Volcanic ash is a useful tool for investigation of the history of volcanic eruptions as it can be found far from
eruptive centers, and is preserved for a long time after initial deposition and has a constant mineral composition.
Imperfection of most methodical investigations of volcanic ashes is their texture sensibility. This factor make difficult
to identify volcanic ashes from the same volcano. Some magnetic properties, saturation magnetization, saturation magnetization field, and Curie Point (Tc) of magnetic minerals, however, are not sensitive to texture, but they are sensitive to magnetic-mineral composition. A more sensitive method for determining the Tc- point is the analysis of the temperature dependence of magnetic susceptibility or of inductive magnetization. The presence of peaks on the curve near the Tc-point for the monomineralic fractions (Hopkinson’s peak) helps to more carefully define individual Tc on the curve for natural mixtures of the different magnetic minerals.

Through radiocarbon techniques we determir the age (30 000 yrs) of the latest in the Late Pleistocene directed blast at the Avachinsky volca and approximately calculated the age of the previous large catastrophic eruption of the same type (35 00( 40 000 yrs). Coarse debris deposits produced by the eruption originally covered the area of 400 km2 a their volume was 16-20 km3. As a result of these eruptions the relief cardinally changed to the south of t Avachinsky and the lower part of the Avacha river channel was transported to the distance of 6-10 km. 11 believed that in the nearest hundreds of years such blasts will not take place but this forecast does not apply the adjacently located Koryaksky volcano.