Banded Iron Formation of Jasper Knob

Banded Iron Formation by Linda Grashoff

Back in August of 2007, Linda & her husband took one of their many trips to Michigan’s Upper Peninsula & visiting Grand Marais, Ishpeming and Copper Harbor. She visited the Jasper Knob just outside of Ishpeming & writes:

It is a banded iron formation. The layers consist of jasper (the red rock) and hematite (the silvery rock). I’m delighted to tell you that some biogeologists believe that banded iron formations were formed by my old pals, the iron bacteria.

Head over to her photo blog for a lot more pictures and for sure check out her book They Breathe Iron for more about iron bacteria.

Up close with Michigan’s state stone: Hexagonaria percarinata, the Petoskey stone

Untitled, photo by Anna Lysa

The Michigan Tech Geology Department explains that Michigan’s state stone is the Hexagonaria percarinata, the Petoskey stone. It is a fossil colonial coral that lived in the warm Michigan seas during the Devonian time around 350 million years ago. They can be found from Traverse City area across the state to Alpena in gravel pits, road beds, and of course beaches, with the largest concentration found on and around Lake Michigan’s Little Traverse Bay near the town of Petoskey. In June of 1965 the Petoskey Stone was named Michigan’s official State Stone and Miss Ella Jane Petoskey, the only living grandchild of Chief Petoskey, attended the formal signing.

Several years ago I shared the story behind the name as told by a young woman I know, Rose Petoskey:

My name is Noozeen (Rose) Nimkiins (Little Thunder) Petoskey (Rising Sun) and I am Anishinaabek.

Many people would associate the word Petoskey with the souvenir stone found on the northern Lake Michigan shorelines. However, to my family, the word Petoskey represents much more than a souvenir.

In the Odawa language, the word Petoskey (Bii-daa-si-ga) means the rising sun, the day’s first light, or the sun’s first rays moving across the water. The Petoskey stone is a fossilized coral created by impressions made in limestone during the last Michigan ice age. These stones were named “Petoskey” because the impressions resembled the rising sun coming up over the water. Just as the image of the rising sun is implanted within the Petoskey stone, the archaeology of a person’s names is implanted within. All names within our Anishinaabek culture reflect an individual’s personal history. Rocks go deep, but names go much deeper to reveal the stories of the past.

View Anna Lysa’s photo bigger and see more in her Michigan slideshow.

Miner’s Castle, before it fell

Miner’s Castle before it fell, photo by spauldi1

Today is the 10th anniversary of the collapse of one of the turrets on the Miner’s Castle formation in the Pictured Rocks National Lakeshore.

On Thursday morning, April 13, 2006, the northeast turret of Miners Castle collapsed. One turret remains on Miners Castle, the best-known feature of Pictured Rocks National Lakeshore. The collapse was reported via cell phone by fisherman in the area, according to chief ranger Larry Hach. Most of the rock fell north and into Lake Superior, and there were no injuries. The lower overlook platform near Miners Castle appears to be unaffected.

While the rockfall at Miners Castle on April 13 was startling, such events are not rare along the Pictured Rocks escarpment.

Click for the full report on Absolute Michigan.

Sue took this back in 2003. View it background big and jump into her slideshow for more pics from “before the fall”at Miner’s Castle.

Michigan Weird Science: The Menominee Crack

The Menominee Crack, photo courtesy Michigan Tech College of Engineering

Gizmodo reports that back in October of 2010 folks near Birch Creek in Menominee County heard a boom, felt the earth rock, and woke up to find a 360′ crack in the ground:

The first clue was the fact that the split happened at the top of a ridge. A pop-up isn’t a wrenching apart of some deep underground structure. It’s a large piece of ground suddenly pushing upwards, so that the ground above splits over it. The researchers discovered the pop-up by the sophisticated technique of slamming a sledgehammer against a metal ball sitting on the ground. The action caused sound waves to move through the rock beneath—and depending on the formation of the rock, the sound moves at different speeds. In this case, it moved in hugely different ways parallel to the crack, as compared to perpendicular to the crack. This indicated that there was a huge fracture in the limestone underneath the crack.

These sudden fractures occur due to extreme strain in the rock—strain that can be pent up for centuries. It’s more common around quarries, when removal of large pieces of rock can cause the rest to suddenly fracture and pop upwards. Other times, it can occur spontaneously. The Menominee Crack, as its now called, was probably the result of a spontaneous fracture—although the researchers speculate it might have happened due to the removal of a large tree from the area.

Read more at Gizmodo and check Michigan Tech for a detailed explanation of the Menominee Crack and Live Science for more photos. If you want to creep yourself out a little more, check out the probably related Wisconsin mystery booms!

