Some of the flows are still so young as to preserve their scoriaceous surface; here the shore-line of the lava contours evenly around the spurs and enters, bay-like, into the valleys of the enclosing mountains, occasionally isolating an outlying mass. [Please select]
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Gases and steam escaping from other similar masses may leave them hollow, when they are termed bombs, or may pit their surfaces with irregular bubble-cavities, when they are called scoriae or scoriaceous. [Please select]
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