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Table of Contents:
Location and NameThe 1600sThe GriffenThe 1700sRevolutionary War and moving of the fortWar of 1812Rest of 1800sModern TimesGEOLOGIC FORMATION OF THE STRAITS
Mackinac Island is located at Latitude 45 degrees 51' 22" North and Longitude 84 degrees 41' 22"West.
Mackinac Island is about 3 miles east and west and 2 miles north and south, and rises about 150 feet above the surface of the straits. The height of the Fort Mackinac parade ground above Lake Huron is 133 feet. The circumference of Mackinac Island is 8 miles, less 20 feet. Its area is 3.47 square miles.
Below I quote a paragraph from a monograph on indian place names written by Ivan H. Walton. I am uncertain of the date of writing. The monograph was included in a compilation called "Readings in the Geograph of Michigan" Charles M. Davis, Professor of Geography, University of Michigan, 1964. He doesn't mention "the gathering place" at all, although that is the most common myth of what the name means.Some indian place names are still further disguised as a result of having been translated or transliterated first into French and from the French into English. One such name that so developed and now causes much confusion is the one applied to the well-known island just east of Point St. Ignace, and also to the Straits which separate the two Peninsulas. The Chippewa name of the island and generally of the surrounding area when the first French arrived seems to have been Mish-i-nim-auk-in-ong which the early French Missionaries generally expressed as Mich-i-li-macki-in-ac (auk) and in time reduced to Mackinac. This French modified Indian name is still applied to the island, to the Straits, and to the county bordering the north shore of the Straits. The village and city that developed later on the site of the old fort on the tip of the southern mainland adopted the English transliteration of the French word, and it became designated Mackinaw. The pronunciation of the last syllable for both spellings is "aw." The name has been interpreted in a number of ways, including "the giant turtle," "place of the giant fairies," and "place of the great uplifted bow" -- referring to Arch Rock on the island. The most convincing interpretation is that, like many other Indian place names, it is commemorative. The endings, "ong, ang, ing," and the French "ac" are locative, meaning "place of," so the original name quite probably meant "place of the Mishinimaki," an ancient tribe that inhabited the island before being exterminated by the indians.
The 1600s ^top
Before the French explored the Mackinac area in the 1600s, the Mackinac area was inhabited by the Ottawa and Chippewa (Ojibwa) and Huron clans.
1633 - 1673 French Jesuit priests arrived first at Sault Ste. Marie and then, in 1671, French Jesuit priests arrived at the Michilimackinac region where St. Ignace presently is located. (Some accounts are that Frenchmen were on Michilimackinac Island before 1626. Marquette founded the Michilimackinac missionary.
The French Jesuit fathers furnished yearly reports to Paris concerning French missionary activity in the Mackinac straits area.
The French established Fort Michilimackinac at a place which is now a part of St. Ignace.
1634 Jean Nicolet discovered the straits of Mackinac. The straits of Mackinac were considered only a part of the general Mackinac area.
1669 Father Jean Claude Allouey recorded the first known account of Mackinac Island by a European.
1670 Marquette, in his letter from Mackinac Island, wrote:
"We ourselves have also wintered here (Michilimackinac Island) in order to make the arrangements for establishing the Mission at St. Ignace."
1671 The Mission at St. Ignace de Michilimackinac was founded by Marquette.
1672 Joliet arrived at St. Ignace.
May, 1673 Pere Jacques Marquette and Joliet departed from Marquette's missionary station, located near where St. Ignace is now located, and proceeded into Lake Michigan, into the rivers of Wisconsin, down the Mississippi, and into western country. Marquette died on his return trip. His body reputedly was exhumed and re-buried at St. Ignace.
The Griffen ^top
1678 - 1679 The Griffen was built by LaSalle on the Niagara River, a few miles above the falls, in 1678 - 79. She was sixty feet long, weighed between forty-five and sixty tons, and had five cannons mounted below her main deck. Her two square sails were ornamented with the fleur-de-lis, her prow with the crest of the house of Louis de Buade, Comte Palluau de Frontenac, i.e., a griffin, the fabled animal having the body of a lion and the head and wings of an eagle.
The French vessel, The Griffen (Griffon), with LaSalle her commander and Hennepin the journalist on board, arrived at what is now St. Ignace. This was the first voyage ever made by Europeans on "these inland seas." The Griffen was anchored in a bay overlooked by two rocky bluffs, known in Native American tradition as He and She Rabbit.
