GC5R5X8 Dune Blow Outs (Earthcache) in Michigan, United States created by Cyclops

GC5R5X8 ▼

A cache by Cyclops Message this owner

Hidden : 4/10/2015

Difficulty:

Terrain:

Size: Size: other (other)

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Geocache Description:

This Earthcache will take you to several waypoints along US 2. Please note there is NO parking on the west bound (north) side of US 2. Use caution as the speed limit is 55 MPH here. Also expect to get some sand in your shoes.

Things you will need to log this Earthcache:

GPS
Camera (optional)

Please stay on the lake side of US 2 to answer the following questions. Several areas are posted as "Protected Areas". Since the features that I want you to examine are across the road, below you will photos with the feature removed. The remaining area of the photos should allow you to pin point the feature correctly. This landscape is dynamic and change is constant so the areas may not match the photos exactly.

To log your find, please E-mail me via my profile, the answers to the following questions:

At the posted waypoint, In the removed area how many blowouts can you see?
At Child waypoint #1, In the removed area is the blow out Active, Starting to be covered with plants or Is completely covered with plants?
At Child waypoint #2, In the removed area, what can you see that damages the dunes?
At Child waypoint #2, No photo for reference. ;Walk closer to the beach and look back in the direction of the road. Describe the dunes / blowouts on the beach side of the road.
At Child waypoint #3, In the removed area, look for the metal sign. Describe to me the difference between the blow outs on each side.
Not required but always appreciated, post to your on-line log a photo of your GPS. Your face can be included if you so wish. Be careful not to include a spoiler in the back ground. Thanks.

To email your answers please click here to open a new email. Depending on your email client, this link may not work.

Definition of Terms
Dune

A dune is a hill of sand built by the wind or currents in water.

Blowouts

A blowout is a hollow or depression formed on an existing sand dune or deposit by wind erosion. Blowouts come in different shapes and sizes and occur on any kind of dune.

Saucer-Shaped Blowouts

A saucer-shaped blowout is a shallow, dish-shaped hollow, sometimes occurring with a steep rim along its margin and a less-pronounced depositional lobe.

Trough Blowouts
A trough blowout is a deep and narrow blowout, sometimes occurring with steep sides and distinct areas of erosion (the deflation basin) and downwind deposition (a depositional lobe). Trough blowouts may form a gap in another dune that funnels wind and wind-blown sand inland.

Parabolic Dunes
Much of the sand sheet is covered with vegetation. If strong winds erode a section of the vegetated sand (commonly referred to as a blowout), a parabolic dune may form. Leeward (down wind) motion occurs if sand from the blowout is deposited on the opposite slope of the parabolic dune. Vegetation holds the "arms" of the dune in place as the leeward "nose" of the dune migrates forward toward the main dune field. Parabolic dunes are common in the sand sheet southwest of the main dune field.

The Geology

The beach is the sole source of sand for coastal dunes, and every single sand grain in a dune has come across the beach at some time in its history. In fact, each grain probably has made the trip many times because when the wind reverses and blows offshore some of the grains go right back to the beach. Dune building is helped along by the characteristic onshore coastal winds. Regardless of the general wind circulation patterns of the region, winds will blow onshore due to the sun warms the land which cause the air to rise, pulling the cooler air from over the water onshore.

Dunes commonly begin as piles of sand accumulated in the lee (down wind) side of beach debris such as piles of seaweed or clumps of vegetation. Beach debris slow down the wind or blocks it, causing sand to accumulate in the wind lee of the object. Eventually, plant seeds find their way to the new piles of sand, germinate, sprout and trap more sand. As the plants grow, it continues to cause more and more sand to accumulate. If all goes well, a new dune is born! As these embryonic dunes grow, the vegetation keeps moving up and out, holding much of the sand in place.

One way in which sand dunes are eroded is by the wind re-mobilizing sand and blowing it out of the dune, a process known as deflation. The most common deflation feature is the blowout, a bowl-shaped depression with a flat floor that lies below the elevation of most of the adjacent dunes. Blowouts can have flat floors because the sand is blown away until the sand surface reaches the top of the water table. At this level, the wet sand resists being blown away and the surface can become vegetated.

Blowouts have historically been caused by natural disturbances, such as fires, wind storms, or plant diseases. However, in recent decades, human disturbance or destruction of the dune's vegetation has initiated blowouts. Off road vehicle traffic and human foot traffic are major causes. Continuous human disturbance has the potential for much more widespread destabilization because it does not allow blowouts to stabilize.

When the glaciers covered this area, they pressed the surface of the Earth lower. Since the glaciers have receded, the land has been slowly rebounding. As the land raised, the old shoreline moved inland. You can see this by the older dunes farther north of US2. They are not affected by the wind so much and have not grown or have had blowouts form. They are typically completely covered with vegetation, including trees.