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Geology 110 > GEOL120 > Flashcards

GEOL120 Flashcards

1
Q

What are some types of Volcanic Rock?

A

Gabbro, Diorite, and Granite are all plutonic Volcanic rock.

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2
Q

What are some other types of Volcanic Rock?

A

Trachyte

Dacite

Komatiite

Tuff

Ignimbrite

Kimberlite

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3
Q

Explain the volcanic rock Trachyte?

A

Trachyte is a volcanic product of parent magma differentiation

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4
Q

Explain Dacite?

A

It’s the volcanic equivalent to Granodiorite, and formed by subduction of early oceanic crust, under thick felsic continental plate.

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5
Q

Explain Komatiite

A

It’s the volcanic equivalent to Peridotite

Oldest ultramafic magmatic rocks (~3.4 GA)

Spinifex bladed Acicular olivine and pyroxene in fine matrix

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6
Q

Explain what a Tuff and Ignimbrite is?

A
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7
Q

Explain Kimberlite

A

Ultramafic mantle-derived material brought to the surface by kimerblite pipes, Dykes, Sills.

Brecciated (rubble/broken fragments)

Brings up diamonds from depths via several emplacement models.

Economically viable Kimberlites tend to occur on Precambrian and Archaean Cratons.

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8
Q

What does a Ancient Kimberlite Volcano look like?

A
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9
Q

What is a Hypabyssal Rock?

A

Rocks that have intruded at shallow depths and characteristics between plutonic and igneous rocks. It’s grain size is typically 1 mm.

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10
Q

What’s the difference between Hypabyssal and Subvolcanic?

A

They’re the same.

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11
Q

What are some Hypabyssal rocks?

A
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12
Q

Regarding Volacanism and Plate tectonics, what are three main ways to produce a magma?

A

Decompression melting

Flux Melting

Increasing temperature

(All methods are controlled by the tectonic environment)

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13
Q

A map of Volcanism and plate tectonics

A
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14
Q

Explain Basaltic Volcanism?

A

It’s the most common form of volcanism on earth,

Occurs in a wide range of tectonic environments such as:

  • MOR’s
  • Island/volcanic Arcs
  • Intraplate Volcanoe’s
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15
Q

What are Submarine eruptions? And what percentage of the earth do they cover?

A

They are a product of Ridge Volcanism in the Mid Ocean ridge, and they cover for 70% of earth’s surface.

They develop along fissures, parallel to the ridge.

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16
Q

What happens in a Submarine eruption?

A

Hot Mantle rock rises to shallow depths and undergoes decompression melting-

Basaltic lava cools quickly underwater and forms pillows-

Circulation of seawater in the crust creates hydrothermal vents, convection - circulating “black smokers” and temperature, where unique organisms and sea life live in abundence.

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17
Q

What is does this picture represent?

A

An outcrop or formation of pillowing from a submarine eruption,

Due to their pillowing and sausage shapes this tells us they were formed underwater.

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18
Q

Desribe the shield volcano of the “Hawaiin” volcanism

A

The large broad shield volcanoes are due to their thin low viscosity basaltic lava flow.

Emitt very little pyroclastic material during eruptions.

They have a steady production of lava fountaining and are considered the safest of volcanoes.

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19
Q

What does this picture represent?

A

The different types of volcanoes, and the diagrams that represent their structure or size relative to one another.

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20
Q

What is a hot spot and how does it form?

A

There are two types of hot spots:

  1. Oceanic hot spots:
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21
Q

Large Igneous provinces are?

A

Enormous sheets of low viscosity basaltic magma continue to be erupted over long timescales producing a basltic plateau.

Developed by a mantle plume beneath an are that is undergoing rifitng.

They are usually basaltic but compose a diverse range of composition.

Frequently assosciated with extinction periods eg Siberian Traps - Permian ex

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22
Q

What are Columnar Basalt’s?

A

It’s a basalt that commonly breaks into regular columns because of contraction when cooling.

This indiccates subaerial cooling.

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23
Q

Exactly, what types of formation is this?

A

Culumnar Basalt.

24
Q

What can you share about Andesitic and Rhyolitic volcanism?

A
  • It’s more viscous than basalt lava and do not folw as easily.
  • Andesitic volcanism commonly associated with subduction but not all.
25
Q

What is the Andesite line?

