Vulcanicity Key Terms

Question 1

Define volcano

Answer 1

An opening in the earth’s crust through which lava, ash and gases erupt. They mark the presence of magma within the earth’s crust

Question 2

Define magma

Answer 2

Molten rock beneath the earth’s surface

Question 3

Define lava

Answer 3

The term used for magma once it has been ejected onto the earth’s surface

Question 4

Define volcanic bombs

Answer 4

Crusted over ash deposits

Question 5

Define tephra

Answer 5

Airborne ash and dust

Question 6

Define conical hill

Answer 6

A common name for a volcano- a mountain that is built around a central vent that connects with reservoirs of molten rock below the earth’s surface

Question 7

Define an active volcano?

Answer 7

Volcanoes that have erupted within living memory

Question 8

Define a dormant volcano

Answer 8

Volcanoes that’ve erupted within historical

Question 9

Define an extinct volcano

Answer 9

Volcanoes that will not erupt again, they haven’t erupted within the last 25,000 years

Question 10

Define an intrusive landform

Answer 10

Molten rocks that’ve been injected into the crust

Question 11

Extrusive landforms

Answer 11

Molten rocks from the mantle that reach the earth’s surface

Question 12

Describe the gaseous emissions of a volcano

Answer 12

Dominated by steam which is often superheated as well as highly dangerous poisonous gases such as sulphur dioxide

Question 13

Define pyroclastic material

Answer 13

It is made up of a wide range of volcanic fragments from finer ash particles to lapilli as well as volcanic bombs

Question 14

Define a lahar

Answer 14

A destructive mudflow down the slopes of a volcano

Question 15

Define lapilli

Answer 15

Tephra in its finest form of hair like trails

Question 16

What is basaltic lava?

Answer 16

It is ‘basic’ lava with a low silica content making it the least viscous type of lava, it also allows gas bubbles to expand and rise to the surface, preventing sudden explosive activity

Question 17

Define andesitic lava

Answer 17

It is formed at destructive plate boundaries where crust is being destroyed. This lava is silica rich, explosive and viscous. It often solidifies before reaching the surface and as a result can lead o a build up of pressure in a volcanoes main vent, leading to a violent explosion.

Question 18

Define rhyolitic lava

Answer 18

It is formed at destructive and collision plate boundaries and has the same characteristics as andesitic lava only more severe

Question 19

Define the solid emissions of a volcano

Answer 19

Ash, dust, and glassy cinders. They may also include blocks of material such as shattered remains of solidified lava that previously plugged the dormant volcano

Question 20

Define the liquid emissions of a volcano

Answer 20

These include lava bombs (also known as tephra or pyroclasts) which solidify in mid-air, such as pumice. Tephra in its finest form of lapilli. Liquid emissions also include the surface lava flowing from vents and fissures

Question 21

Define a fissure eruption

Answer 21

Where lava flows from a crack, they tend to occur at spreading ridges and can cause the formation of a lava field

Question 22

Define a basic shield volcano

Answer 22

Made from basaltic rock and form gently sloping cones from layers of less viscous, free flowing lava. The resulting volcanoes have gentle sides (slopes of 5-10 degrees) and cover a large area

Question 23

Define a composite cone volcano

Answer 23

The classic pyramid shape of volcano with alternating layers of ash a lava. The angle of the slope is 6-10 degrees on the flanks and 30 degrees at the peak

Question 24

Define an acid/dome volcano

Answer 24

Steep sided convex cone consisting of andesitic lava. The slopes are very steep due to the high viscosity of the lava. Lavas may solidify in the vent and be revealed by later erosion

Question 25

Define a caldera volcano

Answer 25

When a particularly violent eruption has removed the peak of a volcanoes cone and leave an enormous crater which could be submerged by a lake or the sea. Eruptions in the caldera may form small cones.

Question 26

Define ash and cinder cone volcanoes

Answer 26

The simplest type of volcano formed from ash, cinders and volcanic bombs ejected from the crater. As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as cinders around the vent in a circular or oval cone.

Question 27

What’re the seven types of volcanic eruption? (Least to most destructive)

Answer 27

1. Icelandic
2. Hawaiian
3. Strombolian
4. Vulcanian
5. Vesuvian
6. Peléean
7. Plinian

Question 28

Define a geyser

Answer 28

A geyser is an intermittent, forceful discharge of superheated water ejected from the surface

Question 29

Define a fumarole

Answer 29

A low pressure outlet of steam

Question 30

Define a hot spring

Answer 30

Where volcanically heated water reaches the surface but is not under pressure like a geyser is

Question 31

Define a batholith

Answer 31

A solidified lava chamber which is often dome shaped

Question 32

Define a dyke

Answer 32

A vertical intrusion with horizontal cooling cracks

Question 33

Define a sill

Answer 33

A horizontal intrusion with vertical cooling cracks