A mountain range or hill range is a series of mountains or hills ranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form, structure and alignment that have arisen from the same cause, usually an orogeny. A mountain chain is a row of high mountain summits, a linear sequence of interconnected or related mountains, or a contiguous ridge of mountains within a larger mountain range. The term is also used for elongated fold mountains with several parallel chains. Sea, ocean, lake. Elongated mountain chains occur most frequently in the orogeny of fold mountains, (that are folded by lateral pressure), and nappe belts (where a sheetlike body of rock has been pushed over another rock mass). Other types of range such as horst ranges, fault block mountain or truncated uplands rarely form parallel mountain chains.