Volcanoes

Question 1

What determines the magnitude and type of volcanic eruption?

Answer 1

Physical processes can determine the magnitude and type of volcanic eruption.

Question 2

1) What is Volcanic Activity?

Answer 2

Essentially it is when magma from inside the earth is released onto the Earth’s surface.

Question 3

Where is the essentially the volcano

Answer 3

The point where the magma escapes the Earth’s crust is called a volcano.

Question 4

How van magma be released?

Answer 4

Magma can be released gently through oozing out from cracks.

Magma can be released violently through eruptions (explosions caused by pressure).

Question 5

Where is more volcanic activity found?

Answer 5

There is more volcanic activity under the sea than on the land.

Question 6

Where does the name volcano derive from?

Answer 6

The name volcano derives from “Vulcano” a volcanic island in the Mediterranean Sea.

Question 7

What does each eruption release?

Answer 7

Each “eruption” will release gases trapped in the mantle into the atmosphere.

Question 8

What has volcanic activity helped to create?

Answer 8

• Over the 4 billion years of the earth’s history the atmosphere has been created largely due to volcanic activity.
• Volcanoes have helped to create the oceans & life.
• Volcanoes also create global cooling.

Question 9

What can volcanoes kill?

Answer 9

Volcanoes can kill people, animals & vegetation.

Question 10

When was volcanic activity greater?

Answer 10

Volcanic activity was far greater in the Earth’s early history.

Question 11

What extinction has volcanic activity has volcanic activity helped with?

Answer 11

Volcanic activity helped the extinction of the dinosaurs 65 million years ago.

Question 12

What has volcanic in-activity has been held responsible for?

Answer 12

Volcanic in-activity has been held responsible for loss of atmosphere, liquid water & decreasing temperatures on Mars.

Question 13

2) Where are volcanoes found on earth?

Answer 13

There are currently 500 “active” volcanoes on Earth.

There are lots of “dormant” (sleeping) volcanoes, which were active in the past and will be again sometime in the future.

There are also “extinct” (dead) volcanoes- e.g Edinburgh Castle

Question 14

Where are the majority of volcanoes found close to?

Answer 14

The majority of volcanoes are found close to or on plate margins: destructive & constructive plate margins

Question 15

What are destructive plate margins?

Answer 15

Mainly in the Pacific Ocean called the “Ring of Fire” around the edge of the ocean there is a lot of volcanic activity.

South America-The Andes, Central America-West coast, North America-Rockies, Aleutian Islands to East Russia to Japan & the Philippines, Solomon Islands to New Zealand.

The type of volcanic activity here is violent with “Composite volcanoes” common.

Question 16

The “Ring of Fire”

Answer 16

Sea page 2 of notes for map

Question 17

What are Constructive Plate Margins?

Answer 17

These are found along ocean ridges.

Most eruptions are gentle & occur under the sea.

The lava cools rapidly due to the sea water, thus creating a ridge.

Most “eruptions” occur in/at cracks in the crust which allows lava to escape.

Question 18

What are hotspots?

Answer 18

Isolated small areas of volcanic activity which occur away from plate margins.

Question 19

What is the type of margin important?

Answer 19

The type of plate margin is a good indicator of the type of volcanic activity.

Question 20

3) Types of Lava:

Answer 20

Basic and acid

Question 21

What kind of viscosity does basic lava have?

Answer 21

This has a very low viscosity (fluid), it is very hot around 1,200 degrees Celsius. Behaves like warm runny treacle.

Question 22

What content of basic lava is low?

Answer 22

It has a low silica content.

Question 23

Does it take a long or short time for basic lava to cool?

Answer 23

It takes a long time to cool and solidify, so it can flow long distances as rivers of molten rock.

Question 24

Where is basic lava found?

Answer 24

This type of lava is found at Constructive plate margins where magma rises above the mantle e.g. mid-Atlantic ridge.

Question 25

What will basic lava regain after eruption?

Answer 25

It will retain its gas content after eruption which helps its mobility.

