from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Of or pertaining to trap; of the nature of trap.
from the GNU version of the Collaborative International Dictionary of English
- adj. Of or pertaining to trap; being of the nature of trap.
from The Century Dictionary and Cyclopedia
- Pertaining to or of the nature of trap or trap-rock.
Dark trappean rocks full of hornblende have in many places burst through these schists, and appear in nodules on the surface.
In fact, the great plutonic action is confined to the central portion of the island; there, rocks of the trappean and volcanic class, including trachyte, basalt, and tuffs and agglomerates associated with streams of lava, have made this a land of supernatural horrors.
By what train of investigations were geologists induced at length to reject these views, and to assent to the igneous origin of the trappean formations?
The lodes are not ribboned, but consist of quartz, jointed across from side to side, exactly like trappean dykes.
These, however, were sufficient to show me that the gneiss of Depilto was overlain conformably by the contorted schists; that the latter were followed by soft trappean beds, and these by thick beds of quartz-conglomerate, apparently derived from the degradation of the schistose rocks, with their numerous quartz veins.
This peculiar form, and the symmetrical arrangement of a few cones which surround the Brigantine, made me at first think that this group, which is wholly calcareous, contained rocks of basaltic or trappean formation.
Fragments of granite have been observed at Teneriffe; the island of Gomora, from the details furnished me by M. Broussonnet, contains a nucleus of micaceous schist: — the quartz disseminated in the sand, which we found on the shore of Graciosa, is a different substance from the lavas and the trappean porphyries so intimately connected with volcanic productions.
This regular disposition of lithoid basaltic lava and feldsparry vitreous lava is analogous to the phenomena of all trappean mountains; it reminds us of those phonolites lying in very ancient basalts, those close mixtures of augite and feldspar which cover the hills of wacke or porous amygdaloids: but why are the porphyritic or feldsparry lavas of the Peak found only on the summit of the volcano?
To this very ambiguous formation belong the trappean porphyries of Chimborazo and of Riobamba in America, of the
Mexico, have taken place in countries covered with trappean porphyry, ancient basalt, and volcanic ashes, so the peak of Teyde has raised itself amidst the wrecks of submarine volcanoes.
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