THE MOUNTAINS AS STABILIZERS FOR THE EARTH
"And the mountains He has fixed firmly, (To be) a provision and benefit for you and your cattle." (Surat An-Nazi'at (Those Who Pull Out): 32-33)
By: Dr. / Zaghloul El-Naggar
a) That the outer rocky layer of the Earth is deeply faulted, and this is explicitly mentioned in the Qur’anic verse "And the earth which splits (with the growth of trees and plants)." (Surat At-Tariq (The Night-Comer): 12).
b) That hot lava flows pour out from such deep faults, particularly in the middle parts of certain seas and oceans, and this is clearly implied in the Qur’anic verse"And the sea kept filled (or it will be fire kindled on the Day of Resurrection)." (Surat At-Tur (The Mount):6).
c) That the flow of such lavas can cause the surface of the Earth to shake and jerk, can lead to the movement of these faulted blocks and the formation of trenches in which deep roots of the mountains are formed. This is implied by both the verses "And the earth which splits (with the growth of trees and plants)." (Surat At-Tariq (The Night-Comer): 12). And "And the mountains as pegs? (Surat An-Naba' (The Great News):7).
d) That these. sudden jerky movements of the continental plates are halted by the formation of mountains and this is clearly emphasized in the verse "And the mountains He has fixed firmly, (Surat An-Nazi'at (Those Who Pull Out): 32)., as well as in many other Qur’anic verses "And it is He Who spread out the earth, and placed therein firm mountains and rivers and of every kind of fruits He made Zawjain Ithnain (two in pairs-may mean two kinds or it may mean: of two varieties, e.g. black and white, sweet and sour, small and big).He brings the night as a cover over the day. Verily, in these things, there are Ayat (proofs, evidences, lessons, signs, etc.) for people who reflect." (Surat Ar-Ra'd (The Thunder): 3);
"And the earth We have spread out, and have placed therein firm mountains, and caused to grow therein all kinds of things in due proportion." (Surat Al-Hijr (The Rocky Tract): 19);
"And We have placed on the earth firm mountains, lest it should shake with them, and We placed therein broad highways for them to pass through, that they may be guided." (Surat Al-Anbiya' (The Prophets): 31);
"Is not He (better than your gods) Who has made the earth as a fixed abode, and has placed rivers in its midst, and has placed firm mountains therein, and has set a barrier between the two seas (of salt and sweet water)? Is there any ilah (god) with Allah? Nay, but most of them know not!" (Surat An-Naml (The Ants): 61);
"And have placed therein firm, and tall mountains, and have given you to drink sweet water?" (Surat Al-Mursalat (Those sent forth): 27);
"And the mountains He has fixed firmly." (Surat An-Nazi'at (Those Who Pull Out): 32)
These facts about our planet started to unfold only in the middle of the nineteenth century, more than 12 centuries after the revelation of the Glorious Qur’an, when George Airy (1865) came to realize that the excess mass of the mountains above sea-level is compensated by a deficiency of mass in the form of underlying roots which provide the buoyant support for the mountains. Airy (Op... cit) proposed that the enormously heavy mountains are not supported by a strong rigid crust below, but that they “float” in a “sea” of dense rocks. In such a plastic, non-rigid “sea” of dense rocks, high mountains are buoyed up at depth in more or less the same way an inceberg is hydrostatically buoyed up by water displaced by the great mass of ice below the water surface. In this manner, a mountain range is isostatic in relation to the surrounding portions of the Earth’s Crust, or in other words, mountains are merely the tops of great masses of rocks mostly hidden below the ground surface, and floating in a more dense substratum as icebergs float in water. A mountainous mass with an average specific gravity of 2.7 (that of granite) can float into a layer of plastic simatic rock (with a specific gravity of 3.0) with a “root” of about 9/10, and a protrusion of 1/10 its total length. This ratio of mountain root to its outward elevation can some times go up to 15:1, depending on the difference in the average densities of both the mountain s rock composition and of the material in which its root is immersed. Such observations have led to the concept of isostacy (Dutton, 1889) and have introduced the principles of gravity surveying. Again, both seismic and gravitational evidences have clearly indicated that the Earth’s crust is thickest under the highest of mountains and is thinnest under the lowest of oceanic basins. These studies have also proved that the shallowest parts of the oceans are situated in their middle parts (mid-oceanic ridges), while their deepest parts are adjacent to continental masses (deep oceanic trenches). Such observations could not be fully understood until the late sixties of this century when the formulation of “the concept of plate tectonics” has started to proceed apace. In this concept the outer rocky zone of the Earth (the lithosphere) is split by major zones of fractures (or rifts) into a number of slabs or plates (65-150 km thick and several thousands or even millions of square kilometers in surface area). These plates float on a denser, more plastic substratum (the asthenosphere) and hence, glide above it and move across the surface of the Earth. The movements of these lithospheric plates are accelerated by the pouring out of lavas at their divergent boundaries ( at the rift zones) by the rotation of the Earth around its own axis as well as by hot plumes and convection currents rising to the bottom of such plates from within the asthenosphere. Consequently, the boundaries of lithospheric plates are outlined by the locations of frequent earthquakes and intensive volcanic activities. In their movements, lithospheric plates are accelerated at their divergent boundaries by the Outpouring lavas (molten rocks) that on cooling form new ocean floors, and are consumed at their convergent boundaries (by exactly the same rate of divergence) by subducting under the adjacent plates and