The St. Francois Mountains in southeast

Missouri Missouri is a state in the Midwestern region of the United States. Ranking 21st in land area, it is bordered by eight states (tied for the most with Tennessee): Iowa to the north, Illinois, Kentucky and Tennessee to the east, Arkansas t ...

are a

mountain range A mountain range or hill range is a series of mountains or hills arranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form, structure, and alignment that have arise ...

of Precambrian

igneous Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or ...

mountains rising over the

Ozark Plateau The Ozarks, also known as the Ozark Mountains, Ozark Highlands or Ozark Plateau, is a physiographic region in the U.S. states of Missouri, Arkansas, Oklahoma and the extreme southeastern corner of Kansas. The Ozarks cover a significant porti ...

. This range is one of the oldest exposures of igneous

rock Rock most often refers to: * Rock (geology), a naturally occurring solid aggregate of minerals or mineraloids * Rock music, a genre of popular music Rock or Rocks may also refer to: Places United Kingdom * Rock, Caerphilly, a location in Wales ...

in North America. The name of the range is spelled out as Saint Francois Mountains in official

GNIS The Geographic Names Information System (GNIS) is a database of name and locative information about more than two million physical and cultural features throughout the United States and its territories, Antarctica, and the associated states of ...

sources, but it is sometimes misspelled in use as St. Francis Mountains to match the

anglicized Anglicisation is the process by which a place or person becomes influenced by English culture or British culture, or a process of cultural and/or linguistic change in which something non-English becomes English. It can also refer to the influenc ...

pronunciation of both the range and St. Francois County.

Name

The name of the range derives from the St. Francis River, which originates in the St. Francois Mountains. The origin of the river's name, which also was originally spelled "François" in the French manner, is unclear. The area, as part of the

Louisiana Louisiana , group=pronunciation (French: ''La Louisiane'') is a state in the Deep South and South Central regions of the United States. It is the 20th-smallest by area and the 25th most populous of the 50 U.S. states. Louisiana is borde ...

district of

New France New France (french: Nouvelle-France) was the area colonized by France in North America, beginning with the exploration of the Gulf of Saint Lawrence by Jacques Cartier in 1534 and ending with the cession of New France to Great Britain and Spa ...

, is near some of the earliest French settlements in Missouri, where many French place names survive. Some sources conjecture that the name honors

St. Francis of Assisi Giovanni di Pietro di Bernardone, better known as Saint Francis of Assisi ( it, Francesco d'Assisi; – 3 October 1226), was a mystic Italian Catholic friar, founder of the Franciscans, and one of the most venerated figures in Christianit ...

(1181/1182–1226), the patron saint of the Franciscan order, but none of the region's early explorers were Franciscans.St. Francois County, Missouri Place Names
, Western Historical Manuscript Collection Others propose that

Jacques Marquette Jacques Marquette S.J. (June 1, 1637 – May 18, 1675), sometimes known as Père Marquette or James Marquette, was a French Jesuit missionary who founded Michigan's first European settlement, Sault Sainte Marie, and later founded Saint Ign ...

, a French Jesuit, named the river when he explored its mouth in present-day

Arkansas Arkansas ( ) is a landlocked state in the South Central United States. It is bordered by Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, and Texas and Oklahoma to the west. Its name is from the O ...

in 1673. Before his voyage down the

Mississippi River The Mississippi River is the second-longest river and chief river of the second-largest drainage system in North America, second only to the Hudson Bay drainage system. From its traditional source of Lake Itasca in northern Minnesota, it fl ...

, Marquette had spent some time at the mission of St. François Xavier, named for the Jesuit missionary

Francis Xavier Francis Xavier (born Francisco de Jasso y Azpilicueta; Latin: ''Franciscus Xaverius''; Basque: ''Frantzisko Xabierkoa''; French: ''François Xavier''; Spanish: ''Francisco Javier''; Portuguese: ''Francisco Xavier''; 7 April 15063 December ...

(1506–1552). The spelling of the river's name shifted from "Francois" to "Francis" in the early 20th century.