Thanks Michigan Tech’s Engineering College for the photos and for all you do to help unravel the mysteries of Michigan!

If you like stuff like this, there’s plenty more Michigan weirdness on Michigan in Pictures!

Sea Cave on Superior

Sea Cave on Lake Superior, photo by Craig

The Pictured Rocks National Lakeshore geology page says (in part) that:

During the Nipissing “high stand,” Chapel Rock and Miners Castle as well as many less prominent features (such as perched sea caves near Little Beaver Lake Campground) were carved into the Cambrian sandstone by wave action.

Quite the whittling job by Gitche Gumee!

View Craig’s photo bigger on his Facebook page and see more jaw-dropping Lake Superior pics on Craig’s Flickr.

Enjoy your weekend everyone!

Under Petit Portal

Under Petit Portal, photo by AllieKF

Here’s a shot from a place on my Michigan kayaking bucket list – Petit Portal (also known as Petit Arch and Arch Rock by some) and other cliff formations of the Pictured Rocks National Lakeshore. The Lakeshore’s Geologic Formations page begins:

The geologic formations of Pictured Rocks National Lakeshore are most spectacularly represented by the 50-200 ft. sandstone cliffs that extend for more than 15 miles along the shoreline. Sea caves, arches, blowholes, turrets, stone spires, and other features have been sculpted from these cliffs over the centuries by unceasing waves and weather.

The name “Pictured Rocks” comes from the streaks of mineral stain that decorate the cliffs. Stunning colors occur when groundwater oozes out of cracks and trickles down the rock face. Iron (red and orange), copper (blue and green), manganese (brown and black), and limonite (white) are among the most common color-producing minerals.

Geologic 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).

You can read on for more about each geologic era, and I think that that this report by Lakeshore Volunteer Geologist Robert Rose (pdf) has some graphics that really help to understand how the layers fit together.

View Allie’s photo background bigtacular and check out her simply awesome Pictured Rocks photos – it’s amazing how huge the formations look from the water.

Lots more Pictured Rocks National Lakeshore and more summer wallpaper on Michigan in Pictures!

North Bar Lake

North Bar Lake, photo by Sarah Hunt

Who’s ready for a break from snow & ice? The Sleeping Bear Dunes National Lakeshore page on the North Bar Lake Overlook says (in part):

The name describes how the lake formed: it is ponded behind a sand bar. At times, the sand bar builds up and separates North Bar Lake from Lake Michigan. At other times, a small connecting channel exists between the two lakes. North Bar Lake occupies part of a former bay on Lake Michigan. This ancient bay was flanked by headlands on both sides: Empire Bluffs on the south and Sleeping Bear Bluffs on the north. Shorelines have a natural tendency to become straighter with time. Wave action focuses on the headlands and wears them back, while shoreline currents carry sediment to the quiet bays and fill them in. Deeper parts of the bay are often left as lakes when sand fills in the shallower parts.

The same process that formed North Bar Lake also formed many of the other lakes in northern Michigan: Glen, Crystal, Elk and Torch Lakes, for example.

Here’s more about the geology of the Sleeping Bear and more about North Bar Lake, to which I’d add that the lake is a great place for skim boards because the channel between North Bar & Lake Michigan is only a few inches deep!

Sarah took this photo last summer. Click it to view background bigalicious and check out lots more of her incredible and adventurous photography at instagram.com/oni_one_.

PS: If you’re still not full-up on winter and ice, might I suggest this pic she took in this area of Sleeping Bear last week!

Layers of the Ledges

Ledges’ Layers, photo by daveumich

The Earth Science class for educators at Michigan Tech has an online textbook on Michigan Geography & Geology that’s pretty cool. The chapter on the Ledges at Grand Ledge includes At the Edge of an Ancient Ocean that talks about the rocks that make up The Ledges and begins:

The rocks at Grand Ledge are significant for several reasons. Grand Ledge is an “oasis” of bedrock in an “ocean” of glacial drift that blankets the Lower Peninsula, providing geologists a window into the distant past. The diverse set of sedimentary rocks contains a wealth of information on the plants and animals that dominated the Pennsylvanian Period, about 320 to 290 million years ago. The characteristics of the rocks allowed geologists to reconstruct the changing environment that marked the demise of a great inland ocean. The rocks have been quarried and hold economic value. Lastly, Grand Ledge is scenic and enjoyed by hikers, paddlers, and climbers.

Nearly all students of Michigan geology make a pilgrimage to Grand Ledge at some point in their careers. Good exposures of sedimentary rocks are rare in the Lower Peninsula. Not only are the rocks well exposed but they offer an opportunity to test your skills in identifying a variety of sandstones, some shale and limestone, and even 2 coal. The rocks are exposed in a few abandon quarries and in exposures along the Grand River. To get a good look at the rocks you will need drive between exposure north and south of the river. But don’t be discouraged; the distances are short.