A

It’s a line around the Pacific Ocean that seperates basaltic oceanic crust from more felsic andesitic crust around continental margins.

26
Q

Describe the silica content in Andesitic and rhylitic volcanism?

A

Andesitic and Rhyolitic has high viscosity due to high silica content, they are explosive (rather then effusive)

27
Q

How does Rhyolitic volacanism present in eruption?

A

More often erupted as a pyroclastic material (rock ash) then a flow.

28
Q

If Volcanic magma is more felsic, what does that indicate about the eruption?

A

The more Felsic composition the more explosive

29
Q

Why is Felsic eruptions more explosive?

A

Felsic magmas have more silica = polymerisation of the silica tetrahedra making the magma more viscous therefor more explosive.

30
Q

Why else are eruptions explosive?

A

Sudden degassing of the magma and releasing of pressure, and increase of volume to the magma shatters into violent fragments.

31
Q

Classifying and plotting rock types?

A
32
Q

Andesitc and Rhyolitic volcanoes can be produced by:

A
33
Q

Are pyroclastic flows the most hazardous of Volcanic processes?

A

Yes.

34
Q

What are the sources of energy in the flows and surges in pyroclastic eruptions?

A
  1. Gravity
  2. Fluidisation
35
Q

What is Cratonisation?

A

The folding of Mobile Belts over geological time, of igneous emplacement, crustal thickening into zones of continental crust, resulting into Cratons.

36
Q

How would you describe the stage of Cratonisation?

A

Almost all mobile belts pass through an orogenic stage of intense folding and metamorphism, then, transitional stage of block-fault mountain building. Followed by late orogenic magmatism, involving extrusion of Felsic volcanoes and developing tectonic stability.

37
Q

Define Epicratonic Basins

A

They are sedimentry basins which form on the craton after it has stabilised.

38
Q

What was geologically happening in Australia 2500 million years ago?

A

Formation of the oldest Australian Cratons - Archaean Pilbara and Yilgram blocks, possibly even before 3000 million years ago in the case of the Pilbara block.

39
Q

Significant Glaciation events in Australia occured in what period?

A

The Creteceous

40
Q

Is Granite a Hypabyssal rock?

A

No

41
Q

The New England Oregon developed on the eastern-most edge of Australia by?

A

Accretion of Oceanic crust along subduction zones in the devonian.

42
Q

A Tuff can be classified as?

A

Both Volcanic and Sedimentry deposit.

43
Q

The Tasman Line seperates?

A

Precambrian Australia and Phanerozoic Australia

44
Q

Basaltic pillow lavas form in what conditions?

A

Eruptions on the seafloor.

45
Q

Melting that is caused by thinning of the crust and uplift of mantle material is called?

A

Decompression melting.

46
Q

Obidian and Pumice are same chemical composition:

True or False

A

True.

47
Q

Match the style of volcanism to the tectonic environment:

  1. Hot Spot volcanism
  2. Mid ocean ridge volcanism
  3. Continental rift
  4. Continental arc
  5. Island arc
A
  1. Hot spot - Intraplate; (continental or oceanic)
  2. Mid ocean ridge - Extension
  3. Continental rift - Extension
  4. Continental arc - Oceanic to continent collision (subduction)
  5. Island arc - Oceanic to Oceanic collision (subduction)
48
Q

Diamon rich kimberlites tend to occur in younger cratons:

True or False?

A

False.

49
Q

The Australian continentant was formally part of which supercontinents?

A
  1. Pangea
  2. Gondwana
50
Q

Felsic lavas are runnier and therefor have more of a gentle safe eruption style:

True or False?

A

False.

51
Q

What is a Terrane?

A

A region with essentially similar geology and geological history.

52
Q

The oldest mineral grains on earth are located in?

A

Western Australia.

53
Q

The following Orogens that make up the Tasman Orogens are?

A
  1. New England Orogen
  2. Lachlan Orogen
54
Q

The Largest volcano in the solarl system is on which planet or moon?

A

Mars, Olympus Mons.

55
Q

Hot spot volcanoes in Eastern Australia are associated with?

A

The Northward migration of Australia towards Papua New Guinea and Indonesia.

56
Q

The Yilgarn Craton in Western Australia is associated with this type of major mineralisation:

A

Gold.

57
Q
A

Geology 110 (2 decks)

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