Lecture 2.2 - Volcanic Landforms

Question 1

Define volcanic landform

Answer 1

Mass of igneous rocks that formed at one location over time with lava from a given magma chamber

Question 2

What are the three features that control the landform creation

Answer 2

I. Viscosity/composition of magma
A: low viscosity = mafic
B: high viscosity = felsic
II. Gas content
A: low gas = coherent lave flows
B: high gas = explosive to give pyroclastic fragments
III. Opening to surface
A: conduit = vent is roughly circular shape
B. Fissure = vent is a long crack on surface

Question 3

Define viscosity

Answer 3

Resistance to flow
Depends on composition

Question 4

Characteristics of shield volcanoes (#1) + location

Answer 4

I. Mafic
II. Low gas
III. Conduit

Mauna Loa, Hawaii

Question 5

What are the two types of basalt flows? Describe them

Answer 5

1. Aa flow
   
   • sharp surface
   • flows through open rivers
2. Pahoehoe flow
   
   • ropy surface
   • flows through subsurface tubes

Question 6

Characteristics of lave plateau (#2) + location

Answer 6

I. Mafic
II. Low gas
III. Fissure

Columbia river plateau

Question 7

Characteristics of cinder cone (#3) + location

Answer 7

I. Mafic
II. High gas
III. Conduit

Sunset crater national monument near flagstaff AZ

Question 8

What are spatter fragments

Answer 8

Liquid (out of vent) —> liquid (hit ground)

Question 9

What are bomb fragments

Answer 9

Liquid (out of vent) —> solid (hit ground)

Question 10

What are block fragments

Answer 10

Solid (out of vent) —> solid (hit ground)

Question 11

Characteristics of composite volcanoes + rock + location

Answer 11

I. Mafic to intermediate
II. 1st high, 2nd low
III. Conduit + side fissures

Porphyritc andesite

Mount Rainer, Seattle & Tacoma, Washington

Question 12

Characteristics of lava dome volcanoes (#5) + rock + location

Answer 12

I. Felsic
II. Low gas
III. Conduit

Rhyolite

Mount Lassen, National park in Northern California