Banda, Enric

Revistes Catalanes amb Accés Obert

T H E  T H E O R Y  O F  P L A T E  
TECTONICS 
TRADITIONALLY, THE CATALAN COMMUNITY OF 
GEOLOGISTS AND GEOPHYSICISTS HAS ALWAYS STUDIED 
THE PYRENEES, THE EBRO BASIN AND THE WESTERN 
MEDITERRANEAN. IN THE LAST FEW YEARS, CATALAN 
RESEARCH GROUPS HAVE COMBINED THEIR EFFORTS AND 
MADE IMPORTANT PROGRESS IN THEIR UNDERSTANDING 
OF THESE GEOLOGICAL STRUCTURES. 
ENRlC B A N D A  D I R E C T O R .  " I N S T I T U T  J A U M E  A L M E R A "  
esearch work carried out by in- 
vestigators in the Sciences of the 
Earth on the formation of 
mountain chains and sedimentary ba- 
sins was completely revolutionized in 
the sixties by the establishment of the 
Theory of Plate Tectonics (this theory 
unified concepts such as that of conti- 
nental dnft and oceanic expansion). But 
the fact is that this theory is difficult to 
apply in certain geological contexts. It is 
in these cases that, through the tech- 
niques of that part of Geophysics which 
studies the solid Earth, we can get to 
know the deep structure of the Earth 
and contribute results of great import- 
ante to our understanding of the evolu- 
tion of certain geological structures in 
terms of Plate Tectonics. 
Traditionally, the Catalan community 
of geologists and geophysicists has al- 
ways studied the Pyrenees, the Ebro Ba- 
sin and the western Mediterranean. In 
the last few years, Catalan research 
groups have combined their efforts and 
made important progress in their un- 
derstanding of these geological struc- 
tures. This has meant that both geolo- 
gical surface studies and geophysical 
depth studies have helped to change, 
sometimes radically, the evolutionary 
models of the areas under study. 
As regards the Pyrenees, it was not until 
geophysical studies of their deep struc- 
ture were available that our interpreta- 
tion of their formation was anything 
more than highly speculative. However, 
geophysical data are often difficult to 
interpret and are therefore susceptible 
to different readings. In the case of the 
Pyrenees, the most reliable results come 
from deep echo seismic studies. Al- 
though we can only see deep structure 
in two dimensions, it has been clearly 
demonstrated that the Ibenan crust is 
dipping under that of Europe. This can 
only be taken as the result of the north- 
south compression by which Iberia 
approached and finally collided with 
Europe. These and other, more detailed 
results are being worked on by different 
research groups and will undoubtedly 
lead to important developments. But 
there is still a long way to go, since only 
isolated data are available at present. A 
more detailed picture will be made pos- 
sible through financia1 effort and the 
work of researchers. 
However, the concept of Plate Tecto- 
nics becomes clearer when applied to 
large structures. In this respect, the 
Pyreneean chain cannot be considered a 
large structure when we compare it 
PYRENEES. 
with, for example, the Urals, the Hima- 
layas or the Andes. On the other hand, 
the "smaller structures" are still of con- 
siderable importance both in our un- 
derstanding of the evolution of the 
Earth and because they also contain na- 
tural resources and concealed risks, two 
factors of special interest to mankind. 
The Ebro basin is a geological structure 
which is rclated to the formation of the 
Pyreneean range, and the two should 
therefore be dealt with together. How- 
ever, what can be mentioned here is that 
the sedimentary covering has been 
studied in considerable detail and that 
the results obtained have been related 
to phenomena of global tectonics. 
Geophysics has contributed less here, 
though recent paleomagnetic research, 
which studies the magnetism of rocks at 
the time of their formation, can be of 
help in the study of the basin. 
The westem Mediterranean has always 
been an attractive field of study for the 
countries that surround it. In spite of 
the large amount of research into 
manne Geology and Geophysics, the 
origin and development of the various 
basins making up the western Medi- 
terranean is still far from clear. In this 
context, a number of Catalan teams are 
studying the Balearic basin (between 
the peninsula and the islands). Interpre- 
tations of this basin in terms of Plate 
Tectonics have been put forward by dif- 
ferent researchers, but, once more, we 
have to admit that they are highly spe- 
culative models which are still in need 
of further experimental data. 
It can be seen, then, that there is con- 
siderable activity in geological and geo- 
physical research in Catalonia. Thanks 
to this activity, we have an appreciable 
volume of results which, if they are sa- 
tisfactory today, can only be expected 
to improve in the near future. m 



The Theory of Plate Tectonics

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Revistes Catalanes amb Accés Obert