Final Exam Flashcards
(374 cards)
1
Q
What is isostasy?
A
The reason that continents can rise above oceans. Buoyant continental lithosphere floats on dense asthenosphere; lithosphere can thicken, forming higher mountains and correspondingly deeper roots.
2
Q
Which is heavier, lithosphere or asthenosphere?
A
Asthenosphere, lithosphere floats on top of it and is buoyant
3
Q
What are mountain building processes collectively called?
A
Orogenesis
4
Q
What kind of belts do mountains form?
A
Orogenic belts
5
Q
What do orogenic belts parallel?
A
Continental margins
6
Q
How does an orogenic belt parallel a divergent margin?
A
At a divergent boundary, the mantle plume rises, uplifts, and splits continental lithosphere forming rift valleys with blocks dropped along normal faults, and volcanoes along valley sides
7
Q
How does an orogenic belt parallel a passive margin?
A
A rift widens, filling with seawater forming a new ocean basin - the sides of the ocean basin experience no seismic activity but gradually subside under the weight of the sediment load
8
Q
How does an orogenic belt parallel a convergent margin?
A
As mountains grow at converget boundaries, they undergo isostatic adjustments which balance their weight
9
Q
When do the highest mountains form?
A
At continental collisions
10
Q
What is an Andean type convergent boundary?
A
Denser oceanic lithosphere subducts beneath continental lithosphere, developing into an accretionary wedge, a continental volcanic arc, and plutons form in the middle of deformed mountains (andesitic and granitic)
11
Q
Which type of margin has no seismic activity?
A
A passive boundary
12
Q
Which type of margin forms a continental volcanic arc?
A
An andean-type, converging margin
13
Q
What is an accretionary wedge?
A
Plastered against the edge of the continental lithosphere, it undergoes metamorphosis
14
Q
What is an Alleution-type convergent boundary?
A
Occurs when oceanic lithosphere subducts under more oceanic lithosphere: forms an oceanic-oceanic volcanic island arc.
15
Q
Which type of margin forms a volcanic island arc?
A
A convergent Alleutian-type boundary
16
Q
What occurs in a convergent, continental collision?
A
An ocean basin closes, subduction stops, and the highest mountains can form. The “suture” is place where the two plates collide. There is no volcanic activity that occurs here.
17
Q
What is a convergent, accreted terrane?
A
Occurs when a foreign piece of crust forcefully attaches to a continental margin (ex. transportation of an island across an ocean). Transportation due to sea floor spreading.
18
Q
What is the Wilson Cycle?
A
When the ocean opens and then closes again. Mountains are builts, and then rebuilt repeatedly, rarely, pieces of the ocean floor are scraped up and elevated with the mountain belt in the form of obduction.
19
Q
What is obduction?
A
When pieces of the oceanic floor got “stuck” on top of continental margins in the Wilson cycle.
20
Q
What are broad, vertical movements in continents?
A
More than just isostatic adjustments alone
21
Q
What is uplift, as a vertical, continent movement?
A
Due to mantle upwelling that pushes up continental lithosphere in the interior of a continent
22
Q
What is subsidence, as a broad, vertical movement in a continent?
A
Subsidence is due to the weight of sediment deposited along passive continental margins as a mountain belt erodes, as well as downward mantle flow pulling on the lithosphere.
23
Q
Where is subsidence likely to occur?
A
At a passive continental margin where mountain belts are eroding to form sediments.
24
Q
How did continental crust originally form?
A
Originally, by the accretion of mantle material. Oceanic crust was subducted below continental crust. Magma differentiated to produce andesitic and granitic volcanic arcs that coalesced to form Earth’s earliest crude continents
25
What was the last supercontinent that was broken up?
Pangaea
26
Where are the earliest rocks found? What do they look like?
Found in shield areas of continental crust. They are highly deformed and metamorphosed, representing multiple cycles of orogenesis and the break-up of supercontinents.
27
28
What are the controls and triggers for mass wasting?
1. Gravity
2. Oversteepened slopes
3. Vegetation (or lack there of)
4. Earthquakes
29
How does gravity impact mass wasting?
