America's Volcanic Past -
Ohio

Volcanic Highlights and Features:
[This list is just a sample of various Ohio volcanic features or events and is by no means inclusive.]

• Ohio
• Ohio Regions
• Ohio - Brief Geologic History
• Ohio's Volcanic Rocks
• Cleveland - Volcanic Building Stones
• Gold in Ohio
• Volcanic Ash Deposits

Ohio's Bentonite:³
The island arcs associated with continental collision were the sites of active volcanoes, as documented by the widespread beds of volcanic ash preserved in Ohio's Ordovician rocks. The ash layers, which to geologists are wonderful time lines because they were deposited instantaneously over a wide geographic area, have been altered to a special type of clay known as a bentonite. There are a number of bentonite beds in Ohio's Ordovician rocks, but two beds in Middle Ordovician rocks, the Deicke bentonite and the Millbrig bentonite, may represent some of the largest explosive volcanic eruptions in the geologic record. These beds have been traced from the Mississippi River eastward across North America and Europe and into Russia. It has been estimated that these eruptions generated about 5,000 times the volume of volcanic ash produced by the eruption of Mt. St. Helens in 1980.

Ohio's Granite and Rhyolite:²
Known Precambrian history of Ohio began with the emplacement of a vast, horizontal, 7-mile-thick layered sheet of granite (coarse-grained igneous rock formed at depth) and rhyolite (fine-grained volcanic equivalent of granite formed near the surface) beneath western Ohio and neighboring states to the west. This emplacement has been attributed to an uprising in the Earth's mantle, known as a superswell. Radioisotopic dating suggests that this event took place between about 1.4 and 1.5 billion years ago, forming what geologists call the Granite-Rhyolite Province. Continued continental doming of the superswell caused the crust beneath western Ohio, Indiana, and Kentucky to extend and split (rifting), resulting in major faulting and consequent downdropping to form a complex rift basin, now known as the East Continent Rift Basin. Molten basalt flowed upward as erosion began to fill the basin with clastic sediment, perhaps as much as 20,000 feet This extensive deposit is known as the Middle Run Formation. About 1 billion years ago, doming ceased and the rift became a failed or aborted rift. Rifting, volcanic activity, and basin filling also ceased.

Ohio's Volcanic Rocks are Beneath the Surface:²
Despite the immense span of time it represents, the Precambrian is the most poorly known of the geologic subdivisions in Ohio, in part because Precambrian rocks are nowhere exposed in the state. These primarily crystalline igneous and metamorphic rocks are deeply buried beneath younger Paleozoic sedimentary rocks at depths ranging from about 2,500 feet in western Ohio to more than 13,000 feet in southeastern Ohio. These rocks are collectively referred to by geologists as the "basement" because they form the foundation for the overlying Paleozoic rocks. Drillers commonly refer to the Precambrian rocks as the "granite," in reference to a common rock type found below the Paleozoic rocks. Ohio's Precambrian rocks appear to have formed in the late Precambrian, between about 1.5 billion and 800 million years ago. Older Precambrian rocks have not as yet been found in the state. Our knowledge of Precambrian rocks is derived from direct sampling of them through deep oil and gas wells or other boreholes or indirect geophysical means such as aeromagnetic and gravity maps, reflection seismic lines, or study of earthquake waves. Geophysical techniques are comparatively new, and it has only been since the early 1980's that geophysical data have become widely available.

Cleveland Public Library:⁷
The Cleveland Public Library Main Building, constructed in 1923-25, is a treasure trove for those who enjoy fine building stone. It is clad with Cherokee marble, a coarse-grained white marble with light-gray veining. The steps of the main entrance are made of North Jay granite quarried in Maine.

Key Tower:⁷
The 57-story Key Tower (formerly known as the Society Tower) was constructed in 1990-91. Most of the facing is Stony Creek granite, quarried in Connecticut. It is more than 245 million years old. Napoleon Red granite from Vanga, Sweden, is used for the lower two floors of the building.

Soldiers' and Sailors' Monument:⁷
The Soldiers' and Sailors' Monument was dedicated in 1894. Much of the monument, including the large ramps and pedestals, a portion of the column, and the trim on the building, is composed of light-colored Berea Sandstone. The outer steps and esplanade are made of red Medina stone. This sandstone also was used for paving in Cleveland at the turn of the century. The formal name of this rock is the Grimsby Sandstone. Most of the outer walls of the building and the tall central column at the top of the monument are composed of dark-gray Quincy Granite, quarried in Quincy, Massachusetts. The building is made of roughly dressed blocks; the column is polished. Each of the 10 blocks of Quincy Granite composing the column weighs about 14 tons. White marble said to have come from Italy, red and green slate, and red and white Medina stone are used in the interior of the monument. The outside of the monument was cleaned in 1966 and 1979. Low stone walls and outer stairways installed around the monument in 1989 are made of Charcoal Black granite and Cavallo buff sandstone. Charcoal Black is a 1.8-billion-year-old Precambrian granite and was quarried in St. Cloud, Minnesota.

