| Agiapuk River | |
| Map Size: | 300 |
| Pushpin Map: | USA Alaska |
| Pushpin Map Size: | 300 |
| Pushpin Map Caption: | Location of the mouth of the Agiapuk River in Alaska |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | State |
| Subdivision Name2: | Alaska |
| Subdivision Type4: | District |
| Subdivision Name4: | Nome Census Area |
| Length: | 60miles |
| Source1: | Seward Peninsula |
| Source1 Location: | Northeast of Black Mountain |
| Source1 Coordinates: | 65.5578°N -166.4958°W |
| Source1 Elevation: | 1188feet[1] |
| Mouth: | Imuruk Basin, Bering Sea |
| Mouth Location: | 21miles southeast of Teller |
| Mouth Coordinates: | 65.1664°N -165.6839°W[2] |
| Mouth Elevation: | 7feet |
Agiapuk River (also Agee-ee-puk, Ageepuk, Agiopuk, Ahgeeapuk) is a waterway on the Seward Peninsula in the U.S. state of Alaska. It is a tributary to Grantley Harbor from the north.[3] American River is a main tributary.
The Agiapuk, flowing into Imuruk Basin from the north, drains an area of from 800x in the center of Seward Peninsula. The river forks about north from Imuruk Basin, the eastern and larger branch being called the American River by the prospectors, while the western branch retains the name Agiapuk. Below the forks, the Agiapuk makes many meanders on a broad flood plain, from which the upland rises by gentle slopes to flat-topped hills with elevations of 600-.[4]
The western branch occupies a broad depression which for about extends parallel with Grantley Harbor and Port Clarence, from which it is separated by an upland of about elevation. Near its western end, this depression has an altitude of about, and is about wide. The California River drains a part of this depression through a new, deep-cut canyon. The depression is limited on the north by flat-topped mountains, which rise to elevations of 1000-. The main part of the Agiapuk emerges from a comparatively narrow valley in these mountains into this depressed area.[4]
The Agiapuk Valley below the forks is filled with flood-plain gravels. These gravels extend up the river. These gravels probably occupy a depression which has been at some time either a lake or arm of the sea and filled with sediments. Where the upper end of the depression is cut by the California River, bed rock is exposed in some places. Schists and limestones with later basalts are exposed in the upland lying between the Agiapuk and Grantley Harbor. North of the Agiapuk, the bed rock consists of Silurian limestones of the Port Clarence formation. These limestones are comparatively unaltered and are generally not mineralized to any extent.[4]