You will need a medium size container that has a cap to collect a water sample. The container should have a cap as the sample will need to be transported back to your home. And a camera.
Herodotus the great historian coined the term delta for the Nile River delta because the sediment deposited at its mouth had the shape of the upper-case Greek letter Delta: ?.
A delta is a landform that is created at the mouth of a river where that river flows into an ocean, sea, estuary, lake, or reservoir or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river. Over long periods of time, this deposition builds the characteristic geographic pattern of a river delta.
River deltas form when a river carrying sediment reaches a body of standing water, such as a lake, ocean, or reservoir. When the flow enters the standing water, it is no longer confined to its channel and expands in width. This flow expansion results in a decrease in the flow velocity, which diminishes the ability of the flow to transport sediment. As a result, sediment drops out of the flow and deposits. Over time, this single channel will build a deltaic lobe (such as the bird's-foot of the Mississippi River deltas), pushing its mouth further into the standing water. As the deltaic lobe advances, the gradient of the river channel becomes lower because the river channel is longer but has the same change in elevation. As the slope of the river channel decreases, it becomes unstable for two reasons. First, water under the force of gravity will tend to flow in the most direct course downslope. If the river could could breach its natural levees as during a flood, it would spill out onto a new course with a shorter route to the ocean, thereby obtaining a more stable steeper slope. Second, as its slope gets lower, the amount of shear stress on the bed will decrease, which will result in deposition of sediment within the channel and for the channel bed to rise relative to the floodplain. This will make it easier for the river breach its levees and cut a new channel that enters the body of standing water at a steeper slope. Oftentimes when the channel does this, some of its flow can remain in the abandoned channel. When these channel switching events happen repeatedly over time, a mature delta will gain a distributary network.
There are several types of deltas, the type we are going to discuss is the Digitate or bird foot delta. The St. Clair River Delta, on the border between Michigan and Ontario is a prime example of a turbulent bed friction-dominated delta with a classic birdfoot shape.
The St. Clair River delta, the largest in the Laurentian Great Lakes system, is located in Lake St. Clair at the mouth of the St. Clair River. It straddles the border between the state of Michigan in the USA and the province of Ontario in Canada. The delta is classified as a river dominated feature with classic “bird’s foot” structure similar to the Mississippi delta model. The delta is composed of two surfaces. The older surface at the delta apex was deposited at a higher lake level some 3,500 to 5,000 years ago. The current delta started to form following a drop in lake level some 3,500 years ago and continues to build to the present day. The delta consists of seven active deep channels averaging 36 feet in depth entering a lake with a mean depth of 10 feet with much shallower water in the delta front region. The channels are stable and are actively eroding into the sediments of the lake creating both under water and above water levee deposits with crevasses. The interdistributary bays are being filled with sandy deposits created by wave energy and by crevasse deposits. At the erosional front of each distributary a narrow erosional notch “leading channel” is being formed which appears to control the direction of lakeward erosion of each deep distributary channel. The emplacement of the delta body in the shallow receiving water body has been termed “burrowing” delta formation and is the mechanism controlling the formation of this sedimentary feature.
The St. Clair delta is the world’s largest delta that enters a freshwater lake. The islands in the delta form popular summer resorts, the largest being Harsens Island, Mich., and Walpole, Ont. The river is an important link in the St. Lawrence Seaway.
To log this Earthcache email the answers to the following questions to this cache owner.
1.) Collect a sample of water and bring it home to allow it to settle. After 48 hours describe to me what the contents look like.
2.) Take a photograph of yourself or team with a GPS and the Snooks Highway Boat Access Sign. Post this with your online log.