Volcanic block

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A volcanic block is a fragment of rock that measures more than 64 mm (2.5 in) in diameter and is erupted in a solid condition.

Blocks are formed from material from previous eruptions or from

(a bomb is a block with streamlined appearance, often expelled in a molten state). Bombs can also occur due to the disruption of the crust of a lava dome that has formed up or over a vent during an eruption.

Features

Blocks are nearly always angular to sub-angular and roughly equidimensional. If the parent rock is flow-foliated lava, sedimentary material or

metamorphic rocks, the blocks may have a plate-like or slab-like form. In other cases, blocks derived from great depths may resemble polished water-worn pebbles and are cobbled due to fluidisation and upwards transport.

Blocks can be enormous and may be transported great distances from the

discharged blocks weighing 2-3 tons over distances of 100-200m.

References