Gravity is important, but gravity and **water is critical.** When water completely fills pores it reduces cohesion and allows grains to slide over each other, while adding weight to the soil
30
How does water impact mass wasting?
When water completely fills pores, it
a) Reduces cohesion between particles (reduces friction)
b) Adds weight to the soil
31
How does oversteepening of slopes cause mass wasting? How does it occur?
It causes loss of support for materials higher up the slope. It occurs by undercutting waves, undercutting streams, and human excavation.
32
How does vegetation impact mass wasting?
Vegetation is anchored into the soil by roots which keeps the soil and regolith in place. Removing plants makes the slope unstable and susceptible to failure.
33
How do earthquakes impact mass wasting?
Earthquakes can dislodge rock and unconsolidated material, resulting in landslides on slopes
34
How are different types of mass wasting classified?
1. The types of materials
2. How fast they move
3. The type of motion (free falling, flowing, sliding)
35
What is a slump?
Type of material: rock and unconsolidated material commonly lubricated by water
Movement: moves as blocks along curved surfaces in a rotational way way, away from a **scarp** with the block's surface tilting back
When it happens: when the slope is undercut by stream, waves, or human excavation
36
What is a rock slide?
Commonly occurs if a slope is cut by a stream, after heavy rain or snow melt, or after an earthquake, in **mountainous areas.** Occurs where strata or a joint **parallels** the slope, or where stronger rocks overlie weaker ones.
Some travel up to **200 km/h!**
37
This mass wasting process may result in rock travelling up to 200 km/h!
Rock slide
38
Debris flow
Mixture of water-saturated soil and regolith that moves **rapidly** down canyons and stream channels of **semi-arid** mountainous regions. Occurs following heavy rainflow.
Also, **volcanic lahars** of wet and muddy ash rushing dow valleys.
39
Where does debris flow usually occur?
Semi-arid mountainsides, canyons, and stream **channels** and near volcanoes after rainflow
40
What is earthflow?
Commonly begins as a **slump.** Very slow and ongoing movement (may occur for years) of mud down **hillsides** in **humid areas.**
Forms a tongue-shaped mass that may move for years.
41
Forms a tongue-shaped mass that may move for years
Earthflow
42
Mass wasting that commonly begins as slump.
Earthflow
43
What is creep?
The gradual, downslope movement of soil and regolith under gravity; caused by **repeated freezing and thawing** or wetting and drying.
Results in **tilted** trees, fences, utility poles, etc.
44
Causes the tilting of utility poles/trees.
Creep
45
What is the mass wasting process of solifluction?
Flow that occurs on saturated ground, overlaying **impermeable** rock such clay, or permafrost in polar areas. Water cannot percolate downwards on the surface, so material moves slowly downwards as **lobes.**
46
What is a submarine landslide?
Occurs as **slumps** under water, with debris flow and **turbidity currents.**
47
What percentage of the water on earth is stored in the ocean?
97%
48
What occurs during the hydrological cycle?
97% of water is stored in the ocean. It is **evaporated**, and then **precipitated** on the land. Some soaks in through **infiltration**, some flows as streams through **runoff**, and some evaporated back into the air is used by plants through **transpiration,** some is also stored in **glaciers.** Most, however, just returns to the ocean through a stream.
49
What is runoff?
A stream created by precipitation.
50
What is infiltration?
When precipitation is absorbed into soil
51
What increases as stream discharge increases?
Width, depth, and the velocity of the water in the stream
52
What two parameters are streamflow affected by?
Gradient and discharge
53
What is streamflow?
The fact that a stream erodes and transports based on its velocity (discharge) and channel shape (gradient)
54
What is a stream gradient?
If the channel slope is steep, the water will flow faster. The slope of the stream over its length.
Cross section is part of the gradient. Cross-sectional shape determines how much of the stream contacts the water. If more is contacting, there will be more friction, slowing it down.
55
Which type of stream will move more quickly; a wide and shallow stream, or a pipelike and semicircular stream?
