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The west consists largely of poor subsoils and is covered with large areas of extensive Atlantic blanket bog, whereas the east is largely a limestone landscape. There is a distinct geological difference between the west and the east of the county. It is one of three counties which claims to have the longest coastline in Ireland, alongside Cork and Donegal. Mayo has 1,168 km (726 mi) of coastline, or approximately 21% of the total coastline of the State. It is the second-largest of Connacht's five counties in both size and population. Mayo is the third-largest of Ireland's 32 counties in area and 18th largest in terms of population. It is bounded on the north and west by the Atlantic Ocean on the south by County Galway on the east by County Roscommon and on the northeast by County Sligo. See also: List of islands of County Mayo, List of loughs of County Mayo, and List of mountains and hills of County Mayo
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