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ESCI 111 > Igneous Rocks > Flashcards

Igneous Rocks Flashcards

1
Q

What are igneous rocks?

A

Igneous rocks are rocks that were once molten or liquid MAGMA. They can either be intrusive or extrusive.

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2
Q

What are intrusive igneous rocks?

A

They have been cooled UNDERGROUND SLOWLY and usually has large crystals as a result (e.g granite).

Are called plutonic.

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3
Q

What are extrusive igneous rocks?

A

They have erupted at the SURFACE and usually FINER grained than intrusive rocks (e.g basalt). This is due to being cooled quickly, not allowing crystallisation.

Are called volcanic.

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4
Q

What are the two types of compositions igneous rocks can have?

A

Mafic and felsic.

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5
Q

What are felsic igneous rocks?

A

Felsic igneous rocks are rich in FELDSPAR and SILICA with a low melting point.

They are LIGHT coloured and lightweight. (e.g granite (intrusive) and rhyolite (extrusive)).

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6
Q

What are mafic igneous rocks?

A

Are rich in Mg and Fe (ferric) and LOW in silica with a high melting point (e.g basalt (extrusive - dense) and gabbro (intrusive)).

They are DARK coloured and heavyweight.

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7
Q

What are the four textures igneous rocks can have?

A
  1. Crystalline Granular
  2. Porphyritic
  3. Glassy
  4. Vesicular
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8
Q

What do crystalline granular igneous rocks mean?

A

INDIVIDUAL crystals are visible to the naked eye, are more or less the same size and form a mosaic of interlocking crystals.

PLUTONIC igneous rock.

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9
Q

What are porphyritic igneous rocks?

A

Have LARGE crystals (called phenocrysts in volcanic rocks) are embedded in a FINER grained or glassy groundmass (or matrix).

VOLCANIC igneous rock.

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10
Q

What are glassy igneous rocks?

A

Refers to igneous rocks that are NON-crystalline, like glass (e.g obsidian).

Can’t see any grains. Doesn’t have time to form (cooled quickly).

VOLCANIC igneous rock.

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11
Q

What are vascular igneous rocks?

A

Refers to igneous rocks with holes (called vesicles), which are evidence of volatiles (gas) being present in the magma (e.g pumice).

VOLCANIC igneous rock.

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12
Q

What type of igneous rock is Gabbro?

A

Gabbro is mafic (low in silica and dark coloured), plutonic (rocks are formed by magma that does not reach the Earth’s surface), and crystalline granular (large individual/interlocking crystals.

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13
Q

What type of igneous rock is Basalt?

A

Basalt is mafic (low in silica and dark coloured), volcanic, extrusive, (erupted from Earth’s surface, and porphyritic (large crystals embedded in finer-grained or glassy groundmass.

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14
Q

What type of igneous rock is Granite?

A

Granite is felsic (high in silica and light coloured), crystalline glandular (large individual/inlocking crystals), intrusive, and plutonic.

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15
Q

What type of igneous rock is rhyolite?

A

Rhyolite is felsic (high in silica and light coloured), volcanic, extrusive, and porphyritic (large crystals embedded in finer-grained or glassy groundmass).

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16
Q

What type of igneous rock is pumice?

A

Pumice is vascular (has holes from gas in the molten or liquid magma), extrusive and felsic (high in silica and light coloured).

17
Q

What type of igneous rock is obsidian?

A

Obsidian is non-vascular (no holes), felsic (high in silica and light coloured).

18
Q

What type of igneous rock is scoria?

A

Scoria is vascular (has holes from the gas present in molten or liquid magma), and mafic (low in silica and dark coloured).

19
Q

What type of igneous rock is basalt glass?

A

Basalt glass is mafic (low in silica and dark coloured), and non-vascular (no holes).

20
Q

What type of igneous rock is dacite?

A

Dacite is felsic (high in silica and light coloured), volcanic, intrusive and porphyritic (large crystals embedded in fine-grained or glassy groundmass).

21
Q

What type of igneous rock is grandolite?

A

Grandolite is felsic (high in silica and light coloured), plutonic, intrusive, and crystalline granular (has large individual/interlocking crystals).

22
Q

What does plutonic mean?

A

Plutonic (intrusive) rocks are formed from magma that does NOT reach the Earth’s surface but is INTRUDED into the Earth’s crust and CRYSTALLISES within the crust.

23
Q

What does volcanic mean?

A

Volcanic (extrusive) rocks are formed when magma has been ERUPTED (extruded) from volcanoes on Earth’s surface.

24
Q

What is the dominant compound present in igneous rocks?

A

Silica (SiO2).

The more silica present in a rock = The lighter its colour.

25
Q

What is an intermediate igneous rock?

A

An intermediate igneous rock is neither felsic nor mafic. (has an equal amount of silica and is not particularly light or dark coloured.

26
Q

What type of igneous rock is andesite?

A

Andesite is an intermediate volcanic, porphyritic igneous rock.

27
Q

What type of igneous rock is Diorite?

A

Diorite is an intermediate plutonic, crystalline granular igneous rock.

ESCI 111 (18 decks)

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