scholarly journals IV.—The Circular form of Mountain Chains

1903 ◽  
Vol 10 (7) ◽  
pp. 305-306
Author(s):  
Philip Lake
Keyword(s):  
Earth’S Crust ◽  
Mountain Ranges ◽  
The Earth ◽  
Circular Form ◽  
Thrust Plane ◽  
Figure Of The Earth ◽  
Mountain Chain ◽  
Earth's Crust ◽  
Reversed Fault

I am a stranger in the field of speculation, and am quite unacquainted with the intricacies of its authorized boundaries. It is therefore with some hesitation, lest I should tread upon forbidden ground, that I venture to offer a suggestion on one point in Professor Sollas's paper on “The Figure of the Earth.”It has long been observed that mountain ranges and chains of islands (which, indeed, are only mountain ranges partially submerged) are generally curvilinear in form, but Professor Sollas is, I believe, the first to show clearly that the curve often coincides almost exactly with an arc of a circle. Such a mountain chain is frequently defined along its convex margin by a great reversed fault over which the mountain mass has slid forward; and in these cases, at least, we may safely adopt Suess's conception, and look upon the chain as the crumpled edge of a ‘scale’ of the earth's crust which has been pushed forward over the part in front of it. The surface along which the movement has taken place is called a thrustplane. If this surface really is a plane, then the edge of the ‘scale’, that is the mountain chain itself, must necessarily be circular in form; for if any plane cuts a sphere, in any position whatever, the outcrop of the plane on the surface of the sphere will always be a circle. There can be no deviation from the circular form unless the ‘sphere’ is not truly spherical, or the ‘thrust-plane’ is not a true plane.

scholarly journals Accelerated non-linear destruction of the earth's crust

2001 ◽  
Vol 6 (4) ◽  
pp. 281-290
Author(s):  
E. V. Artyushkov
Keyword(s):  
Lower Crust ◽  
Sedimentary Basins ◽  
Earth’S Crust ◽  
Mountain Ranges ◽  
Crustal Rocks ◽  
The Earth ◽  
Lithospheric Plates ◽  
Temperature And Pressure ◽  
Earth's Crust ◽  
Major Hydrocarbon

The upper part of the Earth—the lithospheric layer,∼100 km thick, is rigid. Segments of this spherical shell–lithospheric plates are drifting over a ductile asthenosphere. On the continents, the lithosphere includes the Earth's crust,∼40 km thick, which is underlain by peridotitic rocks of the mantle. In most areas, at depths∼20–40 km the continental crust is composed of basalts with density∼2900kg m−3. At temperature and pressure typical for this depth, basalts are metastable and should transform into another assemblage of minerals which corresponds to garnet granulites and eclogites with higher densities 3300–3600 kgm−3. The rate of this transformation is extremely low in dry rocks, and the associated contraction of basalts evolves during the time≥108a. To restore the Archimede's equilibrium, the crust subsides with a formation of sedimentary basins, up to 10–15 km deep.Volumes of hot mantle with a water-containing fluid emerge sometimes from a deep mantle to the base of the lithosphere. Fluids infiltrate into the crust through the mantle part of the lithosphere. They catalyze the reaction in the lower crust which results in rock contraction with a formation of deep water basins at the surface during∼106a. The major hydrocarbon basins of the world were formed in this way. Infiltration of fluids strongly reduces the viscosity of the lithosphere, which is evidenced by narrow-wavelength deformations of this layer. At times of softening of the mantle part of the lithosphere, it becomes convectively replaced by a hotter and lighter asthenosphere. This process has resulted in the formation of many mountain ranges and high plateaus during the last several millions of years. Softening of the whole lithospheric layer which is rigid under normal conditions allows its strong compressive and tensile deformations. At the epochs of compression, a large portion of dense eclogites that were formed from basalts in the lower crust sink deeply into the mantle. In some cases they carry down lighter blocks of granites and sedimentary rocks of the upper crust which delaminate from eclogitic blocks and emerge back to the crust. Such blocks of upper crustal rocks include diamonds and other minerals which were formed at a depth of 100–150 km.

