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GLG216 > Midterm & Glaciers > Flashcards

Midterm & Glaciers Flashcards

1
Q

Relative Time

A

Determines the sequence of events

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2
Q

Absolute Time

A

Determines the date/age of events

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3
Q

Geologic Principles

A
  1. Original Horizontality
  2. Superposition
  3. Inclusions
  4. Cross-cutting relations
  5. Contact margins
  6. Faunal succession
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4
Q

Original Horizontality

A

Rock is initially laid down horizontally; any change in angle has been cause afterwards

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5
Q

Superposition

A

Rocks that are closer to the surface are younger

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6
Q

Inclusions

A

Young rock can contain pieces of older rock

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7
Q

Cross-cutting relations

A

Young rock or features can cut across older rock or features

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8
Q

Contact Margins

A

A young rock/feature can cause changes along the contact line with an older rock/feature

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9
Q

Faunal succession

A

Fossil assemblages can be correlated to specific deposits/time periods

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10
Q

Unconformities

A

Periods of time that are missing from the geologic record

Still help us determine what happened during that time; we know that there was uplift, erosion, etc.

Three types:

  • Angular unconformity
  • Nonconformity
  • Disconformity
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11
Q

Angular unconformity

A

rock is uplifted, eroded, then new sediment is laid horizontally on top

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12
Q

Nonconformity

A

Sedimentary rocks overlie intrusive igneous rocks and/or metamorphic rocks

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13
Q

Disconformity

A

Contact between two beds represents a period during which no deposition occurred - i.e. there is a large gap in the age of the two sediments

So basically they’re like that 51-year-old and 16-year-old getting together

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14
Q

Radiometric dating

A

Radioactive isotopes decay randomly but at a set rat, meaning we can predict how long it takes for them to decay to a certain ratio of daughter and parent isotopes

Assumes that there has been no loss or gain of parent or daughter isotopes, and the rock is below closure temperature (and has been since it was formed)

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15
Q

Body fossils

A

The actual physical remains of an organism (i.e. skeleton) has been left behind and mineralized

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16
Q

Trace fossils

A

Evidence of an organism’s existence in an area has been preserved in the rock (i.e. footprints, coprolite)

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17
Q

Concordia Curve

A

Plotting two things against each other (ex. two half-lifes) to form a curve, then plotting experimental data along the same plot to see if they come up with a similar answer

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18
Q

Fission tracks

A

Disintegration of the nucleus of 238U create sausage-shaped tracks within a mineral

You can determine age by counting tracks

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19
Q

Rhythmic processes

A

Can be used as absolute dating methods, e.g:

  • Varves (yearly patterns in lake sediment deposition)
  • Corals (daily growth marks)
  • Magnetostratigraphy (reversals of earth’s magnetic field)
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20
Q

Geologic Timescale

A

Division of earth’s history into eons, eras, periods, and epochs

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21
Q

Eons

A

Largest division of time on the geologic timescale:

  • Hadean
  • Archean
  • Proterozoic
  • Phanerozoic
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22
Q

Eras

A
  • Palaeozoic
  • Mesozoic
  • Cenozoic
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23
Q

Oldest Rock

A

Acasta gneiss from the Northwest Territories

4,025 +/- 15 Ma

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24
Q

Age of the Earth

A

4.567 Ga

Determined from the age of meteorites believed to be from the same time the solar system was formed

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25
Q

Oldest mineral

A

Zircon in Australian rock

4.3 Ga

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26
Q

Uniformitarianism

A

The present is the key to the past

The processes that worked in the past are the same as the ones that are observable today, so we can infer what happened in the past from our knowledge of the present

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27
Q

Igneous Rocks

Geologic History

A

Signs of intrusions and eruptions of magma

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28
Q

Sedimentary Rocks

Geologic History

A

Record environmental changes
- Mode of transport and environment of deposition

i.e. Climate, life, sea level

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29
Q

Metamorphic Rocks

A

Record collisions of plates, uplift and erosion of mountains

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30
Q

Cenozoic

A

Age of mammals and flowering plants

65 Ma - present

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31
Q

Mesozoic

A 
Age of dinosaurs
- Development of bipedal movement
First birds
First mammals
First angiosperms

251 - 65 Ma

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32
Q

Palaeozoic

A

Cambrian explosion - beginning of the fossil record
Life conquers land: plants, lungs, reptilian eggs
- All animals are reptilian or amphibious

542 - 251 Ma

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33
Q

Phanerozoic

A

Encompasses the time of Earth’s history with a lot of diversification of life: “visible life”

