Ch 5. Volcanism and Earthquakes

Question 1

What is Volcanism ?

Answer 1

When magma is ousted onto the earth’s surface while still liquid, it is called Volcanism

Question 2

Define Lava and Magma (in short)

Answer 2

Magma is the term utilized to denote the molten rocks and related materials seen inside the earth. Lava is the magma on the surface of the earth

Question 3

What is a Pyroclast ?

Answer 3

A dense collection of fragments and gases from a volcanic eruption that flows down the slope of a volcano

Question 4

Acidic lava is also called as ____ ?

Answer 4

Andesitic / Composite / Stratovolcanic lava

Question 5

Major composition of acidic lava is ?

Answer 5

Silica

Question 6

Major components of basic lava are ?

Answer 6

Iron and Magnesium

Question 7

What are Active volcanoes ? Mention few examples

Answer 7

Volcanoes that frequently erupt or have erupted in the recent times. Ex: Mt Etna and Stromboli (Italy)

Question 8

What are Dormant volcanoes ? Give few examples

Answer 8

Those in which eruption has not occurred for a long time but can occur any time in the future. Ex: Barren island, Vesuvius (Italy)

Question 9

What are Extinct volcanoes ? Give few examples

Answer 9

Those in which no eruption has occurred in historic times and possibility of future eruption is also remote. Ex: Mt Popa, Mt Fuji

Question 10

Which volcanoes are thought to be extinct but erupted violently ?

Answer 10

Mt. Vesuvius (Bay of Naples, near Italy) and Mt. Krakatau (Sunda straits b/w Java and Sumatra)

Question 11

What are Batholiths ?

Answer 11

The intrusive igneous rock masses formed due to the cooling and condensation of magma inside the earth’s surface. These form the core of the large mountains

Question 12

What are Laccoliths ?

Answer 12

These are the large dome shaped (igneous mound) intrusive igneous rocks that are connected by a pipe like conduit with magma

Question 13

What is a Lopolith ?

Answer 13

It is developed when the magma moves upwards, fruther, a portion of this magma moves in a horizontal direction where it gets a weak plane. When it forms into saucer shape, it is known as Lopolith

Question 14

What is a Phacolith ?

Answer 14

If a wavy mass of intrusive igneous rocks are developed at the base of synclines or on the top of anticlines having a definite opening with the magma chambers below, they are termed as Phacoliths

Question 15

What is a Sill in Igneous intrusions ?

Answer 15

Sill, also called sheet, flat intrusion of igneous rock that forms between preexisting layers of rock

Question 16

What are Dykes in Igneous intrusions ?

Answer 16

When magma moves upside through the cracks and fissures and condenses perpendicularly to the earth’s surface, they are called as Dykes