Exam 2 part 2

Question 1

What 3 things determine the viscosity of magma?

Answer 1

1) Composition
2) Temperature
2) Dissolved gases

Question 2

What does the viscosity determine for magma?

Answer 2

It will determine just how explosive it will be when it erupts from a volcano

Question 3

How does silica content affect the viscosity of magma?

Answer 3

The higher the silica content there is, the higher the viscosity. The lower the silica content, the lower the viscosity.

Question 4

Which has higher silica content, felsic rocks or mafic rocks?

Answer 4

Felsic has higher silica content than mafic.

Question 5

What is Tetrahedra ?

Answer 5

Silica

Question 6

Which is less viscous, hot magma or cooler magma?

Answer 6

Hotter magma is less viscous

Question 7

How can gases affect magma?

Answer 7

Because gases extend in magma when they near the surface, the violence of the magma’s eruption will be determined by how easily the gases can escape.

Question 8

Which type of magma/lava is more explosive, Basaltic or Andesitic?

Answer 8

Andesitic lava/magma are more explosive than Basaltic

Question 9

What type of behavior does basaltic lava have?

Answer 9

It has a fluid like behavior

Question 10

What are two types of basaltic lava?

Answer 10

1) Pahoehoe lava

2) Aa Lava

Question 11

What is the difference between Pahoehoe lava and Aa lava?

Answer 11

Pahoehoe lava resembles a twisted ropey texture while Aa lava is rough, jagged and bulky.

Question 12

What are the dissolved gases in magma?

Answer 12

Mainly water and Carbon Dioxide

Question 13

What are pyroclastics?

Answer 13

They are fragments extruded from a volcano

Question 14

What are 4 types of pyroclastics?

Answer 14

1) Ash and dust (Glass fragments)
2) Lapilli (walnut-sized pieces of material)
3) Pumice
4) Particles bigger than Lapilli

Question 15

What is Lapilli made of?

Answer 15

Pumice

Question 16

What is the first to fall from a volcanic eruption?

Answer 16

Lapilli

Question 17

Why do volcanoes erupt?

Answer 17

Landslides

Question 18

What are the 4 features of a volcano?

Answer 18

1) Opening at the summit
2) Craters/Calderas
3) Vent spaces connected to the magma chambers
4) Fumaroles

Question 19

What are craters and calderas and what is the difference between them?

Answer 19

Craters and Calderas are both depressions in the volcano but craters are smaller than 1km and calderas are lager than 1km

Question 20

What are the 3 types of volcanos?

Answer 20

1) Shield volcanoes
2) Composite volcanoes
3) Cinder cone volcanoes

Question 21

What are the 4 factors of Shield volcanoes?

Answer 21

1) Broad and slightly domed-shaped
2) Cover large areas
3) Mild eruptions
4) Usually have large calderas

Question 22

What are the 5 factors of cinder cone volcanoes?

Answer 22

1) Built from ejected lava
2) They have steep slope angles
3) Small in size
4) Frequently occur in groups
5) After the gases are gone the lava will flow only as a liquid under the volcano

Question 23

What are the 6 factors of composite volcanoes?

Answer 23

1) Most are located adjacent to the pacific ocean
2) Large, thousands feet high and miles wide
3) Composed of lava flows and pyroclastics
4) Most violent eruptions
5) Lava flows down a different side of the volcano each eruption
6) Over time they build themselves back up after collapsing

Question 24

What is Nu’ee Ardente?

Answer 24

It is a deadly pyroclastic flow that is known for glowing avalanches and can move at speeds of 200km per hour

Question 25

What is a Lahar?

Answer 25

It’s a volcanic mudflow that moves down stream valleys and volcanic slopes

Question 26

What is a caldera eruption?

Answer 26

When a volcano collapses after an eruption and leaves a large depression.

Question 27

What sometimes happens in the calderas of volcanoes?

Answer 27

Sometimes a lake will form in the caldera

Question 28

What is a pyroclastic flow?

Answer 28

When a pyroclastic cloud (That erupted from a volcano) collapses and flows downwards

Question 29

What are volcanic fissures?

Answer 29

They are fluid basaltic lava extruded from crustal fractures

Question 30

What is a lava plateau?

Answer 30

A large flat area in which highly fluid lava flowed over and solidified into a flat surface

Question 31

What are lava domes?

Answer 31

Bulbous mass of congealed lava from an explosive eruption of gas-rich magma

Question 32

Why do lava domes form?

Answer 32

Usually when the volcano is attempting to build itself back up after collapsing.

Question 33

What are volcanic necks?

Answer 33

They are vents inside the volcanic cone that are left over after the volcanic cone has been worn away by erosion

Question 34

What are volcanic pipes?

Answer 34

They are short conduits underneath the volcano that connect a magma chamber to the surface

Question 35

What is a pluton?

Answer 35

It is when magma is cooled and solidified in sheets deep in the earth

Question 36

What is the difference between concordant and discordant plutons?

Answer 36

Concordant plutons are parallel to the surround bedrock while dis-concordant isn’t parallel

Question 37

What is a dike and what is a sill?

Answer 37

A dike is a discordant pluton and a sill is a concordant pluton

Question 38

What is a Laccolith?

Answer 38

Similar to a sill, mushroom shaped mass, arches overlaying strata.

Question 39

What is a Batholith?

Answer 39

It is the largest intrusive body, larger than 100km squared surface exposure and are usually at the cores of mountains

Question 40

What is a fumarole?

Answer 40

A hole in a volcano in which steam rises