VOLCANOES

Question 1

Briefly explain the term active volcano.

Answer 1

An active volcano is a volcano that erupts regularly or is likely to erupt soon. Mount Etna in Italy is an example of an active volcano.

Question 2

Briefly explain the term dormant volcano.

Answer 2

A dormant volcano is a volcano that has not erupted in recent history but is likely to erupt again in the future. Mount Kilimanjaro in Tanzania is an example.

Question 3

Briefly explain the term extinct volcano.

Answer 3

An extinct volcano is a volcano that has not erupted in recent history and is not expected to erupt again in the future as the magma is no longer forcing its way into the chamber. Slemish Co. Antrim is an example.

Question 4

Briefly explain the term lava.

Answer 4

Lava is the name given to magma once it reaches the surface. Lava can be either acidic or basic and the type of lava emitted determines whether an eruption will be violent or gentle.

Question 5

Acidic lava features (3)

Answer 5

Volcanoes at convergent boundaries
Moves slowly
Violent eruption

Question 6

Basic lava features (3)

Answer 6

Volcanoes at divergent boundaries
Moves quickly
Gentle eruption

Question 7

What comes out of a volcano other than lava?

Answer 7

Pyroclastic material (tephra) - ash, dust, and rock fragments
Gases - Carbon dioxide, carbon monoxide, and hydrogen.

Question 8

Volcanoes occur at convergent plate boundaries when an…

Answer 8

Oceanic plate collided with another plate.

Question 9

When the plates collide what process occurs?

Answer 9

Subduction. The heavier plate subducts into the mantle.

Question 10

What depth does the subducting plate reach to melt?

Answer 10

100km

Question 11

What is released from the plate? (Convergent)

Answer 11

Water vapour and gases e.g CO2

Question 12

What happens to the gases released (convergent)

Answer 12

Get trapped in the magma.

Question 13

When the gases get trapped in the magma what happens to the magma?

Answer 13

It’s forced to rise upwards through the overlying plate.

Question 14

As the magma melts it’s way through the crust it forms a…

Answer 14

Magma chamber

Question 15

What prevents the gases from escaping?

Answer 15

The viscosity of the lava.

Question 16

Since the gases can’t escape what happens on the magma chamber?

Answer 16

Pressure builds.

Question 17

When the pressure becomes so great what happens? (Convergent)

Answer 17

It burns its way through the overlying rock and erupts explosively onto the surface.

Question 18

Does the pressure travel far? (Convergent)

Answer 18

No

Question 19

Since the pressure doesn’t travel far what does that lead to? (Convergent)

Answer 19

Formation of
steep sided volcanic cones of alternating layers of tephra and lava.

Question 20

Convergent volcanoes are known as

Answer 20

Stratovolcanoes

Question 21

What’s an example of a stratovolcano?

Answer 21

Mount St. Helens

Question 22

What are the two convergent boundaries that volcanoes form at?

Answer 22

Oceanic oceanic
Oceanic Continental

Question 23

(OO) Repeated eruptions cause what?

Answer 23

The build up of volcanic material to form volcanic island arcs.

Question 24

Example of a volcanic island arc.

Answer 24

Philippine Island Arc - formed form subduction of Pacific plate beneath Eurasian plate

Question 25

(OC) Chains of volcanic mountains are known as..

Answer 25

Volcanic arcs

Question 26

Example of OC volcanic arc.

Answer 26

The Andes - Nazca and South American (Cotopaxi = peak)

Question 27

D: what two plates separate?

Answer 27

Oceanic plates

Question 28

D: As they separate what happens

Answer 28

Fissures form between them

Question 29

D: What rises through these fissures?

Answer 29

Magma onto the sea floor as lava.

Question 30

D: Magma has a ____ silica content

Answer 30

Low

Question 31

Low silica content means that gases

Answer 31

Escape easily

Question 32

If gases escape easily are the eruptions violent or gentler

Answer 32

Gentler

Question 33

Once lava comes in contact with sea water it

Answer 33

Cools quickly and hardens to form basalt.

Question 34

As the basalt builds up it forms what landform?

Answer 34

Mid ocean ridge

Question 35

The Mid Atlantic Ridge has what plates involved?

