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Geology AS > Module 5 - The Rock Cycle > Flashcards

Module 5 - The Rock Cycle Flashcards

1
Q

What is extrusion?

A

The emission of magma onto the Earths surface where it forms a lava flow

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2
Q

What is weathering?

A

The in situ breakdown of rocks

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3
Q

What is erosion?

A

The removal of weathered material, usually by the physical action of transported fragments

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4
Q

What is transport?

A

The means by which weathered material is moved from one place to another

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5
Q

What are the methods of transport?

A

Water, wind, ice or gravity

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6
Q

What is deposition?

A

The laying down of sediment that occurs when a transporting agent loses energy

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7
Q

What is Burial?

A

It occurs when sediment is covered by younger layers of sediment accumulating on top of it

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8
Q

What is Diagenesis?

A

It defines all the processes that take place in sediments at a low temperature and pressure at or near the Earths surface

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9
Q

What is Recrystalisation?

A

The solid state process the changes minerals into new crystalline metamorphic minerals

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10
Q

What is metamorphism?

A

The changing of rocks in the Earths crust by heat and or pressure and or volatile content. It is isochemical and occurs in the solid state

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11
Q

What is partial melting?

A

The incomplete melting of rock in the lower crust or upper Mantle

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12
Q

What is magma accumulation?

A

Magma collecting within a magma chamber

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13
Q

When does crystallisation occur?

A

During the cooling of magma or lava so that solid mineral crystals form

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14
Q

What is an intrusion?

A

An igneous rock formed below the earths surface. The magma can be forced into pre-existing rocks such as along bedding planes and joints or by cutting across the existing rock

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15
Q

What is uplift?

A

The return of buried rocks to the Earths surface by tectonic forces

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16
Q

How long has the rocks cycle been going for?

A

Rocks seem permanent and unchanging but the truth is that they have been changing slowly all the time. The earth was formed 4500 Ma and some rocks have been around the cycle multiple times

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17
Q

What are the two processes that occur at the Earths surface?

A

Igneous and sedimentary

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18
Q

What are the igneous processes?

A

Magma within the Earths crust and upper Mantle can be erupted onto the surface as lava flows. If the eruption is more explosive, solid fragments called pyroclasts are produced. This process forms extrusive igneous rocks. The lava and solid fragments begin to cool at the surface and the lava becomes rock when crystals form from the magma and it becomes solid (crystalisation)

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19
Q

What are sedimentary processes?

A

Weathering takes place when rock is exposed to the Earths atmosphere and water. Rain, temperature changes and plants start to break it down by mechanical, chemical and biological processes. The produced fragments from weathering are removed by erosion and reduced in size during transportation. Transporting agents lose energy sooner or later e.g. Wind loses speed or a fast moving river joins a sea or lake. When this happens deposition occurs

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20
Q

What are the processes that occur below the Earths surface?

A

Sedimentary processes, metamorphic processes and igneous processes

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21
Q

What are the sedimentary processes?

A

Deposition usually occurs in lakes oceans and seas. Burial occurs as sediments are covered by more and more layers of sediments.
•as the sediments are buried more deeply and become compacted the grains of sediment are moved closer in contact due to the pressure above them
•water that circulates between the grains of sediment deposits minerals in the spaces between the grains. These and other changes that occur in buried sediments are part of the processes of diagenesis
•the growth of minerals in pore spaces and the compaction of grains results in the formation of sedimentary rocks

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22
Q

How are rocks effected by tectonic processes?

A

They can be exposed at the surface due to uplifting. Earths movements push rocks up by folding or faulting, so that rocks formed deep below the surface are now at the surface. Erosion over millions of years will expose rocks

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23
Q

What are the metamorphic processes like?

A

Metamorphism is caused when rocks are changed by heat and or pressure. It’s an isochemical process meaning that the chemical elements in the metamorphic rock are the same as those in the parent sedimentary rock. It involves recrystallisation - no melting takes place

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24
Q

What are the igneous processes like?