The pipelike, semicircular one because there will be less friction due to the cross-section. Less water contacts the smoother sides.
56
What is the discharge from a stream? What formula is used to measure it, and what units is it measured in?
The discharge of the stream is the volume of water that flows through the stream cross-section each second.
As discharge increases, all other parameters increase as well.
**Discharge = velocity/second x width x depth**
**Units: m3/s**
57
What three things does a stream do, despite its cross-section and other parameters?
1. Erodes
2. Transports
3. Deposits
58
What occurs during erosion of stream channels?
Particles in transport cause **abrasion**, acting as cutting tools to scour channel walls
**Potholes** are also formed by circular currents of eddies.
59
How is a pothole formed in a stream (erosional process)
By the circular currents of an eddy.
60
What are the four transport processes that occur in streams?
1. Dissolved transport
2. Suspended transport
3. Saltation
4. Bed load
61
What is dissolved transport?
When ions in solution from chemical weathering and groundwater are transported through streams
62
What is suspended transport?
Occurs when sediment remains above the bed and is transported through the water of the stream
63
What is bed load transportation?
When particles are rolling and sliding on the channel floor
64
What is saltation transport?
When particles are jumping and skipping, and alternate between being on the channel floor and within the suspended load
65
What is deposition? What are the two types of channel deposition?
1. Channel deposit
2. Floodplain deposit
Deposition occurs when a stream can no longer carry its suspended load.
66
What occurs in a channel deposit?
Sand and gravel deposited in bars
67
What is a floodplain deposit?
Mud deposited beyond the channel
68
What does deposition often result in?
Graded bedding - larger particles are depositied before smaller particles
69
Does a stream cut vertically or horizontally?
Vertically, but its banks cave in by **mass wasting** to form **narrow**, v-shaped valleys, with waterfalls and rapids in rough channels.
70
Are waterfalls and rapids more common in narrow channels, or wide streams (like floodplains)?
Narrow channels
71
Which is more v-shaped, a narrow stream or a wide stream like a floodplain?
A narrow stream valley
72
What is a narrow stream valley?
V-shaped by downcutting on a steep gradient as the sides cave in
73
What is a wide stream valley?
Form on gentle gradients, cut mainly sideways forming **floodplains,** as the stream shifts back and forth across the valley leaving a thick fill of sediment.
74
What type of stream valley forms on a steep gradient? What about on a gentle one?
Steep: narrow v-shaped river valley
Gentle: wide floodplain
75
Stream channel: width \< depth
Narrow v-shaped valley
76
Stream valley: width \> depth
Floodplain
77
How does a wide stream valley form?
It evolves from a narrow stream valley
78
What are the three drainage patterns that occurs?
1. Dendritic
2. Radial
3. Rectangular
79
Where does dendritic drainage occur?
On uniform bedrock where channels follow local slopes
80
Where does radial drainage occur?
On mountains and volcanoes
81
Where does rectangular drainage occur?
When a stream drains over joints, or a fault system that forms right angles
82
What is an artificial levee?
A method of flood control.
It is **artificial.** Built along stream banks to **increase** the volume that a stream can hold.
83
What is a flood control dam?
Built to store water, and then let it out slowly. This results in reservoirs which can be used for irrigation, power generation and recreation.
84
What are the drawbacks of dams?
They don't typically last for more than 100 years. They flood river valleys, displace wildlife, drown forests, and fill with sediment which reduces their overall holding capacity
85
Where does a meander form?
On a floodplain
86
What is a cut bank?
Formed by a meander, where the stream erodes the outside of bends
87
What is a point bar?
Formed by a meander, deposits on the inside
88
What is an oxbow lake?
Stream cuts across narrow meander necks at **cutoffs.** The result of a meander trying to straighten itself out.
89
What is a delta?
Where a stream enters standing water at its mouth, splitting into distributaries
90
What does a delta split into?
Distributaries
91
What is the most effective way for water to infiltrate into the ground?
Steady (and not heavy) rainfall. Heavy rainfall results in a lot of runoff, the meeting of plant needs, and therefore **little infiltration.**
92
What is the zone of saturation?
