As a rule, those LAVAS which are of inferior specific gravity are much more vesicular than the denser and heavier varieties.
"Geology"
James Geikie
The lava in some places was 600 feet deep and 200 wide, flowing like a mighty river towards the sea, wrapping whole districts in flames, re-melting old LAVAS, opening subterranean caverns, one of its streams reaching the ocean.
"A Girl's Ride in Iceland"
Ethel Brilliana Alec-Tweedie
The heat of this eruption not only re-melted old LAVAS, and opened fresh subterranean caverns, but one of its streams was computed to course the plains to an extent of 50 miles, with a depth of 100 feet, and 12 to 15 feet broad.
"A Girl's Ride in Iceland"
Ethel Brilliana Alec-Tweedie