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Geology > Chapter 5- Volcanic Eruptions > Flashcards

Chapter 5- Volcanic Eruptions Flashcards

1
Q

What is a volcano?

A

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

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2
Q

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

A

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

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3
Q

What is the difference between effusive and explosive volcanoes?

A

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

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4
Q

What is viscosity?

A

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

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5
Q

What affects viscosity?

A

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

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6
Q

What type of lava does a basaltic lava flow have?

A

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

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7
Q

How fast and far can a basaltic lava flow go?

A

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

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8
Q

What is pahoehoe(pahoyhoy)?

A

It is a basaltic lava flow with glassy ropy texture

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9
Q

What is a’a’(ah-ah)?

A

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

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10
Q

What is columnar jointing?

A

When lava cools into vertical hexagonal columns

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11
Q

How are pillow basalts formed?

A

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

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12
Q

What is an andesitic lava?

A

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

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13
Q

What is a rhyolitic lava?

A

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

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14
Q

What is a volcaniclastic deposit?

A

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

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15
Q

What are the three types of pyroclastic material?

A

Pyroclasts, tuff, and specific pyroclast types

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16
Q

What are the specific pyroclast types?

A

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

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17
Q

What is tuff?

A

Rock resulting from pyroclastic deposit

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18
Q

What are the three types of pyroclasts?

A

Volcanic ash, lapilli, and bombs

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19
Q

What are the three types of pyroclastic transport?

A 
Pyroclastic fallout(ejection into air rains like snow)
Pyroclastic flow(horizontal ejection of ash that ride on hot gas. 
Lahar(volcanic mudflow)
20
Q

What is pele’s hair?

A

Strands of glass created by flying lava droplets

21
Q

Why do intermediate and felsic magmas erupt more explosively?

A

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

22
Q

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

A

False, they range from 200 to 450 degrees Celsius

23
Q

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

A

True

24
Q

What are three examples of volcanoes with pyroclastic flow?

A

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

25
Q

How fast can lahars move?

A

Up to 50 km per hour

26
Q

True or false? 20% of magma is gas.

A

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

27
Q

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

A

Water
Carbon dioxide
Sulfur dioxide

28
Q

True or false? Gas is expelled as magma rises.

A

True

29
Q

How does gas escape affect eruption?

A 
Low viscosity(gasses escape early, mellow eruption)
High viscosity(gasses are trapped, violent eruption)
30
Q

What are gas bubbles in rock called?

A

Vesicles

31
Q

What is a crater?

A

A bowl shaped depression atop a volcano

32
Q

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

A

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

33
Q

What are some famous calderas?

A

Crater lake Oregon

Yellowstone national park

34
Q

What is a shield volcano?

A

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

35
Q

What is a cinder cone volcano?

A

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

36
Q

What are stratovolcanoes?

A

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

37
Q

What are some examples of a stratovolcano?

A

Mt. Fuji, mt. Rainier, mt. Vesuvius

38
Q

When did mt. St. Helen’s erupt?

A

May 18 1980 8:32 a.m.

39
Q

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

A

North Dakota

40
Q

At what type of plate boundary do most volcanoes emerge?

A

Convergent boundaries

41
Q

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

A

1000 time greater

42
Q

What is an active volcano?

A

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

43
Q

What is a dormant volcano?

A

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

44
Q

What is an extinct volcano?

A

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

45
Q

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

A

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

46
Q

What is lunar Maria?

A

Dark spots on the moon that are regions of flood basalts

Geology (13 decks)

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