Igneous Rocks

Question 1

What are the 3 main classes of minerals?

Answer 1

1. Igneous
2. Sedimentary
3. Metamorphic

Question 2

What is the Rock Cycle

Answer 2

a concept in geology of dynamic changes that take place on Earth to transform members of one rock class to another

Question 3

Name the 2 characteristics of rocks

Answer 3

1. Composition
2. Texture
3. Sometimes additional geological structures within the rock

Question 4

How do igneous rocks form?

Answer 4

Magma cools and crystallizes

Question 5

How are extrusive rocks formed?

Answer 5

when magma rise and extrude at earth’s surface via volcanoes
quick cooling = extrusive (volcanic) igneous rocks

Question 6

How are intrusive rocks formed?

Answer 6

Magma trapped below Earth’s surface
cool slowly = intrusive (plutonic) igneous rocks

Question 7

Describe the texture of igneous rocks.

Answer 7

Slow cooling below earth’s surface = large crystals
Rapid cooling at/above earth’s surface = tiny or no crystals

Question 8

Describe mineral composition

Answer 8

Magma formed + cooled at high temp
- enriched in ferromagnesian silicate minerals
- DARK ROCKS

Magma formed + cooled at low temp
- smaller amt of ferromagnesian silicate minerals
- LIGHT COLOURED ROCKS

Question 9

What is Phaneritic Texture?

Answer 9

Minerals are easily seen to unaided eye
- cooling is slow + at great depth
- allows crystals to grow

Question 10

What is aphanitic texture?

Answer 10

minerals are too small to be seen with unaided eye (need microscope)
- cooling is fast at or near surface
- little time for crystals to grow

Question 11

What is glassy texture?

Answer 11

mineral crystals are absent
- lava quenched (immediately cooled at surface)
- no time for crystals to grow
ex. obsidian

Question 12

What are ferromagnesian silicates

Answer 12

silica w/ iron +/or magnesium
dark-coloured

Question 13

What are non-ferromagnesian silicates

Answer 13

no iron/magnesium
light-coloured

Question 14

Name the igneous compositions

Answer 14

felsic: light coloured
intermediate: equal light + dark minerals
mafic: dark coloured

Question 15

Temperature + pressure ____ w/ depth

Answer 15

increase

Question 16

What is the concept of moving plates

Answer 16

Plate tectonics

Question 17

What is decompression melting

Answer 17

Upward movement of Earth’s solid mantle
- occurs at divergent plate boundaries(move apart)
- hot material moves to area of lower pressure

Question 18

What is hydration melting

Answer 18

occurs where 2 plates move towards each other (one sliding underneath)
Magma tends to be formed at lower temps than those produced where plates are moving apart
Stream of water released from descending plate, lower melting point of mantle rock