Dikes are sheet-like igneous bodies that cut across pre-existing rock layers and are discordant. Sills are also sheet-like intrusions but are intruded between the pre-existing rock layers and are concordant.
The canary islands is dominated by volcanic rock. The volcanism is caused by the african plate moving slowly over a hotspot in the earth's mantle.
Sills and dykes are amongst the easiest geological features to observe on La Gomera.
The red, pyroclastic flow was laid down first, and then basalt oozed up through a crack in the rock and solidified. The basalt is much harder, so the pyroclastic rock eroded away faster, leaving the basalt sticking out like a wall. It’s called a volcanic dyke, and you see them all over the island.
|Dike Cross-Cutting Sedimentary Rock -Spain. Mass of igneous rock intruded into older red iron rich sedimentary rock. La Palma Island, Canary Islands, Spain.|