Seven million years ago
The oldest rocks to appear in Tenerife would seem to be about seven million years old. Previous submarine eruptions gradually accumulated in the island substrate, which started to emerge from the sea in the area of Teno (the current N.W. slope) and at the base of Anaga in the north east.
What can be seen today of that stage, encompassing an era of between seven and three million years ago, is illustrated in diagram A. This is fissure volcanism, with only the remains of three large volcanoes remaining: Teno, Anaga and Adeje. These may have all been linked and were, of course both more extensive and higher than they are now.
The typical characteristic of these volcanoes is that their centres of emission seemed to be aligned along a major fault line. This has led to volcanic matter piling up like a roof, the crest of which still forms the line of mountain peaks. This first cycle of eruptions culminated with salic emissions (trachitic) which now cover many of Anaga's crests.