Of the total area just under a fifth belongs to the islands: this already shows how much of Greece is closely linked to the sea. But even mainland Greece, due to its marked peninsularity and the deep indentation of its coasts, is a whole, one can say, a maritime country; the central parts of the Peloponnese are no more than 50 or 60 km away from the sea. and only for the more internal territories among those of recent purchase does this distance exceptionally reach 150 km. And the country is all the more tied to the sea, as on the other hand its terrestrial communications are difficult. The high Pindus chain, which starts from near the northern borders and reaches with its various offshoots the Gulf of Corinth, and then seems to continue in the Peloponnese with the harsh region of Arcadia, it effectively divides, like a large backbone, an Ionian and an Aegean side, between which there is no possibility of easy communication. Therefore, even between nearby places, these must prefer the route, often longer but always easier, of the sea. In this Greece is extraordinarily favored by the very nature of its shore line, which, due to the frequency and depth of the indentations, acquires a very remarkable linear development. In the Aegean, when it is abstracted from the Chalkidiki Peninsula with its three long and thin digits, it constitutes as a whole, from the bottom of the Gulf of Thessaloniki, along Thessaly and along the great island of Euboea, a united, rather regular, rocky coast and steep, interrupted almost only by the mouth of the Salambrías. But in front of the Northern Sporades group the Tríkeri channel opens up, to which the wide and sheltered Gulf of Volo is connected, and from which the Ōreoí Channel continues to separate Euboea from the mainland, the Gulf of Lamia, the Atalántē Channel, the Strait of Chalcis, the Euripus Channel, up to the Gulf of Petalioí: all of which constitute a true inland sea, a wonderful communication route between northern and southern Greece. On the whole quite united, regular and also directed by NO. to SE. the opposite coast is shown, Ionic, also provided with beautiful and wide crescents in the Peloponnese, only partly rocky and steep, especially along the Acarnania. More often the floods of rivers, mainly the Artino (Árachthos), the Aspropotamus, the Feídaris in northern Greece, the Peneus and the Alfeo in the Peloponnese, have created coastal plains, with frequent lakes and lagoons (the Missolungi is very notable); nor the Golfo d’Arta, large but with lagoon shores and shallow waters in the mouth, is of special importance. But the southern Ionian Islands, which follow each other closely, also close a small inland sea here, all the more propitious because right in front of the opening of the deep Gulf of Corinth, which with its two basins of Patras and Lepanto penetrates into the earth, almost detaching the great Peloponnese peninsula from the mainland: an extraordinary natural route, through which the high barrier of the Pindus is interrupted and Eastern and Western Greece can certainly communicate with each other.. Still different characters presents the southern coast. Here the four great digits with which the Peloponnese ends at noon, and the minor peninsula of Attica, and the Euboea itself go rocky and steep into the sea, determining as many deep gulfs (Messenian, Laconic, Argolic, Saronic and Petalioí). In front of these great promontories the innumerable islands line up, in wide curvature, up to the opposite coast of Asia Minor.
If we look at the geological structure of Greece, we see that in it, within its current limits, the two tectonic and morphological motifs that characterize the complex of the Balkan Region recur. This, as is known, includes an eastern area, where a mountain range, the Balkans, attaching itself to the Transylvanian Alps at the narrow Danube of the Iron Gates, runs, after a wide curvature, towards the east towards the Black Sea (a typical folded mountain, due to the alpine uplift); and a western area which, attaching itself to the Julian Alps, runs parallel to the Adriatic, now narrower now wider, and constitutes the Bebie (or Velebiti) and Dinaric Alps with the adjacent plateaus of Croatia, Bosnia, Herzegovina and of Montenegro, then the Albanian Alps, from which it passes into the Greek territory: this is also a mountainous area with folds of the Alpine uplift. Between the two, however, is a massive triangle, consisting of a much older lifting mass. These two different reasons also recur in the Greek territory. The central mass of ancient uplift constitutes in fact all of Greek Macedonia, extending up to part of Thessaly: it is what is called “Thracian mass” and which has its greatest extension in southern Bulgaria and in almost all of the Serbian territory. Then there is a second minor one, the “mass of the Cyclades”, which embraces the southern part of Euboea, Attica and the opposite islands. And there is also a third, the “mass of Lydia and Caria”, which extends especially in Anatolia, but it also includes some of the next Aegean islands. This motif, therefore, is widespread in the north-eastern part of the Greek territory and, secondarily and fragmentarily, in the maritime area and in Aegean island species. The other reason, however, of the alpine lifting system occurs exclusively in the entire western part of the Greek territory and in the entire Peloponnese. The trend of the folds is mainly from NNO. to SSE., ie parallel to the Ionian coast; but it tends to curve towards the east. Thus it is found that folded areas insinuate themselves almost between the masses of ancient uplift, between Thessaly and Attica, while from the extreme digits of the Peloponnese they pass into Crete, into Rhodes, into the Dodecanese and then into southern Anatolia. The two tectonic motifs have different characteristics of constitution and morphology. Of constitution: since the masses of the most ancient elevation are naturally composed of soils of even more remote geological antiquity, and largely crystalline; in the folded areas of the alpine uplift, all the more recent, sedimentary soils are represented, marine, of a much longer geological series, which extends from the Paleozoic to the primordia of the Tertiary: locally limestone prevails.
Different characteristics also of morphology: since the masses of the most ancient uplift have been subjected to a much longer degrading action of external agents, which have attenuated and standardized all aspects, shaping a landscape that is never harsh, often rather only gently moved in the its slopes and its backs. That is, they have, behind them, a very long period of continentality, during which large lakes formed in the lowlands which are testified by soils and fossils. The folded mountains, on the other hand, of more recent uplift, have not yet undergone such an intense degrading action, which has only reached the point of carving deep valleys and shaping sharp ridges, not yet drooping and softening these in soft and subtly moved croups..
However, Greece is as a whole a mountainous region, in which very often the relief, even in the immediate vicinity of the sea, reaches 2000 m. But if the character of a true chain can be recognized in the Pindus and its continuation up to the extreme territory in numerous smaller regions. Regional units, these, which are therefore essentially characterized by the fact that they are almost always limited, on each side, by mountain barriers: real basins, in short, flat in the center, mountainous all around. Sometimes in their bottom they still contain lakes, at other times they keep only the remains; in some cases they appear open towards the sea; from other of them the waters flow out through a narrow valley that clearly cuts through the circle of the mountains; from still others the waters themselves find their way out only by underground routes. If we then consider the depths of the sea in the gulfs, in the canals and in the mirrors between the innumerable islands, we will see that most of them also represent basins, but with a submerged bottom. Thus, many small regional units are thus individualized, in which there is a great variety of natural characters.