The Guatemalan Highlands is an upland region in southern Guatemala, lying between the Sierra Madre de Chiapas to the south and the Petén lowlands to the north. The highlands are made up of a series of high valleys enclosed by mountains. The local name for the region is Altos, meaning "highlands", which includes the northern declivity of the Sierra Madre. The mean elevation is greatest in the west (Altos of Quezaltenango) and least in the east (Altos of Guatemala). A few of the streams of the Pacific slope actually rise in the highlands, and force a way through the Sierra Madre at the bottom of deep ravines. One large river, the Chixoy or Salinas River, escapes northwards towards the Gulf of Mexico. The relief of the mountainous country which lies north of the Highlands and drains into the Atlantic is varied by innumerable terraces, ridges and underfalls; but its general configuration is compared by E. Reclus with the appearance of "a stormy sea breaking into parallel billows". The parallel ranges extend east and west with a slight southerly curve towards their centres. A range called the Sierra de Chamá, which, however, changes its name frequently from place to place, strikes eastward towards Belize, and is connected by low hills with the Cockscomb Mountains; another similar range, the Sierra de Santa Cruz, continues east to Cape Cocoli between the Polochic and the Sarstoon; and a third, the Sierra de las Minas or, in its eastern portion, Sierra del Mico, stretches between the Polochic and the Motagua rivers. Between Honduras and Guatemala, the frontier is formed by the Sierra de Merendón.