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10 Incredible Geological Formations
10 Incredible Geological Formations
Published: 2014/03/15
Channel: Alltime10s
25 Strangest Geological Formations On Earth
25 Strangest Geological Formations On Earth
Published: 2013/07/26
Channel: list25
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18 Photos Of The STRANGEST Geological Formations
Published: 2017/02/26
Channel: American Eye
17 Most Unreal Rock Formations
17 Most Unreal Rock Formations
Published: 2016/09/15
Channel: Talltanic
Top 10 Most Amazing Geological Wonders In The World
Top 10 Most Amazing Geological Wonders In The World
Published: 2015/05/24
Channel: facts@WEB
Geology
Geology
Published: 2015/08/31
Channel: Bozeman Science
The Geological History of Earth
The Geological History of Earth
Published: 2015/03/18
Channel: GeoScience Videos
Geologic History of Southern California.mov
Geologic History of Southern California.mov
Published: 2011/08/22
Channel: Wendy Van Norden
Basics of Geology  All About Rocks and Minerals
Basics of Geology All About Rocks and Minerals
Published: 2014/03/09
Channel: ambachke
Formation of an ore deposit
Formation of an ore deposit
Published: 2015/08/24
Channel: W. W. Norton-Marshak Geology
Formation of Karst Landscapes
Formation of Karst Landscapes
Published: 2016/06/08
Channel: Darron Gedge's Geography Channel
National Geographic The Story of Earth HD
National Geographic The Story of Earth HD
Published: 2014/02/07
Channel: Beauty Geography
Hot spot formation
Hot spot formation
Published: 2015/08/26
Channel: W. W. Norton-Marshak Geology
Interpreting the Geology of Bryce & Zion
Interpreting the Geology of Bryce & Zion
Published: 2013/10/22
Channel: interpretation4U
Documentarys 2016  GEOLOGICAL HISTORY OF THE GRAND CANYON  National Geographic Discovery
Documentarys 2016 GEOLOGICAL HISTORY OF THE GRAND CANYON National Geographic Discovery
Published: 2016/03/24
Channel: Ginny Culbertson
Weird geological formation
Weird geological formation
Published: 2016/07/28
Channel: smalltownmoto 1
A HistorY Of Earth
A HistorY Of Earth's Geological Figure - Best Documentary (Bong).
Published: 2017/03/21
Channel: Human Documentary Films
Seven Teacups- Unique Geological Formation (4K Aerial Footage)
Seven Teacups- Unique Geological Formation (4K Aerial Footage)
Published: 2016/04/22
Channel: Matt Skuta
How the Earth Was Made: Hawaii | History
How the Earth Was Made: Hawaii | History
Published: 2009/11/23
Channel: HISTORY
HOW EARTH WAS FORMED ! Amazing Geology Documentary
HOW EARTH WAS FORMED ! Amazing Geology Documentary
Published: 2016/03/30
Channel: OBZURV
How Was the Grand Canyon Formed?
How Was the Grand Canyon Formed?
Published: 2016/04/29
Channel: Smithsonian Channel
Scientist says: Mysterious Geological Formation of Planet Mars Caused by a Massive Asteroid Impact
Scientist says: Mysterious Geological Formation of Planet Mars Caused by a Massive Asteroid Impact
Published: 2017/07/18
Channel: Close Encounters UFO
The Hawaiian Islands : Documentary on the Science of How Hawaii was Formed (Full Documentary)
The Hawaiian Islands : Documentary on the Science of How Hawaii was Formed (Full Documentary)
Published: 2015/12/02
Channel: Franklin Steves
The formation of Uluru
The formation of Uluru
Published: 2017/01/13
Channel: EverythingIsScience
Subnautica 22 Geological Formation Base
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Published: 2016/01/27
Channel: SnakeNACake _
HOW THE EVEREST WAS FORMED ! Amazing Geology Documentary
HOW THE EVEREST WAS FORMED ! Amazing Geology Documentary
Published: 2016/03/24
Channel: OBZURV
Blowing Rocks Geological Formation
Blowing Rocks Geological Formation
Published: 2013/12/01
Channel: Joseph Kilsmith
Documentary ● Alps earth formation
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Published: 2016/08/17
Channel: Explore the world
Preview_The Geological Formation of Bainbridge Island_1
Preview_The Geological Formation of Bainbridge Island_1
Published: 2016/08/02
Channel: snowproductionsBI
Geological Time Scale with reference to India - 4 Eras & 10 Periods Explained
Geological Time Scale with reference to India - 4 Eras & 10 Periods Explained
Published: 2016/04/13
Channel: Examrace
Geological Requirements for the Formation of Springs
Geological Requirements for the Formation of Springs
Published: 2015/01/23
Channel: james pake
Formation Of Uluru and Kata Tjuta
Formation Of Uluru and Kata Tjuta
Published: 2016/04/13
Channel: Kieran Stedman
Columnar Basalt - Geologist explains spectacular stone columns
Columnar Basalt - Geologist explains spectacular stone columns
Published: 2013/05/30
Channel: hugefloods
Big Bend Geology: The Primeval Puzzle - Texas Parks and Wildlife [Official]
Big Bend Geology: The Primeval Puzzle - Texas Parks and Wildlife [Official]
Published: 2014/03/05
Channel: Texas Parks and Wildlife
Where Terranes Collide: The Geology of Western Canada
Where Terranes Collide: The Geology of Western Canada
Published: 2015/04/28
Channel: Geology
Formation of the Mediterranean and the Alps
Formation of the Mediterranean and the Alps
Published: 2015/04/29
Channel: Etta Gonet
The Formation of Coal 3D
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Published: 2013/02/27
Channel: Winner Pictures / BTS-MEDIA
HD Geological rock formation Chartreuse Mountains by Grenoble France Part 2 of 2
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Published: 2015/01/26
Channel: Life In Another Town
Tom Ewing- Texas Geologic History Quick Overview
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Published: 2016/01/22
Channel: HGSGeoEducation
70 Million Years In 2 Minutes - The Himalayas Forming
70 Million Years In 2 Minutes - The Himalayas Forming
Published: 2012/12/17
Channel: злодейский Ломбардо
Geologist Dr. Andrew Snelling: Grand Canyon Formation (Pt 1)
Geologist Dr. Andrew Snelling: Grand Canyon Formation (Pt 1)
Published: 2016/06/10
Channel: EvolutionismAnti-Science Lie
How the Rockies Were Made - History Channel Documentary
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Published: 2016/02/12
Channel: Mountain Springs
The Formation of the Mediterranean Sea
The Formation of the Mediterranean Sea
Published: 2016/06/04
Channel: ZorakGoesOn
Geological Background of India
Geological Background of India
Published: 2017/03/09
Channel: Education Adda
The Unique Continent  - Geological Evolution of Australia
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Published: 2012/04/22
Channel: petbur
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Channel: Artec Educational
Makhtesh Ramon Pt.1 Geological Formation
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Published: 2017/03/16
Channel: Michael Welch
Geological Formations -- Mrs. Feist
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Published: 2016/05/27
Channel: Rita Vondracek
Evidence of ancient
Evidence of ancient 'geological Brexit' revealed
Published: 2017/04/05
Channel: No Copyright Music
"Kande geological formation - Malawi" Cookieluc
"Kande geological formation - Malawi" Cookieluc's photos around Chintheche, Malawi
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Channel: Uawaudqomneyeie
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WIKIPEDIA ARTICLE