I.—Contributions to the Study of Volcanos.—Second Series

1876 ◽  
Vol 3 (8) ◽  
pp. 337-345 ◽  
Author(s):  
John W. Judd
Keyword(s):  
Earth’S Crust ◽  
Abnormal Development ◽  
Preliminary Stage ◽  
Mountain Ranges ◽  
Sedimentary Deposits ◽  
The Earth ◽  
Mountain System ◽  
Earth's Crust ◽  
Green Mountains

The study of the great mountain ranges of America by Rogers, Hall, Dana, Le Conte, Hunt, and other geologists, has now thrown much new light on the earth-movements which precede and accompany the formation of mountain chains. As the result of these researches, it appears certain that the preliminary stage in the formation of every mountain system has consisted in a long-continued depression of the area which is afterwards to become its site; and, in consequence of this prolonged subsidence, the accumulation of an enormous thickness of stratified rocks, within the great trough so formed, has taken place. Of this character, as is now well known, have been the earlier manifestations of the subterranean forces that were concerned in the formation of the Appalachians, Green Mountains, and other American ranges; the districts in which they are situated were subjected to long-continued depression, which permitted of an abnormal development of all the members of the sedimentary deposits formed during this initiatory period; and it was by the folding, metamorphism and crushing together of this abnormally thickened portion of the earth's crust that the indurated and elevated masses have been formed which denudation has sculptured into the existing mountain chains.

scholarly journals III. On the degree of uncertainty which local attraction, if not allowed for, occasions in the map of a country, and in the mean figure of the Earth as determined by geodesy: a method of obtaining the mean figure free from ambiguity, from a comparison of the Anglo-Gallic, Russian, and Indian arcs: and speculations on the constitution of the Earth’s crust

1864 ◽  
Vol 13 ◽  
pp. 18-19
Keyword(s):  
Earth’S Crust ◽  
Plumb Line ◽  
Level Surface ◽  
Middle Latitudes ◽  
The Earth ◽  
Figure Of The Earth ◽  
The Mean ◽  
Earth's Crust

After referring to a former paper in which he had shown that, in the Great Indian Arc of meridian, deflections of the plumb-line amounting to as much as 20" or 30" would be produced if there were no sources of compensation in variations of density beneath the surface of the earth, and after alluding to a remarkable local deflection which M. Otto Struve had discovered in the neighbourhood of Moscow, the author proceeds to consider, in the first instance, the effect of local attraction in mapping a country according to the method followed by geodesists, in which differences of latitude and longitude are determined by means of the measured lengths of arcs, by substituting these lengths and the observed middle latitudes in the known trigonometrical formulae, using the mean figure of the earth, although the actual level surface may differ from that belonging to the mean figure in consequence of local attraction.

VII.—A Reply to Sir H. Howorth's Paper on “Recent Changes of Level.”

1894 ◽  
Vol 1 (11) ◽  
pp. 502-505
Author(s):  
Mark Stirrup
Keyword(s):  
Earth’S Crust ◽  
Relative Level ◽  
Mountain Ranges ◽  
Sequence Of Events ◽  
The Earth ◽  
Earth's Crust ◽  
Relationship Of ◽  
Geological Magazine

In a paper published in the Geological Magazine, September, 1894, Sir Henry Howorth expatiates on recent changes of the relative level of land and sea in support of his views on the Mammoth age and his diluvial catastrophe,inwhich there seems to me some very extraordinary confusion in the matter of geological chronology and sequence of events. The first paragraph reads as follows:—“In some recent papers published in the Geological Magazine, I have endeavoured to show that at the close of the Mammoth age there was a very considerable dislocation of the Earth's crust, and that a consequence of it was the upheaval of Some of the highest masses of land on the earth, including the massive mountains of Asia and the American Cordillera. I now propose to show that (as is a priori probable) there was a concurrent collapse or sinking of the ground over large areas, which, as in the corresponding upheaval, was very rapid, if not sudden” (the italics are mine). The suggested relationship of these various events and their alleged catastrophic character, induces me to again enter this ever-expanding field of controversy.In support of his thesis Sir Henry first refers to the subsidences which resulted in the separation of England from the Continent, and consequent extinction of the Mammoth. Assuming that the course of things was as stated, when it is further suggested that this event was contemporaneous with great dislocation of the Earth's crust, resultinginstupendous upheavals of mountain ranges in Asia and America, he attempts more than can well be proved.

On the degree of uncertainty which local attraction, if not allowed for, occasions in the map of a country, and in the mean figure of the earth as determined by geodesy ; a method of obtaining the mean figure free from ambiguity by a comparison of the Anglo-Gallic, Russian, and Indian Arcs ; and speculations on the constitution of the earth's crust

1864 ◽  
Vol 13 ◽  
pp. 253-276 ◽  
Keyword(s):  
Royal Society ◽  
Earth’S Crust ◽  
Plumb Line ◽  
Remarkable Difference ◽  
Astronomical Society ◽  
Royal Astronomical Society ◽  
The Earth ◽  
Figure Of The Earth ◽  
The Mean ◽  
Earth's Crust

