On July 12th, 2018  I was in Stockholm, Sweden. I immediately booked a ferry to Gotland, Island south of Stockholm, and stayed for two nights. Gotland is a small island in the Baltic sea, off the southeast coast of Sweden. It is home to the raukar, a naturally formed limestone pillars that resemble human figures. On misty days they loom as if from the Viking sagas, staring seaward with expressions of petrified astonishment. 

     The most impressive raukar are to be found between Digerhuvud and Lauterhorn of the coast of Faro, (pictured below), to the north part of Faro island.  The image above was taken in the Langhammar Nature Preserve.

     Mikael Calner, professor and head of the Department of Geology at Lund University says that the raukarna on Faro Island are “erosional remnants that have been carved and sculpted during the latest glacial period and sea-level lowering.”   Sea level has gone up and down several times in the Baltic during the past 15,000 to 20,000 years, and the last glaciers retreated about 12,000 years ago.  Calner says that “the parts left as sea stacks are the cores of the reefs that grew in the Silurian”,  about 443 million to 416 million years ago.

     Calner continues saying, “Most of the continents were clustered south of Earth’s equator, in the Silurian and following in the Devonian, you have the largest reef abundance on Earth ever.” The remains of the reefs captured in the raukarna contains a snapshot of an interesting ecological setting.  Calner says that the shallow waters were home to sponges and corals that thrived in tropical latitudes, building huge sheets of carbonate similar to the Bahamas today.  Stromatoporoids — which are sponges and quite distinct from the microbial mats that form similar-sounding stromatolites— were the main builders of Gotland’s reefs, along with tabulate and rugose corals.

     Apparently, Gotland Island was much nearer to the equator during the Silurian time period.

     Later, I walked down the coastline past the old fishing village of Helgumannen, Digerhuvud and to Slathallar, (pictured below).

     As I walked along the coast, I noticed that the rocks were very pristine and  well-preserved.  Apparently, they were never buried to deep depths, never overrun by orogenies. They are like a frozen reef zones.  

Faro’s fossil record has led geologists to reconsider the Silurian, which was once thought to be a calm period between the violent mass extinctions of the Ordovician and Devonian. The rocks instead reveal multiple small extinction events, in which conodonts and graptolites nearly disappeared from the record in pulses (and then recovered in some cases).  To a geologist, this is a very famous location.

     Faro is also the Burial-Site to legendary Swedish film director Ingmar Bergman and his wife Ingrid, (picture above). Ingmar Bergman, the famed Swedish director, made many of his iconic movies, and lived out the last years of his life, here.