Earth Observations taken by the Expedition 18 Crew

ISS018-E-015908 (29 Dec. 2008) --- The Biokovo Range in Croatia is featured in this image photographed by an Expedition 18 crewmember on the International Space Station. The Biokovo Range in Croatia is part of the Dinaric Alps extending northwest-southeast along the coastline of the Adriatic Sea. The Range itself is the location of a national park; the nearby city of Makarska, located between the mountains and the sea, is a popular tourist destination. The highest peak in the Biokovo Range, Sveti Jure (1762 meters above sea level), is reachable by road or hiking. The Range is comprised mainly of Mesozoic age carbonate rocks ? primarily limestone, a sedimentary rock type rich in calcium carbonate ? deposited in relatively warm, shallow waters. Later tectonic processes uplifted and exposed the carbonate rocks to erosion ? leading to a distinctive geological surface known as karst topography. Karst topography originates due to the chemical erosion of carbonate rocks by acids formed in surface and subsurface water; as the rock is dissolved, underground networks of drainages and caves form. As more underground void space develops through time, the overlaying rock and soil collapses to form a variety of landforms including sinkholes, blind valleys, and towers. In the Biokovo Range, much of the karst surface has a pitted appearance, made easily visible by early morning light in this astronaut photograph. The pitted appearance is produced by numerous circular or semi-circular collapse valleys known locally as vrtace. While this image captures Sveti Jure covered with snow, there are no glaciers or ice fields in the Biokovo Range.