1. In former communications to the Royal Society I have shown that Local Attraction, owing to the amount it in some places attains, is a more troublesome element to deal with in geodetical operations than had generally been supposed. The Mountains and the Ocean were shown to combine to make the deviation of the plumb-line as much as 22".71, 17".23, 21".05, 34".16 (or quantities not differing materially from them) in the four principal stations of the Great Arc of India between Cape Comorin and the Himmalayas—viz. at Punnœ (8° 9' 31"), Damargida (18° 3' 15'), Kalianpur (24° 7' 11"), Kaliana (29° 30' 48") ; and how much these might be increased or lessened by the effect of variations of density in the crust below t was difficult to say. Deviations amounting to at least such quantities as 7''.61 and 7".87 were shown to exist in the stations of the Indian Arc, arising from this last cause (see Phil. Trans. 1861, p. 593 (4) and (5)). M. Otto Struve has lately called attention to similarly important deflections caused by local attraction in Russia—and especially to a remarkable difference of deflection at two stations near Moscow, only about eighteen miles apart, amounting to as much as 18", which is attributed to an invisible unknown cause in the strata below (see Monthly Notices of the Royal Astronomical Society, April 1862).

scholarly journals INQUIRY INTO VERTICAL MOVEMENTS OF THE EARTH‘S CRUST BASED ON SAMPLES FROM EASTERN LITHUANIA

2014 ◽  
Vol 40 (2) ◽  
pp. 58-67
Author(s):  
Ruta Puziene ◽  
Asta Anikeniene ◽  
Gitana Karsokiene
Keyword(s):  
Regression Models ◽  
Earth’S Crust ◽  
Movement Velocity ◽  
Correlation Matrices ◽  
Vertical Movements ◽  
Statistical Correlations ◽  
Horizontal Gradients ◽  
The Earth ◽  
Earth's Crust ◽  
Made In

In the research of vertical movements of the earth’s crust, examination of statistical correlations between the measured vertical movements of the earth’s crust and territorial geo-indexes is accomplished with the help of mathematical statistical analysis. Availability of the precise repeated levelling measuring data coupled with the preferred research methodology offer a chance to determine and predict recent vertical movements of the earth’s crust. For the inquiry into recent vertical movements of the earth’s crust, a Lithuanian class I vertical network levelling polygon was used. Drawing on measurements made in the polygon, vertical velocities of earth’s crust movements were calculated along the following levelling lines. For determining the relations shared by vertical movements of the earth’s crust and territorial geo-parameters, the following territory-defining parameters are accepted. Examination of the special qualities of relations shared by vertical movements of the earth’s crust and geo-parameters in the territory under research contributed to the computation of correlation matrices. Regression models are worked out taking into consideration only particular territory-defining geo-parameters, i.e. only those parameters which exhibit the following correlation coefficient value of the vertical earth’s crust movement velocity: r ≥ 0.50. A forecast of the velocities pertaining to vertical movements of the earth’s crust in the territory under examination was made with the application of regression models. Further in the process of this research, a map was compiled specifying the velocities of vertical movements of the earth’s crust in the territory. In the eastern part of this territory, the earth’s crust rises at a rate of up to 3 mm/year; while in the western part of it, the earth crust lowers at a rate of up to –1.5 mm/year. In order to pinpoint territories characterised by temperate and regular rising/lowering or intensive rising/lowering, a map of horizontal gradients of recent vertical earth crust movements in the territory enclosed by levelling polygon was compiled.

scholarly journals Improving of electrical channels for magnetotelluric sounding instrumentation

2015 ◽  
Vol 4 (2) ◽  
pp. 149-154 ◽  
Author(s):  
A. M. Prystai ◽  
V. O. Pronenko
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Deep Structure ◽  
Experimental Tests ◽  
Magnetotelluric Sounding ◽  
Earth’S Crust ◽  
Geomagnetic Variations ◽  
The Earth ◽  
Wide Range ◽  
Earth's Crust

Abstract. The study of the deep structure of the Earth's crust is of great interest for both applied (e.g. mineral exploration) and scientific research. For this the electromagnetic (EM) studies which enable one to construct the distribution of electrical conductivity in the Earth's crust are of great use. The most common method of EM exploration is magnetotelluric sounding (MT). This passive method of research uses a wide range of natural geomagnetic variations as a powerful source of electromagnetic induction in the Earth, producing telluric current variations there. It includes the measurements of variations of natural electric and magnetic fields in orthogonal directions at the surface of the Earth. By this, the measurements of electric fields are much more complicated metrological processes, and, namely, they limit the precision of MT prospecting. This is especially complicated at deep sounding when measurements of long periods are of interest. The increase in the accuracy of the electric field measurement can significantly improve the quality of MT data. Because of this, the development of a new version of an instrument for the measurements of electric fields at MT – both electric field sensors and the electrometer – with higher levels relative to the known instrument parameter level – was initiated. The paper deals with the peculiarities of this development and the results of experimental tests of the new sensors and electrometers included as a unit in the long-period magnetotelluric station LEMI-420 are given.