Geology

The St. Francois Mountains were formed by

volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates a ...

and intrusive activity 1.485 billion (1.485 x 10⁹) years ago.Denison, Rodger E., et al., ''Geology and Geochemistry of the Precambrian Rocks in the Central Interior Region of the United States'', Geological Survey Professional Paper 1241-C, 1984 By comparison, the

Appalachians The Appalachian Mountains, often called the Appalachians, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They ...

started forming about 460 million years ago, and the

Rockies The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...

a mere 140 million years ago. When the Appalachians started forming, the St. Francois range was already twice as old as the Appalachians are today. The intrusive rocks of the area are composed of three types: subvolcanic

massif In geology, a massif ( or ) is a section of a planet's crust that is demarcated by faults or flexures. In the movement of the crust, a massif tends to retain its internal structure while being displaced as a whole. The term also refers to a ...

s, ring intrusions and central plutons.Sims, P. K., Eva B. Kisvarsanyi and G. B. Morey, 1987, ''Geology and Metallogeny of Archean and Proterozoic Basement Terranes in the Northern Midcontinent, U.S.A.,'' USGS Bulletin 1819 The subvolcanic intrusives are similar in geochemistry to the associated rhyolite volcanics, which they intrude into. They are

granite Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies under ...

with granophyric

quartz Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical ...

perthitic Perthite is used to describe an intergrowth of two feldspars: a host grain of potassium-rich alkali feldspar (near K-feldspar, KAlSi3O8, in composition) includes exsolved lamellae or irregular intergrowths of sodic alkali feldspar (near albite, Na ...

potassium feldspar Potassium feldspar refers to a number of minerals in the feldspar group, and containing potassium: *Orthoclase ( endmember formula K Al Si3 O8), an important tectosilicate mineral that forms igneous rock *Microcline, chemically the same as orthocla ...

, biotite and

magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With th ...

. They are intrusive into the rhyolites with development of fine grained granophyre at the contact. At depth they exhibit a coarse-grained rapakivi texture. The subvolcanic granites are the most widespread igneous rocks and were thought to have been covered with extensive volcanics that have been removed by erosion. The ring intrusives are high silica bodies which were intruded along ring faults associated with

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...

collapse. Rock types include

trachyandesite Trachyandesite is an extrusive igneous rock with a composition between trachyte and andesite. It has little or no free quartz, but is dominated by sodic plagioclase and alkali feldspar. It is formed from the cooling of lava enriched in alka ...

trachyte Trachyte () is an extrusive igneous rock composed mostly of alkali feldspar. It is usually light-colored and aphanitic (fine-grained), with minor amounts of mafic minerals, and is formed by the rapid cooling of lava enriched with silica and al ...

, syenite and amphibole - biotite granite. They are commonly porphyritic. The central plutons are highly evolved two mica (contain both biotite and

muscovite Muscovite (also known as common mica, isinglass, or potash mica) is a hydrated phyllosilicate mineral of aluminium and potassium with formula K Al2(Al Si3 O10)( F,O H)2, or ( KF)2( Al2O3)3( SiO2)6( H2O). It has a highly perfect basal cleavag ...

) granites. Distinctive accessory minerals include:

fluorite Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon. The Mohs sca ...

, topaz, apatite, spinel,

allanite Allanite (also called orthite) is a sorosilicate group of minerals within the broader epidote group that contain a significant amount of rare-earth elements. The mineral occurs mainly in metamorphosed clay-rich sediments and felsic igneous rock ...

sphene Titanite, or sphene (from the Greek ''sphenos'' (σφηνώ), meaning wedge), is a calcium titanium nesosilicate mineral, Ca Ti Si O5. Trace impurities of iron and aluminium are typically present. Also commonly present are rare earth metals in ...

and cassiterite. They are enriched in

tin Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal. Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...

lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid ...

beryllium Beryllium is a chemical element with the symbol Be and atomic number 4. It is a steel-gray, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with other elements to form m ...

, rubidium, barium,

yttrium Yttrium is a chemical element with the symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and has often been classified as a " rare-earth element". Yttrium is almost always found in co ...

, niobium,

uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...

thorium Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high ...

and fluorine and are referred to as "tin granites'. Their circular to oval shape in plan view is consistent with emplacement within resurgent calderas. The exposed igneous rocks of the St. Francois are surrounded at depth by the slightly younger (~100 my) widely distributed igneous Spavinaw terrane. The Spavinaw rocks are intersected in drill core across southern Missouri, southern Illinois, northern Arkansas, southern Kansas and northeastern Oklahoma. The Spavinaw rocks occur in outcrop only near Spavinaw, Oklahoma. The rhyolites and

ash flow A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of b ...