Question 26

What does basic lava produce?

Answer 26

It produces extensive sloping landforms.

Question 27

What kind of eruptions is basic lava associated with?

Answer 27

It is associated with gentle but frequent eruptions where lava & steam is ejected.

Question 28

What kind of viscosity does acid lava have?

Answer 28

This is viscous (sticky), less hot only 800 degrees Celsius. It will flow more slowly and travel over shorter distances.

Question 29

Which content is higher in acid lava?

Answer 29

It has a higher silica content.

Question 30

What does acid lava lose quickly?

Answer 30

The lava will lose gas quickly and become viscous.

Question 31

Where is acid lava found?

Answer 31

This type of lava is found at Destructive plate margins where oceanic crust is destroyed.

Question 32

What kind of landscape does acid lava produce?

Answer 32

It will produce steep sided localised features.

Question 33

What kind of eruptions are seen in volcanoes with acid lava?

Answer 33

The eruptions will be violent & less frequent due to the build up of pressure & gases.

In eruptions with acid lava then ash, steam, rocks & gases are also ejected.

Question 34

4) Types of Volcano

Answer 34

1. Fissure and Fissure volcanoes
2. Acid or Dome volcanoes
3. Basic or shield volcanoes
4. calderas
5. super volcanoes

Question 35

What are fissure volcanoes?

Answer 35

These occur along Constructive plate margins where the lava is ejected through several vents instead of one central vent. They can create a ridge with a Basaltic lava plateaux

Question 36

What are Acid or Dome volcanoes?

Answer 36

These are volcanoes that are steep sided & have a convex cone. This is due to “acid” lava quickly solidifying when exposed to the air. Essentially produces a “dome” shaped volcano.

Question 37

What are Basic or Shield volcanoes?

Answer 37

These are massive volcanoes with low angled slopes and a shield shaped profile. This is due to Basic lava flowing out of a central vent and spreading out over a wide area before becoming solid.

Question 38

What are Composite volcanoes?

Answer 38

These are larger volcanoes that are created by alternating types of eruption in which at first ash and then lava is ejected.

These volcanoes are associated with gentle & violent eruptions.

see image in notes

Question 39

What are calderas?

Answer 39

These are created due to a build up of gases underneath a volcano. The result is a massive eruption/explosion when the summit of the volcano is literally blown away. Over time the resulting crater can subside widening the crater, which can fill with water with an island or new volcanic cone in the centre.

see image in notes

Question 40

What are super volcanoes?

Answer 40

A supervolcano is a volcano on a massive scale.

It is different from a volcano because: it erupts at least 1,000 km3 of material (a large volcano erupts around 1 km3).

There are only a few known supervolcanoes- Yellowstone is one of the largest and erupts on roughly a 600,000 year cycle.

Any eruption would be catastrophic. The caldera of Yellowstone is so big that it could only be identified from Space.

Question 41

What are the 8 types of eruption (from gentle to violent)?

Answer 41

1) Icelandic: lava flows gently erupting from a fissure or crack in the crust.
2) Hawaiian: lava is emitted gently from a vent.
3) Strombolian: These are small but frequent eruptions consisting of lava.
4) Vulcanian: more violent but less frequent eruptions with lava & pyroclastic fragments.
5) Vesuvian: violent eruptions that occur after a long period of inactivity, again consisting of lava & pyroclastic fragments.
6) Krakatoan: exceptionally violent explosions where there is a lot of lava & pyroclastic fragments.
7) Pelean: violent eruptions accompanied by pyroclastic flows.
8) Plinian: massive eruptions where large amounts of lava, pyroclastic material & pyroclastic flows are ejected

Question 42

What is pyroclastic material? (ps ‘pyr’ is fire in Ancient Greek

Answer 42

This is material ejected by volcanoes in a fragment form of different sizes: ash, small stones & large material.

This material is blasted into the air before collapsing to fall down the sides of the volcano extremely quickly.

The material is really hot up to 350 degrees Celsius.