542 Ma - Present
Palaeozoic, Mesozoic, Cenozoic

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34
Q

Proterozoic

A

Photosynthesis puts oxygen into the air
First eukaryotic cells

2,500 Ma - 542 Ma

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35
Q

Archean

A

Earth first becomes habitable
First continental crust
First life

3,800 Ma - 2,500 Ma

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36
Q

Hadean

A

Earth’s early life
Inhabitable

4,567 Ma - 3,800 Ma

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37
Q

Sedimentary rock coverage

A

Sedimentary rock makes up a very small portion of the rock on the earth’s surface, but it is still very important because it holds important clues about earth’s history

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38
Q

Weathering

A

Two types: physical and chemical

They work in conjunction with one another

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39
Q

Physical weathering

A

Weathering of a rock that results in smaller pieces of the rock

  • Jointing
  • Thermal expansion
  • Wedging by frost, roots, salt
  • Burrowing
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40
Q

Chemical weathering

A

Weathering of rock that results in ions that can be moved away

  • Dissolution (ex. salt, limestone)
  • Hydrolysis (ex. feldspar –> clay)
  • Oxidation (ex. biotite/pyrite –> hematite)
  • Hydration (ex. clays)
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41
Q

Sediment sizing

A 
Boulder: > 256mm
Cobble: > 64mm
Pebbles: > 2 mm
Sand: > 1/16 mm
Silt: > 1/256 mm
Mud
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42
Q

Soil

A

A mixture of mineral fragments, water, air, and organic matter

Bedrock breaks down into regolith, which then mixes with organic matter to create humus

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43
Q

Regolith

A

Small rock particles that have the potential to become, but are not yet, soil

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44
Q

Humus

A

Soil that is able to support life

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45
Q

Soil horizons

A 
Zone of leaching - 
- Topsoil (O & A1)
- Transition (A2)
Zone of accumulation
- Subsoil (B)
Bedrock (C)
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46
Q

Desert soil

A

Thin

Occasionally has hard salt/calcite crust

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47
Q

Tropical soil

A

Thick laterite soil, but very nutrient deprived

- No B horizon, but Al-rich A2

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48
Q

Clastic sedimentary rocks

A

The products of physical weathering
Described based on size, composition, roundness, sorting of clasts, and cement type (quartz or calcite)

E.g.

  • Conglomerate/breccia
  • Sandstone/arkose
  • Siltstone
  • Mudstone/shale
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49
Q

Sediment maturity

A

As sediment moves farther from the source, it gets more “mature” - more spherical, better sorted, higher proportion of resilient minerals

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50
Q

Chemical sedimentary rocks

A

Rocks that are formed from chemical precipitation

E.g.

  • Evaporites (rock salt/gypsum, saltwater evaporation)
  • Tavertine (chemical limestone)
  • Banded iron formation: very old
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51
Q

Biochemical sedimentary rocks

A

Rock formed from the remains of prehistoric organisms

  • Limestone (calcite shells)
  • Chert (shells of plankton like radiolaria, diatoms)
  • Coal (plant debris)
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52
Q

Bed

A

Has a recognizable bottom and top

Generally relate to one depositional event

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53
Q

Contact

A

Surface that separates two beds

Can be gradational or abrupt

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54
Q

Lateral contacts

A

Contacts between beds that are beside one another

Can be:

  • Pinched out
  • Interfingering
  • Gradational
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55
Q

Strata

A

A series of beds

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56
Q

Formation

A

A distinctive (and mappable) series of strata

Often named based on the place it was discovered and the rock type (e.g. Toronto Limestone)

57
Q

Conformable strata

A

Laid down with no interruption

58
Q

Hiatus

A

A break in the geologic record

59
Q

Bioturbation

A

Disturbance of rock caused by burrowing animals (ex. worms, clams)

60
Q

Ripples and dunes

A

Deposition within a current of water or wind

Results in cross-bedding

61
Q

Graded bedding

A

Beds within which the coarsest sediment was deposited first and the finest sediment last

Happens in turbid water

62
Q

Load casts

A

Impressions made on the base of a bed where a dense sediment (sand/pebbles/boulders) overlaid a much softer sediment (mud/silt)

63
Q

Flute marks

A

Scours dug into the top part of a bed get filled in by later strata, taking a cast of the scour marks

64
Q

Sedimentary environments

A

Terrestrial:

  • Rivers
  • Lakes
  • Glacial
  • Sedimentary basins

Marine

  • Deltas
  • Beaches
  • Shallow water
  • Carbonate reef
  • Deep ocean
65
Q

Facies Concept

A

Distinct sedimentary characteristics reflect distinct processes

Our knowledge of present-day sedimentary environments can allow us to reconstruct palaeoenvironments from sedimentary rocks

66
Q

Hydrological cycle

A

The cycle of where water is stored and where/how it moves

67
Q

Earth’s water

A

Freshwater accounts for only 3.5% of earth’s water
Of this freshwater, only 0.3% is surface water - the majority is ice cap/glacier and groundwater
Of surface water, most is contained in lakes