Leaving the straits, The Griffen set out on Lake Michigan and sailed as far west and south as Green Bay. Here, LaSalle sent The Griffen back, loaded with furs and bound for Niagara. The vessel was lost, with all 5 hands on board --- in the northern part of Lake Michigan, it is thought by some, and in Lake Huron, it is thought by others. What is known is that The Griffen, her crew, and its cargo vanished without a trace. The loss of The Griffen was the first recorded loss on the Great Lakes of a commercial vessel and her crew. Since the loss of The Griffen, more than six thousand ships have been lost on the Great Lakes.
1694 Cadillac commanded Michilimackinac.
The 1700s ^top
With the exception of the brief abandonment by the French forces from about 1701 to 1714, this region of the straits was a seat of continuous military occupation from the last quarter of the 17th century down to 1895, when the United States abandoned the post. The French post commander who instigated the French abandonment in 1701 in favor of a new settlement at what is now Detroit, was Cadillac. When the French re-opened the Fort at the straits in 1714, the Fort was relocated on the south side of the straits, at a place which is now a part of Mackinaw City.
1721 Jesuit Father Francois-Xavier Charlevoix travelled from Detroit to Mackinac.
1759 After the British conquest of Canada in the Battle of Quebec on the Heights of Abraham in 1759, "all of the country around" came under the English flag.
1760 New France fell to the British.
1761 The first British garrisons occupied the Fort at the site at which Mackinaw City is now located.
July, 1763 Chippewa Chief Pontiac's 350 braves gained entrance to the Fort through the ruse of a ball game and massacred the entire garrison of 93 English soldiers.
Wawatum, a Chippewa indian, saved English trader Alexander Henry, took him to Mackinac Island, and hid him in Skull Cave on Mackinac Island.
1764 Following Pontiac's defeat, the British returned to Fort Michilimackinac.
1766 British Major Robert Rogers arrived at the Fort. He was a romantic hero of the French and Indian War. Major Roberts remained at Fort Michilimackinac for 15 months, until his arrest for treason and subsequent trial at Quebec.
The Revolutionary War and Moving the Fort ^top
1780 The British paid the Chippewas, the proprietors of Mackinac Island, 5000 pounds in exchange for their permission to the British constructing a fort on Mackinac Island.
Between 1779 and 1781 The British abandoned Fort Michilimackinac in order to construct a more defensible fort on Mackinac Island. On October 15, 1779, the war sloop Welcome left Mackinac Island, to take Major DePeyster to Detroit. On November 6, 1779, Major Sinclair arrived at Mackinac Island, to relieve Major DePeyster as commander. The fort on Mackinac Island actually was not completed until 1783.
February and March, 1780 The ice was firm, and the Catholic Church on the south shore was taken down and its logs were hauled over the ice and the Church was re-built on Mackinac Island.
Major Sinclair was succeeded as Fort commander by Captain Daniel Robertson (also pronounced Robinson), who was in command from 1782 - 1787. Captain Robertson was succeeded by Captain Scott, who in turn was followed by Captain Doyle, who remained in charge until delivery of the Fort to the United States in 1796.
1783 Following the Revolutionary War, the Treaty of Paris in 1783 ceded Mackinac Island to the colonies, but the British did not evacuate Fort Mackinac for St. Joseph Island until 13 years later, 1796.
1783 The Trinity Episcopal Church was organized on Mackinac Island.
1783 The Northwest Fur Company was formed, with the principal partners in Montreal and Quebec.
Every year, representatives of the Northwest Fur Company would journey to the Company's wilderness headquarters at Fort Williams, located on the North side of Lake Superior. The Northwest Fur Company competed with the Hudson's Bay Company.
On Mackinac Island was formed the Mackinaw Fur Company and, later, the Southwestern Fur Company, both under British control. John Jacob Astor of New York secured a controlling interest in both of those companies, and he merged those two companies into one company named the American Fur Company. The headquarters of the American Fur Company was at Mackinac Island, long before Chicago, Milwaukee, or St. Paul ever came into existence. The American Fur Company flourished for about 20 years, from 1814 - 1834.
1784 In 1784, John Marshall was a member of the Virginia Legislature. John Marshall expressed disappointment to his friend James Madison, then a member of the Continental Congress, that the Virginia Legislature failed to take action on the matter of debts owed to British creditors. John Marshall favored paying British debts in full because failure to do so, he told Monroe, "offers a pretext to the British to retain possession of the forts on the Great Lakes." It was Marshall's opinion that Virginia's refusal to pay those debts was a violation of the 1783 Treaty of Paris by which the British recognized American independence. (John Marshall later was appointed Chief Justice of the United States Supreme Court by President Samuel Adams, in 1801, and his tenure spanned the terms of five presidents: Jefferson, Madison, Monroe, John Quincy Adams, and Andrew Jackson. James Madison became our country's fourth president.)