The underwater location where pores between particles are completely filled with water
93
What is the zone of aeration?
The underwater location where pores are filled mainly with air.
94
What is the water table?
The water table is the surface separating the zone of saturation (bottom) and the zone of aeration (top). It mimics the ground in terms of elevation (ex. elevates with mountains, and is lowest with valleys).
95
How slowly does ground water move?
In cm/day - very slowly - depending on the nature of materials
96
What is porosity? How does it effect groundwater movement?
Porosity is the space between sediments/particles, including fractures and other openings.
Porosity is reduced by pores filling with cement and finer particles (lithification)
97
What must you have to have permeability?
Porosity
98
What is permeability?
The connection of pores, the ability to transmit water
99
What is permeable ground called?
An aquifer
100
What is impermeable ground called?
An aquitard
101
How does groundwater flow?
Under gravity, from high to low areas, along, curving paths towards a stream
102
What is a spring?
A spring is an area where the water table reaches the ground surface, a natural outpouring of water. May be due to a "perched" water table, perched on an aquitard.
103
What is a hot spring?
Occurs where groundwater is heated by either the **geothermal gradient** or by cooling **magma** and then rises to the surface
104
What is a geyser? Give an example of one; how frequently does it erupt?
A geyser occurs where water is pressurized, and boils, it then vaporizes and blasts water into the air. Usually above a cooling pluton. Water fills the pipe, and this cycle continues. Cyclic events.
Ex. Old Faithful - erupts approximately every hour
105
What is a well?
A well is a hole drilled into the zone of saturation, past the water table. It must be drilled deep enough to retrieve water during a dry season. A well creates a **cone of depression**, which occurs when the water table is drawn towards the well
106
What is a cone of depression?
Occurs where a well drills into the water table, causing the water table to be drawn downward towards the hole.
107
What is an artesian well?
A well drilled into an aquifer that is sandwiched between two aquitards. Therefore the water is pressurized and rises to the surface easily, with minimal pumping.
108
What are two environmental problems associated with wells?
1. Subsidence
2. Ground water contamination
109
How may a well cause subsidence?
If water is removed for irrigation quicker than it can be replenished, underlying sediment may compact, resulting in gradual sinking of the ground surface
110
How is contamination an issue with aquifers and the water table?
From septic tanks, fertilizers, toxic spills, and leaking sanitary tanks. Take many years to flush out of an aquifer. Therefore they should only be deposited in impermeable ground areas.
111
How can contamination of an aquifer be prevented?
By depositing contaminants into impermeable ground (i.e. aquitards)
112
Why does the leaning tower of Pisa lean?
Due to ground subsidence
113
How are caverns formed?
Formed below the water table where groundwater dissolves (dissolution) soluble rocks (ex. with carbonic acid). This occurs just below the water table.
114
What are stalactites and stalagmites?
Needle-like stalactites come down from the ceiling floor by water dripping, stalagmites grow up from the cave floor. Sometimes stalagmites and stalactites join together to form columns.
115
What is karst topography?
The landscape formed by groundwater dissolving soluble rocks. If cavern ceilings cave-in, they result in **sinkholes**, into which streams can disappear.
116
What type of terrain do sinkholes appear in?
In limestone terrain that can be dissolved and collapse to form sinkholes.
117
What are the two types of glaciers?
1. Ice sheets
2. Valley glaciers
118
What is an ice sheet glacier?
A glacier with radial flow. A large ice mass on a continent (ex. Antarctica)
119
What is a valley glacier?
In a mountain, commonly flows down old stream valleys.
120
How quickly does a glacier flow?
cm/day is normal
121
What are the two layers of a glacier?
Upper: brittle (50 m)
Lower: plastic flow
122
Where does internal flow occur in a glacier?
Below the brittle layer in the plastic layer
123
What two factors determine the budget of a glacier?
1. Accumulation
2. Ablation
124
How does accumulation occur?
By gaining snow or ice
125
How does ablation occur?
Through wastage or loss by melting, evaporating, or icebergs calving (breaking) in water
126
What happens if accumulation \> ablation?
