Overview
The Lost River is a river that rises in Vernon Township, Washington County, Indiana, and discharges into the East Fork of the White River in Lost River Township, Martin County, Indiana. The river's unusual hydrology has led to two of its features being named as National Natural Landmarks.
Description
The Lost River is about long, and its name is derived from the fact that at least of the primary course of the river flows completely underground. The river's underground channels may in fact cover hundreds of miles, as the caverns have never been fully explored. The river disappears into a series of sink holes of the type that are abundant in the karstland of southern Indiana. In one square mile there are as many as 1,022 sink holes. The river slips into and out of these sink holes at various points flowing into hidden caverns that connect with multiple other streams, rivers, and springs.
The Lost River begins as a normal river in Washington County, but soon after rising, the river flows over and into a limestone bed (karst) for several miles until the stream bed turns dry; the water is absorbed into the limestone and sinks beneath the surface to a hidden cavern.
The river then flows underground through a network of caves and channels through part of Orleans Township, Paoli Township, and part of Orangeville Township before reappearing on the surface near the village of Orangeville. Where the river rises to the surface in Orange County it produces a spring that is deep, with the very bottom connecting to the actual underground channel. This spring, the second largest in the state, is known as the True Rise, because many inaccurately believe that the Orangeville Rise is the main channel of the river. The Orangeville rise is a likely tributary of the underground Lost River. The river then continues its westward flow above ground. The rise in Orangeville unfortunately is not picturesque, but is little more than a gloomy pond that feeds a muddy stream.
From Wikipedia (CC BY-SA 4.0).