Jebel Hauran, east of the Jordan, is capped by a great sheet of basalt; and many other basalt flows are found, especially in the country north of Lebanon.
The geological core of the system consists of primitive argillaceous schists, capped by quartzite and broken through in places by basalt.
The south-western part is naturally divided into two tracts by the Niagara escarpment, a line of cliffs capped by hard Silurian limestones, running from Queenston Heights near the falls of Niagara west to the head of Lake Ontario near Hamilton, and then northwest to the Bruce Peninsula on Georgian Bay.
In the north the plateau is overlain by red and purple unfossiliferous sandstones, capped near its edge by a cherty limestone also unfossiliferous but possibly of Lower Cretaceous age.
The Iren-khabirga, like the Bogdo-ola and the Terskei Ala-tau, are capped with perpetual snow.
Across at the widest point and yet showing ridges capped with perpetual snows, the rivers, large or small, are mountain torrents, now swollen floods, anon half dry.
Its prevailing aspect is characterized by flat and terraced hills, capped by desert sandstone, with stone-covered flats stretching over long distances.
A notable example is the mesa of Acoma, in Valencia county, capped with volcanic rocks; upon its summit, about 350 ft.
Some of the high plateaus in the north are capped with remnants of heavy lava flows of early eruption.
Clew Bay, with its islets capped by glacial drift, is a submerged part of a synclinal of Carboniferous strata, and Old Red Sandstone comes out on the north side of this, from near Achill to Lough Conn.