a characteristic estuary, with freshwater input from the Yaquina River as well as open access to the Pacific Ocean introducing ocean saltwater. Yaquina Bay is maintained at 6.7 m (22 ft) deep with the help of dredging, but depth decreases upstream with the occurrence of shoals, tidal flats, and other shallow zones. The estuary is about 11.6 km2 at mean tide and can decrease to 9.1 km2 at mean low tide. The North and South Yaquina Jetties, at the junction between the Pacific Ocean and Yaquina Bay, were constructed in 1888. Predictions of tidal height and times are based on National Oceanic Atmospheric Administration (NOAA) data with respect to Hatfield Marine Science Center's Center Dock. Yaquina Bay high and low tidal range is approximately 2.4 m (7.9 ft). Tidal flux is typically vigorous and allows intense mixing near the mouth of the Bay. However, there is seasonal variation on mixing within the estuary. During the summer and early months, June to October, the estuary is well-mixed contrasted to the winter months, November to May, when the estuary is more stratified. Due to the variation in tides and mixing, the salinity changes drastically depending on location within the Bay. Average salinity at the mouth of the Bay is 34 psu, whereas the salinity upriver is 0. The Yaquina River is 95 km (59 mi) long, beginning at the Central Oregon Coast Range, rounding past multiple bordered cities, and eventually opening up into Yaquina Bay. The river provides nutrients for the Bay and supports a variety of biology. Sediments and deposition Sediments that are found within Yaquina Bay are derived from tertiary rocks from the Central Oregon Coast Range, Pleistocene marine sediments and estuarine deposits. These sediments have three realms of deposition; marine deposition, fluviatile, and an intermediate transition state called marine-fluviatile. Marine deposition is found within the initial 2.4 km (1.5 mi) of the estuary and is associated with average ocean salinity and turbulent mixing. The sediment is similar in texture to sand and other fine grains. Fluviatile deposition extends from the point of freshwater input up to 9.7 km (6 mi) into the Bay, with its sediments more coarse. The transition stage between these two realms contains sediment mixes from the marine and fluviatile areas. The last recorded rate of sediment deposition was in 1936, with a recorded estimate of 23 cm (9.1 in) annually. However, deposition is subject to