Continental extension, magmatism and elevation; formal relations and rules of thumb

Lachenbruch, Arthur H.; Morgan, Paul

doi:10.1016/0040-1951(90)90383-j

Cited by 320 publications

(228 citation statements)

References 44 publications

Supporting

Mentioning

224

Contrasting

Order By: Relevance

“…For comparison, in the Mariana forearc east of the Mariana Ridge, similar water depths and plate thicknesses (i.e., from the surface to the Wadati-Benioff seismic zone) are associated with a crust that is about 4 times thicker (20 km at 18°N [Fryer and Hussong, 1981]). Column B further illustrates that, theoretically, in local isostatic equilibrium the surface of a free 50-km-thick plate with a 20-km-thick crust is expected to lie $1 km below sea level [Gvirtzman, 2002;Gvirtzman and Nur, 1999b;Lachenbruch and Morgan, 1990] and not 3.5 km as observed. This suggests that the Mariana forearc is coupled to and pulled down by the underlying subducting plate.…”

Section: Down-pulled Zone Versus Free Floating Zonementioning

confidence: 74%

“…Figure 5a illustrates that the surface of a 50-km-thick oceanic plate with a typical $5-km-thick crust should lie Figure 5. Cartoon illustrating the floating state of various lithospheric columns assuming that the lithosphere is sustained in a flowing asthenosphere (based on Gvirtzman [2002] and Gvirtzman and Nur [1999b] and on Lachenbruch and Morgan [1990]). Column A shows that in 3.5-km-deep ocean the crust is usually about 5-km thick and the entire lithosphere is about 50-km thick.…”

Section: Down-pulled Zone Versus Free Floating Zonementioning

confidence: 99%

“…Column D describes the isostatic state of the Mariana Ridge at 18°N (central Marianas, section 7), where the crust is 11-km thick [Fryer and Hussong, 1981] and water depth is À2 km. Here, isostasy implies that the thickness of the mantle lithosphere should be 20 km [Gvirtzman, 2002;Gvirtzman and Nur, 1999b;Lachenbruch and Morgan, 1990] and thus the base of the lithosphere should be at a depth of about 31 km, nearly 70 km above the top of the subducting plate. We thus conclude that 70 km of asthenosphere lies between the two plates under the ridge and that the overriding plate is freed from the downgoing plate.…”

Section: Down-pulled Zone Versus Free Floating Zonementioning

confidence: 99%

See 2 more Smart Citations

Bathymetry of Mariana trench‐arc system and formation of the Challenger Deep as a consequence of weak plate coupling

Gvirtzman

Stern

2004

Tectonics

View full text Add to dashboard Cite

The Challenger Deep in the southernmost Mariana Trench (western Pacific Ocean) is the deepest point on the Earth's surface (10,920 m below sea level). Its location within a subduction trench, where one plate bends and descends below another, is not surprising. However, why is it located in the southernmost Mariana Trench and not at its central part, where the rate of subduction is higher, where the lithosphere is the oldest (and densest) on the Earth, and where the subducted lithosphere pulling down is the longest in the Earth (∼1000 km or more according to seismic tomography)? We suggest that although subduction rate and slab age generally control trench depth, the width of the plate‐coupling zone is more important. Beneath the central Marianas the subducted slab is attached to the upper plate along a 150‐km‐wide surface that holds the shallow portion of the subducted plate nearly horizontal, in spite of its great load and, thus, counters trench deepening. In contrast, along the south Mariana Trench the subducted length of the lithosphere is much shorter, but its attachment to the upper plate is only along a relatively narrow, 50‐km‐wide, surface. In addition, a tear in the slab beneath this region helps it to sink rapidly through the mantle, and this combination of circumstances allows the slab to steepen and form the deepest trench on the Earth. In a wider perspective, the interrelations shown here between trench deepening, ridge shallowing, slab steepening, and forearc narrowing may shed light on other subduction zones located near edges of rapidly steepening slabs.

show abstract

Section: Down-pulled Zone Versus Free Floating Zonementioning

confidence: 74%

Section: Down-pulled Zone Versus Free Floating Zonementioning

confidence: 99%

Section: Down-pulled Zone Versus Free Floating Zonementioning

confidence: 99%

See 1 more Smart Citation

Bathymetry of Mariana trench‐arc system and formation of the Challenger Deep as a consequence of weak plate coupling

Gvirtzman

Stern

2004

Tectonics

View full text Add to dashboard Cite

show abstract

“…To reduce the uncertainty of temperature estimates, we constrained thermal structure using the relationship between elevation and thermal regime proposed by Lachenbruch and Morgan (1990). According to these authors, a column of solid lithosphere of height b l and mean density q l is in a floating equilibrium over a fluid asthenosphere of density q a .…”

