The Southern Uplands () are the southernmost and least populous of mainland Scotland's three major geographic areas (the others being the Central Lowlands and the Highlands). The term is used both to describe the geographical region and to collectively denote the various ranges of hills and mountains within this region. An overwhelmingly rural and agricultural region, the Southern Uplands are partly forested and contain many areas of open moorland - the hill names in the area are congruent with these characteristics. Geology The Southern Uplands consist mainly of Silurian sedimentary deposits deposited in the Iapetus Ocean 420 million years ago. These rocks were pushed up from the sea bed into an accretionary wedge during the Caledonian orogeny, roughly 400 million years ago (Ma), when the continents and terranes of Laurentia, Baltica and Avalonia collided. The Caledonian orogeny is named for Caledonia, a Latin name for Scotland. The majority of the rocks are weakly metamorphosed coarse greywacke. The tectonic processes involved in the formation of the accretionary wedge, where sediment is scraped off the seafloor as a tectonic plate is subducted, has led to the formation of multiple, major, east–west faults that are now exploited by rivers and define valleys across the Southern Uplands. Levels of deformation associated with these faults is highly variable, but is pervasive in the finer-grained sediments. Secondary mineralisation has further altered these Lower Palaeozoic rocks which are hosts for some distinctive springs, some of which have been exploited for tourism, such as those around Moffat. Geography The Southern Uplands lie south of the Southern Uplands Fault line that runs from Ballantrae on the Ayrshire coast northeastwards to Dunbar in East Lothian on the North Sea coast, a distance of some . Hill ranges There are several ranges of hills and mountains within the Southern Uplands. From east to west these are: Cheviot Hills straddling the eastern end of the Anglo-Scottish border. Lammermuir Hills south of Dunbar. Moorfoot Hills south of Edinburgh. Tweedsmuir or Manor Hills south of Tweedsmuir. Culter Hills south of Biggar. Moffat Hills north-east of Moffat. Ettrick Hills south of Moffatdale. Lowther Hills between Clydesdale/Annandale and Nithsdale. Carsphairn and Scaur Hills between Nithsdale and the Glenkens. Galloway Hills west of the Glenkens. This is a large hill area lying between Loch Doon in the north and the Solway Firth to the south and have the sub-ranges: The Awful Hand, Dungeon Hills, Rhinns of Kells,