returning to the Earth’s interior where they gradually melt. At other boundaries, the plates simply slide past each other along transform faults. In this manner, the plates shift across the Earth’s surface and carry the continents with them, resulting in the phenomenon of continental drift. As the lithospheric plates move horizontally across the Earth’s surface, they eventually collide, producing high mountain ranges that act as a means of fixation for the two moving plates and hence, stop them from further shaking and jerking, although earthquakes and volcanic eruptions may still be felt along the zone of collision. But once the mountainous chain has been trapped within a continental mass it will form a stable craton, without any volcanic activity or earthquakes. When one lithospheric plate is forced under another and starts to melt, magma rises to form island arcs that eventually grow into continents. All continents are believed to have their origins in processes of this kind, and further collision of continent/island arcs or continent/continent can lead to the further growth of continents and to the stability of the Earth’s lithosphere. Lithospheric plates do not all travel at the same speed, and are believed to have been slowing down with time. The details of how the motion occurs are still in doubt, but two hypotheses have been put forward: Convection spreading and gravity spreading, the former of which seems to be gaining more support. Lithospheric plates probably move about in response to the way in which heat arrives at their base. Such movement was much faster in the geologic past, because of the faster rate of rotation of the Earth (or its spinning around its own axis) and the greater quantities of radioactive minerals that have been steadily decaying with time. The facts that the Earth is a deeply fractured and rifted planet, and that red-hot magma flows are steadily pouring out from such rifts are among the most recent discoveries in the field of Earth Sciences. Magmatic flows at mid-oceanic rift zones result in sea-floor spreading, the piling up of mid-oceanic basaltic ridges and in one of the most striking phenomena of our planet where seas and oceans experiencing such activities are actually set on fire and boiling at their bottoms. Again, magmatic flows at mid-oceanic ridges lead to the gradual descent of the oceanic lithospheric plate under the opposite continental one, forming deep oceanic trenches in which massive accumulations of sedimentary, igneous and metamorphic rocks accumulate and are finally crumbled to constitute a mountainous chain with a very deep root, which brings the movement of the two collidinc plates lb a big halt. The function of mountains as stabilizers for the Earth can be clearly seen in the role played by their very deep roots, which penetrate the total thickness of continental lithospheric plates (which are 100-150 km thick) and float into the underlying, dense, viscous, semi-molten asthenosphere. This is justified by the fact that the motions of lithospheric plates come to a big halt when a continent collides with another continent, consuming the oceanic lithospheric plate that used to separate them. This produces what is known as a collisional-type mountain, which is believed to represent the last phase of mountain building. Here, the thickness of the continental lithospheric plate is doubled and mountains reach their maximum downward extensions and hence their greatest capacity of fixation. Without the formation of mountains, the movement of lithospheric plates would have been much faster and their collision more drastic. Again, through the process of orogenesis (mountain-building), the Earth’s crust is periodically rejuvenated and continents are gradually built and accreted. New mineral wealthes are added and new soils are produced (as by the elevation of mountains, weathering and erosional processes are activated). The more the mountainous chain is weathered and eroded, the, more it will be isostatically elevated. This can go on until the mountain root is completely pulled out of the asthenosphere, and then erosion finally wins the battle over the mountain range as there is no more immersed part of the root to uplift the range by isostacy. The lithosphere beneath the eroded down mountain range will have the same thickness as the remainder of the continental interior to which it was plastered, which is more or less an equilibrium thickness. At this point, the old mountain system becomes a part of the stable craton, and hence the size of the continent is gradually increased. This goes on until the continent starts to fragment by an opposite process of rifting and diverging to form two or more continental masses separated by longitudinal seas that spread gradually into oceans (the continent / ocean cycle). These basic facts of our planet started to unfold to human knowledge since the mid-nineteenth century, and was never known before or visualized in anything near the above-mentioned framework until the late sixties of this century, when the concept of plate tectonics was in the process of shaping. The fact that the Glorious Qur’an (which was revealed) more than 14 centuries ago as the Book of Divine guidance) explicitly emphasizes the deeply fractured nature of the Earth and the oceans that are set on fire, as well as describes mountains as pickets (or pegs) and stresses their role as stabilizers for the Earth (in 22 different verses) is only one of numerous testimonies for the Divine nature of this Glorious Book. Prophet Muhammad (phuh) who lived between 570 and 632 A.C. is quoted to have said that: When Allah created the Earth, it started to shake and jerk, then Allah stabilized it by the mountains. This unlettered Prophet was definitely educated by the Divine revelation, as no man at his time and for several centuries after him knew anything about such geological facts which started to unfold only since the mid-nineteenth century and came to be understood only a few decades ago.http://www.elnaggarzr.com/en/main.php?id=54&Shift=0
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