The Late Antique Little Ice Age (LALIA) was a prolonged period of Northern Hemisphere cooling from roughly 536 to 660 CE, marking one of the coldest multi-century intervals in the last 2,000+ years.

It followed the warmer Roman Warm Period and occurred during Late Antiquity, overlapping with major societal transformations including the Plague of Justinian, migrations, the decline/transformation of the Roman/Byzantine Empire, shifts in Persia, Slavic expansions, and political changes in China and Central Asia.

The LALIA core was mid-6th century, but cooling and volcanic activity extended into the 7th century. The Newberry Pumice eruption (~686 ± 2 CE), precisely dated via cryptotephra in Greenland ice cores, falls toward the later phase or tail end of the LALIA window.

This moderate VEI 4 event, with far-traveled ash, exemplifies ongoing Northern Hemisphere volcanism that likely helped sustain cooler conditions and aerosol loading. Studies use such anchors (cryptotephra + sulfur isotopes) to better resolve multiple 7th-century signals, distinguishing sources and cumulative climate forcing amid overlapping eruptions.

Ice cores, tree rings, and historical accounts together paint a picture of repeated volcanic forcing rather than a single event.

The LALIA is distinct from the later “Little Ice Age” (~1300–1850 CE) but shares volcanic and feedback mechanisms. It highlights how clusters of eruptions can trigger decadal-to-centennial cooling, with outsized human impacts in pre-industrial societies. Modern studies integrate tree rings, ice cores (sulfates, cryptotephra), lake sediments, and historical texts for high-resolution reconstructions.

Researchers analyzed Greenland ice cores and identified ash particles (cryptotephra) from the Newberry Pumice eruption of Newberry Volcano in Oregon, USA. By matching the geochemical “fingerprint” (chemical composition) of tiny ash fragments (~0.02 mm) in the ice to deposits near the volcano, they precisely dated the eruption to around 686 ± 2 CE (narrowed from a previous ~140-year window).

The surprise was the long-distance ash transport despite the moderate size. Strong winds at the time likely helped carry fine ash particles far across the Northern Hemisphere.

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Precise dating of the 686 ± 2 CE Newberry Pumice eruption and insights into 7th century volcanism from cryptotephra and sulfur isotopes in Greenland ice

The paper is titled “Precise dating of the 686 ± 2 CE Newberry Pumice eruption and insights into 7th century volcanism from cryptotephra and sulfur isotopes in Greenland ice,” published in Quaternary Science Reviews (2026), DOI: 10.1016/j.quascirev.2026.110036.

Lead author: Dr. Helen Innes (University of St Andrews), with co-authors including researchers like Andrea Burke and William Hutchison.

Ice cores preserve layered records of sulfate aerosols (causing short-term cooling) and cryptotephra for source attribution. This work builds on prior cryptotephra research that links distant eruptions to ice-core signals, improving chronologies and hazard models.

The core innovation is cryptotephra analysis — microscopic volcanic glass shards (~20 micrometers) extracted from a Greenland ice core (likely one with high-resolution annual-layer counting, such as those from NEEM, TUNU, or similar projects).

Researchers performed major- and trace-element geochemical analysis on these shards and achieved an exact match to the proximal Newberry Pumice deposits (the “Big Obsidian” eruptive phase) from Newberry Volcano’s caldera in central Oregon.

Previous uncertainty: Radiocarbon and other terrestrial dating gave a ~140-year window around the late 6th–early 7th century CE.

New precision: The ice-core layer is dated to 686 ± 2 CE using the established Greenland ice-core chronology (GICC or updated equivalents with annual resolution via multiple proxies like seasonal chemistry cycles).

This is one of the farthest-traveled confirmed cryptotephra matches for a moderate eruption: >5,000 km from Oregon across North America and the North Atlantic. Proximal deposits show an eastward lobe due to strong westerly winds, which evidently lofted fine ash high enough for long-range transport.

