On 02/10/2016 13:16, Chris Hogg wrote:
But the region
around Naples, which includes Mount Vesuvius, is very rich mainly
because of two large eruptions 35,000 and 12000 years ago that left
the region blanketed with very thick deposits of tephra which has
since weathered to rich soils.

A little more recent than that.

The eruption that buried Pompeii dropped several metres of ash, then
added a pyroclastic flow. From memory it's over 10 metres at
Herculaneum. IIRC the last eruption was 1940-something - late WW2.

Andy