Stevns Klint
A 17-kilometre sweep of white chalk cliffs on the eastern coast of Zealand exposes the world’s most accessible geological record of the mass extinction event that ended the age of the dinosaurs — the dark “fish clay” layer at Stevns Klint marks the precise moment, 66 million years ago, when an asteroid impact at Chicxulub reshaped life on Earth.
At a glance
Stevns Klint is a coastal cliff formation on the eastern coast of the Danish island of Zealand, stretching approximately 17 kilometres along the Baltic Sea. The cliffs are composed primarily of white Cretaceous chalk (bryozoan limestone) capped by younger Paleogene sediments. At the boundary between these two geological formations lies a thin, dark layer known as the “fish clay” — the visible record of the Cretaceous-Paleogene (K-Pg) boundary, dated to approximately 66 million years ago, when the Chicxulub asteroid impact caused the mass extinction of approximately 75% of all species on Earth, including the non-avian dinosaurs. This geological boundary, with its characteristic iridium enrichment, is visible to the naked eye at multiple points along the cliffs, making Stevns Klint one of the most scientifically significant and accessible geological records of the end-Cretaceous event anywhere in the world. UNESCO inscribed the site on the World Heritage List in 2014.
Key facts
- Location: Stevns Municipality, southern Zealand, Denmark
- Coordinates: 55.2872° N, 12.4444° E
- Cliff length: approximately 17 kilometres
- UNESCO designation: World Heritage Site, 2014
- Geological feature: Cretaceous-Paleogene (K-Pg) boundary — “fish clay” layer, c. 66 million years ago
- Scientific significance: One of the most complete and accessible K-Pg boundary exposures in Europe; high iridium anomaly in fish clay layer
- Additional heritage: Cold War NATO bunker system (Stevnsfort) within the UNESCO buffer zone
- Historic church: Højerup Old Church, whose chancel has partially collapsed onto the cliff face
History
The significance of Stevns Klint as a geological site was first recognised in scientific terms in the late 20th century. In 1980, the physicist Luis Alvarez and his colleagues proposed the asteroid impact hypothesis for the end-Cretaceous mass extinction, pointing to the anomalously high concentrations of iridium (an element rare in Earth’s crust but common in asteroids) found in a thin clay layer at geological sections worldwide. The Stevns Klint “fish clay” was among the key early sites where this iridium anomaly was identified and measured — the name “fish clay” comes from the abundant fish remains (scales, vertebrae, teeth) found within the layer, representing the rapid accumulation of marine animal remains immediately after the impact event.
The cliff has been a place of human settlement and activity for millennia. The medieval church of Højerup (Højerup Gamle Kirke) was built on the cliff top in the 13th century; over the centuries, coastal erosion progressively brought the cliff edge closer to the building. In 1928, the chancel of the church — the eastern end containing the altar — collapsed entirely onto the cliff face below, leaving the nave standing at the very edge of the cliff. The ruins are preserved in situ as a historic monument.
During the Cold War, a major NATO military installation was constructed within the cliff system at Stevns: Stevnsfort, a heavily fortified naval bunker designed to monitor and, if necessary, engage Warsaw Pact naval forces passing through the Øresund and the Baltic. The bunker, operational from 1953 to 1992, is now a museum open to the public and is included within the UNESCO World Heritage buffer zone as a layer of 20th-century history superimposed on the deep geological record.
UNESCO inscription in 2014 recognised the site under criterion (viii), for its exceptional geological testimony to one of the most significant events in the history of life on Earth.
What you see
Walking the cliff path above or along the base of Stevns Klint, the geological sequence is clearly readable. The white chalk of the lower cliff face is Cretaceous bryozoan limestone, formed from the accumulated skeletal remains of marine invertebrates on a warm, shallow sea floor. Above this chalk, a thin dark band — typically 20–30 centimetres thick — marks the K-Pg boundary. This is the “fish clay”: a layer of dark clay enriched in iridium and shocked quartz, deposited in the aftermath of the Chicxulub impact. Above this boundary layer, the sediments transition to Paleogene chalk, representing the recovery of marine life in the post-impact world.
The most accessible and well-explained section of the boundary is near Holtug Kridtbrud (Holtug chalk quarry) and at the base of the cliffs near Stevns Lighthouse. Information boards at these points explain the geological sequence and indicate precisely where the K-Pg boundary layer is visible.
Højerup Gamle Kirke (Højerup Old Church) is one of the most visually striking features of the cliff walk: the 13th-century nave stands at the very edge of the cliff, its chancel end having collapsed in 1928. The site is surrounded by a small medieval churchyard and is used for occasional services.
Stevnsfort, the Cold War bunker museum, is accessible from the clifftop and includes tunnels, gun emplacements, and command facilities from the NATO defensive installation.
Why it matters
Stevns Klint offers something that no museum display can replicate: direct, physical contact with one of the most consequential moments in the history of life on Earth. Standing at the cliff face, a visitor can run a finger along the dark fish clay layer and touch the sediment that was deposited in the immediate aftermath of the impact that ended the Mesozoic Era and cleared the evolutionary space for the eventual emergence of mammals — including humans.
The scientific value of the site derives from the completeness and accessibility of the K-Pg boundary exposure. In many parts of the world, this boundary is either buried, eroded away, or accessible only through drilling. At Stevns Klint, it is exposed in a continuous, well-preserved section at cliff face height, where it can be sampled, dated, and studied. The iridium anomaly here was among the early measurements that helped establish the global nature of the impact event.
The coexistence of geological deep time (66 million years), medieval history (Højerup church), and 20th-century military heritage (Stevnsfort) on a single coastal strip makes Stevns Klint one of the most layered and intellectually stimulating heritage sites in northern Europe.
Practical information
- Location: Stevns Municipality, southern Zealand, Denmark
- Visitor centre: Stevns Klint UNESCO World Heritage Visitor Centre at Højerup
- Stevnsfort museum: Open seasonally; admission fee; guided tours available
- Cliff walk: Freely accessible; waymarked path along the cliff top; some cliff base sections accessible at low water
- Facilities: Café and shop at visitor centre; parking at Højerup
- Best time to visit: May–September for best light and access; winter storms can make cliff base sections dangerous
- Safety: Do not approach cliff edges; coastal erosion is active and cliff faces can be unstable
Getting there
Stevns Klint is located approximately 40 km south of Copenhagen. By car, take the E47/E55 motorway south from Copenhagen toward Køge, then follow regional roads east toward Stevns; the drive takes approximately 45–55 minutes. By public transport: regional trains (S-tog line to Køge, then bus) connect Copenhagen to the area, with bus services to Store Heddinge and onward to Højerup, though connections may require planning. The nearest town with services is Store Heddinge (approximately 5 km from the main cliff section).
Nearby
- Køge (~25 km northwest) — Medieval Danish town with well-preserved town square and half-timbered houses
- Trelleborg (~50 km west) — Viking ring fortress, one of six known Danish geometric fortresses of the Harald Bluetooth era
- Copenhagen (~40 km north) — Capital; Nationalmuseet, Rosenborg Castle, Nyhavn
- Møns Klint (~70 km south) — Comparable chalk cliff formation; also has geological visitor centre
Sources
- Wikipedia — Stevns Klint
- UNESCO World Heritage — Stevns Klint
- Alvarez, L.W. et al. (1980). “Extraterrestrial Cause for the Cretaceous-Tertiary Extinction.” Science 208 (4448): 1095–1108.
- Thibault, N. & Storey, M. (2013). “The K/Pg boundary at Stevns Klint, Denmark.” Episodes 36(1): 73–76.
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