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Earth and Environmental Science Yr 11 > Types Of Rocks > Flashcards

Types Of Rocks Flashcards

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1
Q

What do we use sedimentary rocks for?

A

Studies in Earth’s geological history.
Use of flint and chert as tools in the Neolithic Age.
Building materials – cathedrals and public buildings.
Fuel from oil, coal and natural gas in sedimentary strata.
Sand gravel and limestone in cement production.
Important store of groundwater.
Deposits of metallic (Copper, Uranium, Lead, Zinc, Gold) minerals and diamonds.

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2
Q

What are sedimentary rocks composed of?

A

Fragments of other rocks.
Chemical precipitates such as salt and gypsum.
Organic materials such as vegetation, coral and shells.

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3
Q

Define the terms strata, bedding planes and formations. As a part of your definition, link these terms together.

A

Strata (single layer) defines each layer of a sedimentary rock. These are separated by bedding planes indicating when deposition ceased temporarily. A formation is a combination of strata and covers a large area.

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4
Q

What is a fossil?

A

Evidence of former life (plant and animal).

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5
Q

Why are fossils more common in sedimentary rocks and not in the other two rock types?

A

Usually deposited by water as layers near the surface.
Less stress which might destroy the fossil.
Heat and pressure of igneous and metamorphic rocks might destroy the fossil and these usually occur at depth

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6
Q

Briefly describe the world distribution of sedimentary rocks.

A

Sedimentary rocks cover 75% of the continents and 100% of the ocean floor.

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7
Q

What are the two types of sedimentary rocks?

A

Clastic

Biochemical

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8
Q

Describe clastic sedimentary rocks.

A

Made from gravel, sand silt or clay.
Particles were carried to a site and deposited.
They are classified by grain size.

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9
Q

Describe biochemical sedimentary rocks.

A

Chemical processes move ions dissolved in water to make solid particles.

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10
Q

What are some different types of clastic sedimentary rocks?

A

Conglomerate
Sandstone
Mudrocks

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11
Q

Describe conglomerate.

A

Smooth and round.
Particle size >2mm.
Cemented by sand and mud.

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12
Q

Describe sandstone.

A

Sand grains of 0.6-2mm.
Mostly quartz grains.
Particles cemented by calcite, quartz and iron oxide.

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13
Q

Describe mudrocks.

A

Particle size

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14
Q

What are some different types of biochemical sedimentary rocks?

A

Limestones
Dolostones
Chert
Evaporites

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15
Q

Describe limestones.

A

CaCO3
Great variety of textures including skeletal.
Build up as a deposit when calcite precipitates through the grains, eg: chalk, oolitic and microcrystalline.
Inorganic limestones precipitated by springs, eg: travertine.

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16
Q

Describe dolostones.

A

Carbonate rock formed of dolomite.

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17
Q

Describe chert.

A

Composed of microcrystalline quartz occurring as irregular nodules in
limestone or as thin layers in marine sedimentary rocks.

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18
Q

Describe evaporites.

A

Formed when basins are subject to prolonged evaporation, e.g., halite and gypsum.

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19
Q

Explain the origin of sedimentary strata.

A

Sedimentary strata are deposited in layers or beds by water, wind or ice. Layers form in response to changes in deposition (changes in weather, seasons of climate).

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20
Q

Define and identify the causes of cross-bedding.

A

Cross-bedding occur when layers are angled to the upper and lower surfaces of the bed.
They are typically asymmetrical.
Dunes, deposited by wind, are the usual reason for cross-bedding.

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21
Q

Describe sediments which are graded.

A

Beds which are graded start as large particles and particle size decreases upwards through the bed.

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22
Q

What is turbidity and how does it affect sediments?

A

Turbidity is produced by the variation in density between a current and the surrounding water.
The faster flowing turbid current loses velocity and grades its deposition from coarse to fine particles.

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23
Q

Distinguish between fossils and trace fossils.

A

A fossil is the biological remains of a pre-historic creature or plant.
Trace fossils are is a preserved remnant of a track, burrow or cocoon made by an extinct animal.

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24
Q

List the variety of sedimentary systems.

A 
point bar deposits
stream channel deposits
alluvial fan deposits
dunal deposits
glacial deposits
deltaic deposits
beach or shoreline deposits
lagoonal deposits
tidal flat deposits
reefs
marine deposits
25
Q

Explain how running water (rivers) affect sediments.

