Place Category: Geology
The river mouth of Adventelva is a so-called estuary, influenced by tides and waves, where sweetwater and saltwater mix only slowly and over a large area. There is no sharp boundary between land and sea, between river and fjord. Instead, there is a large, very shallow area, that falls partly dry during low tide, a typical tidal flat. The horizontal distance of the shoreline can here vary with more than one kilometer, even though the vertical tidal range is less than two meters.
During the summer, especially at the time of peak melting, Adventelva is moving large volumes of gravel, sand and suspended solids. The muddy, brown water of Adventelva provide a strong contrast to the often clear, blueish-grey saltwater of the fjord.
The surface water in the fjord is therefore muddy even at a considerable distance from the river mouth, where there is no current.
The reason fort hat is that even with the suspended sediment, the sweetwater has a lower density than the seawater and remains thus as a thin layer at the surface. It takes quite some time until both watermasses finally mix and the fine grained sediments settle down to the sea floor.
During winter, Adventelva is usually frozen and both water and sediment supply to the fjord stop completely. The tidal flat is often covered by stranded blocks of sea ice which only move during the highest tides.