Marine terraces rising high above southern Italy’s present coastline may be far younger—and the land beneath them far more dynamic—than geologists had assumed. New research led by University of Oregon geologist Becky Dorsey finds evidence that terraces in southern Calabria are being uplifted five to 10 times faster than previous estimates suggested.
The work focuses on the Siculo-Calabrian rift zone, a fault belt extending more than 100 miles across southern Italy. It is a region of active tectonics, where understanding the pace and cause of vertical land movement can improve the interpretation of earthquake hazards.
Testing terraces at unusual elevations
In 2025, the research team collected sand samples from marine terraces at elevations of up to roughly 1,000 meters, or 3,300 feet, above sea level. Marine terraces are step-like landforms that can record former coastlines. Their elevation and age provide a geological record of how land and sea level have changed over time.
Sampling terraces at these heights for luminescence dating was an unusual step. Geologists had generally considered the high terraces to be about 1 million years old, which would put them beyond the expected useful range of the dating approach. Luminescence dating can determine when mineral grains were last exposed to sunlight or sufficient heat, making it useful for establishing the timing of sediment deposition.
The researchers nevertheless applied the method to the high-elevation samples. According to the University of Oregon’s account of the work, the results support Dorsey’s hypothesis that the terraces are substantially younger than most geologists had inferred. If a terrace reached its current elevation in a shorter interval, the implied rate of uplift is much higher.
A challenge to prevailing explanations
The findings, published November 6 in Communications Earth & Environment, challenge prevailing explanations for why Calabria’s marine terraces have risen so far above sea level. The study argues for a different mechanism: an active tear in the Ionian slab directly beneath southern Calabria.
The Ionian slab is an oceanic segment of the African tectonic plate involved in the region’s subduction system. In subduction zones, one tectonic plate moves beneath another, producing complex deformation, earthquakes and, in some settings, volcanism. Changes in the geometry or continuity of a descending slab can affect the forces acting on the overriding crust.
The study’s interpretation is that a tear in this slab is driving rapid, transient uplift in southern Calabria. That proposed mechanism connects the unexpected ages of the terraces to deep tectonic processes rather than treating the landforms as a simple, long-term record of gradual uplift.
Why the new chronology matters
Terrace landscapes are often used as archives of regional deformation. But that record depends on reliable ages. A high terrace may appear to signal slow uplift over a very long period, or faster uplift over a shorter period; its height alone cannot distinguish between those possibilities.
By obtaining luminescence dates from terraces previously thought too old to test this way, the team has provided a new chronology for part of southern Calabria’s landscape. The result does not merely refine a local date. It changes the inferred pace of crustal movement and redirects attention toward the state of the subducting Ionian slab.
That distinction is especially important in a seismically active region. Hazard assessment requires an understanding of active faults and earthquake history, but it also benefits from a clearer picture of the tectonic processes that load, deform and reshape the crust over time. Faster-than-expected uplift indicates that the region’s tectonic evolution may include episodes of more rapid change than older models allowed.
Broader lessons from an Italian subduction zone
Southern Calabria offers an unusually well-documented setting for studying slab detachment and related deformation. The researchers say examining the dynamics of a slab tear there can help scientists think about hazards in other active settings, including the Cascadia Subduction Zone in the Pacific Northwest.
The comparison does not mean that Calabria and Cascadia are identical. Rather, it highlights the value of observing active processes in one subduction system when interpreting the possible behavior of another. Deep plate processes are difficult to observe directly, so surface features such as uplifted terraces can provide essential constraints.
The study also illustrates the scientific value of revisiting a methodological assumption. The high terraces had been treated as too old for luminescence dating. Sampling them anyway produced evidence inconsistent with that expectation and opened a different explanation for the landscape’s history.
Further work will be needed to test how the inferred slab tear relates to deformation across the wider region and to incorporate the revised uplift history into hazard models. But the new dates provide a strong reason to reassess the speed at which southern Calabria has been rising—and the tectonic forces responsible.
For a landscape that preserves former shorelines hundreds of meters above today’s sea, the conclusion is consequential: the terraces may not be simply ancient relics of slow geological change. They may instead record a comparatively rapid phase of uplift linked to a changing plate boundary deep below southern Italy.
This article is based on reporting by Phys.org. Read the original article.
Originally published on phys.org