A

Running water is an effective form of sediment transport. Rivers carry large amounts of sediment to the sea. The change in the energy of a river will grade the deposits.

26
Q

What information can we derive from a facies?

A

A facie is a small depositional area within the system.
Each facie has its own distinct characteristics.
They indicate how the deposit was formed within a large area.
e.g. in a delta facies will indicate channel, between channels and channel mouth deposits.

27
Q

Define compaction and cementation.

A

Compaction occurs when the weight of overlying material compresses the sediments into a tight coherent mass driving out the water. Cementation occurs when water precipitates dissolved ions as its seeps through the pores in the sediments.

28
Q

Describe the changes to sediments when sea level transgresses or regresses on a coastline.

A

Transgression and regression of sea level alters the type and depositional form of sediments.
In transgression, shoreline deposits cover stream deposits.
In retreat, limestone is covered by mud, then sand.

29
Q

Why do geologists study sedimentary sequences and not just the individual layers?

A

To detect worldwide changes in sea level.

30
Q

What is an unconformity?

A

An erosion surface on which sediments are deposited.

31
Q

Distinguish between intrusive and extrusive igneous rocks in terms of location of formation.

A

Extrusive igneous rocks are emplaced on or near the surface.

Intrusive igneous rocks are emplaced at depth.

32
Q

What is the structure of extrusive igneous rocks?

A

Fine crystalline structure.
Cooled rapidly.
Composed of small crystals or glass.

33
Q

What is the structure of intrusive igneous rocks?

A

Coarse crystalline structure.
Cools slowly.
Allows time for the growth and interlocking of large crystal.

34
Q

Examples of extrusive igneous rocks.

A

Lavas such as basalt
Pyroclastic rocks such as pumice
Obsidian

35
Q

What are felsic igneous rocks poor in?

A

Iron, Magnesium

36
Q

What are mafic igneous rocks poor in?

A

Plagioclase

No quartz

37
Q

What are felsic igneous rocks rich in?

A

Silica

38
Q

What are mafic igneous rocks rich in?

A

Pyroxenes, Magnesium, Iron

39
Q

Are intermediate rocks poor or rich in silica?

A

Neither. They have a balance of silica.

40
Q

What minerals are in felsic igneous rocks?

A

Quartz
Orthoclase
Plagioclase

41
Q

What minerals are in intermediate igneous rocks?

A

Plagioclase dominant,

Biotite

42
Q

What are rocks at the Earth’s surface constantly changed by?

A

Water, air, temperature, variations and other factors.

43
Q

Define weathering.

A

The group of destructive processes that change physical and chemical character of rocks at or near Earth’s surface.

44
Q

Define erosion.

A

Physical picking up of rock particles by water, ice or wind.

45
Q

Define transportation.

A

The movement of eroded particles by water, ice or wind.

46
Q

At present, what is nearly unique to our planet?

A

Earth-style weathering (water, ice, wind)

47
Q

Where do small a amounts of weathering still occur?

A

Mars

Water erosion appears to have been important there in the distant past.

48
Q

What is critical to chemical weathering?

A

Oxygen and Carbon Dioxide

49
Q

What is critical to chemical and mechanical weathering?

A

Water cycled through the atmosphere.

50
Q

What contributes to biological action that can produce chemical and mechanical weathering.

A

Air in soils

51
Q

What is necessary for chemical weathering.

A

Water

52
Q

What does Oxygen dissolved in water do?

A

Oxidises Iron in rocks (Oxidation)

53
Q

What does Carbon Dioxide dissolved in water do?

A

Creates Carbonic acid (carbonation)

54
Q

What does running water do?

A

Loosens and abrades particles.

55
Q

What does glacial ice do?

A

Removes and abrades particles.

56
Q

What does freeze/thaw cycling do?

A

Mechanically weathers.

57
Q

What are most sediments produced by?

A

Weathering in air (Oxidation)

58
Q

What is sand and dust transported by?

A

Wind

59
Q

What is water a primary agent in?

A

Sediment production, transportation, deposition, cement action and formation of sedimentary rocks.

Earth and Environmental Science Yr 11 (6 decks)

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