Passing from the coast to the tableland, a distinct climatic region is entered.
The peninsula is almost wholly composed of a bed of coralline and porous limestone rocks, forming a low tableland, which rises gradually toward the S.
The basin is comparatively narrow, and the Tagus, like the other rivers of the Iberian tableland, generally flows in a rather confined valley, often at the bottom of a rocky gorge below the general level of the adjacent country.
As the tableland runs northward it decreases both in height and width, until it narrows to a few miles only, with an elevation of scarcely 1500 ft.; under the name of the Blue Mountains the plateau widens again and increases in altitude, the chief peaks being Mount Clarence(4000 ft.), Mount Victoria (3525 ft.), and Mount Hay (3270 ft.).
Cooma, with a mean summer temperature of 65.4°, and a mean winter temperature of 41.4°, may be taken as illustrative of the climate of the southern tableland, and Armidale of the northern.