Answer 35

North American and Eurasian

Question 36

A chain of volcanoes form volcanic arcs but also

Answer 36

Hotspots

Question 37

Unlike other volcanic formations hotspots are located

Answer 37

Away from plate boundaries

Question 38

The usually occur on what plates (hotspots)

Answer 38

Oceanic

Question 39

What are hotspots

Answer 39

Areas of Earths mantle that are much hotter than the magma around it

Question 40

Hotspots: the magma is so hot that

Answer 40

It melts through the oceanic plate to form a volcano

Question 41

The magma for hotspots is low or high in silica content

Answer 41

Low

Question 42

Landforms created from volcanoes can be either

Answer 42

Extrusive - on the surface Intrusive - inside the crust

Question 43

An extrusive landform is

Answer 43

Volcanic cones

Question 44

Where do volcanic cones form at?

Answer 44

Convergent and divergent plate boundaries and hotspots.

Question 45

What are the four types of volcanic cones?

Answer 45

Composite cones Cinder cones Calderas Shield volcanoes

Question 46

What are composite cones also known as?

Answer 46

Stratovolcanoes

Question 47

Where do composite cones form at?

Answer 47

Convergent boundaries

Question 48

What are composite cones made up of?

Answer 48

Alternating layers of pyroclastic material and acidic lava.

Question 49

Example of a stratovolcano?

Answer 49

Mount Fuji, Japan.

Question 50

Cinder cones rarely reach heights of more than.

Answer 50

300m

Question 51

What is the most common type of volcano found on the earth?

Answer 51

Cinder cones

Question 52

What are cinder cones made up of?

Answer 52

Pyroclastic material that stuck together after explosive eruption.

Question 53

What volcanic cone only erupts once?

Answer 53

Cinder cone

Question 54

Why do cinder volcanoes only erupt once?

Answer 54

The eruption is so powerful that it destroys its shape.

Question 55

Over 100 cinder cones surround

Answer 55

Mauna Lao in Hawaii

Question 56

How are calderas formed?

Answer 56

When composite cones explode violently

Question 57

What is a depression and how is it formed?

Answer 57

An area of land that sank downwards after fractured rock collapsed into an empty magma chamber.

Question 58

Where do shield volcanoes form?

Answer 58

Divergent boundaries and hotspots.

Question 59

How are shield volcanoes formed?

Answer 59

From gentler eruptions of basic lava which spreads over a wide area.

Question 60

Example of a shield volcano

Answer 60

Mauna Lao in Hawaii

Question 60

What type of volcanic cone is the largest?

Answer 60

Shiel volcano

Question 61

How is a lava plateau formed?

Answer 61

large streams of basic lava are released onto the surface from fissure eruptions. Lava spreads over a wide area and cools and hardens. Repeated eruptions lead to the formation.

Question 62

Example of a lava plateau

Answer 62

Antrim-Derry Plateau

Question 63

Hexagonal columns at A-D Plateau are known as

Answer 63

The Giants Causeway

Question 64

Examples of intrusive landforms.

Answer 64

Batholith and Sill

Question 65

What are batholiths?

Answer 65

Large areas of igneous rock that form when magma cools slowly inside the Earths crust.

Question 66

When do batholiths form

Answer 66

During fold mountain building.

Question 67

Example of a batholith and what plates collided to form it.

Answer 67

Leinster Batholith - North American and Eurasian

Question 68

How can you predict volcanic activity?

Answer 68

Historic records - studying past eruptions to find patterns e.g. time before eruptions. Gas emissions - increases in gas like CO2 being released in volcano can mean that its close to erupting

Question 69

How can you predict volcanic activity? p.2 not HR or GE

Answer 69

Ground deformation: If a volcano's cone changes in steepness, it can be close to erupting. Tiltmeters are used to check this: an air bubble in water moves if the slope changes. Seismic activity: It increases under a volcano before an eruption because magma and gas are forcing their way into a magma chamber. Seismographs - as magma moves it records vibrations in the crust.

Question 70

What are some positive impacts of volcanoes?

Answer 70

New land is created - Iceland formed after a build-up of basalt on Mid Atlantic Ridge (North American and Eurasian plates) Tourism - Tourists are attracted to landforms formed. Iceland's economy has been boosted because of the activity. Foreign tourists = 42% of income. Employment goes up. Tourists go hiking or sightseeing. Geothermal energy - Renewable energy. Iceland uses it. Igneous rock absorbs heat from magma causing groundwater to heat up. Groundwater turns into steam and taken to power stations then filtered through turbines and then produces electricity.