Terminal Tower:⁷
The Terminal Tower is Cleveland's best know landmark. It is 52 stories and 708 feet high, measured from the concourse level. At the time it was built, in 1927-28, the Terminal Tower was the second tallest building in the United States. Much of the exterior of the Terminal Tower is clad with Salem Limestone, quarried in southern Indiana. A small amount of granite is used along the base of the exterior of the Terminal Tower.

Gold:⁵
Gold originates in primary vein deposits that were formed in association with silica-rich igneous rocks. These veins are rich in quartz and sulfide minerals such as pyrite and were deposited by hot, mineral-bearing (hydrothermal) solutions that ascended from deep within crystalline rocks. Upon weathering and erosion, the chemically inert gold is washed into streams and is mechanically concentrated by flowing waters to form secondary or placer deposits. All gold that has been found in Ohio is of the secondary or placer type. It is a long-accepted theory that the placer gold in the state originated in the igneous rocks of Canada (Canadian Shield) and was transported to Ohio during one or more episodes of Pleistocene glaciation. This theory has support because Ohio gold is always found in association with glacial deposits formed by meltwater from the glaciers. In addition, gold-bearing areas of Canada lie north of Ohio, more or less in line with the projected paths of the southward flow of various ice sheets. Gold can be found in small quantities throughout the glaciated two-thirds of Ohio. Most reported occurrences are in the zone of Illinoian and Wisconsinan end moraines--areas which commonly mark the farthest advance of these ice sheets. The highest concentrations of gold appear to be associated with Illinoian deposits. Almost all gold recovered is in the form of tiny, flattened flakes only a millimeter or so in diameter. Less common are pieces the size of a wheat grain, and rare are those the size of a pea. At most productive locations, several hours of panning will produce only a few flakes. No locality has been demonstrated to have concentrations sufficient for commercial exploitation, although many attempts were made in the 1800's and early 1900's to mine gold in the state. Most of these ventures were in Clermont County, near Batavia, in southwestern Ohio and in Richland County, near Bellville, in north-central Ohio. All of them were financial failures.

Ohio's Volcanic Ash Beds - Ordovician:³
During the Ordovician, Ohio was in southern tropical latitudes and dominated by warm, shallow seas. The Iapetus, or proto-Atlantic, Ocean, which formed in Late Precambrian and Cambrian time, began to close during the Ordovician. Collision between the North American and European continents during the Middle Ordovician formed a series of island arcs and mountains to the east of Ohio. This event, the Taconic Orogeny, which culminated in the Late Ordovician, is recorded in rocks stretching from Newfoundland to Alabama. Although Ordovician rocks in Ohio were not directly involved in the collisional event, they record these activities. The widespread Knox unconformity, an episode of emergence and erosion, was formed when the land surface bulged upward (known as a peripheral bulge), accompanying development of a foreland basin to the east at the edge of the orogenic belt. As the Taconic Orogeny reached its zenith in the Late Ordovician, sediments eroded from the rising mountains were carried westward, forming a complex delta system that discharged mud into the shallow seas that covered Ohio and adjacent areas. The development of this delta, the Queenston Delta, is recorded by the many beds of shale in Upper Ordovician rocks exposed in southwestern Ohio. The island arcs associated with continental collision were the sites of active volcanoes, as documented by the widespread beds of volcanic ash preserved in Ohio's Ordovician rocks. The ash layers, which to geologists are wonderful time lines because they were deposited instantaneously over a wide geographic area, have been altered to a special type of clay known as a bentonite. There are a number of bentonite beds in Ohio's Ordovician rocks, but two beds in Middle Ordovician rocks, the Deicke bentonite and the Millbrig bentonite, may represent some of the largest explosive volcanic eruptions in the geologic record. These beds have been traced from the Mississippi River eastward across North America and Europe and into Russia. It has been estimated that these eruptions generated about 5,000 times the volume of volcanic ash produced by the eruption of Mount St. Helens in 1980.

