CHAP. I 
EFFACEMENT OF OLD VOLCANOES 
3 
planet can only, if ever, be disi^elled by the patient stndy of these vents of 
coniniunication between the interior and the surface. 
If, however, we desire to fortu some adequate idea of the part which 
'"olcanic action has played in the past history of the earth, we should be 
misled were we to coniine orir attention to the phenomena of the eruptions 
ol the present day. An attentive examination of any modern volcano will 
convince us that of some of the most startling features of an eruption no 
enduring memorial remains. The convulsive earthquakes tliat accompany a 
great volcanic paroxysm, unless where they actually fissure the ground, leave 
little or no trace behind them. Lamentably destructive as they are to 
human life and property, the havoc which they work is mostly superficial. 
Ill a year or two the ruins have been cleared aw'ay, the earth-falls have been 
healed over, the prostrated trees have been removed, and, save in the memories 
mid chronicles of the inhabitants, no record of the catastrophe may survive. 
Ihe clouds of dust and show'ers of ashes which destroyed the crops and 
crushed in the roofs of houses soon disappear from the air, and the covei- 
itig which they leave over the surface of a district gradually mingles with 
the soil. Vegetation eventually regains its place, and the landscape becomes 
ugain as smiling as befoi'e. 
Even where the materials thrown out Ifom the crater accumulate in 
much greater mass, where thick deposits of ashes or solid sheets of la^'a bury 
the old land-surface, the look of barren desolation, though in some cases it 
may endure for long centuries, may in others vanish in a few years. The 
surface-features of the district are altered indeed, ljut the new topograjdiy 
soon ceases to look new*. Another generation of inhabitants loses recollec- 
tion of the old landmarks, and can hardly realize that what has become so 
familiar to itself differs so much from what w'as familiar to its fathers. 
But even wiien the volcanic covering, thus throwm athwart a wide tract 
of country, has been concealed under a new growth of soil and vegetation, it 
still remains a prey to the ceaseless processes of decay and degradation which 
everywhere affect tlie surface of the land. Ko feature of a modern 
volcano is more impressive than the lesson which it conveys of the reality 
^nd potency of this continual waste. The northern slopes of Vesuvius, for 
example, are trenched with deep ravines, which in the course of centuries 
liave been dug out of the lavas and tuffs of Monte Somma by rain and 
melted snowx Year by year these chasms are growing deeper and widei', 
while the ridges between them are becoming narrower. In some cases, 
ludeed, the intervening ridges have been reduced to sharp crests which are 
split up and lowered by the unceasing inffuence of the weather. The slopes 
of such a volcanic cone have been aptly compared to a half-opened umbrella. 
If reqirires little effort of imagination to picture a time, by no means 
1 emote in a geological sense, when, unless renovated Ijy the effects of fresh 
eruptions, the cone will have been so levelled with the surrounding country 
that the peasants of the future will trail their vines and build their cots over 
m site of the old volcano, in happy ignorance of what has been the history 
of the ground beneath their feet. 