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock ...

s of the Spavinaw are essentially identical to the volcanics of the St. Francois mountains (the Washington County volcanics). The Saint Francois Mountains were formed by igneous activity, whereas most of the surrounding Ozarks are developed on

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...

sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

s as a

dissected plateau A dissected plateau is a plateau area that has been severely eroded such that the relief is sharp. Such an area may be referred to as mountainous, but dissected plateaus are distinguishable from orogenic mountain belts by the lack of folding, ...

. The localized vertical relief was caused by

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is dis ...

following uplift during the Pennsylvanian and

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last ...

periods produced by the Ouachita orogeny to the south. Elevations and strata dips in the Ozark

structural A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such ...

dome generally radiate downward and outward away from the Saint Francois mountains. These ancient mountains may be the only area in the

Midwestern United States The Midwestern United States, also referred to as the Midwest or the American Midwest, is one of four census regions of the United States Census Bureau (also known as "Region 2"). It occupies the northern central part of the United States. I ...

never to have been submerged, (as evidenced by the lack of marine fossils) existing as an island

archipelago An archipelago ( ), sometimes called an island group or island chain, is a chain, cluster, or collection of islands, or sometimes a sea containing a small number of scattered islands. Examples of archipelagos include: the Indonesian Arc ...

in the

seas.

Fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

ized

coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and ...

, the remains of ancient

reef A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic processes— deposition of sand, wave erosion planing down rock o ...

s, can be found among the

rocks In geology, rock (or stone) is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its chemical composition, and the way in which it is formed. Rocks form the Earth's ...

around the flanks of the mountains. These ancient reef complexes formed the localizing structures for the mineralizing fluids that resulted in the rich

ore Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 Apr ...

deposits of the area. The igneous rocks of the Saint Francois Mts. are interpreted to be a series of caldera complexes, similar in scale to the

Yellowstone Caldera The Yellowstone Caldera, sometimes referred to as the Yellowstone Supervolcano, is a volcanic caldera and supervolcano in Yellowstone National Park in the Western United States. The caldera and most of the park are located in the northwest corn ...

complex. However, it is debated whether the igneous activity was related to a hotspot, like Yellowstone, or whether it was related to an ancient subduction zone.

Mineral resources

The St. Francois Mountains are the center of the Lead Belt, a

mining Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. The exploitation of these deposits for raw material is based on the economic ...

region yielding

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

iron Iron () is a chemical element with Symbol (chemistry), symbol Fe (from la, Wikt:ferrum, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 element, group 8 of the periodic table. It is, Abundanc ...

, baryte,

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...

silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...

manganese Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...

cobalt Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, p ...

, and

nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow ...

ores. Historic Mine La Motte near Fredericktown was the site of lead mining activity by the French as early as 1720. The area today accounts for over 90% of primary lead production in the United States.

Granite Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies under ...

has been commercially quarried since 1869 in the vicinity of

Elephant Rocks State Park Elephant Rocks State Park is a state-owned geologic reserve and public recreation area encompassing an outcropping of Precambrian granite in the Saint Francois Mountains in the U.S. state of Missouri. The state park is named for a string of large ...

, a

tor Tor, TOR or ToR may refer to: Places * Tor, Pallars, a village in Spain * Tor, former name of Sloviansk, Ukraine, a city * Mount Tor, Tasmania, Australia, an extinct volcano * Tor Bay, Devon, England * Tor River, Western New Guinea, Indonesia Sc ...

with huge weathered granite boulders. The red architectural granite quarried in the area has been used in buildings in St. Louis and other areas in the country. It is currently marketed as Missouri Red monument stone.

Structural features

Hughes Mountain contains a good example of

columnar jointing Columnar jointing is a geological structure where sets of intersecting closely spaced fractures, referred to as joints, result in the formation of a regular array of polygonal prisms, or columns. Columnar jointing occurs in many types of igneo ...

in igneous rhyolite, the same process that formed

Devils Tower Devils Tower (also known as Bear Lodge Butte) is a butte, possibly laccolithic, composed of igneous rock in the Bear Lodge Ranger District of the Black Hills, near Hulett and Sundance in Crook County, northeastern Wyoming, above the Belle Fo ...

