Sand Dunes

Grand Sable Banks and Dunes on the eastern side of the park

NPS photo

The Grand Sable Dunes west of Grand Marais are one of the major features of the national lakeshore and among the best examples of perched dune systems in the world. Perched dunes are those that form on top of an existing coastal bluff. Michigan has two outstanding examples of these dune systems: here at Pictured Rocks and also at Sleeping Bear Dunes National Lakeshore.

Rising more than 300 feet above the lake, the Grand Sable Dunes are the highest formation in the park. They comprise five square miles and contain uncommon plant species and communities, including the richest orchid flora in the Great Lakes and the federally endangered Pitcher's thistle. The dunes support other rare species, including Lake Huron tansy and moonwort ferns. Scattered grasses and many kinds of desert-loving plants grow throughout, while patches of jack pine forest can be found in sheltered dune valleys.

When the last glacial age ended about 10,000 years ago, piles of stone rubble left behind in terraces and moraines created the rocky bluffs of the Grand Sable Banks. Water levels of still-forming Lake Superior rose and fell in response to the turbulent geologic changes occurring in the region. During the last high water period (between 4,000 and 6,000 years ago), wave action eroded the rocky cliff face and the sand-size eroded material was then blown by onshore winds on top of the bluff to create the present-day dunes.

Recent studies hypothesize that when lake levels are low, sand supply to the dunes is decreased and vegetation communities are able to expand and stabilize the soil. During high levels, sand supply increases and plants are buried. Old buried tree trunks sometimes reappear as "ghost forests" as sands move and shift. Comparison of aerial photos taken in 1938, 1967, and 1992 suggests a significant expansion of jack pine dune forests occurred in response to diminished sand supply during a 100-year fall in lake level, 1840-1940.

These jack pine forest patches are rich in understory diversity and provide habitat for many rare plants. More common plants in the dunes include beach heath, sand cherry, dune willow, common juniper, beach pea, hairy goldenrod, wormwood, evening primrose, and horsetail, as well as several native dune grasses and rushes. White-tailed deer and black bear are the largest mammals seen in the dunes, and a few deer usually winter in sheltered jack pine areas. Bald eagles and harriers soar over the open stretches.

Click here for images of the Grand Sable Dunes

 

Open Transcript 

Transcript

Pictured Rocks National Lakeshore is well-known for its stunning multi-colored cliffs and beautiful wild beaches. But it has a third main feature that is just as stunning and just as beautiful: the Grand Sable Dunes. The dunes themselves are just the top layer of a large pile of rock rubble and debris left by ancient glaciers, called the Grand Sable Banks. Spanning five square miles, the Banks make up the eastern third of the park. And at 300 feet above Lake Superior, they are also the tallest feature in the lakeshore. Since the dunes are “perched” on top of the Grand Sable Banks, they comprise one of the best examples of a perched dune system in the world. More than just hot, dry sand, the dunes also contain dense jack pine forests and unique plants in their sheltered valleys. What makes this area so special? Let’s walk on the Dunes Trail and find out. The Dunes Trail starts at the far eastern end of the park, near the town of Grand Marais at Sable Falls. Look for the big brown trail sign near the top of the falls. After walking on the trail for a while you may wonder, as you look at the dense forest around you, “Where are the dunes?” Believe it or not, you are standing on them! But these are old, old dunes that have long been claimed and settled by many generations of plants. Newer dunes have open sands that are always changing and shifting. Look above and you’ll see the tall jack pines that dominate these older dunes. Look down and you’ll see that the trail is made of sand, not dirt. Walking on the trail is like walking forward in time, from older to younger dunes. Soon you see bare sand ahead. A quick walk up a sandy slope… and there is the first view of the top of these younger dunes, with open sand mixed with grasses, thickets, and forests beyond in sheltered valleys. If you pick up a handful of sand, you’ll see that all the grains are the same size and color. As waves erode the dune slopes facing the lake, wind blows the lighter sand up high to form the dune layer. These lighter grains are easy to blow about and sometimes they bury whole forests, as well as anything humans put in the dunes like this trail exhibit. In summer, the smell of wild roses fills the air. Sand cherries ripen in the heat. On cool evenings, small animals scurry over the sand under cover of darkness, leaving faint tracks behind.

Standing at the top of the dunes you can see deep blue Lake Superior ahead. How strange it is to have a desert-like environment so close to one of the great bodies of water on the planet. The Grand Sable Dunes are one of the most ecologically pristine of all the landscapes here in the park. Neither native Americans nor Europeans ever inhabited them. They have never been mined or logged. There are few trails that access them. These wild and open dunelands offer visitors a unique experience of solitude and silence. If you visit this dynamic, yet fragile part of the national lakeshore, please take care to walk only on trails and open sand, as many rare plants live here. Take in the sights and sounds and wildness of this special place. Don’t worry about leaving footprints behind. They will soon be erased by the wind.

Duration:

5 minutes, 8 seconds

Take a virtual hike and explore the Grand Sable Dunes at Pictured Rocks National Lakeshore. Experience the unique ecosystem of this rare landscape.

 

The undisturbed nature of the Grand Sable Dunes offers outstanding opportunities for scientific research.

Hiawatha Interpretive Association photo

Research Natural Area
Due to its exceptional features, a portion of the Grand Sable Dunes was designated a Research Natural Area (RNA) in 1994. Research Natural Areas are part of a national network of field ecological areas in ecosystems with very limited public use or disturbance. They are designated for research and education, and to maintain biological diversity. The Grand Sable Dunes RNA offers a pristine environment for scientific study of climate change, lake level history, coastal landforms, soil development, rare plant communities, and vegetation succession.

Researchers are particularly interested in the dynamics between lake levels and dune building, and the resulting interplay between soils and vegetation. These studies are important for predicting how rare plant species will fare as the dunes change over time and are also relevant to global climate change questions. Soil studies are particularly important in understanding how the dunes formed and how vegetation communities developed. The Grand Sable Dunes system represents one of the few areas in the northern Great Lakes where buried soils are preserved and material is available for radiocarbon dating.

Grand Sable Dunes is also a designated critical dune area by the Michigan Department of Environmental Quality.

 

Park staff carry herbicide in backpack sprayers as they look for invasive plants in the dunes.

NPS photo

Non-Native Plants
Encroachment from non-native invasive plants such as spotted knapweed, white sweet clover, and several species of hawkweed is a continual threat to the integrity of the Grand Sable Dunes. Park staff focus much of their invasive plant control efforts in this area and have been successful in reducing the extent and impact of some invasive plants while preventing newly introduced invasive species from becoming established.