 long has a general westward direction down to the confluence with the Atabapo and Guaviare rivers at San Fernando de Atabapo; the second flows northward, for about 290 kilometers , along the Venezuelan–Colombian border, flanked on both sides by the westernmost granitic upwellings of the Guiana Shield which impede the development of a flood plain, to the Atures rapids near the confluence with the Meta River at Puerto Carreño