How Mountains are Made
Mountain building (or, in the jargon, orogeny) is a topic which has been been one of the basics of geology. Details of the manner and conditions under which most of the Earth's present mountain chains were formed, and the times at which they arose, have reached a settled state.However the basic mechanisms by which mountains have been formed are not so settled, there has been no completely satisfying explanation for why mountains have been formed where they were. If you look at the mountains on Earth, they mostly fall into one of two classes, which we can call 'long' and 'fat'.
The 'long' mountains are those which form extensive chains. A prime example is the Andes Mountains in South America, stretching right down the west coast of the continent. Often they are regarded as an extension of the Rocky Mountains of North America, connected to these by the mountain chain running right through Central America. Other mountain chains have been identified which are partly submerged, like the Aleutian Island chain in the north Pacific, or even wholly submerged like the mid-Atlantic ridges.
'Long' mountains are almost always associated with volcanic activity, either now or in the past. As a result, they are usually assumed to have been formed by volcanic activity. If the mountain chain is part of a continent, the rocks which make it up are usually high in silica, of a class called 'acidic' or continental. In contrast, mountain chains formed in the sea have rocks which, like the sea-bed around them, are lower in silica and are called 'basic' or oceanic. Both types of rock are classed as 'igneous' (derived from fire), that is, they are assumed to have been formed from the cooling down of molten rock.
'Fat' mountains, in the sense used here, tend to be oval in outline rather than linear, and often contain plateaus and wide basins. The rocks they contain are often of sedimentary origin rather than of igneous (volcanic) origin, and sometimes they contain elaborate folded structures, in which beds of sedimentary rock have clearly been crumpled up and pushed against each other, sometimes right over each other. They usually don't contain volcanos. And they are not found submerged, as 'undersea massifs', on the deeper ocean beds.
A clear example of 'fat' mountains is the Himalayas. Fat mountains are assumed to result from various forces of compression occurring in the Earth's crust. The origin of these forces is often glossed over, but is sometimes purely a matter of impact. The Himalayas are now generally accepted as resulting from an impact between India (drifting north after breaking off from Gondwanaland) and that part of Laurasia which is now occupied by western China and the south-eastern section of the USSR.
Fig. 8.1. Mountains of the western USA
Other mountains appear more mixed in origin. However, in these, it is usually possible to say that both the 'long' mechanism and the 'fat' mechanism have operated, rather than a single 'intermediate' mechanism. Thus the mountains of the western United States (Fig. 8.1) appear to consist of a 'long' component, running along parallel to the coast, backed by a 'fat' component (the 'Rockies' proper) further inland.
In Chapter 7 we had evidence that most of the present land surface is a patchwork of 'domains' of very varying sizes, pushed together or pulled apart by forces associated with Earth expansion. This leads very naturally to the suggestion that all mountain-building is a result of forces due to Earth expansion, expressed through the interaction of Earth domains.
Proposition 8A
All mountains have been created through the interaction of
domains
Taking the 'fat' mechanism first, the suggestion is that all 'fat' mountains have been formed by impacts between Earth domains. As the domains are very varied in size, composition, and origin, the resulting landforms are themselves very varied. Some areas may have been worked over more than once, having been impacted from more than one side. As already noted, such a mechanism has already been accepted for the origin of the Himalayas. Other fairly clear 'fat' areas are the Swiss-Austrian Alps, formed by the impact of Italy against what is now central Europe, and the Pyrenees, formed by Spain hitting against France.
Proposition 8B
'Fat' mountains have been created by domain impacts
The suggested origin of 'long' mountains is more controversial. As these mountains are almost invariably associated with volcanos, to date it has been implicitly assumed that the volcanism caused the mountains. From the evidence already given in this book, it appears that a simpler and more reasonable explanation is that 'long' mountains are formed by the frictional action of domains sliding one against the other, causing melting and volcanism. As before, the domains are in motion because of Earth expansion.
Proposition 8C
'Long' mountains have been created by domain rubbing
It is reasonable that any two domains in sliding contact will have somewhat rough edges, which do not match each other. If they move relative to one another, the 'burrs' along the edges will naturally pile up to create local high spots. If they continue to slide and rub, or if there is a chain of them active in a shuffle belt, eventually a whole mountain chain will be built up along the junction.