The glacier's terminus will advance
127
What happens if accumulation \< ablation?
The glacier's terminus retreats
128
Which way does a glacier always move? (even during retreat)
Towards the front
129
Where is the zone of accumulation? Where is the zone of ablation?
Accumulation: top of hill
Ablation: bottom of hill
130
What two things are involved in glacier-driven erosion?
1. Plucking - glaciers "freeze-on" loose bedrock
2. Abrasion - glacier and rock debris scour, scrape, and gouge subglacial floor and sides
131
What is the result of glacial abrasion?
striations and grooves
132
What is a glaciated valley? What does it become?
A U-shaped valley; it becomes a fjord - as deep as a mountain is high
133
What is a cirque?
Rock bowls at the heads of glaciers.
134
What does the word arete mean?
"Knife-edged" - a knife edged ridge
135
What is a glacier horn?
Sharp mountain ridges and peaks
136
Where can a fjord be found?
Along a coastline
137
Where do horns and aretes form?
On the sides of where a cirque glacier came through
138
What is glacial drift?
Glacially derived sediment
139
What are the two types of glacial drift?
Till (stony mud with polished stones and striated stones) and striated drift
140
When are glacial deposits of glacial drift released?
When a glacier melts
141
What is till?
Rocks that come in a great variety of particle sizes; directly from glacier ice. Stones tend to appear scratched or polished and faceted from glacial transport.
142
What is a lateral moraine?
Formed from till along the sides of valley glaciers
143
What is an end moraine?
Formed from till at the terminus of a glacier, from debris being dumped and bulldozed
144
What is ground moraine?
Till plastered beneath a glacier
145
What is a drumlin?
A mound that becomes streamlined under a glacier - the blunt end points **up glacier**
146
How is till formed, how is striated drift formed?
Till: directly from glacier ice
Striated drift: deposition by glacial melt-water
147
What is till comprised of? What is striated drift comprised of?
Till: scratched and polished stones, in a variety of sizes
Striated drift: sand and gravel - provides an excellent source of aggregate to build cities
148
What provides an excellent source of aggregate to build cities?
Striated drift
149
What is a kettle?
A depression in the ground left by a piece of a glacier that melted there.
150
What is a kame?
A debris mound that was lowered to the ground by a glacier surface as it melted.
151
What is an esker?
A winding gravel ridge commonly formed in a subglacial tunnel
152
How frequently does glaciation occur?
About every 100,000 years
153
How does glaciation occur?
Controlled by 3 cycles related to Earth's orbit and the sun. Plate tectonics and continental drift bring a major continent over a pole, which brings global cooling to a start.
When conditions combine for **minimal contrast between seasons**, at **mid-high altitudes** more snow falls during mild winters, and less snow melts during cooler summers. This induces major glaciation.
154
What is a desert?
A dry place with low precipitation and little vegetation
155
How does weathering occur in a desert? How quickly does it occur?
It is almost entirely mechanical due to the lack of precipitation. However, clays and thin soils eventually form by **oxidation of ferromagnesian silicates**
156
In what forms is water found in the desert?
Short intense rainstorms happen from time to time. These create **ephemeral streams** and flashfloods. This does most of the erosion of desert surfaces, especially that that is not anchored by vegetation
157
What is the rock that forms in a desert called, by oxidation of ferromagnesian silicates?
"Rock varnish"
158
How is sediment transported in the desert?
By the wind, which can move faster, and lift sediments higher than streams can.
159
How does bedload move in the desert?
By saltation, with grain collisions, and sand rolling over the ground.
160
What is suspended load in the desert?
Occurs when dust particles are swept into the air by saltation grains. They are carried in **dense clouds** up into the air.
161
What two processes are are involved in wind erosion in the desert?
1. Deflation
2. Abrasion
162
What is desert deflation?
When fine sediments blow away to form **blowouts**, while coarser particles are left behind to form **desert pavements.**
163
How are blowouts formed?
By deflation
164
What is desert abrasion?
