Chapter 5- Volcanic Eruptions

Question 1

What is a volcano?

Answer 1

An erupting vent through which molten rock surfaces, or, a mountain built from magmatic eruptions.

Question 2

When did mount Vesuvius erupt and how many people were killed from the pyroclastic flow?

Answer 2

It erupted in 79 A.D. And killed 20,000 people in Pompeii

Question 3

What is the difference between effusive and explosive volcanoes?

Answer 3

Effusive volcanoes erupt into lava flows while explosive volcanoes erupt in pyroclasts(volcanic fragments)

Question 4

What is viscosity?

Answer 4

It is a measure of a materials resistance to flow. E.g. Honey has high viscosity.

Question 5

What affects viscosity?

Answer 5

Temperature and composition(higher silica content equals higher viscosity) and gasses

Question 6

What type of lava does a basaltic lava flow have?

Answer 6

It has magic lava which is hot with low silica content and viscosity.

Question 7

How fast and far can a basaltic lava flow go?

Answer 7

It an travel up to100 km an hour and at distances up to 100 km

Question 8

What is pahoehoe(pahoyhoy)?

Answer 8

It is a basaltic lava flow with glassy ropy texture

Question 9

What is a’a’(ah-ah)?

Answer 9

It is a basaltic lava that solidifies with an angular jagged surface.

Question 10

What is columnar jointing?

Answer 10

When lava cools into vertical hexagonal columns

Question 11

How are pillow basalts formed?

Answer 11

It is a mound of lava from a mid ocean ridge that cools instantly into a round ball or “pillow”

Question 12

What is an andesitic lava?

Answer 12

It is high in silicates and thus very viscous. Slow moving flow that stays close to the vent.

Question 13

What is a rhyolitic lava?

Answer 13

It has the highest silicate content and thus is the most viscous lava. Usually plugs the vent as a lava dome.

Question 14

What is a volcaniclastic deposit?

Answer 14

It is fragments of igneous materials accumulated in a cooled flow.

Question 15

What are the three types of pyroclastic material?

Answer 15

Pyroclasts, tuff, and specific pyroclast types

Question 16

What are the specific pyroclast types?

Answer 16

Pumice-rhyolite with an abundance of vesicles
Scoria- pumice of basaltic composition
Cinder-lapilli-size basaltic pumice

Question 17

What is tuff?

Answer 17

Rock resulting from pyroclastic deposit

Question 18

What are the three types of pyroclasts?

Answer 18

Volcanic ash, lapilli, and bombs

Question 19

What are the three types of pyroclastic transport?

Answer 19

Pyroclastic fallout(ejection into air rains like snow)
Pyroclastic flow(horizontal ejection of ash that ride on hot gas. 
Lahar(volcanic mudflow)

Question 20

What is pele’s hair?

Answer 20

Strands of glass created by flying lava droplets

Question 21

Why do intermediate and felsic magmas erupt more explosively?

Answer 21

Because they are more viscous than basaltic magma and they produce more ash

Question 22

True or false? Pyroclastic flows can range in temperature from 100 to 325 degrees Celsius.

Answer 22

False, they range from 200 to 450 degrees Celsius

Question 23

True or false? Pyroclastic flows can move up to 300 kilometers per hour.

Answer 23

True

Question 24

What are three examples of volcanoes with pyroclastic flow?

Answer 24

Mt. Vesuvius, mt. Pelee, and mt. Augustine

Question 25

How fast can lahars move?

Answer 25

Up to 50 km per hour

Question 26

True or false? 20% of magma is gas.

Answer 26

False, gas content in magma can go as high as 9%

Question 27

What are the most abundant gasses in magma in order of abundance?

Answer 27

Water Carbon dioxide Sulfur dioxide

Question 28

True or false? Gas is expelled as magma rises.

Answer 28

True

Question 29

How does gas escape affect eruption?

Answer 29

``` Low viscosity(gasses escape early, mellow eruption) High viscosity(gasses are trapped, violent eruption) ```

Question 30

What are gas bubbles in rock called?

Answer 30

Vesicles

Question 31

What is a crater?

Answer 31

A bowl shaped depression atop a volcano

Question 32

What is a caldera and how long is their typical width?

Answer 32

It's a gigantic volcanic depression formed from massive eruptions that collapse the volcano. They range from 1-10 km in width

Question 33

What are some famous calderas?

Answer 33

Crater lake Oregon | Yellowstone national park

Question 34

What is a shield volcano?

Answer 34

It is a large volcano that is short but very wide due to low viscosity basaltic lava flows

Question 35

What is a cinder cone volcano?

Answer 35

It is a cone shaped pile of tephra that is comprised of lapilli piled up at the vent. It is the smallest type of volcano

Question 36

What are stratovolcanoes?

Answer 36

Large cone shaped volcanoes composed of alternating layers of tephra and lava, often symmetrical.

Question 37

What are some examples of a stratovolcano?

Answer 37

Mt. Fuji, mt. Rainier, mt. Vesuvius

Question 38

When did mt. St. Helen's erupt?

Answer 38

May 18 1980 8:32 a.m.

Question 39

How far away did ash travel from mt. St. Helen's?

Answer 39

North Dakota

Question 40

At what type of plate boundary do most volcanoes emerge?

Answer 40

Convergent boundaries

Question 41

How much greater was the Yellowstone eruption compared to mt. St. Helen's?

Answer 41

1000 time greater

Question 42

What is an active volcano?

Answer 42

It is a volcano that is erupting has recently erupted or is likely to erupt.

Question 43

What is a dormant volcano?

Answer 43

It is a volcano that has not erupted for hundreds to thousands of years.

Question 44

What is an extinct volcano?

Answer 44

It is a volcano that is no longer capable of erupting.

Question 45

What are the four warning signs that an eruption is about to occur?

Answer 45

Earthquake activity Heat flow(magma causes volcanoes to heat up) Changes in shape(volcanoes will inflate) Changes in gas mix and volume

Question 46

What is lunar Maria?

Answer 46

Dark spots on the moon that are regions of flood basalts