Personal Narrative Of Travels To The Equinoctial Regions Of America During The Years 1799-1804 - Volume 1 - By Alexander Von Humboldt And Aime Bonpland.
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Near The Port Of Santa Cruz, The Strength Of The
Vegetation Is An Obstacle To Geological Research.
We passed along
the base of two small hills, which rise in the form of bells.
Observations made at Vesuvius and in Auvergne lead us to think that
these hills owe their origin to lateral eruptions of the great
volcano.
The hill called Montanita de la Villa seems indeed to have
emitted lavas; and according to the tradition of the Guanches, an
eruption took place in 1430. Colonel Franqui assured Borda, that
the place is still to be seen whence the melted matter issued; and
that the ashes which covered the ground adjacent, were not yet
fertilized. Whenever the rock appeared, we discovered basaltic
amygdaloid* (* Basaltartiger Mandelstein. Werner.) covered with
hardened clay,* (* Bimstein-Conglomerat. W.) which contains
rapilli, or fragments of pumice-stone. This last formation
resembles the tufas of Pausilippo, and the strata of puzzolana,
which I found in the valley of Quito, at the foot of the volcano of
Pichincha. The amygdaloid has very long pores, like the superior
strata of the lavas of Vesuvius, arising probably from the action
of an elastic fluid forcing its way through the matter in fusion.
Notwithstanding these analogies, I must here repeat, that in all
the low region of the peak of Teneriffe, on the side of Orotava, I
have met with no flow of lava, nor any current, the limits of which
are strongly marked. Torrents and inundations change the surface of
the globe, and when a great number of currents of lava meet and
spread over a plain, as I have seen at Vesuvius, in the Atrio dei
Cavalli, they seem to be confounded together, and wear the
appearance of real strata.
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