Hesperus Mountain, showing wedges and sheets of trachyte intruded into the shales, from the laccolith of Mt. Moss.

Hesperus Mountain

Hesperus Mountain, showing wedges and sheets of trachyte intruded into the shales, from the laccolith…

Ideal section of La Plata Mountain, Colorado, showing the supposed original form of the laccolith of Mt. Moss.

La Plata Mountain

Ideal section of La Plata Mountain, Colorado, showing the supposed original form of the laccolith of…

"Conduit of Tilford laccolith, showing porphyry (P) breaking across limestone (L)." -Walcott, 1901

Laccolith

"Conduit of Tilford laccolith, showing porphyry (P) breaking across limestone (L)." -Walcott, 1901