Describe in general how the history of the volcano, as determined in this particular valley, has changed through time as revealed by the deposits found with depth in the drill hole. In particular note how the SiO2 content of the magmas has changed with time and whether or not this is reflected in the explosivity of the eruptions as revealed by the deposits

As described below.

Explanation:

As the magma from the volcano rises up it begins to settle as crystals and causes the chemical compositions to change and the magma has less of magnesium and more of the silica contents.  A volcano that has more of silica oxide and a high temperature but low silica contents results in a more fluid or basaltic magma and a high content result in a viscous magma and they are of high explosive in nature like the Stromboli volcano and Mount Vesuvius.

East european plain and russian russkaya ravina.

The answer i think is d