Thursday, April 01, 2021

Geology Through Literature - Han Christian Andersen's: A Story from the Sand Dunes

Geology Through Literature: 

Hans Christian Andersen's: A Story from the Sand Dunes (1859)

For the fifth entry we continue on through Hans Christian Andersen's oeuvre to our next geological reference.

For other Geology Through Literature entries, please check them out compiled on my website.

A Story from the Sand Dunes (1859)

Shoreline Erosion
Still, it is easy to imagine yourself back in times more remote than even the reign of Christian VII, for now, as then, the brown heath of Jutland stretches for miles with its barrow, its mirages, its winding, rough, sandy roads. To the west, where broad streams flow into the fjords, there are marshes and meadows, encircled by the high sand hills which rise up toward the sea like an Alpine chain with jagged summits, broken only by high banks of clay. From these the waves eat off giant mouthfuls year after year, so that the edges and summits topple down as though shaken by an earthquake. That's how it looks today, and that's how it looked many years ago...

 The passage describes the persistent erosion along the western shore of Jutland, a region of Denmark, with Western Jutland bordering the North Sea. 

Map of Jutland, Denmark. Image courtesy of Wikitravel.

The beaches and the sand dunes of the Jutland coast were deposited during the last Ice Age consisting of clay and fine sand that total 100 meters of sediment deposited over 100,000 years. These deposits are known as the Skærumhede series.

The Jutland western shore. Image by Lucia Margheritini and courtesy of Science Nordic.

These sediments make up much of the western coast, but they are slowly being transported out to sea due to coastal erosion. As the cliff faces are worn away at the bottom, the upper layers eventually collapse and then are carried away by the waves. Much of the erosion occurs during the winter months when the water levels are higher and storm levels are stronger, producing winds and waves capable of wearing away at the cliff face that is otherwise out of reach during calm, summer days. 

The sediment along the coast is then transported through the longshore current from south to north. However, the amount of sediment removed is more than the sediment supplied by the current, so the coastline is in a losing scenario. It is estimate that it has been in a losing scenario since the last ice age, ~10,000 years ago. 

And although this erosion has been continuing since long before and after Andersen's time, the current rate of erosion has been increasing. There are several reasons for this but mainly they can boil down to manmade impacts and climate change. Structures on the beach, scientists know, have a tendency to alter the erosion patterns, often producing more erosion in areas beyond where the structure are built. Think dams and sea walls. These structures stop erosion where they are built, but the lack of sediment within the water beyond these points allows for more erosion than would otherwise occur. With climate change there are many reasons for potentially accelerated erosion including: more and/or stronger storms, rising sea levels, and changes in weather patterns. It is estimated in this region that the changes in weather patterns, specifically more rain, has been the cause of the accelerated erosion, with the increased rain breaking down the cliff edges more readily than they were before. 


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