A

Melting is caused at depths where the temperatures are high enough, but different minerals have different melting points so that part of rock will melt whilst the rest remains solid (partial melting). Because it is hot and expanded, magma has a lower density than the rocks surrounding it and this caused it to rise and join with other rising magma. This magma accumulation creates underground magma chambers. The magma cools when it rises and forces its way onto joints or bedding planes etc. crystallisation may take place below the Earths surface surface. The rock cycle is completed when lava and pyroclasts are extruded at the Earths surface to form extrusive igneous rocks

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25
Q

What are all rocks composed of?

A

Minerals

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26
Q

What are minerals?

A

A naturally occurring chemical compound that has a definite composition and crystalline structure. Most rock forming minerals are silicates, the main exception being calcite, which forms the sedimentary rock limestone and the metamorphic rock marble.

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27
Q

What does feldspar look like?

A

Usually white or pink and has a vitreous lustre

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28
Q

What’s are the 7 characteristics of rock forming minerals?

A
  • Habit
  • Colour
  • Hardness
  • Cleavage and fracture
  • Lustre
  • Specific gravity
  • Reaction with acid
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29
Q

What is a thin section of rock?

A

A thin (0.03mm) slice of rock that is translucent, mounted on a glass slide and viewed through a microscope

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30
Q

What is a rock?

A

An aggregate or mixture of one or more minerals

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31
Q

What are minerals?

A

Naturally occurring inorganic crystalline compounds with a definite chemical composition

32
Q

What is the habit of a rock?

A

The habit or shape of some mineral crystals can be very distinctive. Cubic crystals such as halite and fluorite are easy to recognise. Garner is a dodecahedron shape. Quartz is a hexagonal shape. Feldspars show twinning due to the fact they grow in pairs

33
Q

What can the colour characteristic of rock show?

A

Can be used to identify minerals. Not very useful as they can occur in several different colours. Can be used to distinguish biotite and muscovite mica. B is black

34
Q

What does Moh’s hardness scale measure?

A

The hardness of minerals. It measures the resistance to scratching.

35
Q

Which minerals can be scratched by fingernail?

A

Talc and gypsum

36
Q

Which can be scratched by a 2p coin?

A

Calcite

37
Q

Which minerals can be scratched by steel nail?

A

Fluorite and apatite

38
Q

Which mineral can just be scratched by steel nails?

A

Feldspar

39
Q

Which minerals can be scratched by glass?

A

Quartz, Topaz, corundum and Diamond (the hardest)

40
Q

What are the subcategories for cleavage?

A

Cleavage can be perfect, good or poor depending on how easily it splits along a cleavage plane

41
Q

What is the cleavage like in muscovite?

A

Cleavage is perfect in One Direction so that the mineral splits into thin sheets

42
Q

What is a conchoidal fracture?

A

When there are a series of Concentric curved cracks

43
Q

What does lustre depend on?

A

It’s ability to reflect light. Minerals that are shiny like metal have metallic luster. Minerals that are full are described as a earthy

44
Q

What is specific gravity?

A

The ratio of the mass of a mineral compared with the mass of an equal volume of water

45
Q

What is a clast?

A

A fragment of broken rock

46
Q

What are sedimentary rocks?

A

They are composed of fragments that have been deposited compacted and cemented

47
Q

What are igneous rocks?

A

Rocks that have crystallised from magma

48
Q

What are silicates?

A

The most important and abundant group of rock forming minerals, with an atomic structure containing SiO4 arranged as tetrahedra

49
Q

How do sedimentary rocks form?

A

At a relatively low temperature and pressure at shallow depths below the Earths surface.

50
Q

How are rocks exposed at the surface broken down?

A

By weathering and erosion

51
Q

How is sandstone formed?

A

Over millions of years more and more fragments are deposited, buried and compacted into layers

52
Q

What are sedimentary rocks made from?

A

Made from clasts and held together by a cement, rather than interlocking crystals.

53
Q

What is the grain size f clasts like?

A

It greatly varies

54
Q

How are other sedimentary rocks formed?

