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Geologist: Paldiski cliff will recede by about 25 meters over next century

Last Tuesday, an observation platform on the cliff at Paldiski collapsed onto the beach below, Olle Hints, the head of the Geological Institute and associate professor at Tallinn University of Technology (TalTech), said the cliff will naturally recede by approximately 25 meters over the next 100 years.

"There is nothing special here. These processes have been going on here for thousands of years and they will continue," Hints told "Ringvaade".

The old Pakri lighthouse on Pakri Peninsula, erected in 1760, was once a safe distance from the sea, but not anymore.

"This disintegration of the coastline is happening bit by bit. It's constantly crumbling down below, where the sea, wind, and waves are chipping away, but up above the limestone is waiting its time. If the bottom part is empty, then after a while such collapses will occur," the scientist said.

One of the biggest collapses occurred in 2008, when an estimated 20,000 of soil collapsed. 

The old lighthouse at Pakri. Source: ERR

Hints said it is very difficult to predict when the next collapse may occur, but the erosion process is continuous and on average the bank coast recedes by about 25 meters every century. 

He estimated that, in 300 years, the tallest lighthouse in Estonia will also be in danger.

Collapses usually occur in winter and spring. "There are several reasons for this: the wind is harder, the swell is harder, but it is also the ice that is affected. On the surface, everything is frozen, but groundwater is still moving inside the rocks. It gets into the cracks, freezes, swells, starts to break it down," Hints explained.

The local government has already mapped the most dangerous areas.

"We don't look at it nervously, we know the processes of the sea," said Lääne-Harju Vice Mayor Erki Ruben. "These processes always happen unexpectedly, hence the warning signs, you have to be extremely careful when moving around."

The lighthouse at Paldiski. Source: Siim Lõvi /ERR

Hints said the cliff is a good archive of world history from the Ordovician and Cambrian eras. "The time span in that 25 meters is somewhere between 50-60 million years, which we can read like a history book," he said.

The lower layer is composed of soft sandstone, followed by mudstone, or graptolite argilite, or "black shale", which Hints says also contains a fair amount of uranium. Another layer of sandstone sits above, but this time greenish in color, which comes from a mineral called glauconite. The top third is limestone.

Hints said the material that falls into the sea is broken up and carried elsewhere by the waves, where it forms again on land.

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Editor: Rasmus Kuningas, Helen Wright

Source: Ringvaade

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