Volc Quiz 3

Pyroclast

Fragments of volcanic material

Tephra

Unconsolidated material

Pyroclastic rock

consolidated material

Bomb

Twisted shapes that indicated solidified fluid flying through the air then solidifying

Blocks

Large chunks of rock from the sides of the volcano, cover the underlying magma

Lapillus

Individual fragments of mineral or rock materials, two categories are scoria and pumice

Ash grain

Mineral, glass or rock fragment less than 2 millimeters in diameter

Pumice

Lightweight and porous, lightweight, light-color, FELSIC

Scoria

Dark red or black, dense, MAFIC, bombs

Mechanisms by which pyroclastic flows are generated

Column collapse or dome collapse

Ash-fall deposits

Well-sorted, fine, continuous layers that blankets topography evenly and falls from the air, generated by column collapse

Pyroclastic-flow deposits

Poorly sorted, various sizes, and little bedding that fills valleys and low areas generated by dome and column collapse

Pyroclastic-surge deposits

Fills valleys and slightly overtops hills, intermediate sorting, of smaller sizes.

Pumice flows

High flow density, low clast density due to being blown apart by expanding gas bubbles immediately upon column collapse.

Surges

Medium clast density, low flow density

Block and ash flows

High clast density and high flow density due to collapsing dome of hardened rock

Monogenetic

Volcanoes that only erupt once

Polygenetic

Erupts repeatedly over thousands or millions of years

Shield volcanoes

Very large, flat volcanoes with Hawaiian eruptions and mafic magma. Polygenetic, mostly located on intraplate hotspots but also subduction zones

Composite volcanoes

Medium “volcano’ shape, mainly andesitic magma with vulcanian eruptions, typically polygenetic and in subduction zones but can also occur in continental rifts

Cinder cone

Smallest volcanoes, mostly mafic in character, low viscosity, monogenetic, most abundant and can occur in any tectonic environment

Caldera formation

Giant collapse structures resulting from highly explosive magma withdrawal

Crater formation

Either from the creation of a volcanic cone or destruction of original volcanic cone

Maars

Volcanic craters filled with water after said water comes in contact with magma during phreatomagmatic eruptions