structural:reformatting, quality:corruption
Geology

The seven major islands, one minor island, and several small islets were originally volcanic islands, formed by the Canary hotspot. The Canary Islands is the only place in Spain where volcanic eruptions have been recorded during the Modern Era, with some volcanoes still active (El Hierro, 2011). Volcanic islands such as those in the Canary chain often have steep ocean cliffs caused by catastrophic debris avalanches and landslides. The island chain's most recent eruption occurred at Cumbre Vieja, a volcanic ridge on La Palma, in 2021.

The Teide volcano on Tenerife is the highest mountain in Spain, and the third tallest volcano on Earth on a volcanic ocean island. All the islands except La Gomera have been active in the last million years. Four of them, Lanzarote, Tenerife, La Palma and El Hierro, have historical records of eruptions since European discovery. The islands rise from Jurassic oceanic crust associated with the opening of the Atlantic. Underwater magmatism began during the Cretaceous, and continued to the present day. The current islands reached the ocean's surface during the Miocene. The islands were once considered as a distinct physiographic section of the Atlas Mountains province, which is part of the larger African Alpine System division, but are now recognized as being related to a magmatic hot spot.

In the summer of 2011, a series of low-magnitude earthquakes occurred beneath El Hierro. These had a linear trend of northeast–southwest. In October a submarine eruption occurred about 2 km (1 + 1 ⁄ 4 mi) south of Restinga. This eruption produced gases and pumice, but no explosive activity was reported.

The following table shows the highest mountains in each of the islands: