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CIVE40009 - Geotechnics > An introduction to the properties of rocks and their composition > Flashcards

An introduction to the properties of rocks and their composition Flashcards

1
Q

Where do rocks come from?

A
  • Formed from cooling magma
  • From igneous or sedimentary
  • Metamorphism
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2
Q

What is involved in the global tectonic?

A
  • Tectonic drift
  • Convection currents - plates slides on top and past each other
  • Elevated temps and higher pressures - metamorphism
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3
Q

What are the 3 types of rocks?

A
  • Sedimentary
  • Igneous
  • Metamorphic
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4
Q

What are minerals?

A

Naturally occurring inorganic substance which has a definite chemical composition and presents an ordered atomic arrangement.

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5
Q

What are rocks?

A

Any naturally occurring aggregate of one or more mineral or mineraloid matter.

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6
Q

How do igneous rocks form

A

Underground and crystallised from molten magma

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7
Q

What are features of igneous rocks?

A
  • Uniform high strength
  • Massive
  • Mosaic of interlocking crystals
    e.g., granite, basalt
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8
Q

How are sedimentary rocks formed?

A

Erosional debris on Earth’s surface and deposition basins; mainly in the sea

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9
Q

What are features of sedimentary rocks?

A
  • Granular and cemented
  • Layered, bedding planes
  • Low variability rock strength
    e.g., sandstone, clay
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10
Q

How are metamorphic rocks formed?

A
  • Altered by heat and/or pressure
  • Deep inside mountain chains
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11
Q

What are features of metamorphic rocks?

A
  • Mosaic of interlocking crystals
  • High variability in strength
    e.g., Gneiss, slate
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12
Q

What are some characteristics of minerals?

A
  1. Colour
  2. Lustre (appearance/ reflectance)
  3. Form (shape/ grouping/ clustering)
  4. Hardness (resistance to abrasion)
  5. Cleavage (preferential split)
  6. Fracture (nature of broken surfaces – lack of cleavage)
  7. Tenacity (response upon sudden impact i.e. malleable vs brittle)
  8. Specific gravity
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13
Q

What does cleavage mean?

A

The tendency of a mineral to break along flat planar surfaces as determined by the structure of its crystal lattice.

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14
Q

What are the two mineral classes?

A
  1. Silicate
  2. Non-silicate
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15
Q

What are the mineral groups and their colours?

A
  1. Olivine - pale green
  2. Pyroxene - dark colour (black)
  3. Amphibole - various dark colours
  4. Mica - vitreous
  5. Feldspar - pink, white, colourless
  6. Silica - colourless
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16
Q

What types of rock structures are there?

A
  • Crystalline
  • Polycrystalline
17
Q

What does polycrystalline mean?

A

Consisting of many crystalline parts that are randomly oriented with respect to each other.

18
Q

What does amorphous mean?

A

When you cool something down very quickly

19
Q

What type of mineral is mica?

A

Silicate

20
Q

What are two examples of minerals in the mica group?

A
  1. Muscovite
  2. Biotite
21
Q

What happens when mica is weathered?

A

Metal ions are removed from the mineral. Reaction results in soluble metal ions and clay minerals.

22
Q

What type of mineral is feldspar?

A

Silicate

23
Q

Where is feldspar’s found?

A

Earth’s continental crust

24
Q

What are two very common variations of feldspar?

A
  1. Alkali feldspar (Pink or white)
  2. Plagioclase feldspar (White, colourless or grey)
25
Q

What are the types of igneous rocks?

A
  • Extrusive
  • Intrusive
  • Felsic
  • Mafic
26
Q

What does extrusive mean?

A

Produced when magma exits and cools above (or very near) the Earth’s surface - cool quickly - small crystals

27
Q

What does intrusive mean?

A

Also called plutonic rock, formed from magma forced into older rocks at depths within the Earth’s crust, which then slowly solidifies below the Earth’s surface, though it may later be exposed by erosion - large crystals

28
Q

What are the two main type of eruptions which cause extrusive igneous rocks?

A
  1. Fissure eruptions - low viscosity - fine grained rock
  2. Central eruptions - ejection of lava and ash + broken rock
29
Q

What does euhedral mean?

A

Well defined shapes

30
Q

What does anhedral mean?

A

Imperfect shape

31
Q

What textures/ structures can you have?

A
  • Equigranular
  • Aphanitic = can’t see anything
  • Inequigranular
  • Porphyritic = large crystals surrounded by small crystals
  • Glassy
  • Vesicular - cavities
32
Q

What are the three types of magma?

A

Basaltic, andesitic, and rhyolitic

33
Q

What is Bowens reaction series?

A

Bowen’s Reaction Series describes the temperature at which minerals crystallize when cooled, or melt when heated

34
Q

What is Goldichs dissolution series?

A

This series summarises the relative resistance to weathering of the common rock-forming silicates

CIVE40009 - Geotechnics (13 decks)

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