Pyroclastic rock

  • usgs scientist examines pumice blocks at the edge of a pyroclastic flow from mount st. helens
    rocks from the bishop tuff, uncompressed with pumice on left; compressed with fiamme on right.
    file:volcanic stone 2d.ogvplay media
    flight through a μct-image stack of a lapillus of the volcano katla in iceland. find spot: beach near vik at the end of road 215. acquisition done using "ct alpha" by "procon x-ray gmbh", garbsen, germany. resolution 11,2μm/voxel, width approx. 24 mm.
    file:volcanic stone 3d.ogvplay media
    3d-rendering of the above image stack, in parts transparent. heavy particles in red.

    pyroclastic rocks or pyroclastics (derived from the greek: πῦρ, meaning fire; and κλαστός, meaning broken) are sedimentary clastic rocks composed solely or primarily of volcanic materials. where the volcanic material has been transported and reworked through mechanical action, such as by wind or water, these rocks are termed volcaniclastic. commonly associated with unsieved volcanic activity—such as plinian or krakatoan eruption styles, or phreatomagmatic eruptions—pyroclastic deposits are commonly formed from airborne ash, lapilli and bombs or blocks ejected from the volcano itself, mixed in with shattered country rock. tephra is any sized material formed by a volcanic eruption.

    pyroclastic rocks may be a range of clast sizes, from the largest agglomerates, to very fine ashes and tuffs. pyroclasts of different sizes are classified as volcanic bombs, lapilli, and volcanic ash. ash is considered to be pyroclastic because it is a fine dust made up of volcanic rock. one of the most spectacular forms of pyroclastic deposit are the ignimbrites, deposits formed by the high-temperature gas-and-ash mix of a pyroclastic flow event.

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USGS scientist examines pumice blocks at the edge of a pyroclastic flow from Mount St. Helens
Rocks from the Bishop Tuff, uncompressed with pumice on left; compressed with fiamme on right.
Flight through a μCT-image stack of a lapillus of the volcano Katla in Iceland. Find spot: Beach near Vik at the end of road 215. Acquisition done using "CT Alpha" by "Procon X-Ray GmbH", Garbsen, Germany. Resolution 11,2μm/Voxel, width approx. 24 mm.
3D-Rendering of the above image stack, in parts transparent. Heavy particles in red.

Pyroclastic rocks or pyroclastics (derived from the Greek: πῦρ, meaning fire; and κλαστός, meaning broken) are sedimentary clastic rocks composed solely or primarily of volcanic materials. Where the volcanic material has been transported and reworked through mechanical action, such as by wind or water, these rocks are termed volcaniclastic. Commonly associated with unsieved volcanic activity—such as Plinian or krakatoan eruption styles, or phreatomagmatic eruptions—pyroclastic deposits are commonly formed from airborne ash, lapilli and bombs or blocks ejected from the volcano itself, mixed in with shattered country rock. Tephra is any sized material formed by a volcanic eruption.

Pyroclastic rocks may be a range of clast sizes, from the largest agglomerates, to very fine ashes and tuffs. Pyroclasts of different sizes are classified as volcanic bombs, lapilli, and volcanic ash. Ash is considered to be pyroclastic because it is a fine dust made up of volcanic rock. One of the most spectacular forms of pyroclastic deposit are the ignimbrites, deposits formed by the high-temperature gas-and-ash mix of a pyroclastic flow event.

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