Large coastal cliff with Eemian and Weichselian deposits and a wide range of glacial tectonic structures. Northwest of the cliff is a smaller Holocene marine foreland with dune formations
Vejsnæs Nakke (The neck of Vejnæs) is Ærø's southernmost point and consists of a large knoll intersected by a 2 km long and up to 20 m high coastal cliff. The cliff follows the curve of the coast and therefore faces both southwest and southeast. Parking is available near both ends of the cliff. Next to the western parking lot, at the end of Østersøvej by Dunkær Mark and Sjoen, is a popular beach with small dunes. From here you can follow the beach a few hundred meters to the high cliffs at the northwest end of the cliff.
At the northeastern end of the cliff is a fortified area with a rampart and moat, as well as the remains of St. Albert's church and cemetery. The fortification was built around the year 700 and was probably in use until sometime in the 13th century.
At Havsmarken, 500 m north of St. Albert's Church, there was a large trading post in the Viking Age. Coins, weights, potsherds, silver objects and ship nails have been found here. Among other things, textiles and jewelry were traded, and metal crafts emerged on the site. The site is only partially excavated, so what else was going on and what was traded is still a secret buried in the dirt.
The fortification and the trading post are roughly contemporary and were probably closely connected. However, the church was first built in the Middle Ages and was in use until the Reformation around 1530, after which it was demolished and the materials reused for the construction of Rise Church.
There are great views of the area from the high ground at Lindsbjerg (45 m) near Havsmarken.
Photo:Illustration: Søren Skibsted.
The ice age landscape at Vejsnæs Nakke
The impressive coastal cliff shows deposits from the last interglacial period, the Eemian (130-115,000 years before present) and the Weichselian (115-11,700 years before present). It is possible that layers from the preceding Saale Ice Age (390-130,000 years before present) are also present. The cliff has not yet been investigated in detail.
The layer series includes the same layers that are also found in Ristinge Klint on Langeland: moraine clay and meltwater deposits from four different Weichselian ice advances, namely the Ristinge Advance (55-50,000 years before present), the 'Northeast Ice' (23-21,000 years before present) and the two Young Baltic ice advances (19-17,000 years before present). In addition, the 'White Sand' from the Weichselian (deposited by wind and water in an Arctic climate characterized by permafrost), as well as the 'White Clay' and the marine 'Cyprina Clay' from the Eemian interglacial.
In addition, Vejsnæs Nakke also contains freshwater clay and peat, alternating dark clay and sand layers, as well as several units of meltwater sand and gravel that do not occur in Ristinge Klint.
Vejsnæs Nakke has a complex structure and in many places the layers have been folded, pushed over each other or even turned upside down by the glaciers during the last ice age. This is partly because the landscape was created by several ice streams. Firstly, the ice has 'pulled' the hills in the area into elongated shapes (so-called drumlins) in the southeast-northwest direction, and secondly, Vejsnæs Nakke is part of an ice margin created by the Bælthav Ice Stream ('Lillebælts Glacier') 18-17,000 years ago, along which the ice pushed the layers several times.
The dynamic coastal landscape
After the sea invaded the area south of Funen in the Holocene (the period after the last ice age) and created the South Funen Archipelago, the constant wear and tear of the sea on the glacial landscape created distinctive cliffs along the southern coast of Ærø. From here, coastal currents carried the loosened materials to areas with shallower and calmer water where they could be deposited and build new land - so-called marine foreland.
At Sjoen, 500 m northwest of Vejsnæs Nakke, a small bay has been filled with clay, sand and gravel brought in by the sea. Today, the area appears as a marine foreland with grassy salt marshes with damp depressions (overgrown beach lakes) and seawalls covered by a narrow belt of low coastal dunes.
The landscape in the future
From a geological perspective, the drumlinized glacial landscape in the cliff hinterland is unlikely to change in the foreseeable future. Apart from the human impact on the surface terrain, e.g. through normal farming, changes to the landscape are expected to be limited. However, the hilly landscape will lose character through afforestation, the establishment of larger solar cell installations and further wind turbines as part of the green transition. There are already several turbines in the area and at Sjoen.
With the prospect of an expected rise in sea level and climate change, which is expected to increase the frequency of storms and high water situations, the degradation of the coast is likely to accelerate.
Two types of erosion are distinguished: (1) Chronic erosion, which is the daily wave, current and wind impact on the coast; (2) Acute erosion, which typically occurs during storms in combination with high tides and strong wave action. Severe acute erosion of cliffs, especially during storm surges, can cause landslides and loss of land. Similarly, increased precipitation will increase the risk of landslides.
Aerial photos show several large, older landslides along the coast, which is a normal and characteristic feature of many of Ærø's cliff coasts. The cause of the landslide activity is due to the combination of precipitation, groundwater seepage, sea erosion and, not least, the geological conditions, where the cliffs often contain ice-disturbed layers of fat clay (primarily 'The Shiny Clay' and 'Cyprina Clay' from the Eemian interglacial period). Such layers have a water leveling effect and act as soapy sliding surfaces, on top of which the overlying soil layers slide out.
However, as part of the preservation of the natural characteristics and geodiversity of the geopark, the cliffs should be kept free from coastal protection as far as possible, so that the natural coastal processes can continue to operate freely while keeping the illustrative geological profiles open.
A rising sea level will potentially increase the risk of saltwater intrusion into coastal drinking water wells and/or aquifers.
Due to the morphology and formation history of the area, the surrounding moraine landscape contains relatively few depressions with small areas of moss and low-lying soils. However, increased precipitation together with rising sea levels can affect groundwater levels and runoff conditions and locally raise water levels, potentially causing problems for properties and farmland in the area.
As the terrain slopes are relatively moderate and the surface soils are predominantly clayey, more frequent cloudbursts are unlikely to lead to significant changes in surface erosion. Most of the landscape in the hinterland is cultivated. Increased precipitation also influences the natural soil-forming processes and could, for example, lead to increased leaching of clay, salts, minerals and nutrients from the upper soil layers.
In addition to changes in erosion rates along Vejsnæs Nakke, the greatest coastal changes associated with sea level rise are likely to occur around the marine foreland, Sjoen. In extreme high tide situations, large parts of the low-lying area will be flooded.
Due to the curved course of the coastline and thus the south-east-north-west and south-west-north-east orientation of the cliff, it is possible to observe the complex glacial tectonic structures of the cliff from several sides. In addition, the contemporary landslide-related processes add further complexity to the various structures seen in the cliff. Together with the extensive Late Quaternary succession, these factors make Vejsnæs Nakke an ideal research and teaching site.
Vejsnæs Nakke is protected under Natura 2000 site no. 127 and Habitat area H111. Together with Sjoen, Vejsnæs Nakke has recently been classified as a site of regional geological interest (RGI).