Occurs with saltation when particles sandblast things. Forms **ventifacts and yardangs.**
165
What is a ventifact?
When wind polishes, pits, and facets stones sitting on the desert floor
166
What is a yardang?
A streamlined ridge in the desert
167
How are ventifacts and yardangs formed by?
Abrasion in the desert
168
How do wind deposits form in the desert?
Wind slows down and is no longer able to carry its load, produces landforms made of silt and sand
169
What is a sand dune, and how is it formed?
Found in wind shadows around obstacles. A small mound of sand is produced that self-perpetuates and grows.
The **slipface** forms on the **leeward, downwind** side and is steeper than the other side (34o angle). The **upwind** side is farther away.
The dune migrates in the direction of the slip-face.
170
What is the bedding of a sand dune like?
Cross-bedded.
171
What are the different types of sand dunes?
1. Barchan
2. Transverse
3. Longitudinal
4. Parabolic
5. Loess
172
What is a barchan?
Crescent shaped dune with tips pointing down-wind. Supplies of sand are limited and the ground surface is flat and lacking vegetation. The slip-face is on the inside of the crescent.
173
What is a transverse sand dune?
A series of ridges and troughs elongated **perpendicularly** to wind direction, commonly along coasts where wind is steady, sand is abundant, and there is little vegetation.
174
What is a longitudinal dune?
A dune positioned parallel to wind direction, where sand is moderate in large deserts. They can be 10s of km.
175
What is a parabolic sand dune?
A crescent-shaped sand dune where tips point **upwind.** Commonly anchored by vegetation, in places where lots of sand occurs along coasts and wind blows on shore.
Slip face is on the outside of the crescent.
176
What is a loess?
Forms from deflation of dust, carried far from deserts, or from glacier deposits of outwash or till, eventually deposited as a blanket over a landscape, makes very fertile farmland.
177
What type of deposit forms very fertile farmland?
A loess
178
What is a wave?
Wind generated energy, from wind blowing over the surface of the water. Molecules move up and down and from side to side.
179
What happens as a wave approaches the shoreline?
It "feels the bottom" and breaks into **surf**. It moves up the beach as **swash** and retreats as **backwash**.
180
How do storm waves erode headlands?
Mostly by abrasion, and undercutting, as wave impact compresses air in fractures.
181
What is wave refraction?
Waves bend at irregular shorelines and deposit in bays
182
What type of waves form longshore currents?
Oblique waves
183
What is beach drift?
The zig zag pattern of swash and backwash
184
What direction does a longshore current move in in relation to the shoreline?
Parallel
185
What moves sediment at shorelines? Where does this sediment come from?
Long shore currents, the sediment comes mostly from rivers
186
What is beach drift?
A sawtooth, zig zag pattern formed by swash and backwash in which their is a net direction of movement that parallels the longshore current
187
What is a wave-cut cliff, and what does it form?
Occurs by the cutting action of surf against the base of a cliff, resulting in collapse and retreat of the cliff. The debris is then swept out to sea, leaving a **wave-cut platform.**
188
What is an arch, and what does it form?
Where waves cut into the sides of headlands until caves join. Eventually the arch collapses and forms a **stack,** sitting alone on the wave cut platform.
189
What is a spit? What may it become?
A spit is an elongated sand ridge that forms when a longshore current and beach drift moves sand into the mouth of bays. If a ridge crosses a bay it is a **bay-mouthed bar.**
190
What is a tombolo?
A sand ridge that connects an island to land or an island to another island
191
How do shorelines straighten?
Most begin as an irregular shape as a series of headlands and bays but continued cliff retreat and sand deposition straighten it out.
192
What are jetties? What are groins? What is their downside?
Jetties are built to keep sand out of river mouths, they extend the channel beyond the mouth to prevent beach drift. Groins are perpendicular to the shoreline to trap sand and **widen** beaches. **Sand is deposited on the updrift side and eroded on the downdrift side.**
Their downside is that they cause erosion on the downdrift side of the jetties and groins, forcing their neighbours to build more stuctures.
193
What is a breakwater? What is a seawall?
