Stora Allvaret

Story

Stora Alvaret is a limestone barren plain on the island of Öland, Sweden. Because of the thin soil mantle and high pH levels, a great assortment of vegetation is found including numerous rare species. Stora Alvaret has been designated as a World Heritage Site by UNESCO due to its extraordinary biodiversity and prehistory. The area of this formation exceeds, making it the largest such expanse in Europe and comprising over one fourth of the land area of the island. Stora Alvaret is not devoid of trees, contrary to a common misconception; in fact, it holds a variety of sparse stunted trees akin to a pygmy forest. Stora Alvaret is a dagger shaped expanse almost long and about at the widest north end.Geological originsThe limestone plain was created by glacial action from earlier ice age advances. The limestone formation itself was created about 500 million years ago in more southerly seas. Gradually hardening into limestone and drifting northward, the limestone of Stora Alvaret contains a rich fossil record of some of the marine creatures who contributed to it. For example, orthoceratites are found in some of the present day structures on the island.Only as recently as 11,000 years ago did the first portions of the island of Öland emerge from the Baltic Sea, after the overpressure of the last glaciers was relieved by melting. Over the next several thousand years, more ice melted and the first wave of large mammals including humans migrated across the ice bridge from the mainland. Finally a thin soil mantle (only two centimeters at the deepest) was formed by plant colonisation of the bare limestone and some wind driven deposition, to create the alvar formation of the present. In many places the limestone has no soil whatsoever upon it.