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Flashcards in Igneous Rocks Deck (35)
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1

What is the difference between magma and lava?

Both are hot liquid rock with crystals, fragments of rock, and gas, but lava exists at the surface of the earth, while magma resides below.

2

Three ways to melt a rock

Raise Temp, lower pressure, move the phase boundary

3

What three main locations generate magma and igneous rocks?

hotspots, spreading ridges, and subduction zones

4

How do spreading ridges melt rock?

They increase temperature and significantly decrease the pressure. (decompression melting)

5

How do subduction zones melt rock?

The presence of water shifts the melting point of rock down, and partial melting can occur at lower temperatures (flux melting)

6

lava that crystallizes form what kind of rocks?

extrusive rocks (volcanic)

7

Magma that crystallizes before reaching the surface forms what kind of rocks?

intrusive (plutonic)

8

How are igneous rocks classified?

texture (grain size) and chemical composition

9

What is the texture of volcanic rocks?

Fine grained to glassy

10

What is the texture of plutonic rocks

coarse grained (slow cooling)

11

Give an example of ultramaific material

mantle (low in silica)

12

Give an example of mafic material

basalt, oceanic crust

13

Give an example of felsic material?

granite, high in silica

14

What is Bowens Reaction Series?

Minerals crystalize and settle out of magma in a definite sequence, starting with olivine and certain feldspars, and ends with quartz. RULE: mafic materials crystalize first, felsic materials crystalize last.

15

Define viscosity

resistance to flow

16

What has higher viscosity, felsic or maific magma?

felsic (more silicates)

17

What defines mafic lava flow? (3)

1. large, lower viscoisty flows. 2. less explosive eruptions. 3. low ratio of pyroclastic sediment to lava

18

What defines felsic lava flow? (3)

1. smaller, higher viscosity lava flows. 2. explosive eruptions. (since lava is thick and can build a lot of pressure before finally erupting) 3. High ratio of pyroclastic sediment to lava

19

Define pyroclastic sediment

 broken up particles of rocks and minerals deposited during volanic eruption

20

What makes shield volcanoes

The low viscosity of mafic magma

21

What makes stratovolcano

felsic, high viscosity of lava

22

what kind of magma does a mid-oceanic ridge produce>?

maific magma, since there is little fractionation

23

What is fractionation?

time spent in magma chamber, so the longer you are there, the more minerals that can crystalize out

24

What kind of magma is made by island arc volcanoes?

mafic to intermediate magma produced

25

what kind of lava is produced in continental margin volcanoes?

maific to felsic magma

26

what kind of magma is produced by hotspots?

mafic (oceanic ones) to mafic and felsic magma (continental hotspots)

27

Many igneous rocks crystallize at great depth in the Earth’s crust.
How is it possible that these rocks are exposed at the Earth’s surface
today?

Tectonic uplift and erosion

28

. Lava generates
a) igneous rock with small crystals.
b) stratovolcanoes, not shield volcanoes.
c) most granite in the crust.
d) None of the above.

a

29

Flux melting generates magma at
a) subduction zones
b) spreading ridges
c) hotspots
d) All of the above

a

30

Decompression melting generates magma at
a) subduction zones
b) spreading ridges
c) hotspots
d) All of the above.

b