Metamorphic Rocks

2018 ◽  
Author(s):  
Alex Maltman
Keyword(s):  
Metamorphic Rock ◽  
Central Area ◽  
Tectonic Stress ◽  
Earth’S Crust ◽  
Metamorphic Rocks ◽  
Tectonic Plates ◽  
The Earth ◽  
Two Factors ◽  
Earth's Crust ◽  
Increased Pressure

We come now to the metamorphic rocks, the result of modifications to already existing rock. I’m well aware that this can all seem a bit mysterious. After all, no one has ever seen the changes take place; no one has ever witnessed a metamorphic rock form—the processes are imperceptibly slow, and they happen deep in the Earth’s crust, way out of sight. Why should these changes happen? Well, they are primarily driven by increases in pressure and temperature, so we begin with a look at these two factors. There are sites in the Earth’s crust where material becomes progressively buried. It happens, for example, where a tectonic plate is driving underneath another one, taking rocks ever deeper as it descends. It can happen in the central area of a plate that is stretching and sagging, allowing thick accumulations of sediment. It’s pretty self-evident that as buried material gets deeper, because of the growing weight of rocks above bearing down due to gravity, it becomes subjected to increasing burial pressure. Less intuitive, though, is the fact that this pressure acts on a volume of rock equally in all directions. Imagine a small volume of rock at depth. It’s bearing the weight of the rocks above it, and so it responds by trying to move downward and to spread out laterally. Of course, it can’t because it’s constrained all around by other volumes of rock that are trying to do exactly the same thing. And so the downward gravity is translated into an all-around pressure. It’s the same effect as diving down to the bottom of a swimming pool. You feel the increased pressure owing to the weight of water above, but you feel it equally in all directions. All-round pressure like this can cause things to change in volume, through changing their density, but it can’t change their shape. However, there can be another kind of pressure as well, and this does have direction, and it can cause change of shape. In the Earth, we call it tectonic stress. It comes about through heat-driven motions in the Earth, including the movement of tectonic plates.

scholarly journals Critically Stressed Areas of Earth’s Crust as Medium for Man-caused Hazards

2018 ◽  
Vol 56 ◽  
pp. 02007 ◽  
Author(s):  
Andrian Batugin
Keyword(s):  
Critical Stress ◽  
Earth’S Crust ◽  
Mining Operations ◽  
Induced Earthquake ◽  
The Earth ◽  
Stress Zone ◽  
Mining Works ◽  
Earth's Crust ◽  
Rock Strata ◽  
Insight Into

Despite advances in rockburst studies, suddenness of major geodynamic events is reported in a number of cases. Phenomenological tectonophysical model is suggested to explain some geodynamics phenomena. Prof. Petukhov I.M. suggested a concept: the Earth crust's critical stress condition is developed due to horizontal compressive forces and entrains rock strata from the sub-surface to a certain depth. The conditions that induced earthquake in 2013 at Bachat coal field in south west Kuzbass are considered in terms of critical stress developed in the top layer of the Earth crust. Estimates show that the size of the critical stress zone, produced presumably by interaction of huge (over 100 km) crustal blocks is at least 10km. Whereas critical stress zone is located in the top part of Earth's crust, mining operations in the pit including blast operations was making a direct impact on this area. Shallow occurrence of critical stress area and its size can provide insight into why mining works brought about induced earthquake with hypocenter at the depth of several kilometers. The conclusion has been made that regional areas of critical stress within rock massif developed as a result of crustal blocks interaction create hazard medium for mining.

scholarly journals On the shapes of the isogeotherms under mountain ranges in radio-active districts

1910 ◽  
Vol 83 (563) ◽  
pp. 339-346 ◽  
Keyword(s):  
Physical Condition ◽  
Accurate Solution ◽  
Earth’S Crust ◽  
Mountain Range ◽  
Mountain Ranges ◽  
Earth's Crust

The importance attached by geologists to the distribution of temperature within the earth’s crust as a factor in the production of movements of the crust, and in particular in the formation of mountain ranges, has made it necessary to consider if it is possible to determine the distribution of temperature under and in the neighbourhood of a mountain range, by a method more rigid and accurate than that used by Fisher, and more closely following the physical condition of the problem than that used by Thoma. In what follows it will be shown that an accurate solution can be obtained in certain simple cases, even when the soil is radio-active.

Sign in / Sign up

Export Citation Format

Share Document