Andesitic Pyroclastic Sequence

Along the road that leads to Lakki, within the inner Northeastern caldera rim, one can enjoy a fascinating volcanological sequence.

During the Early Shield Volcano eruptive cycle, three characteristic eruptive events took place, with a relatively short time interval among them, producing pyroclastics and lavas with basaltic andesite composition, but slightly different in their eruption characteristics. On top of the three pyroclastic and lava cycles described above, two volcanoclastic, lacustrine sedimentary successions are found. They are continuous over a distance of five hundred meters, divided by a few meters thick subaerial basaltic andesite lava, indicating the presence of an “internal lake” within a period of minor volcanic activity.

The varved beds of the two intra-caldera lakes and associated volcanic cycles indicate sedimentation of volcanic ashes and fine-grained lapilli mixed with sandy layers within an aqueous system. The lifetime of the two lacustrine cycles could not have exceeded several hundred to a thousand years due to the restricted thickness of the varved successions.