Thousands of visitors flock to the Lake Michigan shoreline each year to vacation at the lake's fabulous beaches. Few of these beachgoers realize, however, that the soft golden sand on which they are sunbathing and the water in which they are splashing actually originated from massive glaciers... or realize that the beaches themselves are moving.
Approximately 16,000 years ago, what is now the Michigan area was covered by glaciers, humongous sheets of flowing ice thousands of feet thick. Within the ice, glaciers carried a variety of debris, much of it consisting of boulders, rocks, and soil the ice picked up as the glaciers gouged their way down the land. When these ice sheets retreated, the land left behind had been reshaped, moraines and drumlins creating rolling hills in some places, and ponds and lakes -- including all five Great Lakes -- in other areas. The water in the Great Lakes comes mainly from the glacial ice that melted thousands of years ago. The Lake Michigan-Huron system comprises one of the largest freshwater lakes in the world.
The glaciers were not just responsible for the lake water. The sand that comprises Lake Michigan's popular beaches is also glacial in origin, either brought to the shoreline from inland rivers, which carry the glacially-deposited sand to the lake, or eroded by the lake's wave activity on site. Lake Michigan's waves continue to affect the shoreline through littoral drift, carrying enormous quantities of sand away from the beaches and literally -- and littorally -- changing the topography of the Lake Michigan shoreline.
Beyond the beaches and heading inland, sand dunes rise up from the ground. These giant accumulations of sand slowly migrate inland, and are able to grow in height thanks to the presence of beach grass. This grass thrives in the shifting sands, sending shoots called rhizomes deep underground and allowing the plant to grown increasingly taller. The rhizomes hold the dune sand in place, while the tall grass leaves trap the moving sand, enabling the dunes to grow higher. Lake Michigan's coastal dunes, including the dune system at North Beach Park, have become an important ecosystem, with animals such as the Eastern hognose snake, the Eastern bluebird, and the Fowler's toad making their home in this habitat.
To receive credit for this cache, please email Team FMA the following information (do not post a "found" log until Team FMA has sent you approval):
1. From the coordinates, look towards Lake Michigan and observe North Beach. What would happen to North Beach (the beach and its sand, not the human structures) if it were severely affected by littoral drift? Please be specific and descriptive, and remember that there are no magicians in coastal zone geomorphology.
2. Read the information panel at the Earthcache site. What kind of sea grass is chiefly responsible for anchoring the dunes in place and allowing them to grow higher? Observe how the grass grows amidst the dune sand. What would happen to the North Beach Dunes if this sea grass were damaged, disturbed, or removed? Again, please be descriptive in your explanation.
3. Take an altimeter reading by the information panel, then follow the wooden dune walkway to the very top of the North Beach Dunes. Take another altimeter reading here. What is the difference in height between the two altimeter readings? Alternative: estimate the height of the top of the sand dunes and calculate the difference in height.
4. Next, examine the area between the beach and the dunes. This U-shaped area is called a parabolic dune. Notice the houses, the roads, and other signs of human habitation. How did the presence of humans affect the dunes that were once here? Be descriptive regarding how construction and continual human presence lead to the creation of the parabolic dune. Short, nondescript answers like "it eroded" are not accepted!
5. Note the signs posted around the dune, restricting access to the dunes. What would happen if ATVs, mountain bikes, or even hikers were allowed full access to the North Beach Dunes? Use your answers to questions 2 and 4 to help you elaborate here.
6. Optional: post a photo of you or your GPSr by the North Beach Dunes informational panel.
Thank you for visiting the North Beach Dunes! Be sure to fully enjoy this park by taking the wooden dune stairway for a spectacular view of Lake Michigan. North Beach Park also features a barrier-free beach walkway and other barrier-free facilities.Also, please bear in mind that the North Beach Dunes are a fragile ecosystem, so please stay off the dunes and remain on the provided pathways.
Please note that any found logs whose ADLs are not received within 24 hours of posting the find will be deleted. No excuses; we've heard them all, including "my dog suddenly got sick" and "l was planning on sending in my answers once I wrote my research paper in a few months." If you believe you will be unable to complete the ADLs, please either wait to log this Earthcache as found, use the "write a note" function instead of the "find," or don't do this Earthcache. Those who submit incorrect or incomplete answers will have two weeks from the date of submission to submit the correct answers. Thank you!
Our thanks to Willy, first to complete our Earthcache!