Rock City, Kansas - AbsoluteAstronomy.com

Rock City is a park located on hillsides overlooking the Solomon River

Solomon River

The Solomon River, often referred to as the "Solomon Fork", is a river in the central Great Plains of North America. The entire length of the river lies in the U.S. state of Kansas. It is a tributary of the Smoky Hill River.-Names:...

in Ottawa County, Kansas

Ottawa County, Kansas

Ottawa County is a county located in the U.S. state of Kansas. As of the 2010 census, the county population was 6,091. The largest city and county seat is Minneapolis...

. It is 3.6 miles south of Minneapolis, Kansas

Minneapolis, Kansas

Minneapolis is a city in and the county seat of Ottawa County, Kansas, United States. As of the 2010 census, the city population was 2,032. Minneapolis is part of the Salina Micropolitan Statistical Area.-Geography:...

and just over 0.5 mile west of Kansas highway K-106 and the Minneapolis City County Airport on Ivy Road at 39°5′27.20"N 97°44′7.99"W. In a patch of prairie about 500 meters (1600 feet) long and 40 meters (130 feet) wide, Rock City contains three clusters of large spherical boulders. These three clusters contain a total of 200 spherical boulders. It has been designated as a National Natural Landmark

National Natural Landmark

The National Natural Landmark program recognizes and encourages the conservation of outstanding examples of the natural history of the United States. It is the only natural areas program of national scope that identifies and recognizes the best examples of biological and geological features in...

.

The park, owned by a non-profit corporation, has a visitor center and picnic tables. A small admission fee, which is used to maintain this park, is charged.

The remarkable size and spherical shape of these rock formation

Rock formations in the United States

The following is a partial list of rock formations in the United States, by state:-Arizona:*Canyon de Chelly National Monument**Spider Rock*Chiricahua National Monument**Duck on a Rock**Organ Pipe**Mushroom Rock**Sea Captain*Monument Valley...

was first noted by Bell. Later, these boulders were either noted or described by Gould, Landes, Shaffer, Ward, and Swineford. Shaffer was the first person to map the distribution of these boulders at Rock City and investigate their petrography

Petrography

Petrography is a branch of petrology that focuses on detailed descriptions of rocks. Someone who studies petrography is called a petrographer. The mineral content and the textural relationships within the rock are described in detail. Petrographic descriptions start with the field notes at the...

in detail.

Physical characteristics

The large spherical boulders in Rock City are giant calcite-cemented concretions, typically called "cannonball concretions" because of their shape. They range in diameter from 3 to 6 meters (10 to 20 feet) with the average diameter being 3.6 meters (12 feet). These concretions lie 2 to 8 meters (6.6 to 26 feet) apart. Similar giant calcite-cemented concretions have also been found in a quartzite quarry within Lincoln County

Lincoln County, Kansas

Lincoln County is a county located in the U.S. state of Kansas. As of the 2010 census, the county population was 3,241...

and in exposures of the similar age sandstones in Utah and Wyoming.

These boulders consist of well-sorted, medium-grained sandstone

Sandstone

Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...

, which is tightly cemented by calcite

Calcite

Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...

. The sandstone consists or more than 95 percent quartz

Quartz

Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...

sand

Sand

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...

. About 20 percent of the original sandstone, mostly feldspar

Feldspar

Feldspars are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's crust....

grains, has been replaced by the calcite. Pyrite

Pyrite

The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...

, which is now oxidized to goethite

Goethite

Goethite , named after the German polymath Johann Wolfgang von Goethe, is an iron bearing oxide mineral found in soil and other low-temperature environments. Goethite has been well known since prehistoric times for its use as a pigment. Evidence has been found of its use in paint pigment samples...

, occurs within the calcite cement of these concretions as microscopic crystals and very small, knobby concretions. The pyrite concretions typically are about 30 cm (1 foot) in diameter. Also, included within these calcite concretions are smaller calcite concretions, which have been engulfed by the growth of the larger concretions.

The host rock, which contained these spherical boulders, consists of well-sorted, medium-grained, highly porous, and friable sandstone. Being only weakly indurated by small amounts of iron oxide, sometimes seen as Liesegang rings

Liesegang rings

Liesegang rings are a phenomenon seen in many, if not most, chemical systems undergoing a precipitation reaction, under certain conditions of concentration and in the absence of convection.-History:...

(banding) at Rock City, it is considerably softer and very much more easily eroded than the calcite concretions. The sand comprising it accumulated within a river channel, which is part of the Dakota Sandstone

Dakota Sandstone

The Dakota Sandstone is a general term for an ill-defined early Cretaceous formation of the Rocky Mountains and Great Plains. It consists of sandy, shallow-marine deposits with intermittent mud flat sediments, and occasional stream deposits...

, which accumulated within a low-lying coastal plain. Differential cementation and later erosion of cross-bedding

Cross-bedding

In geology, the sedimentary structures known as cross-bedding refer to horizontal units that are internally composed of inclined layers. This is a case in geology in which the original depositional layering is tilted, and the tilting is not a result of post-depositional deformation...

inherited from the riverine sand, in which these concretions occur, created the "ornamentation", which these concretions exhibit.

Origin

In the past, the origin of the spherical boulders found at Rock City had been erroneously interpreted as glacial boulders, corals, concretionary masses of limestone, and normal erosional remnants of sandstone. Shaffer was the first person to recognize them as calcite-cemented concretions. From a detailed examination of the mineralogy

Mineralogy

Mineralogy is the study of chemistry, crystal structure, and physical properties of minerals. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical distribution, as well as their utilization.-History:Early writing...

of these concretions and the carbon and oxygen isotopes of the calcite cement comprising them, McBride and others concluded that they formed as the result of diffusion of calcium

Calcium

Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...

through and precipitation of calcite within the sandstone containing them after being deeply buried. The carbon

Carbon

Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

and calcium

Calcium

comprising these concretions came either from marine

Marine (ocean)

Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...

limestone

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

, shells, anhydrite

Anhydrite

Anhydrite is a mineral – anhydrous calcium sulfate, CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the orthorhombic barium and strontium sulfates, as might be expected from the...

, or some combination of these in addition to bicarbonate

Bicarbonate

In inorganic chemistry, bicarbonate is an intermediate form in the deprotonation of carbonic acid...

derived from oxidized methane

Methane

Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

from strata

Stratum

In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...

outside of, but hydrologically

Hydrology

Hydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...

connected to, the Dakota Sandstone. After the formation of the concretions, differential erosion of the considerably softer sandstone surrounding them exposed as free-standing boulders.

External links

Rock City, Minneapolis, Kansas
Rock City
Rock City Park, Kansas
Kansas Geological Survey, nd, Smoky Hills—Places to Visit
Biek, B., 2002, Concretions and Nodules in North Dakota North Dakota Geological Survey, Bismark, North Dakota. Explains how concretions are created.
Dietrich, R.V., 2002, Carbonate Concretions--A Bibliography
Hansen, M.C., 1994, Ohio Shale Concretions PDF version, 270 KB Ohio Division of Geological Survey GeoFacts n. 4, pp. 1-2.
Heinrich, P.V., 2007, The Giant Concretions of Rock City Kansas PDF version, 836 KB BackBender's Gazette. vol. 38, no. 8, pp. 6-12.
Kansas Geological Survey, 2004, Educational Resources, Photos from Ottawa County

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Physical characteristics

Origin

See also

External links