A reversing falls occurs when the geology of a river places the opening of tidal estuary at a point that is between the mean high and low tides for the area where this occurs.
The tides on the east coast of Nova Scotia are smaller than those of the more well known Fundy tides, but are still high enough to create a reversing falls when the conditions are met.
Twice a day the the water level in the ocean passes through a cycle of high and low, corresponding to the relative position of the moon. When the high point of a wave created by the gravity of the moon passes a river mouth, the flow of the river will reverse and water will flow up the river. When this flow meets an obstruction that has an elevation between the high and low tide levels, a reversing falls will occur. The water flowing up river rises until it reaches the level of the water above the obstruction and the flow of the river halts. As the flow of the river tops the level of the obstruction, the river will reverse course and pick up speed as the difference in the levels increases. Once the flow becomes pronounced enough, the force of the water over underwater features will cause the rapids or Falls to be reversed and flow in an upstream direction.
Once high tide is reached and the water in the river starts to ebb, the falls will gradually slow as the difference in water levels reaches equilibrium. Once the tide has lowered enough that the level below the obstruction is lower thathan the level above, the falls will resume it's more normal or downstream flow.
Obstructions may be at a narrowing of a river, a ledge formed across the river or the mouth of another smaller brook or river that branches off the main river. The Reversing Falls of Milton is of the last kind.
To log this Earthcache use the tide table for Liverpool, NS http://www.tide-forecast.com/locations/Liverpool-Nova-Scotia/tides/latest to determine the time of high or low tide. State the amount of time before or after high tide and observe the direction of the flow at this small falls.
With the help of your GPS estimate the level of the falls in respect of Sea Level.
Optional: Take a picture of your GPS at the posted coords showing the level above Sea Level.
Care should be taken in the area as slippery rocks and fast moving water can be encountered at water level. All requirement can be met without venturing into danger.
Enjoy a rare combination of water and geology that gives us a reversing falls.