1795 While the delivery of Mackinac Island and the post from the British to the United States was pending, U. S. General Wayne effected the Treaty of Greenville with the Native Americans, in 1795. By that Treaty, the Native Americans ceded to the United States a tract of land on which Fort Michilimackinac then stood. The United States paid to the Chippewas $20,000.00, and were to pay an additional $9,500.00 annually. $1,000.00 to the Wyandots, $1,000.00 to the Delawares, $1,000.00 to the Shawnees, $1,000.00 to the Miamis, $1,000.00 to the Ottawas, $1,000.00 to the Chippewas, $1,000.00 to the Pottawatimas, and $500.00 each to the Kickapoo, the Wea, the Eel River, the Piankeshaw and the Kaskaskia tribes. The
In addition, as a voluntary gift, the Chippewas also cededto the United States Bois Blanc, or White Wood, Island.
September 1, 1796 Lieutenant Andrew Foster impatiently signed his name to the descriptive inventory of Fort Mackinac's buildings and defensive works. Completing the inventory and lowering the Union Jack would be his final acts as commander of the fort. Major Henry Burbeck, newly arrived from Detroit, was equally anxious to complete the transfer. The American commander quickly studied Foster's inventory. Satisfied with its contents, Burbeck nodded to a nearby sergeant, who barked a series of commands that sent a squad of blue-coated soldiers to raise the Stars and Stripes over Fort Mackinac, and Mackinac Island finally became part of the United States. (Ref. Michigan History, July-August, 1996.)
1796 The British troops were withdrawn to St. Joseph Island, and Mackinac Island became occupied by United States troops.
The War of 1812 ^top
June 12, 1812 President Madison declared war, and thus began the War of 1812.
June 21, 1812 British General Brock of the Michigan Command found out about President Madison's June 12, 1812 declaration of war.
June 26, 1812 General Hull, the United States' Michigan Commander, found out about President Madison's June 12, 1812 declaration of war.
July 15, 1812 British Captain Roberts, on St. Joseph Island, learned of President Madison's June 12, 1812 declaration of war.
July 16, 1812 British General Brock ordered Captain Roberts to attack the Fort on Mackinac Island. On the morning of July 16, 1812, Captain Roberts embarked for Michilimackinac, on the Northwestern Fur Company's ship, Caledonia, with two iron six-pounders, ten batteaux (flat-bottom boats), and seventy canoes.
On July 16, 1812, Lieutenant Hanks dispatched Captain Dousman to St. Joseph Island, to watch the movements of the Indians. Captain Dousman left about sunset, and met the British forces within 10 or 15 miles of Mackinac Island. The British made Captain Dousman a prisoner and put him on his parole of honor. He was landed at Mackinac Island at daybreak, with instructions not to tell anyone what he knew. He was instructed by the British to take the inhabitants of the Village, indiscriminately, to a place on the west side of the Island. British Captain Roberts' force arrived at Mackinac Island at 3:00 a.m. on July 17, 1812. A Doctor Day on the Island was one of the inhabitants told to go to the west side of the Island, and Doctor Day reported to Lieutenant Hanks that the inhabitants were fleeing for refuge to the British. Lieutenant Hanks immediately prepared for action, but at about 9:00 o'clock in the morning of July 17, 1812, he discovered that the British were in possession of the heights and that one piece of British artillery was directed to the most defenseless part of the Fort. At 11:30 o'clock in the morning, the British sent in a flag of truce, which was the first intimation to Lieutenant Hanks of Madison's declaration of war.
July 17, 1812 The 57 United States officers and enlisted men at the Fort surrendered. After this victory, the British constructed Fort George (now known as Fort Holmes) about a half-mile back of the Fort. Captain Roberts' force consisted of 42 regulars and 4 officers, 260 Canadians, 572 Chippewas and Ottawas, 56 Sioux, 48 Winnebagoes, and 39 Menomonies.
September, 1813 British Captain Roberts was relieved of his command in September, 1813, and Captain Bullock was appointed in his place. Colonel McDouall (also known as McDonall) assumed command in the Spring of 1814.
April, 1814 A United States expedition was proposed to capture Michilimackinac and destroy certain British vessels.
On June 2, 1814, orders were issued, and a fleet of vessels was fitted out consisting of the United States sloops of war Niagara and Lawrence, each having twenty guns, and the smaller schooners Tigress, Detroit, Caledonia, Scorpion, and others. Captain Sinclair was the commodore on board, with a land force of 750 officers and men, under the command of Colonel Croghan.
