Epeirogenic movement
Encyclopedia
In geology
, epeirogenic movement (from Greek epeiros, land, and genesis, birth) refers to upheavals or depressions of land exhibiting long wavelength
s and little folding
apart from broad undulations. The broad central parts of continents are called cratons, and are subject to epeirogeny. The movement may be one of subsidence toward, or of uplift from, the centre of the Earth. The movement is caused by a set of forces acting along an Earth radius, such as those contributing to isostasy
and faulting in the lithosphere
.
Epeirogenic movement can be permanent or transient. Transient uplift can occur over a thermal anomaly due to convecting anomalously hot mantle
, and disappears when convection wanes. Permanent uplift can occur when igneous material is injected into the crust
, and circular or elliptical structural uplift (that is, without folding) over a large radius (tens to thousands of km) is one characteristic of a mantle plume
.
Epeirogenic movement has caused the southern Rocky Mountain region to be uplifted from 1300 to 2000 m since the Eocene
.This followed and is distinct from the creation of the Rocky Mountains during the Laramide Orogeny
during the Late Cretaceous
–early Cenozoic
. The uplift is interpreted as due to lithospheric heating resulting from thinning and the intrusion of widespread middle Tertiary
batholith
s of relatively low density.
In contrast to epeirogenic movement, orogenic movement
is a more complicated deformation of the Earth's crust, associated with crustal thickening, notably associated with the convergence of tectonic plates
. Such plate convergence forms orogenic belts
that are characterized by “the folding and faulting of layers of rock, by the intrusion of magma, and by volcanism”.
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
, epeirogenic movement (from Greek epeiros, land, and genesis, birth) refers to upheavals or depressions of land exhibiting long wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
s and little folding
Fold (geology)
The term fold is used in geology when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of permanent deformation. Synsedimentary folds are those due to slumping of sedimentary material before it is lithified. Folds in rocks vary in...
apart from broad undulations. The broad central parts of continents are called cratons, and are subject to epeirogeny. The movement may be one of subsidence toward, or of uplift from, the centre of the Earth. The movement is caused by a set of forces acting along an Earth radius, such as those contributing to isostasy
Isostasy
Isostasy is a term used in geology to refer to the state of gravitational equilibrium between the earth's lithosphere and asthenosphere such that the tectonic plates "float" at an elevation which depends on their thickness and density. This concept is invoked to explain how different topographic...
and faulting in the lithosphere
Lithosphere
The lithosphere is the rigid outermost shell of a rocky planet. On Earth, it comprises the crust and the portion of the upper mantle that behaves elastically on time scales of thousands of years or greater.- Earth's lithosphere :...
.
Epeirogenic movement can be permanent or transient. Transient uplift can occur over a thermal anomaly due to convecting anomalously hot mantle
Mantle (geology)
The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiation by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core....
, and disappears when convection wanes. Permanent uplift can occur when igneous material is injected into the crust
Crust (geology)
In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle...
, and circular or elliptical structural uplift (that is, without folding) over a large radius (tens to thousands of km) is one characteristic of a mantle plume
Mantle plume
A mantle plume is a hypothetical thermal diapir of abnormally hot rock that nucleates at the core-mantle boundary and rises through the Earth's mantle. Such plumes were invoked in 1971 to explain volcanic regions that were not thought to be explicable by the then-new theory of plate tectonics. Some...
.
Epeirogenic movement has caused the southern Rocky Mountain region to be uplifted from 1300 to 2000 m since the Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
.This followed and is distinct from the creation of the Rocky Mountains during the Laramide Orogeny
Laramide orogeny
The Laramide orogeny was a period of mountain building in western North America, which started in the Late Cretaceous, 70 to 80 million years ago, and ended 35 to 55 million years ago. The exact duration and ages of beginning and end of the orogeny are in dispute, as is the cause. The Laramide...
during the Late Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
–early Cenozoic
Cenozoic
The Cenozoic era is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 mya to the present. The era began in the wake of the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and...
. The uplift is interpreted as due to lithospheric heating resulting from thinning and the intrusion of widespread middle Tertiary
Tertiary
The Tertiary is a deprecated term for a geologic period 65 million to 2.6 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary...
batholith
Batholith
A batholith is a large emplacement of igneous intrusive rock that forms from cooled magma deep in the Earth's crust...
s of relatively low density.
In contrast to epeirogenic movement, orogenic movement
Orogeny
Orogeny refers to forces and events leading to a severe structural deformation of the Earth's crust due to the engagement of tectonic plates. Response to such engagement results in the formation of long tracts of highly deformed rock called orogens or orogenic belts...
is a more complicated deformation of the Earth's crust, associated with crustal thickening, notably associated with the convergence of tectonic plates
Tectonic Plates
Tectonic Plates is a 1992 independent Canadian film directed by Peter Mettler. Mettler also wrote the screenplay based on the play by Robert Lepage. The film stars Marie Gignac, Céline Bonnier and Robert Lepage.-Plot summary:...
. Such plate convergence forms orogenic belts
Orogeny
Orogeny refers to forces and events leading to a severe structural deformation of the Earth's crust due to the engagement of tectonic plates. Response to such engagement results in the formation of long tracts of highly deformed rock called orogens or orogenic belts...
that are characterized by “the folding and faulting of layers of rock, by the intrusion of magma, and by volcanism”.