The lecturer first showed a world chart showing distribution of
volcanoes, showing general tendency of eruptive explosions to occur
in lines. After following these lines in other parts of the world he
showed difficulty of finding symmetrical linear distribution near
McMurdo Sound. He pointed out incidentally the important inference
which could be drawn from the discovery of altered sandstones in the
Erebus region. He went to the shapes of volcanoes:
The massive type formed by very fluid lavas--Mauna Loa (Hawaii),
Vesuvius, examples.
The more perfect cones formed by ash talus--Fujiama, Discovery.
The explosive type with parasitic cones--Erebus, Morning, Etna.
Fissure eruption--historic only in Iceland, but best prehistoric
examples Deccan (India) and Oregon (U.S.).
There is small ground for supposing relation between adjacent
volcanoes--activity in one is rarely accompanied by activity in the
other. It seems most likely that vent tubes are entirely separate.
_Products of volcanoes_.--The lecturer mentioned the escape of
quantities of free hydrogen--there was some discussion on this
point afterwards; that water is broken up is easily understood, but
what becomes of the oxygen? Simpson suggests the presence of much
oxidizable material.
CO_2 as a noxious gas also mentioned and discussed--causes mythical
'upas' tree--sulphurous fumes attend final stages.
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