W7 Pyroclastic eruptions and rocks

Question 1

Pyroclastioc materials are

Answer 1

the products of explosive eruptions

Question 2

pyroclastic material useful because

Answer 2

if you find pyroclastics on the ground → future life threatening volcano
can be useful to predict future

Question 3

channem shape proves lava is

Answer 3

channel shape proves that lava is highly viscous

Question 4

Particle Size classifications

Answer 4

according to size not shape
>64 mm - bombs or blocks
64 - 4 mm - “lapilli” (little stones)
< 4 mm - ash

Question 5

Surge Deposits

Answer 5

ground surge produce very characteristic depositis: surge deposits
as moves further away less energy less material
shows cross bedding pattern, go up and down slopes
first pyroclsastic material from this type of volcanic event

Question 6

Airfall Deposists

Answer 6

blasted up and then fall back down
very fine ash particles, windborne (could stay in atmospheere for years)
but mast majority fall out
form thin layers (1-2 cm thick)

Question 7

Accretionary Lapilli

Answer 7

type of pyroclastic deposit called a tuff
Birds eye tuff, rounded → tuff
also lightning during eruptions (particles may have charge and produce lightning)

Question 8

Surge

Answer 8

cross bed unit, angles are every shallow

Question 9

Pumice Flows and Falls

Answer 9

white ish , vesiculated glass fibers and strands
big porosity, evidence for gas present within the magma
the gas is what energizes the magma and drives the eruption
very low density, floats on water
Pumice falls are often the first phase of a Plinian eruption

Question 10

Pyroclastic Flows

Answer 10

goverend by topography

tend to flow down into valleys than up hills etc

Question 11

Ignimbrites

Answer 11

pyroclastic units which are upto 100 km 3 large
often welded because they were hot deposits, not lava flows but flowed over land surface at some point
shape os thought to be geology o fmagma chamber upside down aka dark material over light so dense material at top less dense underneath

spires where hot gases/ fluids were escaping during formation, then helped to cement local ash parts into unit so geologically spires harder and more interesting

Question 12

flame Structures

Answer 12

Flame or Fiamme in a welded tuff
eutaxitic texture
because one material used to be hotten then welded together

Question 13

Volcanic Mudflows

Ladus

Answer 13

hot

Question 14

Volcanic Mudflows Lahars

Answer 14

cold

remobilished ash carried in river systems, extremely destructive

Question 15

Volcanic Avalanches

Answer 15

collapse of volcanic structures

Question 16

Bombs

Answer 16

executed as liquid and rotate while traveling through air → aerodynamic shape → solidify during ejections
Blocks are similar but were never liquid clasts, ejected as solids
big size range category of particles
bigger they are the closer to eruption source