CHAPTER 8
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 Earth has a molten
core is quite wrong. 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 'superheated' 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 well-known 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