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A geologic cross section of the Grand Canyon. Black numbers correspond to groups of formations and white numbers correspond to formations (click on picture for more information).

A formation or geological formation is the fundamental unit of lithostratigraphy. A formation consists of a certain number of rock strata that have a comparable lithology, facies or other similar properties. Formations are not defined by the thickness of the rock strata they consist of and the thickness of different formations can therefore vary widely.

The concept of formally defined layers or strata is central to the geologic discipline of stratigraphy. Formations can be divided into members and are themselves frequently parcelled together in groups.

Usefulness of formations[edit]

The definition and recognition of formations allow geologists to correlate geologic strata across wide distances between outcrops and exposures of rock strata.

Formations were initially described to be the essential geologic time markers based on relative ages and the law of superposition. The divisions of the geological time scale were the formations described and put in chronological order by the geologists and stratigraphers of the 18th and 19th centuries.

Modern revision of the geologic sciences has restricted formations to lithologies, because lithological units are formed by depositional environments, some of which may persist for hundreds of millions of years and will transgress chronostratigraphic intervals or fossil-based methods of correlating rocks. For example, the Hamersley Basin of Western Australia is a Proterozoic sedimentary basin where up to 1200 million years of sedimentation is preserved within the intact sedimentary stratigraphy, with up to 300 million years represented by a single lithological unit of banded iron formation and shale.

Geologic formations are usually sedimentary rock layers, but may also be metamorphic rocks and volcanic flows. Igneous intrusive rocks are generally not divided into formations.

Defining lithostratigraphic formations[edit]

The Permian through Jurassic strata of the Colorado Plateau area of southeastern Utah demonstrate the principles of stratigraphy. These strata make up much of the famous prominent rock formations in widely spaced protected areas such as Capitol Reef National Park and Canyonlands National Park. From top to bottom: Rounded tan domes of the Navajo Sandstone, layered red Kayenta Formation, cliff-forming, vertically jointed, red Wingate Sandstone, slope-forming, purplish Chinle Formation, layered, lighter-red Moenkopi Formation, and white, layered Cutler Formation sandstone. Picture from Glen Canyon National Recreation Area, Utah.

Formations are the only formal lithostratigraphic units into which the stratigraphic column everywhere should be divided completely on the basis of lithology.

The contrast in lithology between formations required to justify their establishment varies with the complexity of the geology of a region and the detail needed for geologic mapping and to work out its geologic history.

Formations must be able to be delineated at the scale of geologic mapping practiced in the region. The thickness of formations may range from less than a meter to several thousand meters.

Geologic formations are typically named for the geographic area in which they were first described.

Strictly, formations cannot be defined on any other criteria except primary lithology. However, it is often useful to define biostratigraphic units based on paleontological criteria, chronostratigraphic units based on the age of the rocks, and chemostratigraphic units based on geochemical criteria.

Sequence stratigraphy is a concept which challenges the idea of strict lithostratigraphic units by defining units based on events in sedimentary basins such as oceanic regressions and transgressions. These sequences are a combination of chronostratigraphic units, linked by time, and depositional environment linked by the geologic events which occurred at that time, regardless of the grain size of the sediments.

The term "formation" is often used informally to refer to a specific grouping of rocks, such as those encountered within a certain depth range in an oil well.

Other uses of the term[edit]

"Formation" is also used informally to describe the sometimes odd shapes (forms) that rocks acquire through erosional or depositional processes. Such a formation is said to be abandoned when it is no longer affected by the geologic agent that produced it. Some well known cave formations include stalactites and stalagmites.

See also[edit]

Further reading[edit]

  • Brookfield, Michael E. (2008). Principles of Stratigraphy. John Wiley & Sons. pp. 111–114, 200. ISBN 9780470693223. 
  • Rey, Jacques; Simone Galeotti, eds. (2008). Stratigraphy : terminology and practice. Paris, France: Editions OPHRYS. ISBN 9782710809104. 


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