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Cuspate Foreland, Anholt, Denmark

Satellite images often make ground features more obvious. Here is a satellite image (Google Map) of the noth-western part of the Danish island Anholt. It shows nicely how coastal erosion (retreat) and progradation go hand in hand.

To the east is a nice example of a (partly truncated) beachridge-swale system (for the Danes among you “rimmer og dopper”, see note). A rounded protrusion (a cuspate foreland) on the north coast is eroded on the west side by longshore currents driven by westerly winds, and the sediments are transported to the east side all the time forming new dune ridges intervened by (moist) depressions (“swales”). A swale is a low tract of land, especially one that is moist or marshy.

The evolution of this acute foreland is well described in a new paper published in the (Open Acces) Bulletin of the Geological Society of Denmark.

Illustration from Clemmensen (2011) - showing coastlines in different years (1792 …2009).

Reorganisation of the foreland started after 1887 and is most likely linked to the construction of the harbour at the northwest corner of the island in 1902. The eastward shift of the cuspate foreland accelerated around 1934. It is now going on with an astounding pace with an erosion rate of up to 6.5 m/year between 2006 and 2010

Not least to the information for the non-native English speakers among you, a cusp is an end where two curves meet - like the point or horn of the moon, or the point of a spear. The word comes from Latin cuspis "point, spear, pointed end, head". In connection with beach landforms the word also turns up in the term “beach cusp”. Beach cusps are shoreline formations made up of various grades of sediment in an arc pattern. Danish beach cusps (at Skallingen) are described in a paper by Rasch, Nielsen & Nielsen from 1993 (see references).

Illustration from Rasch (1993) - showing beach cusp morphology.

A =Anholt, S = Skallingen

I described a few other coastal landforms in my post on coastal landforms.

References:
Clemmensen et al.
Coastal evolution of a cuspate foreland (Flakket, Anholt, Denmark) between 2006 and 2010
Bulletin of the Geological Society of Denmark • Volume 59 (Open Access)

Rasch, Nielsen & Nielsen
Variations of Spacings between Beach Cusps discussed in relation to Edge Wave Theory
Geografisk Tidsskrift, Bind 93 (1993)

http://2dgf.dk/publikationer/bulletin/193bull59.html#4http://www.tidsskrift.dk/visning.jsp?markup=&print=no&id=72832

Danish note/dansk note:
Rimmer og dopper. (Rimme) kommer fra oldnordisk rimi 'jordryg, sandryg', doppe kommer fra jysk dialekt 'smal strimmel mose- eller engjord', af nedertysk dobbe 'lavt, sumpet land'). Et doppe-rimme-landskab er en hav- og vindaflejret slette, der består af parallelle, lave sandrygge, rimmer, adskilt af svage lavninger, dopper. Begge er oftest 10-100 m brede, og højdeforskellene 1-8 m. Rimmerne består af klit- og strandsand aflejret på en gammel kystbarriere, dopperne har tørvedannelse og er de tilhørende laguner. Jeg kender navnlig denne terræntype fra Skagens Odde, idet store dele af odden er opbygget af så danne rimmer og dopper.

Stratigraphy.net | Impressum

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