On July 3, 1814, the expedition sailed and entered Lake Huron on July 12, 1814. It was decided to have part of the fleet cruise about Mackinac Island, and the rest of the fleet attack St. Joseph's Island before attacking Michilimackinac.
On July 20, 1814, Colonel Croghan attacked the British forces on St. Joseph's Island, and burned the fort there, but left the town and the Northwest Fur Company's warehouses intact. Colonel Croghan's forces captured that company's schooner, Mink, bound from Mackinac Island to Sault Ste. Marie with flour. From parties on the Mink, Colonel Croghan learned that the flour was to be transported to Fort Williams, by the Northwest Fur Company's schooner Perseverance, a new schooner of upwards of 100 tons. United States Lieutenant Turner, with a naval party, was dispatched to capture the Perseverance, and, if possible, to get her below St. Mary's Falls.
Lieutenant Turner and his naval party and Major Holmes in charge of the land forces proceeded up the St. Mary's River, toward Lake Superior, in launches. They rowed night and day, but having a distance to go of some 60 miles, against a strong current, the British at St. Mary's learned of Turner's approach two hours before Turner arrived, from indians who could travel faster in their light canoes. Turner saw the Indians and chased them up the St. Mary's River, and killed some of them, and captured some of them, but others escaped to spread word to the British at St. Mary's of Turner's impending attack. The British attempted to scuttle the Perseverance by burning her. Major Holmes' forces subdued Fort Williams and Turner's forces extinguished the flames on the Perseverance and prepared for sailing her down the St. Mary's Falls. On July 26, 1814, Turner's forces tried to get the Perseverance down the St. Mary's River, but they could not. Turner reported that the fall of the St. Mary's River was 45 feet in three-quarters of a mile, the channel was rocky, and Turner reported the current to be from 20 to 30 knots. At one place in the River, Turner reported a perpendicular leap of ten feet between three rocks, where the Perseverance bilged. Turner's forces burned her.
After Turner and Holmes returned from St. Mary's Falls, with the launches, to St. Joseph's Island, the squadron sailed for Michilimackinac, arriving on July 26, 1814. British Lieutenant-Colonel Robert McDouall's forces on Mackinac Island saw the squadron off Bois Blanc Island, and had time to place his cannon and to rally Canadian and Indian allies to defend against the impending attack.
The United States fleet anchored at the foot of Round Island, but at once it had to move closer to Bois Blanc Island to avoid the range of the British cannon. Colonel Croghan then sent a force in launches to Round Island, to reconnoiter, with the intent to establishing a battery on the water front opposite Fort Mackinac. The United States force landed on Round Island, located a site for the battery, and then proceeded leisurely to walk back through the woods to its launches, eating raspberries as it proceeded. The British sent over to Round Island a large party of Indians in 200 - 300 canoes and several flat-bottom boats (batteaux). The British chased the stragglers, and captured one, a Frenchman. Captain Sinclair directed a small, one-gun vessel, to sail up through the Round Island channel to head off the Indians and retake the prisoner. Indians were swarming on the Round Island beach, and whenever the vessel neared the shore she was fired upon. The Indians kept their prisoner.
As the Indians were returning from Round Island to Mackinac Island, the Lawrence fired a shot at them, without effect. When the Indians landed at Mackinac Island with their prisoner, the British removed the prisoner to the Fort.
On July 21, 1814, the Lawrence, in fog, drifted to within range of the British west-end battery on Mackinac Island. The Lawrence returned one shot, but found she could not elevate her guns sufficiently to strike the Fort. For the next several days, unfavorable weather prevented operations.
Croghan and Sinclair decided to make a landing in the northwest bay of Mackinac Island, where Roberts had debarked two years before, and make a lodgment from which the United States could annoy and starve out the British.
August 4, 1814 The United States attacked and invaded Mackinac Island in 1814. The attack was unsuccessful. 15 U.S. soldiers were killed and 50 U.S. soldiers were wounded. U.S. Major Holmes, second-in-command to Colonel Croghan, was one of the 15 killed. Holmes was a Virginian and had been a friend of Thomas Jefferson. The battle was fought on Michael Dousman's farm, in a field, westward of the road leading from the Fort to British Landing.
1814 The United States attempted, unsuccessfully, to blockade the British on Mackinac Island with the ships Tigress and Scorpion. 150 British sailors and soldiers and 250 Indians captured first, the Tigress, and then, the Scorpion.
