THE MOUNTAINS AS STABILIZERS FOR THE EARTH

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

"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) In
these two Qur’anic verses it is explicitly stated that the
stabilization of the Earth by means of its mountains was a specific
stage in the long process of creation of our planet and still is a very
important phenomenon in making that planet suitable for living. Now, the
following question arises: how can modern Earth Scientists visualize
mountains as means of fixation for the Earth? As mentioned above, the
rocky outer cover of the Earth (the lithosphere, which is 65-70 km thick
under oceans and 100-150 km thick under continents) is broken up by
deep rift systems into separate plates (major, lesser and minor plates
as well as micro plates, plate fragments and plate remains). Each of
these rigid, outer, rocky covers of the Earth floats on the semi-molten,
plastic outermost zone of the Earth’s Mantle (the asthenosphere) and
move freely away from, past or towards adjacent plates. At the diverging
boundary of each plate, molten magma rises and solidifies to form
strips of new ocean floor, and at the opposite boundary (the converging
boundary) the plate dives underneath the adjacent plate ‘(subducts) to
be gradually consumed in the underlying uppermost mantle zone (the
asthenosphere) at exactly the same rate of sea-floor spreading on the
opposite boundary. An ideal rectangular, lithospheric plate would thus
have one edge growing at a mid-oceanic rift zone (diverging boundary),
the opposite edge being consumed into he asthenosphere of the
overriding plate (converging or subduction boundary) and the other two
edges sliding past the edges of adjacent plates along transform faults
(transcurrent or transform fault boundaries, sliding or gliding
boundaries). In this way, the lithospheric plates are constantly
shifting around the Earth, despite their rigidity, and as they are
carrying continents with them, such continents are also constantly
drifting away or towards each other. As a plate is forced under another
plate and gets gradually consumed by melting, magmatic activity is set
into action. More viscous magmas are intruded, while lighter and more
fluid ones are extruded to form island arcs that eventually grow into
continents, are plastered to the margins of nearby continents or are
squeezed between two colliding continents. Traces of what is believed to
have been former island-arcs are now detected along the margins and in
the interiors of many of today’s continents (e.g. the Arabian Shield).
The divergence and convergence of lithospheric plates are not confined
to ocean basins, but are also active within continents and along their
margins. This can be demonstrated, by both the Red Sea and the Gulf of California
troughs which are extensions of oceanic rifts and are currently
widening at the rate of 3cm/year in the former case and 6 cm/year in the
latter. Again the collision of the Indian Plate with the Eurasian Plate
(which is a valid example of continent/continent collision) has
resulted in the formation of the Himalayan Chain, with the highest peaks
currently found on the surface of the Earth. Earthquakes are common at
all plates’ boundaries, but are most abundant and most destructive along
the collisional ones. Throughout the length of the divergent plate
boundary, earthquakes are shallow seated, but along the subduction
zones, these come from shallow, intermediate and deep foci (down to a
depth of 700 kin), accompanying the downward movement of the subducting
plate below the over-riding one. Seismic events also take place at the
plane’s transcurrent fault boundaries where ii slides past the adjacent
plates along transform faults. Plate movements along fault planes do not
occur continuously, but in interrupted, sudden jerks, which release
accumulated strain. Moreover, it has to be mentioned that lithospheric
plates do not all travel at the same speed, but this varies from one
case to another. Where the plates are rapidly diverging, the extruding
lava in the plane of divergence spreads out over a wide expanse of the
ocean bottom and heaps up to form a broad mid-oceanic ridge, with
gradually sloping sides (e.g. the East Pacific Rise). Contrary to this,
slow divergence of plates gives time for the erupting lava flows to
accumulate in much higher heaps, with steep crests (e.g. the
Mid-Atlantic Ridge). The rates of plate movements away from their
respective spreading centers can be easily calculated by measuring the
distances of each pair of magnetic anomaly strips on both sides of the
plane of spreading. Such strips can be easily identified and dated, the
distance of each from its spreading center can be measured, and hence
the average spreading rate can be calculated .Spreading rates at
mid-oceanic ridges are usually given as half-rates, while plate
velocities at trenches are full rates. This is simply because the rate
at which one lithospheric plate moves away from its spreading center
represents half the movement at that center as the full spreading rate
is the velocity differential between the two diverging plates which were
separated at the spreading center (the mid-oceanic ridge). In studying
the pattern of motion of plates and plate boundaries, nothing is fixed,
as all velocities are relative. Spreading rates vary from about 1
cm/year in the Arctic Ocean, to about 18cm/year in the Pacific Ocean, with the average being 4-5 cm/year. Apparently, the Pacific Ocean is now spreading almost ten times faster than the Atlantic
(c.f. Dott and Batten, 1988). Rates of convergence between plates at
oceanic trenches and mountain belts can be computed by vector addition
of known plate rotations (Cf. Le Pichon, 1968). These can be as high as 9
cm/year at oceanic trenches and 6 cm/year along mountain belts (Le
Pichon, op. c.i.t) Rates of slip along the transform fault boundaries of
the lithospheric plate can also be calculated, once the rates of plate
rotation are known. The patterns of magnetic anomaly strips and sediment
thickness suggest that spreading patterns and velocities have been
