect is on the magnitude of seasonal temp changes - IIRC, he focuses mainly on large landmasses in the N hemisphere where the swings are more pronounced than in the oceans. It will be interesting if they can really connect all those dots, between orbital and obliquity forcings and things like Fe deposition in marine sediments.

I might have switched from bio to geo in college, if calzones had been involved.

1 hour ago, exchemist said:

The geology of the British Isles is like a Rubik’s Cube. It takes many twists and moves to unscramble it over geological time.

Not heard that one before. Excellent analogy!

1 hour ago, TheVat said:

IIRC, he focuses mainly on large landmasses in the N hemisphere where the swings are more pronounced than in the oceans.

IIRC from my studies of the Geology of the English Lake District, magnetic orientation placed its Ordovician location in the current latitude of the Falkland Islands (they're ours! they're ours!). Can't confidently locate anything significant in the Northern hemisphere at the time other than the Panthalassic Ocean.