Visiting an Earthcache in a National Park is more than just "Logging A Find", it is an Earth Science Lesson that we hope you will enjoy.

Pictured Rocks National Lakeshore is America's first National Lakeshore, established by the 89th Congress of the United States on October 15, 1966. There are opportunities for many recreational activities thanks to the development of trails, campgrounds and roads in and around the Lakeshore’s boundaries. Pictured Rocks National Lakeshore has two gateways – Grand Marais at the eastern edge and Munising at the west. Sleeping Bear Dunes, The Apostle Islands and Indiana Dunes are the three other national lakeshores that were authorized in subsequent years.

Permission for this Earthcache was granted by the Pictured Rocks National Lake Shore Park Service because of Earthcache’s Leave No Trace principles, and the fact there is no placement of any physical cache container. Having a cache container placed anywhere within any National Park Service boundaries is strictly prohibited. Munising Falls, Grand Sable Dunes – A Perched Dune, Miners Castle Sea Cave, Miners River, Miners Castle, Miners Falls and Pictured Rocks View Earth Cache are the other earthcaches currently available at the Lakeshore.

I must stress that this EarthCache is only accessible by a water craft via Lake Superior. If you are not comfortable navigating the waters of Lake Superior, do not attempt to do this cache. Lake Superior can be dangerous at times for small water craft such as kayaks or canoes. Before attempting this EarthCache, use common sense and a few safety procedures, such as telling someone where and what you will be doing and wearing a life jacket. Continually monitor the weather conditions as they may suddenly change and there are a limited number of take out points along the 12 miles of cliffs. It is strongly suggested you research your trip. Choose a day when the winds are calm. I put my kayak in the water at Miners Beach which was 0.13 miles from the posted coordinates.

During your visit to the Pictured Rocks National Lakeshore you will have the opportunity to see three prominent natural features. The Grand Sable Dunes on the eastern end of the Lakeshore, miles of pristine sand beaches in the middle third and Lakeshore’s name sake – the multi-colored sandstone cliffs – on the western end.

Geological history recorded in the sedimentary rocks and surficial deposits of Pictured Rocks National Lakeshore is limited to two widely separated intervals of geologic time, the Late Precambrian, Cambrian, and Early Ordovician Periods (500-800 million years before present) and the Late Quaternary Period (two million years before present to the present).

During the Cambrian and Early Ordovician periods, sediments were deposited in the shallow seas and near-shore deltas that covered what is now northern Michigan. These deposits became the sandstone units that are exposed within the Lakeshore. Except for their exposure near Lake Superior, these units are presently covered by a veneer of Quaternary glacial drift.

Bedrock is best observed in the western one-third of the Lakeshore where cliffs rise up to 180 feet from Lake Superior. These extend along the lake about 17 miles from Munising to Beaver Basin. For a short distance inland from the escarpment, bedrock is occasionally exposed.

Geologists originally thought four North American glacial stages advanced and retreated through the area during the Pleistocene epoch. However, more recent research indicates up to 24 major glaciations occurred. (Pictured Rocks Resource Report by William L. Blewett, Shippensburg University of Pennsylvania) A brief re-advance of ice occurred 10,000 years ago in northern Upper Michigan. Melting of glacial ice within the Superior Basin produced huge rivers that deposited millions of tons of pulverized rock rubble in various configurations to the south of the Superior basin. A sheet of outwash, of varying thickness, was deposited along the south edge of Pictured Rocks National Lakeshore. Meltwater carved several channels into Cambrian sandstone bedrock.

The best way to fully appreciate The Pictured Rocks is from the water. The cliffs rise majestically from Lake Superior showing their brilliant colors as the sun shifts in the sky. Sandstone cliffs of ochre, tan, and brown - sandwiched with layers of white, green, orange, and black - glisten against the cloud-streaked sky and clear waters of Lake Superior. Where the lake meets the cliffs, many sea caves have been carved out by the lake’s powerful, pounding force. The Pictured Rocks are the subject of this EarthCache.

The Pictured Rocks from Lake Superior

If you put in at Miners Beach your paddle will be less than three miles round trip. Along the way you will experience breathtaking views of the Pictured Rocks. As you paddle along cliffs you will see large boulders on the lake’s bottom through the crystal clear water of Lake Superior. The sea caves and ledges will give you a sense of the power of the Earth’s water, sand and wind’s ability to cut through the bedrock. As you approach the posted coordinates you will see a large boulder that appears to be perched atop a pedestal. The boulder will be part of you logging requirements.

There are three logging requirements for the Miners Castle Sea Caves EarthCache.

First: Post with your log your picture of you, holding your gpsr, with the half “dome like” sea cave behind you. It could be too dangerous to paddle into the sea cave so it is strongly suggested you admire it from a safe distance.

Second: In your log state the air and water temperatures and the time of your visit. When I visited the site, on July 14, 2009, the water temperature was 54° Fahrenheit and the air temperature was 41° Fahrenheit at 7:00 am. Go to the National Buoy Data Center’s Buoy 45004 inLake Superior. Compare your readings to the buoy’s reading on the day and approximate time of you visit. (ATMP = air temp. and WTMP = water temp. Click on the icon at the top of the column for a five day history)

Email me the following information:

Third: Estimate the weight of the boulder that rests on top of the pedestal. The average weight of solid sand stone is about 145 pounds per cubic foot. Estimate the height, width and depth of the boulder. You can determine the boulder’s volume but multiplying the three dimensions together and then multiplying that figure by 145. Email your measurement estimates and the boulders weight.

Did You Know?

Chapel Lake is one of several plunge pool lakes created by post glacial rivers after the Marquette advance of the most recent ice age. Its greatest depth is 140 feet. Other plunge pool lakes include Deer Lake and Ginpole Lake in Alger County, home of Pictured Rocks National Lakeshore.