different in the past, and that activity along mid-oceanic ridges varies
in both time and space. Consequently such ridges appear, migrate and
disappear. Spreading from the Mid-Atlantic rift zone began between 200
and 150 MYBP, from the northwestern Indian Ocean rift zone between 100
and 80 MYBP, while both Australia and Antarctica
did not separate until 65 MYBP (cf. Dott and Batten, bc. cit.).
Volcanoes also abound at divergent boundaries, whether under the sea or
on land. Most of these volcanoes have been active for a period of 20-30
million years or even more (e.g. the Canary Islands).
During such long periods of activity, older volcanoes were gradually
carried away from the spreading zone and its constantly renewed plate
edge, until they became out of reach of the magma body that used to feed
them and hence gradually faded out and died. The floor of the
present-day Pacific Ocean is spudded
with a large number of submerged, non-eruptive volcanic cones (guyots)
that are believed to have come into being by a similar process.
Continental orogenic belts are the result of plate boundary interaction,
which reaches its climax when two continents come into collision, after
consuming the ocean floor that used to separate them. Such
continent/continent collision results in the scraping off of all
sediments and sedimentary rocks, as well as volcanic rocks that have
accumulated on the ocean floor and in the oceanic trenches and squeezing
them between the two colliding continents. This results in considerable
crumpling of the margins of the two continents, followed by the
cessation of plate movement at the junction. The two continental plates
become welded together, with considerable crystal shortening (in the
form of giant thrusts and infrastructural nappes) and considerable
crystal thickening (in the form of the decoupling of the two
lithospheric plates as well as their penetration by the deep downward
extensions of the mountainous chains then formed). Such downward
extensions of the mountains are commonly known as mountain roots” and
are several times their protrusion above the ground surface. Such deep
roots stabilize the continental masses (or plates), as plate motions are
almost completely halted by their formation, especially when the
mountain mass is entrapped within a continent as an old craton. Again,
the notion of a plastic layer (asthenosphere) directly below the outer
rocky cover of the Earth (lithosphere) makes it possible to understand
why the continents are elevated above the oceanic basins, why the crust
beneath them is much thicker (30-40 kin) than it is beneath the oceans
(5-8 kin) and why the thickness of the continental plates (100-150 kin)
is much greater than that of the oceanic plates (65-70 kin). This is
simply because of the fact that the less dense lithosphere (about 2.7 to
2.9 gm/cm3) is believed to float on top of the denser, and more easily
deformed, plastic asthenosphere (> 3.5 gm 1cm3), in exactly the same
way an inceberg floats in the oceanic waters. Inasmuch as mountains have
very deep roots, all other elevated regions such as plateaus and
continents must have corresponding (although much shallower) roots,
extending downward into the asthenosphere. In other words, the entire
lithosphere is floating above the plastic or semiplastic asthenosphere,
and its elevated structures are held steadily by their downwardly
plunging roots .Lithospheric plates move about along the surface of the
Earth in response to the way in which heat flows arrive at the base of
the lithosphere, aided by the rotation of the Earth around its own axis.
There is enough geologic evidence to support the fact that both
processes have been much more active in the distant geologic past,
slowing gradually with time. Consequently, it is believed that plate
movements have operated much more rapidly in the early stages of the
creation of the Earth and have been steadily slowing down with the
steady building-up of mountains and the accretion of continents. This
slowing down of plate movements may also have been aided by a steady
slowing down in the Earth’s rotation around its own axis (due to the
operating influence of tides which is attributed to the gravitational
pull of both the sun and the moon) and also by a steady decrease in the
amount of heat arriving from the interior of the Earth to its surface as
a result of the continued consumption of the source of such heat flows
which is believed to be the decay of radioactive materials. The above
mentioned discussion clearly indicates that one of the basic functions
of mountains is its role in stabilizing continental masses lest these
would shake and jerk, making life virtually impossible on the surface of
such continents) The precedence of the Glorious Qur’an with more than
14 centuries in describing this phenomenon is a clear testimony for the
fact that this Noble Book is the word of the Creator in its divine
purity and that Muhammad (pbuh) is His final Messenger. In an authentic
saying, this noble profit 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 lived at a time between 570 and 632 A.C.) When no
other man was aware of such facts, which only started to unfold by the
beginning of the twentieth century, and was not finally formulated until
towards its very end. The above mentioned four examples of Qur’anic
verses include the basic foundations of the most recently established
concept in Earth Sciences, namely “the concept of Plate Tectonics”. This
concept was only formulated in the late sixties and the early seventies
of this century (cf. McKenzie 1967; Maxwell and others, 1970; etc.),
i.e. about 1335 years after the time of Prophet Muhammad (pbuh) the
concept is based on the following observed facts:

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]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).

[b]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);

[b]"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);
[/b]
"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);

[b]"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
plas
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.

[/b][/b][/b]