Откуда Дойель это взял?
В тех источниках, которые я "от корки до корки" такого я не нашел.
Так же я не видел никакой лавы в самом Геркулануме. Есть несколько слоев затвердевшей грязи, лежащих на около метра слое пемзы и лапиллей.





Само слово "лава" в итальянском происходит от "лаваре" - смывать, стирать.

Здесь очевидно произошло недоразумение из-за смешения разнесенных во времени определениях.

"""The circumstances of the burial of Herculaneum are very diverse from those of Pompeii…Whilst at Pompeii there was a regular stratification of eruptive material due to the rain of ashes and fragments of lava transported by the wind, which was at the most 5 or 6 meters deep, upon Herculaneum there descended, swept down by the enormous volumes of water that always accompany great volcanic convulsions, a shapeless mass of erupted material
which had previously collected around the crater and rushed down the
steep mountain side upon the city in the form of an immense torrent of mud, overturning and submerging all that stood in its path. First the villas lying above the city and then the city itself, all were submerged by this terrifying alluvion which, having invaded and filled up all spaces, totally transformed the aspect of the district. This mud-lava that in its liquid state was able to penetrate into every void, now that it is solidified has assumed
the appearance of a compact bank. It reaches the hardness of tufa, and presents the characteristics of a tufoid formation (pappamonte), varying both in composition and in density according to the different flows of lava. The depth of the layer thus accumulated above the buried city, including the vegetation stratum, varies from 12 to 20 meters or more."""" (Maiuri, 1945: 7-8)