PYROCLASTS

Question 1

what is ash

Answer 1

very fine-grained fragments (<2mm)

generally dominated by broken volcanic glass shards, but with variable amounts of broken crystals/lithic(rock) fragments

Question 2

what is lapilli

Answer 2

pyroclasts 2-64mm

often look like cinders

in water-rich eruptions, accretion of wet ash form accretionary lapilli

Question 3

what is blocks/bombs

Answer 3

fragments >64mm

ejected as incandescent lava fragments which were semi-molten airborne

block ejected as solid fragments with angular shapes

Question 4

pyroclastic fall

Answer 4

deposits produced when volcanic fragments are explosively ejected into atmosphere and fall back under influence of gravity

Question 5

pyroclastic flow

Answer 5

deposits produced by hot surface flows of volcanic fragments and gas

have high particle concentration

topographically controlled/travel at speed of >100km/h

Question 6

pyroclastic surge

Answer 6

deposits produced by expanded low particle concentration pyroclastic flows with high gas components that move fast and turbulently

some types of pyroclastic-surge deposits are associated with pyroclastic-flow deposits

Question 7

three types of ways volcanic rocks are transported/deposited

Answer 7

• pyroclastic fall
• pyroclastic surge
• pyroclastic flow

Question 8

isopachs

Answer 8

contour lines of equal deposit thickness over an area

Question 9

isopach maps

Answer 9

allow determination of pyroclastic deposit