A remarkable volcanic chain runs along the northern and western
margins of the Pacific Ocean. It embraces the Aleutian Islands, the
peninsula of Kamtschatka, the Kurile, the Japanese, and the
Philippine Islands. The most interesting are the volcanoes of
Kamtschatka, in which there is an oft-renewed struggle between
opposing forces--the snow and glaciers predominating for a while,
to be in their turn overpowered by torrents of liquid fire.
CHAPTER IX.
Atolls, or Coral Islands--Their strange Appearance--Their
Connexion with Volcanoes--Their Mode of Formation--Antarctic
Volcanoes--Diatomaceous Deposits
To the southward of the Sandwich Islands, on the other side of the
equator, there is a large group of islands in the Pacific, which
have a very peculiar appearance. They are called Atolls or Coral
Islands. Although not exactly of volcanic origin, yet the manner in
which they are formed has some connexion with submarine volcanic
action.
An atoll consists essentially of a ring of coral rocks but little
elevated above the level of the sea, and having in its centre a
lagoon or salt-water lake, which generally communicates by a deep
narrow channel with the sea. The ring of rocks is flat on the
surface, which is composed of friable soil, and sustains a
luxuriant vegetation, chiefly of cocoa-nut palms.
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