Volcanoes - Chapter 3

Question 1

Volcanic plugs

Answer 1

Tall pillar of igneous rock that remains when a volcanic cone is eroded away. Represents the lava that solidifies within the vent
Eg. Puy in France

Question 2

Volcanic explosivity index

Answer 2

Scale to measure the force of a volcanic eruption. Uses height of ash cloud and amount of ash produced to rank eruptions from 1-8

Question 3

Volcanic domes

Answer 3

Upturned bowl shaped mound of acidic lava that builds up to form a cone with steep convex slopes or a dome within the crater

Question 4

Volcanic bombs

Answer 4

Large rocks thrown out of a volcano during an eruption

Question 5

Volcanic cone

Answer 5

Mountain formed by the eruption and built up of layers of lava and ash

Question 5

Vent

Answer 5

Hole in the ground from where lava erupts to form a volcanic cone

Question 6

Tephra

Answer 6

Build up of pyroclastic material such as pumice and ash

Question 7

Shield volcano

Answer 7

Volcano with gentle, concave slopes and a wide base. Formed by eruption of basic lava
Eg. Mauna Lao, Hawaii

Question 8

Pyroclasts

Answer 8

Hot ash and rock ejected from a volcano

Question 9

Pumice

Answer 9

Grey rock full of holes (porous) that form when frothy lava solidifies trapping air bubbles. So light is can float on water

Question 9

Pyroclastic flow

Answer 9

Heavy mix of hot lava blocks, pumice, ash and gas. Very destructive. Moves at high speeds down slopes typically following valleys

Question 10

Plutonic landforms

Answer 10

Underground landforms made by intrusion of igneous rock into the crust
Eg. Batholiths

Question 11

Plateau

Answer 11

Area of flat high ground often with steep sides

Question 12

Metamorphic aureole

Answer 12

Area of rock surrounding an igneous intrusion that has been changed by heat and pressure from the hot magma

Question 13

Lapolith

Answer 13

Bowl shaped layer of magma that is injected between 2 layers of sedimentary rock. Weight causes underlying rock layers to bed downwards
Eg. Bushveldt lapolith in South Africa

Question 14

Lava plateau

Answer 14

Steep sided, flat, wide surface that forms when lava comes out of the ground and separates out. layers of lava can build up to form the lava plateau
Eg. The Giants Causeway

Question 15

Lava

Answer 15

Molten rock that erupts from a volcano

Question 16

Lahar

Answer 16

Type of mud flow triggered by a volcanic eruption. Composed of ash, rocky debris and water. Flows down volcano typically along a river valley

Question 17

Laccolith

Answer 17

Layer of magma that has been injected between 2 layers of sedimentary rock. pressure of magma is so high overlying strata forces up giving laccolith dome like form with a generally flat base
Eg. North Dakota

Question 18

Fissure

Answer 18

Long deep crack in earths surface from which lava can escape

Question 19

Extrusive

Answer 19

Igneous rock and volcanic cones that form on the surface when lava erupts and cools quickly

Question 20

Extinct Volcano

Answer 20

Volcano that hasn’t erupted in last 10,000 years and not expected to erupt again
Eg. Slemish, Antrim

Question 21

Dykes

Answer 21

Wall of basalt cutting across sedimentary rock layers. Form when sheets of lava pass through cracks in rock and solidify

Question 22

Dormant volcano

Answer 22

Volcano that is expected to erupt again
Eg Mount Fuji, Japan

Question 23

Crater

Answer 23

Hollow at the top of a volcanic cone

Question 24

Caldera

Answer 24

Large volcanic depression. Type of volcanic crater formed by collapse of an empties magma chamber. Formed by big explosive eruptions
Eg. Crater Lake, Oregon

Question 25

Batholith

Answer 25

Large boy of igneous rock injected into crust that cools and solidifies deep underground
Eg. Leinster Batholith

Question 26

Basic lava

Answer 26

Lava with low silica content of 55% or less. Runny and flows for many kilometers

Question 27

Active volcano

Answer 27

A volcano that is currently erupting or has had at least 1 eruption in the last 10,000 years
Eg. Mt. Stramboli

Question 28

Acidic lava

Answer 28

Lava with high silica content of 70% or more. Very sticky and doesn’t flow very far, forms steep sided domes
Eg. Mount St Helens