As always in geology, the best place to start is at the base of the stratigraphic section, the oldest rocks. The lower part of the section contains shale, siltstone, and type of sandstone called greywacke. The shale is gray and so fine-grained that you cannot see the mud-sized particles that compose it. If you are brave, you might put a tiny piece in your mouth and push it around a bit. Shale feels smooth, almost creamy, a result of the mud. The shale is also soft and erodes to relatively gentle slopes. Shale is exposed at the base of the layers at the Face Brick Quarry. Think of the light-colored siltstone as a silty shale. You might rub the rock against your thumb and see if any small, visible grains come loose. Again, a taste test might be in order. Siltstone will leave a 3 gritty feel in your mouth. Siltstone is exposed at the base of the rock layers at the American Vitrified Quarry. The greywacke is a greenish-gray colored sandstone and the sand grains are visible to your unaided eye, no tasting required. With a hand lens you can see the rock is made of a mixture of sand sizes, what geologists call poor sorting, and a variety of sand compositions, including quartz, feldspar, mica, and fragments of pre-existing rocks. Greywacke is exposed just above the beach at the Face Brick Quarry.

Read on for more and visit Fitzgerald Park at Pure Michigan for more on this cool West Michigan park.

View Dave’s photo background bigalicious, see more in his Grand Ledge, Michigan slideshow and check out more photos from The Ledges on his Marvins’ Gardens blog!

More winter wallpaper on Michigan in Pictures.

Winter at Turnip Rock

“Turnip Rock” Pointe Aux Barques, Lake Huron, photo by Michigan Nut

Michigan’s Little Finger has been getting a lot of national media attention for the fantastic ice caves that have formed off the Leelanau Peninsula, but it’s a good time to check out the Thumb as well! Turnip Rock is on private property and reachable in the summer only by boat. In wintertime, however, walking on publicly owned Lake Huron becomes an option.

The Point Aux Barques – Turnip Rock geocache explains:

Everyone that received their grade school education in Michigan learned that glaciers pushed their way over Michigan several times. The result is glacial drift averaging 200 to 300 feet deep covering on top of the bedrock. The thickness of drift has measured over 1,000 feet in a few Michigan locations. Rarely can we see exposed bedrock that has been sculptured by non glacier forces. This is one of the locations in southern Michigan where the sandstone bedrock is exposed at the surface. The amount of shoreline that has exposed sandstone is about one mile, but a lot of beauty has been sculptured in the stone.

The locals call the main structure here “Turnip Rock”, because of it’s shape. Geologists call it a “Sea Stack”. A definition of a sea stack is an isolated pillar-like rocky island or mass near a cliff shore, detached from a headland by wave erosion assisted by weathering. Waves force air and small pieces of rock into small cracks, future opening them. The cracks then gradually get larger and turn into a small cave. When the cave wears through the headland, an arch forms. Further erosion causes the arch to collapse. This causes a pillar of hard rock standing away from the coast. Generally occurring in sedimentary rocks, sea stacks can occur in any rock type.

Here’s a map to Turnip Rock.

View John’s photo bigger and see more including nearby Point Aux Barques Lighthouse in his Lake Huron slideshow.

Pictured Blue: Miner’s Castle in the Pictured Rocks National Lakeshore

Pictured Blue, photo by Kiiraaan

View this jaw-dropping photo of Miner’s Castle bigger and see more in Kiran’s Landscape slideshow.

The Pictured Rocks National Lakeshore’s Geology Field Notes page has this barely comprehensible stuff to say about Miner’s Castle:

The Miners Castle Member is a soft, crumbly, quartz sandstone (with abundant garnet content) about 140 feet thick; its complete section is exposed in the Pictured Rocks Cliffs between Sand Point and Miners Castle. Sediments of this member are generally poorly sorted.

Capping the easily eroded Miners Castle Member of the Munising Formation in the western half of Pictured Rocks, is the resistant Early Ordovician (480-500 million years old) Au Train formation. The Au Train Formation is a light brown to white dolomitic sandstone that forms the resistant cap to the underlying softer sandstones. The numerous falls in Pictured Rocks National Lakeshore are the result of this caprock.

Read on for much more about the geology of Pictured Rocks. Erosion is indeed a factor with one of the most visible instances being April 13, 2006, when one of the pillars of Miner’s Castle collapsed.

You can see more of Pictured Rocks from Absolute Michigan and at the Pictured Rocks National Lakeshore web site.