A
  • biologically - remains of organisms

* chemically - precipitation of ions from sea water

55
Q

How are igneous rocks formed?

A

From magma within the earth. They form at high or low pressure depending on depth but all at high temperatures.

56
Q

What are the two main types of igneous rocks?

A

Intrusive and extrusive

57
Q

What are intrusive igneous rocks?

A
  • Hypabyssal or Plutonic
  • medium sized crystals if cooled fairly slowly at intermediate depth - DOLERITE
  • coarse crystal size if magma cooled slowly at greater depth - GRANITE
  • the minerals are hard silicates - QUARTZ or FELDSPAR
  • individual crystals can usually be seen
58
Q

What are extrusive igneous rocks?

A
  • volcanic
  • fine crystal size - magma reached the Earths surface
  • erupted as lava or ejected as fragments
  • cooled rapidly - BASALT or PUMICE
  • individual crystals can’t usually be seen
59
Q

What are metamorphic rocks?

A

They are formed by the recrystallisation of other rocks in the solid state due to pressure, temperature or both

60
Q

What is foliation?

A

A texture of metamorphic rocks formed by the preferred alignment of flat/tabular minerals

61
Q

How are metamorphic rocks formed?

A
  • Under heat and/or pressure.
  • causes mineral composition and texture to change
  • minerals in parent rock recrystallise in the solid state to form new minerals
  • composed of interlocking crystals - often show preference alignment if they have been affected by pressure
  • 3 main types - BURIAL, CONTACT and REGIONAL
62
Q

What type of metamorphism is it if they contain flat crystals?

A

Burial or regional - show foliation

Micas

63
Q

Igneous facts?

A
  • crystalline
  • minerals interlocked in mosaic
  • crystals have no preferred alignment
  • main minerals - Quartz, Plagioclase feldspar, Hornblende (amphibole), Augite (pyroxene), Olivine, Micas (muscovite and biotite)
  • crystallised from magma
  • features as igneous intrusions - dyke, sill, batholiths or lava flows, no beds
  • no fossils
  • hard to brake
64
Q

Sedimentary facts?

A
  • fragmental
  • made of grains/fragments or fossils cemented together
  • grains not usually lined up
  • main minerals - Quartz, Potash feldspar, Calcite, Mica (muscovite), Clay minerals, rock fragments
  • forms from deposition of rock and mineral particles
  • features - in beds
  • fossils may be present
  • can be soft and crumbly or hard to break if well cemented
65
Q

Metamorphic facts?

A
  • crystalline
  • minerals interlocked in mosaic
  • crystals aligned - show foliation if affected by pressure
  • main minerals - Quartz, Plagioclase and Potash feldspar, Micas (muscovite and biotite), Garnet, Calcite and Al2SiO5 polymorphs
  • recrystallisation of other rocks
  • cover large areas
  • usually no fossils - deformed if there are
  • hard but may split in layers
66
Q

What is the geological column?

A

A table that contains all the ears and systems in the correct tone sequence.

67
Q

What is an era?

A

A major unit of time that contains several systems

68
Q

What is a system?

A

It refers to rocks laid down in a named time period and is shorter than an era

69
Q

What is relative dating?

A

•uses comparisons rather than years

70
Q

What is the law of superposition?

A

It states that sedimentary layers are deposited one in top of the other, so that the higher layers are younger than the lower ones

71
Q

What is the law of horizontality?

A

It states that all sedimentary rocks were originally laid down in a nearly horizontal position

72
Q

What is the law of cross cutting relationships?

A

It states that faults or igneous intrusions must be younger that they rocks they cut through

73
Q

What is the principle of included fragments?

A

It states that any sedimentary rock that has fossils or fragments of another rock than it must be younger than the included rock fragments

74
Q

How can you date using fossils?

A

Fossils are very distinctive in particular periods. Ammonites occur only in the Jurassic period therefore you can use fossils to say that a rock belongs to a particular system.

75
Q

What is absolute dating?

A

Uses dates of rocks for all the geological systems using the process of radioactive decay. This is used to put actual dates on the geological column

Geology AS (8 decks)

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