Section: Thermal Modellingmentioning

confidence: 99%

“…H 0 is the buoyant height of sea level above the free asthenosphere surface (H 0 i2.4 km; Lachenbruch and Morgan, 1990). Crust contribution is estimated from:…”

Section: Thermal Modellingmentioning

confidence: 99%

Thermal and mechanical structure of the central Iberian Peninsula lithosphere

Tejero

Ruíz

2002

Tectonophysics

View full text Add to dashboard Cite

The central Iberian Peninsula (Spain) is made up of three main tectonic units: a mountain range, the Spanish Central System and two Tertiary basins (those of the rivers Duero and Tajo). These units are the result of widespread foreland deformation of the Iberian plate interior in response to Alpine convergence of European and African plates. The present study was designed to investigate thermal structure and rheological stratification in this region of central Spain. Surface heat flow has been described to range from f 80 to f 60 mW m À2 . Highest surface heat flow values correspond to the Central System and northern part of the Tajo Basin. The relationship between elevation and thermal state was used to construct a one-dimensional thermal model. Mantle heat flow drops from 34 mW m À2 (Duero Basin) to 27 mW m À2 (Tajo Basin), and increases with diminishing surface heat flow. Strength predictions made by extrapolating experimental data indicate varying rheological stratification throughout the area. In general, in compression, ductile fields predominate in the middle and lower crusts and lithospheric mantle. Brittle behaviour is restricted to the first f 8 km of the upper crust and to a thin layer at the top of the middle crust. In tension, brittle layers are slightly more extended, while the lower crust and lithospheric mantle remain ductile in the case of a wet peridotite composition. Discontinuities in brittle and ductile layer thickness determine lateral rheological anisotropy. Tectonic units roughly correspond to rheological domains. Brittle layers reach their maximum thickness beneath the Duero Basin and are of least thickness under the Tajo Basin, especially its northern area. Estimated total lithospheric strength shows a range from 2.5Â10 12 to 8Â10 12 N m À1 in compression, and from 1.3Â10 12 to 1.6Â10 12 N m À1 in tension. Highest values were estimated for the Duero Basin. Depth versus frequency of earthquakes correlates well with strength predictions. Earthquake foci concentrate mainly in the upper crust, showing a peak close to maximum strength depth. Most earthquakes occur in the southern margin of the Central System and southeast Tajo Basin. Seismicity is related to major faults, some bounding rheological domains. The Duero Basin is a relative quiescence zone characterised by higher total lithospheric strength than the remaining units. D

show abstract

Origins of topography in the western U.S.: Mapping crustal and upper mantle density variations using a uniform seismic velocity model

et al. 2014

View full text Add to dashboard Cite

To investigate the physical basis for support of topography in the western U.S., we construct a subcontinent scale, 3-D density model using~1000 estimated crustal thicknesses and S velocity profiles to 150 km depth at each of 947 seismic stations. Crustal temperature and composition are considered, but we assume that mantle velocity variations are thermal in origin. From these densities, we calculate crustal and mantle topographic contributions. Typical 2σ uncertainty of topography is~500 m, and elevations in 84% of the region are reproduced within error. Remaining deviations from observed elevations are attributed to melt, variations in crustal quartz content, and dynamic topography; compositional variations in the mantle, while plausible, are not necessary to reproduce topography. Support for western U.S. topography is heterogeneous, with each province having a unique combination of mechanisms. Topography due to mantle buoyancy is nearly constant (within~250 m) across the Cordillera; relief there (>2 km) results from variations in crustal chemistry and thickness. Cold mantle provides~1.5 km of ballast to the thick crust of the Great Plains and Wyoming craton. Crustal temperature variations and dynamic pressures have smaller magnitude and/or more localized impacts. Positive gravitational potential energy (GPE) anomalies (~2 × 10 12 N/m) calculated from our model promote extension in the northern Basin and Range and near the Sierra Nevada. Negative GPE anomalies (À3 × 10 12 N/m) along the western North American margin and Yakima fold and thrust belt add compressive stresses. Stresses derived from lithospheric density variations may strongly modulate tectonic stresses in the western U.S. continental interior.

show abstract

Continental extension, magmatism and elevation; formal relations and rules of thumb

Cited by 320 publications

References 44 publications

Bathymetry of Mariana trench‐arc system and formation of the Challenger Deep as a consequence of weak plate coupling

Bathymetry of Mariana trench‐arc system and formation of the Challenger Deep as a consequence of weak plate coupling

Thermal and mechanical structure of the central Iberian Peninsula lithosphere

Origins of topography in the western U.S.: Mapping crustal and upper mantle density variations using a uniform seismic velocity model

Contact Info

Product

Resources

About