In the San Francisco mountains, in the north central part of the state, three peaks rise to from io,000 to 12,794 ft.; three others are above 9000 ft.; all are eruptive cones, and among the lesser summits are old cinder cones.
Immense -sheets of dolerite, gabbro, or allied basic rocks indicate eruptive materials intruded as sills or poured out as lavas contemporaneously with the sedimentary formations among which they lie.
Most of the island is occupied by the band of the old rocks, which include mica, glaucophane and sericite-schists and slates; there are small intrusions of granite, and numerous dikes and masses of basic eruptive rocks.
It is not infrequently found in serpentine, and in basic eruptive rocks, where it occurs as veins and in amygdales.
Recent eruptive and volcanic rocks are met with in the interior of Korea and also in the island of Quelpart.
Farther northwards they give way again, as in the south, to schists and eruptive rocks.
The eruptive prominences, called also metallic, because it is they which show at their bases a complete bright line spectrum of the metallic elements, rush upwards at speeds which it is difficult to associate with transfers of matter; the velocity often exceeds loo m.
The Eastern Cordillera is composed of gneiss, mica and chlorite schist and other crystalline rocks of ancient date; the Western Cordillera, on the other hand, is formed of porphyritic eruptive rocks of Mesozoic age, together with sedimentary deposits containing Cretaceous fossils.
In some cases it appears to have segregated from a basic eruptive magma, and in other cases to have resulted from metamorphic action.
Curacao consists of eruptive rocks, chiefly diorite and diabase, and is surrounded by coral reefs.