Activity Lavas W5L2

Question 1

Basic Lavas

Answer 1

Basalts

Question 2

Intermeediate Lavas

Answer 2

Trachytes, Andesites

Question 3

Acid Lavas

Answer 3

Dacites, Rhyolites

Question 4

Texture VEscicles

Answer 4

gas bubbles

Question 5

Amygdales

Answer 5

mineral infilled gas bubbles

Question 6

Phenocrysts texture

Answer 6

crystal distinctly larger than the grains of the rock groundmass of an igneous rock

Question 7

Porphyries

Answer 7

textural term for an igneous rock consisting of large-grained crystals

Question 8

Basalt viscosity example Pahoehoe

Answer 8

lowest viscosity 
ropey surface texture
flows around obstacles, doenst undermine them
low flow fronts
long distance flow

Question 9

aa flow

Answer 9

higher visocisty basalt flow
rubbly surface texture (can not become pahoehoe)
high flow fronts
advance slow but bulldoze evrything in their way
have a vesuvius texture

Question 10

spatter

Answer 10

blebs of basalt

Question 11

pillow lavas

Answer 11

only form i subawuous erupitons

Question 12

intermediate lavas

Answer 12

Andesites and dacites are viscous; flows are uncommon
• flows only travel on steep
slopes
• flows travel for only a few
hundred metres
• characterised by blocky
surfaces - ‘block flows’

Question 13

coulées

Answer 13

high viscosity intermediate lava flow

Question 14

Acid lavas

Answer 14

very high vicosity lavas
• as a rule, don’t flow!
• occassionally form obsidian flows (similar to coulées)