Breakwater: an **offshore** wall that runs parallel to the shore to prevent shoreline damage from storm waves. Protects marinas and beaches.
Seawall: a wall **at the shoreline** that prevents damage from storm waves.
194
What is the downfall of seawalls and breakwaters?
Both must be maintained at a high cost.
195
What is beach nourishments? What are its drawbacks?
Beach nourishment is attempting to restore a beach from an eroded state.
It is costly, requires a lot of sand, requires continual maintenance, and only lasts for a few years.
196
What is the best solution for preventing damage to buildings along shorelines of beaches that are hit by heavy storms?
Relocating them, and letting nature reclaim the beach
197
198
What in a mineral deposit that is mined for a profit called?
Ore
199
What are non-metallic minerals mined for?
For industrial materials
200
Where can heavy, magmatic crytals such as chromite, platinum and magnetite be found?
In a cooling pluton
201
Where can the lightest magmatic minerals with rare elements and huge crystals be found?
In **pegmatite dykes**
202
What kind of minerals are found in magmatic deposits?
Heavy: magnetite, platinum, and chromite
Light: in pegmatite dykes
203
What kind of minerals are hydrothermal?
Silver and gold
204
What are hydrothermal mineral deposits?
Hot fluids with metal precipitate ore in **vein deposits** (silver and gold)
There are also **disseminated deposits** which spread throughout the host rock and are non-concentrated. Minerals include copper and molybdenum ore which are spread throughout porphyritic rock.
Also, **volcanogenic massive sulfide** deposits in ancient seafloor at oceanic ridges, where fresh seafloor reacted with seawater
205
What are sedimentary mineral deposits?
Banded iron formation in the **Precambrian** sea
There is no oxygen for oxidation, instead, bacteria oxidize, forming minerals such as chert, magnetite, and hematite
There are also **placer deposits of gold**, and **diamonds** by running water (concentrations of heavy minerals)
206
What are metamorphic mineral deposits?
**Skarns**, by plutons cooking limestone and surrounding contact metamorphism.
Rich in zinc, lead, copper, gold
207
What metallic mineral deposits are formed by weathering?
Bauxite in the tropics, providing aluminum ore
Occurs by hydrolysis of silicate minerals
208
What are non-metallic minerals important in?
Contruction, food, chemicals, etc.
209
What are aggregate and stone used for? What are some examples of them? (non-metallic resources)
Crushed stone, sand and gravel, used for concrete and asphalt.
Cut stone used in building faces, walkways, and countertops
ex. granite, gneiss, and slate.
210
What are diamonds mined for? (non-metallic industrial minerals)
Diamonds are mined for gems and abrasives; they form in the deepest roots of a mountain belts, then picked up by rising bodies of **kimberlite magma from the asthenosphere.**
211
What are clays used for? (Non-metallic industrial minerals)
From silicate weathering; used for bricks, sewer pipes, pottery, and chemical industry.
212
What is calcite used for? (non-metallic industrial)
Limestone; for cement, asphalt, and the chemical industry
213
What are evaporite salts used for? (non-metallic industrial)
Gypsum for plaster (drywall), salt for food and chemicals, potash for fertilizer
214
What is phosphate used for? (Non-metallic industrial)
Used for agriculture, mined from marine sedimentary rocks
215
Where does sulphur come from? (non-metallic industrial)
Mined from coal, oil, and gas
216
What are non-renewable energy sources, by definition?
Fossil fuels, whose use is hard on the environment
217
What is petroleum? (non-renewable resources)
Petroleum is mainly used for plastics and fuel.
It is formed in ancient seas from remains of plankton that were buried, and then progressively heated to **kerogen,** which is an oil/natural gas.
Because they are lighter than water - migrate up to permeable **reservoir rocks**, until they hit a **petroleum trap** where **cap rock** meets reservoir rocks.
218
What is coal? (non-renewable resources)
Mainly used for fuel. Formed from decayed land plants in ancient swamps that were buried, compressed, and cooked to form coal.