Ohio's Volcanic Ash Beds - Devonian:⁴
Devonian rocks crop out in two areas in Ohio. They are best exposed in a 20-mile-wide, north-south-oriented belt in the central part of the state. At its northern terminus, the outcrop belt narrows and swings eastward along the southern shore of Lake Erie. These rocks dip and thicken southeastward into the Appalachian Basin and are present in the subsurface of eastern Ohio. An arcuate belt of Devonian rocks is present in northwestern Ohio, although there are few exposures of these rocks because of a thick mantle of glacial sediment. These rocks dip northwestward into the Michigan Basin. A small area of Devonian rock crops out on the Bellefontaine Outlier in Logan and Champaign Counties. With one exception, all of the outcropping Devonian rocks in the state are of Middle or Late Devonian age. The exception is the Holland Quarry Shale, a Lower Devonian unit known only from a single, small, lens-shaped outcrop in a now-reclaimed quarry in Lucas County, west of Toledo.

By Middle Devonian time the warm, shallow seas once again spread across the state and limy sediment began to accumulate. These limestones were part of the "Cliff limestone," which also included Silurian limestone units, in the classification of John Locke in 1838 during his reconnaissance work for the first Geological Survey of Ohio. New York State Geologist James Hall in 1843 referred to the Middle Devonian limestones of Ohio as the "Coniferous Limestone," correlating them with carbonate rocks of that name in New York State. In 1859, William W. Mather, Ohio's first State Geologist (1837-1838), used the name Columbus Limestone in reference to Middle Devonian limestones encountered during drilling of an artesian well at the Ohio State House in Columbus. In 1878, Edward Orton, Ohio's third State Geologist (1878-1899), formally divided this limestone sequence into the Columbus Limestone and the overlying Delaware Limestone, subdivisions that are still used. Clinton R. Stauffer, in his 1909 Ohio Survey bulletin (No. 10), The Middle Devonian of Ohio, divided the Columbus and Delaware Limestones into a series of alphabetical zones. Later researchers have proposed other subdivisions. The Columbus Limestone reaches a thickness of a little more than 100 feet, whereas the Delaware averages about 35 feet in thickness. These units pinch out to the south but continue northward to Lake Erie. The Columbus Limestone is present on the Bellefontaine Outlier in Logan County, 30 miles west of the contiguous outcrop belt in central Ohio, but the Delaware Limestone appears to be absent. The Columbus is a fairly pure limestone, dolomitic in the lower part and very fossiliferous in the upper part. The Delaware Limestone, by contrast, is less pure, having a higher silt content that gives it a darker gray or bluish color; this unit has been referred to informally as the "Blue Limestone."

The change in lithology between the Columbus and the Delaware reflects large-scale events, namely the beginning of the Acadian Orogeny, as North America and Europe met once again on their periodic collisional course. The rise of the Acadian Mountains to the east is reflected not only by clastic sediment beginning to be washed into the Middle Devonian seas, but also by the evidence for significant volcanic activity associated with this mountain building. A series of ash beds, collectively called the Tioga Bentonite, are present in Middle Devonian rocks throughout much of the Appalachian Basin and into the Illinois and Michigan Basins. The Tioga volcanism is thought to have originated from a source in eastern Virginia. In the subsurface of eastern Ohio, the Columbus and Delaware Limestones are referred to as the Onondaga Limestone.

Excerpts from:
1) Ohio Department of Natural Resources, Division of Geological Survey, Ohio Geological Survey Website, 2002, A Brief Summary of the Geologic History of Ohio, GeoFacts No.23., Time assignments are based on Geological Society of America Decade of North American Geology 1983 Geologic Time Scale.
2) Michael C. Hansen, The Geology of Ohio -- The Precambrian, GeoFacts No. 13, Ohio Department of Natural Resources, Division of Geological Survey, Ohio Geological Survey Website, 2001
3) Michael C. Hansen, The Geology of Ohio -- The Ordovician, Ohio Geology, Fall 1997, Ohio Department of Natural Resources, Division of Geological Survey, Ohio Geological Survey Website, 2002
4) Michael C. Hansen, The Geology of Ohio -- The Devonian, Ohio Geology, 1999 No.1, Ohio Department of Natural Resources, Division of Geological Survey, Ohio Geological Survey Website, 2002
5) Ohio Department of Natural Resources, Division of Geological Survey, Ohio Geological Survey Website, 2002, Gold in Ohio, GeoFacts No.9.
6) USGS/NPS Geology in the Parks Website, 2001
7) Building Stone in the Vicinity of Public Square, Cleveland, Ohio, Ohio Department of Natural Resources, Ohio Geological Survey Website, 2002.
8) Ohio Historical Society Website, 2002

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