This gives a simple explanation for an observed phenomenon. It also leads to a most important conclusion relating to volcanos and other geothermic phenomena such as hot springs.
The Origin of Volcanos
Volcanos are hot -- hot enough to contain molten rock. It has been more or less taken for granted in the past that this hot rock has welled up from the molten core of the Earth, which has pushed up through 'lines of weakness' in the crust.In the next chapter, we will see that the concept that the heat of volcanos comes from the Earth's molten core has little evidence to support it. Leaving the evidence of this point aside for the moment, we can see that it has a vital implication for the origin of volcanos. If their heat does not come from the molten core of the Earth, where does it come from?
It appears likely to me that the heat in volcanos is generated by frictional heating of the edge rocks of two domains sliding one against the other. The intense heat generated through friction is well known -- a classic example is making fire by rubbing two sticks together.
The heat generated through friction is usually dependent on the coefficient of friction ('roughness') and the masses and relative speed of the objects rubbing together. When we are talking about about Earth domains, these masses are enormously large compared to the everyday objects we see involved in friction, and their capacity to generate heat is equally enormous. It is certainly easily great enough to melt rocks.
Proposition 8D
Volcanos are created by the friction between rubbing
domains
This proposition accords well with the fact that the molten rocks coming out of volcanos are generally of similar overall chemical composition to the surrounding country. If they were really formed by molten core rock, pushing up through 'weak places' in the Earth's crust, they might all be expected to be of 'basic' composition like the rock assumed to underlie the 'acidic' continental material. In practice, only volcanos sitting on oceanic-rock sea beds produce basic-rock flows, those which are sited on typical continental rocks produce acidic-rock flows.
The proposition also fits in with the known physical properties of rocks, especially their thermal properties. Rocks conduct heat quite poorly and also hold a lot of heat well. This is just the sort of situation where, if a massive amount of heat is injected through friction, a section of rock will melt and possibly become hot enough for the heat to spread slowly into adjacent rocks.
If the heat input is great enough, or is created close enough to the surface, it may spread enough to melt its way through to the surface and create a volcano -- essentially an artesian molten-rock flow or rock 'gusher'. If there is not enough heat for this, the molten rock will slowly cool, insulated by the surrounding rock, and allow crystallization to occur -- visible crystals are specially characteristic of acidic rocks such as granite.
Igneous Rocks
An important corollary of Proposition 8D relates to the rock the volcanos produce, and also to other igneous rocks. That is, that igneous rocks are produced by domain friction, and are not 'primeval' products left over from the Earth's assumed molten beginnings.Proposition 8E
Igneous rocks are produced locally, through domain rubbing,
and not from a 'primeval' Earth source
The existence under the surface of vaguely spherical bodies of igneous rocks is well known; smaller ones are represented as 'magma chambers' (magma is molten rock), and larger, solidified ones as 'batholiths'. An interesting point is that batholiths are normally elongated along the line of a mountain chain
Figure 8.2 is a conventional representation of the rise of hot molten rock from the Earth's largely unknown inner reaches, and its further ascent to form a volcano. Shown is a large batholith, at the base of a thick layer of crustal rocks, itself connected to a magma chamber which has intruded into the layers of sedimentary rock beneath the land surface. This again is connected through a magma pipe with the cone and mouth of a volcano formed by the rock which solidified after flowing out from it.
Fig. 8.2. Conventional
representation of volcanos
and batholiths
Why should the magma come up from below and force its way through at this particular point? This is assumed to be due to 'weaknesses' in the Earth's crust at those points.
Now Figure 8.2 is obviously very diagrammatic and not to scale, but the situation it illustrates is, in my view, nonsense. No credible mechanisms have ever been suggested for why immense batholiths should happen to form at particular places, no reason for magma to be intruded and melt out 'chambers' at odd points within the sedimentary layers. In fact such behaviour is quite contrary to what we know about the flow of heat through materials such as rocks.
Worst of all, as we shall see in the next chapter, there is no evidence that the inner reaches of the Earth are made up of molten rock in the ordinary sense. This takes away the whole basis for the supposed pushing out of molten rock from volcanos through pressure from reserves within the Earth.
The concept of igneous rocks being formed locally, through the heat of friction caused by domain-edge rubbing, provides a far more satisfactory explanation for the observed facts. It explains why bodies of molten rock can be formed at quite different depths (friction having been more active there, due to waviness of the domain- edge surfaces). It removes the need to explain how molten rock manages to intrude into particular spots of the crust and melt out chambers. And it explains why batholiths are elongated, they are elongated along the rubbing domain edges.