Although the United States surrendered Fort Mackinac to the British during the War of 1812, the U. S. won it back through the Treaty of Ghent in 1814.
February 18, 1815 The Treaty of Ghent was proclaimed, following which Mackinac Island was returned to the United States, and the United States flag again flew over Mackinac Island. The name of Fort George was changed to Fort Holmes. The United States has held Mackinac Island ever since. The British forces turned over to the United States the Fort at Mackinac Island on February 15, 1815. The British retired 40 miles away, to Drummond Island. U. S. Colonel Butler took command. Colonel Butler was succeeded by Major Morgan, who was succeeded by Colonel Chambers.
The Rest of the Nineteenth Century ^top
1815 - 1820 Lt. John S. Pierce, a brother of President Pierce, served as an officer at Fort Michilimackinac.
1820 Henry Schoolcraft visited Mackinac Island for the first time.
1822 John G. Bigsby, a British Army surgeon and geologist, visited Mackinac Island in 1822 while serving as a secretary to the British Boundary Commission that ran the line between Fort Williams and Lake of the Woods. The Commission found, much to the chagrin of the British soldiers who had relocated their fort on Drummond Island following the War of 1812, that their island lay on the American side. In 1828, the British turned Drummond Island over to the United States.
In 1822 also Alexis St. Martin was accidentally wounded while handling a shotgun in the retail store of the American Fur Company. St. Martin was an employee of the American Fur Company. Dr. William Beaumont was the Post Surgeon.
1829 - 1830 The Presbyterian Old Mission Church was constructed on Mackinac Island. Henry Schoolcraft was one of the Church's ruling elders. There were no Protestant clergy on Mackinac Island, and Schoolcraft conducted the service. A sergeant at the Fort conducted the choir. The appearance of the congregation was striking: officers and privates were mingled together with well-dressed ladies and gentlemen of the village, along with those of simpler attire, along with Native Americans.
1833 - 1841 Henry Rowe Schoolcraft resided in the "Old Agency House," which was constructed by the U. S. government for the use by its Agent in Indian Affairs.
1840 Lieutenant Pemberton served at the Fort. 23 years later, he was commander at Vicksburg, with Grant's besieging army around him.
1846 William Cullen Bryant, America's earliest poet of distinction, stopped twice at Mackinac Island in 1846.
Civil War The United States withdrew from the Fort all troops, except one non-commissioned officer (known as "Old Serjeant").
Confederate prisoners were lodged at the Fort, under the eye of Michigan volunteer troops.
Modern Times ^top
After the Civil War About 50 - 60 men served at the Fort until 1895, when the United States abandoned the Fort and gave it and 1100 acres to the State of Michigan.
1900 The Union Congregational Church was organized on Mackinac Island.
1943 During World War II the Fort's large collection of historic cannons was taken down the hill and melted down. The brass, bronze, and iron were used to relieve the metal shortage and helped the Allies win the war..
1955 Replacement (replica) cannons were built near Brighton, Michigan and returned to the Fort.
1957 Mackinac Bridge is built
GEOLOGIC FORMATION OF THE STRAITS ^top
Chet Finster is a good friend to the members of our office. His friendship with us has continued for more than 40 years. Before his retirement, Chet used his Michigan State University engineering degree, and his native talent as an engineer and geologist, for the State of Michigan Highway Department. Chet played no small part in the construction of the Big Mac Bridge. When engineering survey teams ventured onto the Straits ice for the purpose of determining the location of the proposed Mackinac Bridge, Chet was there. What follows is Chet's description of the geology of the Mackinac Straits. When Chet was at the top of his game, he devoted many hours to teaching Michigan geology. He handed out books of his work, without charge. Because of illness, Chet cannot do that now. We believe that we can best express our thanks to Chet by continuing the distribution of his work. Thank you, Chet.
Creation of The Straits Of Mackinacor
The Geology Of The Straits Of Mackinac
- by Chester Finster
To do justice to this little talk we have to first study the historical background of the Straits of Mackinac, in other words its geology.
Pre-Cambrian or Archeozoic Era
There are actually several phases in its development. First it had to have a footing or a foundation. This occurred during the solidification of the semiviscous, or plastic igneous (fire rock) magma which formed the earth's crust and is mainly granite rock. Granite has three ingredients or minerals, quartz, feldspar, and mica. This period in its history is called the pre-cambrian or archeozoic era.
This crustal skin is between 40 and 50 miles in thickness for the continents and 4 to 10 miles in thickness for the oceans. Considering the radius of this earth to be 4,000 miles then the thickness of the crustal skin is only 1% of the radius or in terms of the pages of-a book it would be one sheet out of 100 pages. That's a pretty thin tectonic plate.