68
Q

Human use of freshwater

A
  1. Irrigation (39.6%)
  2. Thermoelectric Power (39.3%)
  3. Public and Domestic Use (13.5%)
  4. Industrial Use (5.3%)
  5. Aquaculture (1.1%)
  6. Mining (0.6%)
  7. Livestock (0.5%)
69
Q

Drainage Basin

A

A drainage network that collects water from a broad region

AKA watershed

70
Q

Drainage divide

A

The highland or ridge that separates one watershed from another

71
Q

Drainage patterns

A

The patterns that water tends to follow when draining from a source into the basin

  • Dentritic
  • Radial
  • Structurally controlled
72
Q

Dentritic drainage

A

Resemble the branches on a tree

Form on a land with uniform substrate

73
Q

Radial drainage

A

Water drains radially from a centre point

Generally happens when the source is the high point of a conical mountain

74
Q

Structurally controlled drainage

A

Water follows the path of the well-defined topography underneath

I.e. through joints, along valleys

75
Q

Equilibrium Profile

A

Measures the elevation, sediment load, water load, or water velocity of a river against the distance from its source

76
Q

River erosion

A

Occurs through scouring, breaking, lifting, abrasion, and dissolution

Depends on discharge and sediment content

77
Q

Braided River

A

Looks like the intertwining hairs in a braid

  • Large volume of bedload
  • Banks erode very easily
  • Shifting bars
78
Q

Meandering River

A

Looks like a snake winding across the landscape

  • Mostly suspended load
  • Cohesive banks
  • Cutbanks, point bars, oxbow lakes
  • Erosion takes place on the outer edges of meanders
79
Q

Point bar

A

The area of sediment deposition on the inside of the meanders of a river

80
Q

Oxbow lake

A

Lakes that have been formed when a meander of a river cuts in so close that it cuts itself off

81
Q

Suspended load

A

Sediment carried within the body of a river; smaller particles that the water is able to float along with it

82
Q

Bedload

A

Sediment that is dragged, bounced, or rolled along the bed of a stream; larger particles that can only be moved by a large amount of force

83
Q

Dissolved load

A

Ions that are dissolved in the stream and carried along with it

84
Q

Mountain streams

A

Typically form steep V-shaped valleys

85
Q

Terrace

A

River downcuts into the ground, leaving a “terrace” of raised ground surrounding its floodplain

86
Q

Rapids

A

Particularly turbulent water with a rough surface; forms when:

  • Water flows over steps or large clasts in the channel floor
  • Channel abruptly narrows
  • Gradient abruptly changes
87
Q

Waterfall

A

Forms where the gradient of a stream becomes so steep the water free-falls down the stream bed

88
Q

Alluvial fan

A

Gently sloping apron of sediment

Forms when a fast-moving stream abruptly emerges from a confined space and spreads out, slowing down and quickly dropping its sediment load

89
Q

Levee

A

Accumulation of sediment in a pair of low ridges on either side of a stream

90
Q

Flood

A

When the volume of water flowing exceeds the capacity of the stream channel and flows over into the floodplain areas on either side of the stream

91
Q

Shallow-marine sediments

A

Gradient deposition, with larger clasts deposited closer to shore and finer clasts further out; clasts are well-sorted and rounded

Contain marine fossils and tend to become siltstone/mudstone

92
Q

Tropical marine sediments

A

Shallow marine environments that contain a large amount of carbonate shell debris

Indicate the presence of a reef

93
Q

River sediments

A

Fine sediments are deposited along the shores

Sediment ripples due to being deposited within a current - cross bedding

Sandstone, siltstone, shale

94
Q

Delta sediments

A

Present as thick sequences where deeper-water sediments slowly grade into river sediments

95
Q

Saturated zone

A

Area of groundwater where all pores are filled with water - no air

96
Q

Water table

A

Line that separates the saturated zone of groundwater from the unsaturated zone

97
Q

Vadose zone

A

Area above the water table where water partially fills the pores in the ground but not fully

98
Q

Porosity

A

Actual amount of space there is in between particles that can be filled by water

99
Q

Permeability

A

Connectivity between pores - allows water to flow within a substance

100
Q

Groundwater flow

A

Will always flow from high to low hydraulic head

101
Q

Hydraulic head

A

Potential energy available to drive the flow of a given volume of groundwater at a location

102
Q

Aquifer

A

Sediment rocks that transmit water easily

Provides water to wells

103
Q

Aquitard

A

Sediment/rock that does not transmit water easily and therefore slows it down

104
Q

Cone of depression

A

When water is pumped out a well too quickly and the water table sinks down around the well, forming a pointed-down cone shape

105
Q

Karst

A

A network of underground caves that have been carved out of limestone by water

Collapse of these caves causes a landscape of sinkholes or limestone spires

106
Q

Sinkhole

A

Circular depression in the ground that happens when an underground cave collapses

