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geology > Igneous rocks- magma > Flashcards

Igneous rocks- magma Flashcards

1
Q

what is lava?

A

molten rock that has reached the earth’s surface

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2
Q

What is magma?

A

molten rock that is stored in the earths crust

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3
Q

when does the mantle melt?

A

Decompression melting
addition of Volatiles
rising magma comes in contact with other rocks and melts them

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4
Q

what is decompression melting?

A

the pressure on rock is reduced

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5
Q

what are volatiles?

A

substances that evaporate quickly and exist as gas at the surface of the earth (h2O, Co2, N2, H2, SO4) that weaken bonds lowering melting temperature

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6
Q

what is assimilation?

A

block of rock falls into magma and melts

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7
Q

what is contamination?

A

partial melting of rock mixes with magma from below

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8
Q

where does magma come from?

A

convergent boundaries
divergent boundaries
hot spots

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9
Q

how does magma come from convergent boundaries?

A

sea water stored in crust is released
water released from hydrous heats up
melting from overlying mantle due to addition of volatiles

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10
Q

how does magma come from convergent boundaries?

A

hot rocks rise
pressure drops
decompression melting

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11
Q

how does magma come from hot spots?

A

hot rock rises
pressure drops
decompression melting

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12
Q

what types of magma exists?

A

felsic
intermediate
mafic
ultramafic

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13
Q

what factors affect magma composition?

A

composition of the source rock
partial melting
crystal settling

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14
Q

what is a source rock?

A

the rock that melted

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15
Q

what is partial melting?

A

only 2-30% of a rock melts before magma migrates away

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16
Q

characteristics of partial melting?

A

minerals with higher silica content have lower melting temperatures
higher silica content is extracted first
residual rock is more mafic that the source rock

17
Q

what is crystal settling?

A

mafic minerals form first and settle out of the melt forming a cumulate
residual melt is more felsic
mafic crystals are denser and fall to bottom

18
Q

what is magma mixing?

A

magmas mixing with different compositions
causes chemical composition to change

19
Q

what affects the rate of cooling?

A

depth of the magma
size and shape of the magma body
the presence of ground water

20
Q

depth of magma in cooling?

A

the closer the magma is to the surface the faster it cools

21
Q

size and shape of magma body in cooling?

A

the more surface area the body has the faster it looses heat
the surface area to volume ratio increases as size decreases

22
Q

the presence of ground water in cooling?

A

water passing through magma absorbs heat and carries away heat, cooling off the magma faster

geology (15 decks)

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