However, the oceanic tectonic plates are still thinner: the relationship of 10 miles in thickness to a radius of 4,000 miles is 0.25%.
Referring back to the continental plates: the cooling of the internal fluid magma beneath the tectonic plates results in its shrinking a little bit in volume. this shrinkage created some 17 shallow basins across the united states and some 20 domes. One of these basins is the Michigan basin.
The Michigan Basin - Paleozoic Era
The Michigan basin is approximately 500 miles in diameter and 3 miles in depth. it extends from west of the west shore of lake Michigan easterly to the east shore of Georgian Bay and from the south end of Georgian Bay east to Kingston, Ontario. The northern boundary is the south shore of Lake Superior and the southern boundary is in the neighborhood of Cincinnati, Ohio. Its greatest depth is in the Bay City-Saginaw area.
Into this basin poured six major seas: listing them in order from the earliest to the latest we have: cambrian, ordovician, silurian, devonian, mississippian and pennsylvanian. There were some sixty sub-seas in total or about ten per major sea.
Some of these seas brought in sediments of silt, sand, gravel, and clay from the erosion of the granite rock of the Canadian Shield to the north of us.
The first shell of the Michigan basin is the cambrian. Rivers and streams brought into the basin silt, sand, gravel, and clays from the erosion of the granite rocks from off the Canadian shield to the north of us. These sediments were the first to begin to fill the basin. They formed sedimentary rocks of sand stones such as pictured rocks that can be seen on the south shore of Lake Superior northeast of Munising. Shale was also deposited as a sedimentary rock.
Other marine deposits were brought into the basin by the ocean such as calcium chloride, calcium carbonate (limestone), calcium-magnesium carbonate (dolomite), sodium chloride (rock salt), potassium carbonate (potash) and calcium sulfate (gypsum, alabaster), and many of the salts of bromide, iodine, fluoride and the other halogens.
The fossils of marine life (skeletons),when pulverized and under pressure form limestone. Their fatty bodies form the mineral oils in the formations. Muck naturally compressed to 1/20 of its original state forms coal measures.
It must be remembered that each sub-sea brought into the basin a type of sediment or marine life which produced sediment when it ceased to exist. These individual layers or shells were compressed into sedimentary rocks by new sediments deposited upon them. The fatty parts of their bodies form the pools of crude oil found in sedimentary rock. Eventually the entire basin was filled up with a multitude of nested-shells of layers of sedimentary rocks.
You probably wondered why we went to all the effort to explain the silting in the Michigan basin. It was principally for one reason:
Salina Evaporates & Brecciated Bed Rocks
Certain specific sedimentary beds of rocks were formed in the silurian seas or silurian rock formations which had a great influence upon the creation of the Straits.
These rock formations were: (1) pointes aux chenes (point of land with oaks) formation which at one time included shale, rock salt, and gypsum of the salina group of the silurian period seas and (2) the Mackinac breccia formation which includes the dolomite of the St. Ignace formation of the silurain period and the bois blanc formation (possibly white birches) also of the silurian period.
The salina group: this formation is mined throughout the state for rock salt at 1,000' depth in a 400' drift in the Detroit area; secured from wells through a dissolving method in 1,000' drifts in both the Ludington and Manistee areas. It lies in a bed 1,700' thick under Midland (Dow Company) and in a bed 1,150' thick in the Alpena area.
The above two formations caused a great amount of concern in-the design of the footings of the Big Mackinac Straits Bridge: (1) the possibility that there remained beds of rock salt and gypsum or that there were voids or hollow caves in the rock strata where such mineral beds had been leached out and, (2) the brecciated (brick-like) formations of limestone, dolomite, and shale.
These two factors ultimately required some 53 diamond drill core borings to determine if there were any hollow caves and to secure rock cores upon which load bearing tests were made in the laboratory.
Brief Summary to Date
Now that we have the stage all set let's continue. So far we have created the earth's crust called the lithosphere (rock-sphere), the Michigan basin, and have filled her up with some sixty nested, stratified, sedimentary beds of rocks that have completely filled the basin.
We have pin-pointed two types of rocks that have contributed to the construction of the Straits: the salina evaporate series (rock salt, gypsum, etc.) and the limestone, dolomites, and shales which were originally solid stratifications and were later violently shaken and broken up into various sized blocks (brecciated) and then recemented into weaker rocks.
Formation of The Original Straits of Mackinac
We will now go on with the story or geological history and describe the formation of the original Straits of Mackinac which was some 3 miles in width and 100 feet in depth in the middle of the span.
