Igneous Rocks

Front 1

Porphyritic

Back 1

Large phenocrysts in a fine ground mass.

Front 2

Flow Banding

Back 2

Light and dark bands contorted by plastic flow. Typical of viscous lavas, usually find grained

Front 3

Vesicular

Back 3

Gas bubbles developed under low pressure.

Front 4

Amygdaloidal

Back 4

Vesicles which have become I filled by minerals at a later date. Usually distinguished from phenocrysts by rounded and irregular outlines.

Front 5

What crystal size does slow cooling result in?

Back 5

Big crystals as they have plenty of time to grow. Grow further away from their origin.

Front 6

Crystal size that occurs from fast cooling?

Back 6

Small crystals, little time to grow and form close to origin.

Front 7

Leucocratic (silcic)

Back 7

Acidic igneous rocks are light coloured.

Front 8

Mesocratic

Back 8

Medium coloured intermediate rocks.

Front 9

Diorite

Back 9

1 stage of slow cooling in a pluton. Intermediate colour, feldspars, horneblende, mica and some quartz.

Front 10

Obsidian

Back 10

Very fast cooling, no crystals, glassy texture, formed on the surface in lava flow.

Front 11

Vesicular Basalt

Back 11

Fast cooling, on surface in lava flow, mica, Augite, Olivine. Mafic, fine, vesicular.

Front 12

Equicrystalline Basalt

Back 12

Fast cooling, on surface in lava flow, mafic and fine. Augite, Olivine, minor flecksdol of P. feld and mica.

Front 13

Dolerite

Back 13

Medium cooling, 1 stage underground in a sill or dyke. Mafic, equicrystalline. P felds, Augite, Olivine.

Front 14

Basalt (Amygdaloidal)

Back 14

Fast cooling, on surface underwater. Feldspar, Augite, Olivine, infilled with calcite.

Front 15

Pumice

Back 15

Very fast cooling under pressure on land. Vesicular, silicic/intermediate.

Front 16

Andesite

Back 16

Slow cooling- 2 stages on surface in lava flow. Hornblende and P feldspar. Fine grain mass.

Front 17

Mid Ocean Hotspots e.g Hawaii and Constructive plate margins

Back 17

Basalt (Gabbro) magma produced by partial melting of mantle peridotite.

Front 18

Destructive plate margin (subduction zones)

Back 18

Andesite (Diorite) magma produced by partial melting of subducted ocean crust.

Front 19

Destructive plate margin (continental collision zone)

Back 19

Granite magma is produced from partial melting of dry granite continental crust.

Front 20

Which magma is explosive?

Back 20

Andesitic- magma is full of steam due to subduction zone and basaltic wet ocean plate.

Front 21

Ultra basic (peridotite)

Back 21

Green due to olivine.

Front 22

Euhedral

Back 22

Well formed crystals.

Front 23

Subhedral

Back 23

Poorly developed with few crystal faces.

Front 24

Anhedral

Back 24

Irregular outlines.

Front 25

How many stages of cooling for grain sizes to be roughly the same size?

Back 25

One.

Front 26

How many stages of cooling for the grain sizes to be differing?

Back 26

Two.

Front 27

Granite

Back 27

Slow: Two stages of cooling, formed in a pluton. Contains quartz, mica, feldspar. Porphyritic.

Front 28

Gabbro

Back 28

Slow- one stage of cooling. Formed deep underground in a pluton. Feldspars, mica, augite, olivine. Usually equicrystalline and Melanocratic (mafic)

Front 29

Mesocratic

Back 29

Medium coloured intermediate rocks.

Front 30

Melanocratic (mafic)

Back 30

Basic rocks are dark coloured.

Front 31

Obsidian

Back 31

Very fast cooling, no crystals, glassy texture, formed on the surface in lava flow.

Front 32

Vesicular Basalt

Back 32

Fast cooling, on surface in lava flow, mica, Augite, Olivine. Mafic, fine, vesicular.

Front 33

Equicrystalline Basalt

Back 33

Fast cooling, on surface in lava flow, mafic and fine. Augite, Olivine, minor flecksdol of P. feld and mica.

Front 34

Dolerite

Back 34

Medium cooling, 1 stage underground in a sill or dyke. Mafic, equicrystalline. P felds, Augite, Olivine.

Front 35

Andesite

Back 35

Slow cooling- 2 stages on surface in lava flow. Hornblende and P feldspar. Fine grain mass.

