Principle of original horizontality

Principle of original horizontality
A stratigraphic section of Ordovician rock exposed in central Tennessee, USA. The sediments composing these rocks were formed in an ocean and deposited in horizontal layers.
The Permian through Jurassic stratigraphy of the Colorado Plateau area of southeastern Utah is a great example of Original Horizontality. 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.

The Principle of Original Horizontality was proposed by the Danish geological pioneer Nicholas Steno (1638–1686). This principle states that layers of sediment are originally deposited horizontally under the action of gravity.[1] The principle is important to the analysis of folded and tilted strata.

From these observations is derived the conclusion that the Earth has not been static and that great forces have been at work over long periods of time, further leading to the conclusions of the science of plate tectonics; that movement and collisions of large plates of the Earth's crust is the cause of folded strata.

As one of Steno's Laws, the Principle of Original Horizontality served well in the nascent days of geological science. However, it is now known that not all sedimentary layers are deposited purely horizontally.

For instance, coarser grained sediments such as sand may be deposited at angles of up to 15 degrees, held up by the internal friction between grains which prevents them slumping to a lower angle without additional reworking or effort. This is known as the angle of repose, and a prime example is the surface of sand dunes.

Similarly, sediments may drape over a pre-existing inclined surface: these sediments are usually deposited conformably to the pre-existing surface. Also sedimentary beds may pinch out along strike, implying that slight angles existed during their deposition.

Thus the Principle of Original Horizontality is widely, but not universally, applicable in the study of sedimentology, stratigraphy and structural geology.

See also

References


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Original horizontality — The Original Horizontality is part of the Danish scientist Nicolaus Steno 1667 who laid the foundations for the modern science of stratigraphy.This principle states that sediments are deposited under the influence of gravity as nearly horizontal… …   Wikipedia

  • Principle of faunal succession — The principle of faunal succession is based on the observation that sedimentary rock strata contain fossilised flora and fauna, and that these fossils succeed each other vertically in a specific, reliable order that can be identified over wide… …   Wikipedia

  • Law of superposition — The law of superposition (or the principle of superposition) is a key axiom based on observations of natural history that is a foundational principle of sedimentary stratigraphy and so of other geology dependent natural sciences: The principle… …   Wikipedia

  • Geology — Oceanic crustContinental Crust] Geology (from Greek: γη, gê , earth ; and λόγος, logos , speech lit. to talk about the earth) is the science and study of the solid and liquid matter that constitute the Earth. The field of geology encompasses the… …   Wikipedia

  • Cross-cutting relationships — Cross cutting relations can be used to determine the relative ages of rock strata and other geological structures. Explanations: A folded rock strata cut by a thrust fault; B large intrusion (cutting through A); C erosional angular unconformity… …   Wikipedia

  • Stratification (archeology) — In archaeology, especially in the course of excavation, stratification is a paramount and base concept. It is largely based on the Law of Superposition. When archaeological finds are below the surface of the ground (as is most commonly the case) …   Wikipedia

  • Topic outline of geology — For a more comprehensive list, see the List of geology topics. Geology is the science and study of the solid matter that constitutes the Earth (the lithosphere). It is one of the Earth sciences. Geology studies the composition, structure,… …   Wikipedia

  • Outline of geology — See also: Index of geology articles The following outline is provided as an overview of and topical guide to geology: Geology – one of the Earth sciences, it is the study of the Earth, with the general exclusion of present day life, flow within… …   Wikipedia

  • Sedimentology — encompasses the study of modern sediments such as sand [ Raymond Siever, Sand, Scientific American Library, New York (1988), ISBN 0 7167 5021 X.] , mud (silt), [ P.E. Potter, J.B. Maynard, and P.J. Depetris, Mud and Mudstones: Introduction and… …   Wikipedia

  • Metamorphism — For other uses, see Metamorphism (disambiguation). Schematic representation of a metamorphic reaction. Abbreviations of minerals: act = actinolite; chl = chlorite; ep = epidote; gt = garnet; hbl = hornblende; plag = plagioclase. Two minerals… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”