The study doesn’t just date one eruption — it uses the cryptotephra as an anchor to examine sulfate (volcanic aerosol) signals in the ice around 680–690 CE and applies sulfur isotope ratios (δ³⁴S) for source discrimination and process insights.

Sulfate peaks in ice cores record stratospheric/tropospheric aerosols that cause short-term global/regional cooling by reflecting sunlight. However, multiple eruptions can overlap, and distinguishing sources is hard without tephra.

Sulfur isotopes help: Different volcanic sources and eruption styles (e.g., tropospheric vs. stratospheric injection, magma composition, interaction with seawater/ crust) produce distinct δ³⁴S signatures. Combined with cryptotephra, this allows better attribution.

Around 682–687 CE window: The paper discusses other volcanic signals in this narrow interval, including a possible 682 CE event, and uses the Newberry anchor (~686–687 CE) plus isotopes to characterize multiple Northern Hemisphere extratropical eruptions. This refines understanding of aerosol loading, plume heights, and cumulative climate forcing in the mid-7th century.

Broader 7th-century context:

The 6th–7th centuries saw clusters of volcanic activity (e.g., the 536–540 “volcanic winter” events and follow-ons), contributing to climatic downturns, societal stresses, and the Late Antique Little Ice Age. This work adds high-precision data points, helping disentangle individual contributions vs. cumulative effects. It also improves ice-core chronologies by providing a firm terrestrial tie-point.

Cryptotephra fingerprinting is a key technique in tephrochronology, the use of volcanic ash layers (tephra) as precise time markers (isochrons) across distant sites. Cryptotephra refers to invisible or microscopic volcanic glass shards and minerals (typically <100–150 μm, often ~10–20 μm or smaller) dispersed far from the source.

It revolutionizes correlation and dating in ice cores, lake/peat sediments, marine records, and more by linking distal deposits to specific eruptions via unique geochemical “fingerprints.”

 Published: Quaternary Science Reviews

DOI: 10.1016/j.quascirev.2026.110036

Provided:  University of St Andrews

Authors: Helen M. Innes,
William Hutchison, Helen M. Innes, William Hutchison, Michael Sigl, Joseph R. McConnell, Nathan J. Chellman, Britta J.L. Jensen, Jakub T. Sliwinski, Andrea Burke

Abstract

Greenland ice core sulfate records reveal several large-magnitude volcanic events during the 7th Century of the Common Era (CE).

The largest eruptions, in 626 and 682 CE, coincide with negative tree ring growth anomalies and documented evidence of climate cooling and societal crises.

However, their volcanic sources remain unidentified, leaving major uncertainties about eruption latitude, sulfur injection height and climate forcing potential.

Here, we analyse sulfur isotopes of deposited sulfate aerosol and cryptotephra geochemistry in Greenland ice core Tunu2013 to better constrain eruptive sources for the 626 and 682 CE eruptions, and additionally, a sulfate peak at 698 CE and a tephra deposit at 686.

We present the first identification of the Newberry Pumice tephra in Greenland ice (686 ± 2 CE), extending the known spatial distribution of this North American tephrostratigraphic marker.

Sulfur isotope data indicates this Newberry eruption injected sulfur primarily into the troposphere, consistent with previous studies.

Isotopic evidence confirms that the 626 and 682 CE eruptions had stratospheric plume heights and were from extratropical Northern Hemisphere and tropical sources, respectively.

The 698 CE sulfate peak is revised from an assumed tropical eruption to a tropospheric, extratropical Northern Hemisphere eruption.

Although cryptotephra geochemistry does not conclusively match known volcanic events, shards coincident with the 626 CE peak suggest an unidentified North Pacific arc source.

Recurrent rhyolitic tephra throughout our sample set may reflect pulses of Southern Mono Craters activity, multiple unrelated volcanic events, or secondary remobilisation and deposition.

These results demonstrate the value of integrating sulfur isotope and tephra analyses to refine reconstructions of volcanic–climate linkages.