Front 36

Mid Ocean Hotspots e.g Hawaii and Constructive plate margins

Back 36

Basalt (Gabbro) magma produced by partial melting of mantle peridotite.

Front 37

Destructive plate margin (subduction zones)

Back 37

Andesite (Diorite) magma produced by partial melting of subducted ocean crust.

Front 38

Eu

Back 38

Basic rocks are dark coloured.

Front 39

Destructive plate margin (continental collision zone)

Back 39

Granite magma is produced from partial melting of dry granite continental crust.

Front 40

Which magma is explosive?

Back 40

Andesitic- magma is full of steam due to subduction zone and basaltic wet ocean plate.

Front 41

Which magma is less dangerous?

Back 41

Basaltic- uplift of the ocean ridge causes lowering pressure.

Front 42

Pillow Lava

Back 42

Under glaciers, in oceans..

The rind ruptures, the skin stretches and the next pillow forms.

Shattered glassy breccia.

Front 43

Pumice.

Back 43

Very fast cooling under pressure on land. Vesicular, silicic/intermediate.

Front 44

Baked and Cooled Margins.

Back 44

Baked margins- at rim of heat altered rock. Contact metamorphism. Included fragments of mudstone and sandstone.

Chilled margins- Magma at contact that cooled rapidly. Grain size always increases in the centre.

Front 45

Lava flows in stratified rocks

Back 45

Eroded fragments of lava in new rock. Reddened erosional surface. Might get vesicles from gas in lava flow.

Front 46

Phenocrysts within a pluton

Back 46

Stage 1: Phenocrysts form. Slow cooling pluton deep underground.

Stage 2: Bouyant pluton rises.

Front 47

Dykes

Back 47

Discordant- cuts through country rock.

Thin dykes: fine grained basalt

Thick dykes: medium grained dolerite.

Front 48

Sills

Back 48

Concordant- follows boundaries of country rock. Generally thicker than dykes as they cool slower.

Front 49

Ultra basic (peridotite)

Back 49

Green due to olivine.

Front 50

Volcanic

Back 50

Hhh

Front 51

Euhedral

Back 51

Well formed crystals.

Front 52

Subhedral

Back 52

Poorly developed with few crystal faces.

Front 53

Anhedral

Back 53

Irregular outlines.

Front 54

Gran

Back 54

One.

Front 55

Gabbr

Back 55

Two.

Front 56

Granite

Back 56

Slow: Two stages of cooling, formed in a pluton. Contains quartz, mica, feldspar. Porphyritic.

Front 57

Andesitic volcanoes

Back 57

-high viscosity (thick and sticky)

-pressure builds- slow lava

-big eruptions (explosive)- higher gas content makes it more bouyant.

Front 58

Shield volcano

Back 58

Lower viscosity (free flowing) decrease in gas content, higher temperature.

Front 59

Basaltic magmas (e.g Hawaiian Islands)

Back 59

- partial melting of mantle peridotite

-low viscosity magma(free flowing)

-low gas content (non explosive)

-less likely to block the vent leading to pressure build up

-easier to predict and more regular.

-most scary due to free flowing magma.

Front 60

Andesitic magmas e.g Mt Etna

Back 60

- harder to predict

-high gas content

-higher viscosity than basalt

-violent explosions and steep sided volcanoes

-pyroclastic flows, lahars and explosions limited to steep sides of volcano

Front 61

Granitic magma e.g Yellowstone

Back 61

-high gas content

-high viscosity

-may explode violently

-formed by partial melting of continental crust in mountain roots

-not scary

Front 62

Monitoring technique: Seismometers

Back 62

Magma moves and causes seismic disturbances. Rising magma fractures the surrounding cold, brittle rock and forces its way upward causing pressure build up and release, generating small earthquakes. More seismic data=volcano eruption imminent.

Front 63

Ground Deformation

Back 63

As magma rises, the volcano inflates. Tiltmeters are used to measure changes in the angle of slope which increases as the rising magma causes uplift. Allows us to see how close it is to surface as greater tilt=more pressure.

Front 64

Managing the risks: concrete spillways in Japan

Back 64

Used to channel lahars and steer them from vulnerable areas. Concrete and steel pillars in the channels filter out the large debris, reducing potentials of mudflows. Cameras and electronic sensors give early warning of movement in the channels.

Front 65

Hazard Mapping

Back 65

Studying lavas and pyroclastic deposits of historical eruptions to predict the future activity of a volcano to identify areas most at risk of lava flows, pyroclastic flows and lahars.

Front 66

Done

Back 66

Yay