Wyoming Wyoming () is a state in the Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the southwest, and Colorado to the s ...

and the

Giant's Causeway The Giant's Causeway is an area of about 40,000 interlocking basalt columns, the result of an ancient volcanic fissure eruption. It is located in County Antrim on the north coast of Northern Ireland, about three miles (5 km) northeast of ...

Ireland Ireland ( ; ga, Éire ; Ulster Scots dialect, Ulster-Scots: ) is an island in the Atlantic Ocean, North Atlantic Ocean, in Northwestern Europe, north-western Europe. It is separated from Great Britain to its east by the North Channel (Grea ...

. The columnar jointing in this area is called the Devil's Honeycomb.

Peaks

Mountains in this range include;

Taum Sauk Mountain Taum Sauk Mountain in the Saint Francois Mountains is the highest natural point in the U.S. state of Missouri at 1,772 feet (540 m). The topography of Taum Sauk is that of an elongated ridge with a NNW-SSE orientation rather than a peak. Desc ...

, Bell Mountain, Buford Mountain, Proffit Mountain, Pilot Knob,

Hughes Mountain Hughes Mountain and the Hughes Mountain State Natural Area are located in southern Washington County, Missouri (Sections 28 and 33, T36N R3E) just south of the Big River and Highway M on Cedar Creek Road in the St. Francois Mountains range of ...

, Goggin Mountain and Lead Hill Mountain. The elevations range from . Taum Sauk Mountain is the highest peak in the range, and the highest point in the state, with an elevation of . In the southernmost reaches of the range is Clark's Mountain, elevation , with the distinction of being the highest isolated point in the range and in the state; it reaches its top from surrounding terrain of about in less than . Black Mountain, in Madison County, has the highest rise in elevation from its base, along the St. Francis River (540 feet above sea level) to its summit (1,502 feet above sea level), a rise of just under 1,000 feet in elevation.

Recreation

Five Missouri state parks – Johnson's Shut-Ins,

, St. Joe, Sam A. Baker and Elephant Rocks – are located in this region.

Public land In all modern states, a portion of land is held by central or local governments. This is called public land, state land, or Crown land (Australia, and Canada). The system of tenure of public land, and the terminology used, varies between countrie ...

s held by the

Missouri Department of Conservation The Missouri Department of Conservation (MDC) and the Missouri Conservation Commission were created by Article IV Sections 40-42 of the Missouri Constitution, which were adopted by the voters of the state in 1936 as Amendment 4 to the constitution ...

provide access for

hiking Hiking is a long, vigorous walk, usually on trails or footpaths in the countryside. Walking for pleasure developed in Europe during the eighteenth century.AMATO, JOSEPH A. "Mind over Foot: Romantic Walking and Rambling." In ''On Foot: A Histor ...

backpacking Backpacking may refer to: * Backpacking (travel), low-cost, independent, international travel * Backpacking (hiking), trekking and camping overnight in the wilderness * Ultralight backpacking, a style of wilderness backpacking with an emphasis on ...

hunting Hunting is the human practice of seeking, pursuing, capturing, or killing wildlife or feral animals. The most common reasons for humans to hunt are to harvest food (i.e. meat) and useful animal products ( fur/ hide, bone/tusks, horn/antler, ...

fishing Fishing is the activity of trying to catch fish. Fish are often caught as wildlife from the natural environment, but may also be caught from stocked bodies of water such as ponds, canals, park wetlands and reservoirs. Fishing techniques inclu ...

, canoeing, and boating. The

Mark Twain National Forest Mark Twain National Forest (MTNF) is a U.S. National Forest located in the southern half of Missouri. MTNF was established on September 11, 1939. It is named for author Mark Twain, a Missouri native. The MTNF covers of which is public owned, ...

contains additional public lands, including the

Bell Mountain Wilderness The United States Congress designated the Bell Mountain Wilderness in 1980. The wilderness area now has a total of . Bell Mountain is located within the Potosi-Fredericktown Ranger District of the Mark Twain National Forest, south of Potosi, M ...

. A section of the Ozark Trail winds through parts of the St. Francois Mountains, including a popular segment that crosses Taum Sauk and Proffit mountains. The St. Francis River in this area is a

whitewater Whitewater forms in a rapid context, in particular, when a river's gradient changes enough to generate so much turbulence that air is trapped within the water. This forms an unstable current that froths, making the water appear opaque and ...

stream in the spring when water levels are up, and it has hosted the Missouri Whitewater Championships annually since 1968.

References