The rocks which created Nea and Palea Kameni are all lavas of the
same type, the minor differences among them being of form rather than
All the lavas of these islands belong to the group which geologists call
dacites: a volcanic rock whose chemical composition consists of 65-67%
silica (SiO~) and 13-15% alumina, with other elements (principally iron,
sodium, calcium, potassium and magnesium) in small quantities (2-5%).
These elements are found in both the amorphous volcanic glass. and
the mineral crystals which, together with the glass, make up these rocks.
The principal minerals found in the Kameni dacites are:
feldspars: silica-aluminum minerals with white, transparent crystais,
- pyroxenes: silica-calcium-iron-magnesium minerals, with crystals
varying from dark green to black, and
olivines: magnesium-iron-silica minerals, with transparent honey-
coloured or dark-green crystals.
The main differences in the appearance of the various lavas are ones of
colour, which are due to different cooling rates. The dark-coloured, more
fragmented lavas, like most of those forming Nea Kameni, underwent very
rapid cooling, with the result that they contain a high percentage of volcanic
glass. Slower cooling permits the formation of many minerals, giving the lava
a light ashen colour and a more granular texture. Most of the lavas forming
Palea Kameni are of this type.
Both laboratory studies of the Kameni rocks and all the physicai and
chemical parameters measured in the area tend to indicate that the magma
which feeds the Kameni volcanic centers is located at a depth of two to four
kilometres beneath the islands at a temperature of 950-1000 degrees
centigrade, where it is concentrated in small pockets (magma chambers)
which in turn are fed with molten rock from deeper layers.
The Volcano of Santorini