Geysers and Hot Springs
As well as volcanos, there are a number of other 'geothermal' phenomena which are not so dramatic in nature, such as geysers and hot springs.With geysers, visible jets of hot water and steam are emitted periodically from holes in the earth, and some wellknown ones have remarkably regular intervals between eruptions. Geysers and hot springs are very often associated with volcanic regions, but they need not be. Along the Perth coastal sandplain, just inland from Rottnest and close to the low granite hills of the Darling Range, some hot springs and hot artesian bores are known. There is no sign of volcanic activity in the area.
From the domainographic viewpoint, these more minor geothermal phenomena are just a natural consequence of less dramatic domain movements. In the Perth case, the sandplain area is a slowly-moving microdomain shuffle belt, wending its way south with just enough frictional movement to produce the odd hot spring.
Proposition 8F
All geothermal phenomena obtain their heat components
from domain rubbing
Metamorphic Rocks
Intermediate between the igneous rocks, cooled down from the molten state, and the sedimentary rocks made from aggregates of erosion particles, there lie the metamorphic rocks.Metamorphic rocks are ones which have been changed or 'metamorphosed' from their original condition. Mostly they were once sedimentary rocks, such as limestone, which can be metamorphosed into marble, although igneous rocks can be metamorphosed too. Often they show marked layering; this can be a relic of the original sedimentary layering, but is sometimes clearly a result of the metamorphic process. The sheets of the transparent mineral known as mica are an example.
It is hard to explain some of the features of metamorphic rocks on the conventional concept of minor heat flows from a hot inner core. How could such minor heat flows lead to the perfectly level layered features found in metamorphic rocks, tens or hundreds of kilometres above the presumed heat source?
A natural explanation is found in the domainographic approach, which can supply the required localized sources of heat and pressure from the grinding together of moving domain edges.
Proposition 8G
Metamorphic rocks are formed by the heat and pressure
produced by rubbing domain edges
Earthquakes
What causes earthquakes? Even though earthquakes have been an object of terror since the earliest days of man, and have been studied in detail for several centuries, no satisfactory answer to this question has ever been given.Of course, when Continental Drift was discovered, impacts between drifting 'plates' were suggested. Unfortunately for this idea, the 'fat' mountains formed by impact are not the usual places where earthquakes appear. Earthquakes are almost invariably associated with 'long' mountains.
Then, when the idea of hot-rock 'convection cells' was put forward, the movements associated with these were a candidate. This was closer, in that earthquakes are associated with active mid-ocean ridges, supposed sites of upwelling hot rock. But they are not associated with the deep ocean trenches, into which subducted material was supposed to be disappearing. And the convection cells had no immediate connection with the established mountain chains which are the real places where earthquakes are most active.
We can see now that earthquakes are a natural consequence of domain movement, in fact, they are domain movements. When one Earth domain moves relative to another adjacent one, it is performing an earth movement, which is another name for an earthquake. The stating of this proposition is therefore almost a logical redundancy:
Proposition 8H
Earthquakes are the relative movements of adjacent domains
A few points which clearly support this proposition. First, it is common in earthquakes for surface displacements to occur, to create 'steps' in railways or roads of a metre or more. This would be expected if one domain was moving relative to another. Moreover, the displacements give the direction of relative domain movements. For example, on the California coast, which is accepted as moving north compared to the adjacent main mass of North America, displacement should normally reflect this relative movement.
Then there is the matter of the depth of earthquakes. The focus of an earthquake, the point where it is most active (the assumed actual shearing zone), is not usually on the surface of the Earth, but deeper down. In a particular broad area, the earthquake foci are not at identical depth, but they do tend to cluster at somewhat similar depths. The focus can lie anywhere from a few kilometres down to as much as 700 km below the surface. The cause of these last 'deep' earthquakes is completely unknown.
If the inner Earth is expanding, and this may be in a very regular way, then adjustments to the surface can be expected to extend quite deeply down. And, more important, a rational reason can be given for the fact that earthquake foci occur at different depths. The differences are due to differences in the size, shape, and physical compositions of the different domains.