107
Q

Speleothems

A

Formations that grow in caves from the accumulation of dripstone

Stalactite: hangs from the ceiling
Stalagmite: emerges from the ground
Limestone column: happens when a stalactite and stalagmite merge

108
Q

Disappearing Stream

A

Where a surface stream enters into a crack or hole and travels for some time in underground caves

109
Q

Spreading of contaminants (groundwater)

A

Contaminants can enter the groundwater and then travel within the water, potentially ending up in well water

110
Q

Map scales

A

Expressed as a ratio (e.g. 1:500,000)

Means that one unit measured on the map is equal to 500,000 units on the ground
- 1 cm = 500,000cms or 5km in reality

111
Q

Topographic contour lines

A

Connect all points of equal height above a certain datum (usually sea level)

112
Q

Contour interval

A

Height difference between two subsequent contour lines

113
Q

Cross-section

A

Represents the topography and geological structures on a specific line across the earth

114
Q

UTM

A

Universe Transverse Mercator

Uses Northing and Easting instead of Latitude and Longitude

115
Q

Northing

A

Distance to the equator (km)

116
Q

Easting

A

Measured to a central meridian (degrees)

117
Q

Azimuth

A

Position on a sphere measured in degrees

For true-north, north is 0%, south is 180%

118
Q

Zone of Accumulation

A

Area of glacier where ice accumulates and begins to flow downhill

119
Q

Zone of Wastage

A

Area of glacier where ice melts and begins to recede

AKA zone of ablation

120
Q

Glacier advance/retreat

A

Advances if accumulation > wastage

Retreats if accumulation < wastage

121
Q

Valley glacier

A

Basically a river of ice flows down a mountain side into a valley

122
Q

Moraines

A

Pile of debris deposited by a glacier

Lateral moraines: Formed along the edges
Medial moraines: Formed where two glaciers meet, run in the middle of the composite
Terminal moraines: Formed at the toe of the glacier

123
Q

Glacial valleys

A

U-shaped

Formed because the glacial abrasion/plucking both lower the floor of the valley and bevel its sides

124
Q

Arretes

A

Residual edge of a rock that resembles the edge of a knife

Pointy edge of the mountainous region surrounding the valley

125
Q

Roche moutonee

A

Glacially eroded hill, elongate in direction of flow

  • Upstream part = gentle slope (rasping)
  • Downstream edge = steep slope (plucking)
126
Q

Esker

A

Snake-like ridges of sand and gravel that form when sediment fills meltwater tunnels at the base of a glacier

127
Q

Drumlin

A

Streamlined, elongate hills that have been molded by the flow of a glacier

128
Q

Glacial Striations

A

Long gouges, grooves, or scratches within the bedrock over which a glacier passes
- Caused by rasping of large clasts that are being carried along with the glacier

129
Q

Erratic

A

A boulder or cobble that was picked up by a glacier and deposited hundred of kilometres away from the outcrop from which it detached

130
Q

Till

A

A mixture of unsorted sediment deposited by glaciers

131
Q

Greenhouse effect

A

Trapping of solar heat inside the Earth’s atmosphere by carbon dioxide and other greenhouse gasses that absorb infrared radiation

Changes the average temperature on earth from -19 to +15 degrees Celsius

132
Q

Climate Forcing

A

Caused by:

  • Greenhouse effect
  • Variation in earth’s orbit/tilt/precession
  • Thermohaline circulation
  • Albedo
133
Q

Eccentricity

A

Over the coure of 100,000 years, earth’s orbit will change from more eccentric (more oval) to less eccentric (more circular)

Changes the length of seasons and variability in temperature

134
Q

Tilt

A

Over a period of 41,000 years, the tilt of earth’s rotational axis changes from 22.1° and 24.5° and back again

Changes the variability in temperature across the planet - more variability with more tilt

135
Q

Precession

A

Over 23,000 years, the north pole changes from pointing to the North Star to Vega

136
Q

Thermohaline circulation

A

The rising and sinking of water within the oceans, driven by differences in water density
- Change in density due to differences in temperature and salinity (colder/more saline = denser)

Circulation involves both surface and deep-water ocean currents
- Water in polar areas sinks and flows along the bottom of the ocean toward the equator

Prevention of thermohaline circulation shuts down the Gulf Stream

137
Q

Albedo

A

The reflectivity of a surface
- Ice is highly reflective, so lots of ice = less heat absorbed

Increasing albedo causes cooling, decreasing albedo causes warming

138
Q

Climate Change in Earth’s History

A

Today, temperature is fairly cold in comparison to how it has been in the past
- There have been multiple ice ages in the past

We can also record past CO2 levels from ice cores taken from the Antarctic

GLG216 (2 decks)

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