Formation of Basins for Lakes Michigan and Huron; Pleistocene Epoch
First of all we will describe the formation of Lake Michigan, 924' deep, and lake Huron, 750' deep basins or troughs.
The surface of these existing lakes was originally the surface of the outcrop of the edge of the limestone formations of the devonian period. This as you previously noted was one of the major nested saucers or bowls of the Michigan basin.
These two surfaces (Lakes Michigan and Huron) were principally limestone which was still soft marl when the two lobes of glacial ice plowed into and down them, bull-dozing them out into shallow troughs of 924' and 750' depths.
The ice lobes 1.5 to 2.0 miles in height had a bearing value of 225 to 250 tons/sq. ft., which not only could depress the earth's crust but could bull-doze and scoop up any soft material in its path and carry it as drift down south and deposit it as the ice sheet melted and retreated northerly.
Please note that there were four major glaciers: from the earliest to the most recent they were: Nebrascan, Kansan, Illinoin, and Wisconsin. This was called the Pleistocene epoch. All of these glaciers excavated out the troughs for the future Lakes Michigan and Huron leaving these basins much as they are today.
Interglacial Stage of Pleistocene Epoch
During interglacial stages of the Pleistocene epoch the Lake Michigan basin filled with water to its fullest capacity. as there was no Chicago drainageway to the south the water began to seep through the salina salt formation and into the Huron basin.
Sub-Terranean River
This continued for a long time and eventually the seepage dissolved away enough rock salt to form the underground river channel between the two lakes.
This subsequently became about 3 miles in width and 200' more or less in height at its center.
Collapse of Ceiling of Sub-Terranean River
Now note that limestone and dolomite have an ultimate crushing strength (compression) of 5 tons per square inch whereas its tensile strength is only 10 pounds per square inch.
Getting back to the design of beams and arches please note that there was no steel in the arched roof of the underground river channel to increase the factor of tension and the tensile strength of the limestone was too low to be of any value, therefore the roof or ceiling of the channel collapsed and dropped to the floor of the channel.
Mackinac Breccia
The limestone, dolomite, and shale ceiling fell as one unit and cracked or broke up into an infinitesimal number of blocks of all sizes from smaller than the size of bricks to blocks of several hundred feet in dimension.
Over a great length of time the limestone and dolomite blocks recemented themselves together into a weak stratification of rocks and which is known as the Mackinac breccia.
The original flat plane (Mackinac Straits) now became a 3 mile wide river valley with a depth of 100' at its center. This became the second drainage outlet for Lake Michigan into Lake Huron.
Mackinac River Gorge; Continental Depression & Up-Lift
The next step in the geological history of the Straits of Mackinac is the development of the deep Mackinac river gorge which is 3,800' wide, 250' deep and 50 miles long between the two lakes.
100' deep original channel plus 250' deep Mackinac river gorge = 350' total depth.
This formation of the gorge again involves the Atlantic Ocean and the last glacier, the Wisconsin, and what is termed continental depression and continental up-lift.
As previously stated the 1.5 mile to 2.0 mile in height of the ice sheet exerted a bearing stress of between 225 and 250 tons pressure per square foot upon the surface over which it travels or flows.
During the glacier's drive toward the Ohio and Missouri rivers (terminal rivers for the Kansan and Nebraska glaciers) it first flowed into the Lake Superior syncline. In leaving the syncline it divided into three ice lobes one of which came down the center of the State while the other two ice lobes chose to follow down the troughs of Lakes Michigan and Huron.
These last two ice lobes after filling their troughs over-flowed their banks and moved laterally until they joined up with the lobe moving down the center of the lower peninsula. The three then moved as one huge full ice sheet of ice southerly in Michigan.
Continental Depression & Post Glacial Lake Algonquin Hinge Line
The ice sheet of glacier (because of its tremendous weight) depressed the upper half of the lower peninsula and the upper peninsula like a trap door from what is termed a hinge line.
This particular hinge line lies between Arcadia (just south of Frankfort) and Forestville (north of Port Huron). Note: this is but one of several hinge lines across the State.
This specific hinge line is called the Algonquin hinge line and refers to shore lines of post glacial Lake Algonquin which occurred after the Wisconsin ice sheet retreated north from Michigan and southern Canada.
Lake Algonquin was a large lake which included all three lakes: Michigan, Huron, and Superior confluent. Its shore line was 25 feet (as it exists today) higher than lake Michigan from Acadia south to Chicago and north to Two Rivers, Wisconsin, and 25 feet higher than Lake Huron from Forestville south to Port Huron and north to Goderich, Ontario.
