Editing Mindanao (section)

=== Valleys, rivers, and plains ===
[[File:Rio Grande de Mindanao (Cotabato City).jpg|thumb|[[Rio Grande de Mindanao]]]]
Mindanao contains two large lowland areas in the valleys of the [[Agusan River]] in Agusan, and the [[Rio Grande de Mindanao]] in [[Cotabato City]].

There is some indication that the Agusan Valley occupies a broad syncline between the central mountains and the east-coast mountains. This valley measures {{convert|110|mi|km}} from south to north and varies from {{convert|20|to|30|mi|km}} in width. {{convert|35|mi|km}} north of the head of [[Davao Gulf]] lies the watershed between the Agusan and the tributaries of the Libuganon River, which flows to the gulf. The elevation of this divide is well under {{Convert|200|m|abbr=on}}, indicating the almost continuous nature of the lowland from the [[Mindanao Sea]] on the north to [[Davao Gulf]].

The [[Rio Grande de Mindanao]] and its main tributaries, the Catisan and the [[Pulangi River|Pulangi]], form a valley with a maximum length of {{convert|120|mi|km}} and a width which varies from {{convert|12|mi|km}} at the river mouth to about {{convert|60|mi|km}} in central [[Cotabato]]. The southern extensions of this Cotabato Valley extend uninterrupted across a {{Convert|350|m|sp=us|adj=on}} [[drainage divide|watershed]] from [[Illana Bay]] on the northwest to [[Sarangani Bay]] on the southeast.

Other lowlands of a coastal nature are to be found in various parts of Mindanao. Many of these are tiny isolated pockets, along the northwest coast of [[Zamboanga Peninsula|Zamboanga]]. In other areas such as the Davao Plain, these coastal lowlands are {{Convert|16|km|abbr=on}} wide and several times in length.

From [[Dipolog]], eastward along the northern coast of Mindanao approaching [[Butuan]], extends a rolling coastal plain of varying width. In [[Misamis Occidental]], the now dormant [[Mount Malindang]] has created a lowland averaging {{Convert|13|km|abbr=on}} in width. Shallow [[Panguil Bay]] divides this province from [[Lanao del Norte]], and is bordered by low-lying, poorly drained lowlands and extensive mangroves. In [[Misamis Oriental]], the plain is narrower and in places whittle into rugged capes that reach the sea. East of [[Cagayan de Oro]], a rugged peninsula extends into the [[Mindanao Sea]].