So far, we have mostly looked at domains as two-dimensional objects, flat areas on the surface of the Earth. To get a more exact idea of what is happening with earthquakes, it is necessary to consider domains as three-dimensional objects, with not only width and breadth, but also height.
We had the first intimation of this concept with Proposition 5E, where it was suggested that the split of the original holodomain of continental material into Laurasia and Gondwanaland was not an isolated event, but was just the time when continuing expansion had reached the point of exposing underlying oceanic rock for the first time. Now we need to look at the outer layer of the Earth as being made up of layers of domains of varying thicknesses and sizes.
Proposition 8I
Domains are three-dimensional objects of varying thicknesses,
and the surface domains which are directly observable
may be underlain by other domain-type structures
An incidental consequence of this Proposition is that there will be considerable heat generated by friction between surface domain bottoms and sub-domain tops. A more important consequence is that multi-level domain concepts can be developed in a quantitative way which, for the first time, gives a real possibility of being able to predict earthquakes. This would be a very useful thing to be able to do.
Earthquakes happen when shearing occurs between the sides of two adjacent domains. Before the actual earthquake, huge tensions build up as the rock faces are compressed or stretched; it is sometimes possible to detect these forces with strain gauges. Although very rigid, different rocks have known physical properties, and the tearing, stretching or compression they will undergo under given conditions can be calculated quite precisely.
I can see no reason why it would not be possible to calculate where and when earthquakes will occur, once a better knowledge of the physical dimensions of domains and of the physical properties of their component materials is obtained, and a value for the rate of Earth expansion assumed. Such calculations may be complex and tedious, but there is nothing basically new about them.
Proposition 8J
It should be possible to calculate where and when earthquakes
will occur, once fuller data on the domains involved is
known
Hot Spots
Another mountain-building phenomenon which has been examined in recent years is known as 'hot spots'. According to this theory, within the Earth there are a number of localized sources of heat, of unknown origin. As the 'tectonic plates' pass over these hot spots, each in a string of volcanic mountains is formed over the hot spot. From the ages of the various members of a volcanic-mountain string, the direction and speed of the associated plate movement can be calculated.The hot-spot theory does not fit in at all with the concepts I have proposed. It is undeniable that strings of volcanic mountains exist, and it is perfectly feasible to join up the isolated points and conclude they represent the path of a tectonic plate over a hot spot. I believe this conclusion is wrong.
I suspect that the apparent 'hot spots' are what is called an 'artifact'. They can be seen, but paradoxically, they are not real. Like a moving dislocation vacancy in a crystal structure, or the passage of an electron 'hole' in a semiconductor, the movement is only apparent, not real. The situation is comparable to when the head of an organization resigns and is replaced by his deputy, who is replaced by his deputy, and so on down the tree until eventually a new recruit is taken in at the bottom.
In this situation, the job 'vacancy' starts at the top, and appears to move downwards through the organizational tree until it is filled by the new recruit sucked in at the bottom. In the same way, I suspect that the apparent 'hot spots' are only artifacts, created perhaps by opposing chance protrusions in adjacent domain boundaries happening to come together as the domains move.
Proposition 8K
'Hot Spots' in the Earth are artifacts created by domain edge
movements, and not real phenomena
Of course the acceptance of this Proposition removes the nagging need to explain the source of the energy needed to drive the hot spots. These sources would have to be pretty special, if they were able to raise mountain after mountain, maintaining their power for many millions of years unchanged.
We have now spent some time looking at the surface of the Earth and its uppermost layers. We are ready now to plunge down, deep into the core of the planet.
(Full list of references at NURefs)
NU009: Inside The Earth
NU007: Putting The Earth Back Together
Go to the NUSite Home Page
Version 1.0, printed edition ("Nuteeriat: Nut Trees, the Expanding Earth, Rottnest Island, and All That...", Planetary Development Group, Tree Crops Centre, 1989).
Version 2.0, 2004, PDFs etc on World Wide Web (http://www.aoi.com.au/matrix/Nuteeriat.htm)
Version 3.0, 2014 Sep 22, Reworked from Chapter 7 of "Nuteeriat" as one article in a suite on the World Wide Web.
Version 2.0, 2004, PDFs etc on World Wide Web (http://www.aoi.com.au/matrix/Nuteeriat.htm)
Version 3.0, 2014 Sep 22, Reworked from Chapter 7 of "Nuteeriat" as one article in a suite on the World Wide Web.