North of the Hinge Line the Shore Lines of Lake Algonquin Rise Rapidly and Dramatically as Noted Below:
Arcadia -------------------------------------------------------- 605' A.T. (Atlantic Table)
Frankfort ------------------------------------------------------ 609'
Suttons Bay -------------------------------------------------- 654'
Northport ------------------------------------------------------674'
Charlevoix -----------------------------------------------------690'
Petoskey -------------------------------------------------------709'
Cross Village ---------------------------------------------------746'
Mackinaw City -------------------------------------------------804'
Wetmore (Munising) ----------------------------------------960' (storm beach)
Sault Ste. Marie, Ontario -------------------------------1,015'
In other words the depression of the trap door at Soo, Ontario was at one time 410'. According to geologist Stanard G. Bergquist, the uplift is continuing at the rate of 1' per 100 years per 100 miles north of the hinge line.
The Wisconsin glacial ice depressed the area east of Michigan to the Atlantic coast in a similar manner. This included the North Bay, Ontario glacial drainageway and Georgian Bay, whose land was depressed around 400'.
The North Bay glacial drainageway began at the north end of Georgian Bay with the French River, it then ran easterly to Lake Nipissing and the city of North Bay at its east end; thence easterly through Trout Lake; thence easterly through the Mattawa River valley, and through Lake Talon to the city of Mattawa where it entered the Ottawa River valley; and thence ran easterly to the St. Lawrence River and on into the Atlantic Ocean.
Retreat of Wisconsin Ice Sheet From Michigan
The next epoch in this historical drama of the development of the Straits of Mackinac was the retreat of the ice from the Michigan area.
This permitted the formation of post-glacial-Lake Algonquin and caused its shore lines to become established upon the undepressed area of the state of Michigan south of the hinge line and upon the depressed area north of the hinge line.
Continental Up-Lift of Michigan; Areas Unaffected - Green Bay, North Bay & Easterly
Almost immediately after establishing of the shore line of Lake Algonquin, continental up-lift occurred in the Michigan area and the area which was depressed was uplifted considerably.
However, the eastern half of Lake Huron, Georgian Bay and the North Bay glacial drainageway remained depressed about 400' and had an elevation of less than 200' above the Atlantic Ocean.
Straits of Mackinac Dam or Weir
This condition allowed or forced the water in Lake Huron to drain out through Georgian Bay, the Trent glacial drainageway and the North Bay glacial drainageway and into the Atlantic Ocean.
This lowered the water table of Lake Huron to 180' A.T. (Atlantic Table). Now we have two great lakes with very great differences in water tables: Lake Michigan (580' A.T.) and Lake Huron (180' A.T.).
We also have the Straits of Mackinac between them with a natural waterway 100' deep. This leaves a real difference of only 300' between the two lakes if the water table of Lake Michigan were to be lowered to the sill of the Straits.
The Straits of Mackinac now becomes a dam or weir with a 300' head of water plus an additional 100' of free head.
Rapid Erosion of Straits of Mackinac to Form Mackinac River Gorge
Water from Lake Michigan now began to roar through the Straits. It began to cut down a river channel like a gorge 3,800' wide and 50 miles long through the weakly cemented Mackinac shales, and dolomites, and limestone (breccia). Eventually the channel was cut down 250' with almost shear river walls.
Lakes Chippewa & Stanley (Formerly Lakes Michigan & Huron)
This now lowered the water table of Lake Michigan 350' to an elevation of 230' A.T. The Lake was now considerably smaller and was called Lake Chippewa.
Lake Huron with an elevation of 180' A.T. is also considerably smaller and called Lake Stanley.
The erosion of the 50 mile long by 250' deep by 3,800' wide gorge took place in a very short interval of time. Had the rock been solid, and not brecciated it would have taken several million years to do the same job.
Foundation Problem for "Big Mac"
Eventually the areas east of Michigan raised through continental up-lift and returned to their normal levels. Lakes Michigan and Huron again established elevations of 580' A.T. And then along came the bridge builders. They found it was not as simple as they had earlier believed. The 3,800' gorge controlled the simple span of the suspension bridge. Had the suspension bridge been shorter, the 116' diameter caisson footings for the cable suspension supporting towers would have had to be lengthened between 250' and 300', which would have doubled the one hundred million dollar cost of the bridge.
Chester H. Finster Reg. Prof. Eng. No. 3602 (Mich)
Mark E. Smathers, P.C.
Cadillac, Michigan
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