Intrusion of Basaltic Dikes in Volcanic Rocks

The basaltic and trachytic dikes on Porto Santo Island are thought to have intruded into the volcanic rocks during a period of increased volcanic activity in the Middle Miocene. The dikes are typically narrow and vertical, and they can be traced for several kilometers along the island.

The intrusion of the dikes has had a significant impact on the volcanic rocks on Porto Santo Island. The dikes have baked the surrounding rocks and caused them to become harder and more resistant to erosion. The dikes have also altered the chemical composition of the surrounding rocks.

Dike is a sheet of rock that is formed in a fracture of a pre-existing rock body. Dikes can be either magmatic or sedimentary in origin. Magmatic dikes form when magma flows into a crack then solidifies as a sheet intrusion, either cutting across layers of rock or through a contiguous mass of rock. Clastic dikes are formed when sediment fills a pre-existing crack.

Intrusion of Basaltic Dikes in Volcanic Rocks. Photo: Prof.  Mário Cachão.

Intrusão de diques basálticos e traquíticos em rochas vulcânicas do Miocénico Médio (ilha de Porto Santo, Portugal).