My experiments with volcanoesJaggar, Thomas Augustus
Science
My experiments with volcanoes
Jaggar, Thomas Augustus
Geologists -- Biography; Volcanoes
The rim we could see ahead was the edge of the crater itself. The
abruptness of the fall off, when we finally came to it, was startling
in the extreme. The wind was pelting our necks with stinging sand
grains which, incidentally, were ruinous to my new Kodak. Only
occasionally did sunshine sift through the mixture of sand, steam,
and cloud. We could make out an inward slope of thirty-five degrees,
terminated 100 feet below by a jutting, fuming precipice. The circular
curvature of the crater was embayed. The only noise was the howling
wind. We could not see the opposite side of the collapsed cauldron a
half mile across. The summit was 4,000 feet above sea level by aneroid
measure, 350 feet lower than before the eruption. There was a great
notch northeast toward Ottajano where thousands of tons of gravel were
hurled clear over the top of Monte Somma, the encircling old ridge. The
east-west diameter was left much greater than that of the north-south.
The radial ridges and gullies were like a corrugated roof, and sand
made a flattened angle of scree at the base of the scoured cone. The
corrugations were not rain erosion, but were made by backfallen debris
sliding. I got some photographs and Mr. Perret gave me others.
The big thing was the line of mountain blocks of earth crust. In Italy
it is made up of Ischia, Pozzuoli, Vesuvius, Lipari, and Etna, whereas
the Carribbee line is made up of Mount Misery, Montserrat, Guadeloupe,
Dominica, Martinique, and St. Vincent. Such a line of broken earth
blocks is a volcanic system. Hundreds of miles long, it is never
quiet. A single place seems quiet because superficially we are totally
unconscious of the other places. A microbe on the scalp knows nothing
of the skin of the toes. Men are mere microbes on the skin of shore,
sea, and island. And they are remote from any consciousness of sea
bottom.
Vast distances and long intervals are writing records, but man does not
measure them. He measures civilization, wars, and dynasties, not the
adventures of the ground he dwells upon. Ground he considers static.
Actually it is intensely dynamic. Occasionally it explodes and man
is destroyed. Earth history and volcanic systems make wars look very
small.
The tremendous accumulations of broken rocks over lava beds on the cone
of Vesuvius, and on all the Caribbee Islands, recall the breccias, or
volcanic conglomerates, of the Yellowstone and of the High Plateaus
of Utah. Floods of basalt alternate with vast falls or outwashes of
volcanic gravel. Avalanches, landslides, torrents, floods--call them
what you will--cover immense areas of the Cordillera. Vesuvius and
Pelée pile up cones, but the Caribbees and Italy are also heaped with
agglomerates. Erosion destroys cones, but erosion makes agglomerations
or valley fills of rocks and mud. This is the history of every volcanic
system on the globe. Stübel discovered smooth basalt domes like Mauna
Loa under every volcanic system.
Public-domain text, read in full here on John Shaqi.
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