Chapter-4 Igneous Rocks

Question 1

are rocks derived from molten magma/lava that flows from the interior of the earth.

Answer 1

Igneous rocks

Note:Igneous rocks are the mother of all other rocks and soils.

Question 2

comes from the greek word “magma” meaning “a mixture” or “massein”, meaning “to knead”
Molten rock that is still underground

Answer 2

Magma

Question 3

comes from the Latin “labes” meaning “to fall” or “to slide”

Molten rock after it has eruption

Answer 3

Lava

Question 4

are collection of volcanic materials regardless of composition, fragment size or mechanism of ejection.

Answer 4

Tephra

Question 5

are airborne fragments

Answer 5

Pyroclasts

Question 6

Rocks form when magma is extruded onto the earth’s surface to create a volcano

Answer 6

Extrusive Igneous Rocks

Question 7

Rocks are formed when magma solidifies below the surface of the earth

Answer 7

Intrusive Igneous Rocks

Question 8

also known as volcanic rocks, cooling is quick, so crystals formed are small

Answer 8

Extrusive

Question 9

also known as plutonic rocks, cooling is slow

Answer 9

Intrusive

Question 10

basaltic lava flow characterized by a rough or rubbly surface composed of broken lava blocks

Answer 10

Aa (or a’a)

Question 11

basaltic lava that has a smooth, billowy, undulating surface. Formed due to a very fluid lava.

Answer 11

Pahoehoe

Question 12

similar to aa, but they are more viscous, forming smooth-sided angular blocks of solidified lava

Answer 12

Block Lava

Question 13

are formed by viscous magma being erupted effusively onto the surface and then piling up around the vent.

Answer 13

Lava Dome

Question 14

formed when lava emerges from an underwater volcanic vent or sub-glacial volcanoes, immediate contact with water oozes additional blobs or pillows

Answer 14

Pillow Lava

Question 15

Froms of Lava/Extrusive Flow:

Answer 15

Aa (or a'a)
Pahoehoe
Block lava
Lava Dome
Pillow Lava

Question 16

dome-shaped mass of magma intruded between strata

Answer 16

Laccoliths

Question 17

huge mass of intrusive rocks which are exposed by erosion at the surface

Answer 17

Batholiths

Question 18

smaller sheet intrusions formed where magma has flowed into a fissure

Answer 18

Dike/Dykes

Question 19

smaller sheet intrusions formed where magma has flowed into a fissure

Answer 19

Sills

Question 20

forms when magma hardens within a vent of an active volcano

Answer 20

Volcanic Neck

Question 21

– special type of simple volcanoes which have a bowl-shaped crater at the summit

Answer 21

Cinder Cone

Question 22

Forms of Intrusive Rocks:

Answer 22

Laccoliths
Bathotliths
Dikes/Dykes
Sills
Volcanic Neck
Cinder Cone