Canada is a major exporter
219
Heavy oil sands? (non-renewable resources)
Abundant in Alberta, but are viscous and therefore must be heated to extract the oil.
220
Nuclear (non-renewable energy)
Uranium atoms are split (nuclear fission), **uraninite** is the main ore.
221
Renewable fuel sources, by definition.
Geologically-related alternatives to fossil fuels.
222
Hydroelectric (renewable energy sources)
Damming streams to give clean energy. This supplies most of canada's energy, but dams do not last forever.
Reservoirs fill with sediment, and lose capacity.
223
What is geothermal energy? (renewable energy sources)
Heated groundwater in volcanic areas is tapped, and the energy is used to power turbines that convert energy to electricity.
224
How do glaciers form?
By compaction, recrystallization, and snow that eventually turns to ice
225
What is the difference between a horn and an arete?
Horn = pyramid-shaped peak
Arete = sharp-ridges
226
What does the world geology mean? Why is it important?
Geo = earth
Ology = the study of
Therefore geology is the study of the earth.
It is important for energy and natural resources, solving environmental problems, building cities and highways, and predicting and preventing natural disasters.
227
What is the fundamental principle of the concept of uniformitarianism, and what does it mean? What is the timescale of the earth measured in?
The present is the key to the past. This means that the processes that we see shaping th earth today are the same as the processes that shaped the earth millions of years ago. Geological time is meausred in billions of years.
228
When when did the Big Bang occur?
~14 billion years ago
229
What theory is generally excepted as correctly explaining the formation of the solar system? Describe it.
The Nebular theory - 5 billion years ago. A nebular made up of hot gasses - mainly hydrogen and helium. The nebular cloud contracted under gravity and began rotating. The rotating instigating central pedal force, which caused elements to concentrate in the centre. Gravitational energy converted to thermal energy. This became the sun. The other, heavier elements began to fuse together into planets and moons, which continued to rotate around the sun.
230
Explain how the earth was formed, and what layers formed.
Formed by rock collisions. The heavier elements (Fe, Mg) migrated inwards and became the core. The lighter elements (oxygen rich elements) migrated outwards and formed a very thin crust. The middle area between the crust and the core is called the mantle. In the process, gasses escaped and formed the atmosphere.
231
Describe the names and the layers of the world.
1. Lithosphere ("sphere of rock")
- the crust AND the upper most mantle - split into plates that move over top of the asthenosphere
2. Asthenosphere ("weak sphere")
- liquid - due to unequal heat distribution in the earth convection currents occur here, the lithosphere rides on top of them, in CONTINENTAL DRIFT
3. Core
- very dense and under extreme heat, intense pressure keeps the core a solid - Ni, Fe
232
What causes more geological activity, convergent or divergent boundaries?
Convergent boundaries
233
What is a divergent boundary?
Occurs when plates move apart due to tensional stress. This allows for upwellling of material in the mantle, forming ridges and rifts. It is the cause of SEA-FLOOR SPREADING.
234
What is a convergent boundary?
The primary cause of geological activity. Occurs when denser, oceanic plate descends below lighter, continental plate. This is known as SUBDUCTION, and it forms a trench. The denser, oceanic plate reaches far enough into the asthenosphere that it begins to melt. Sometimes, this allows for melted magma to protrude and form a volcano, which eventually erodes into sediment. It is at convergent boundaries that earthquakes and volcanoes often form.
235
What is subduction?
The descent of the denser oceanic lithosphere beneath the lighter, continental lithosphere.
236
What does Pangaea mean? What evidence is there to support it?
Pan = all, Gaea = earth
1. Fit of the continents
- South America and Africa fit together at a depth of 900 meters (at the continental shelf)
2. Fossil evidence
- Fossils match across continents (ex. Mesosaurus fossils found in East S.A. and South Africa)
3. Rocks and Structures
- ex. Appalachian mountains and Scandinavian mountains form a continuous chain
4. Paleoclimatic Similarities
- ex. finding coal in ancient tropical swamps in places that are now glaciated; finding striations from glaciers in tropical areas today
237
What are the 4 spheres of the earth? How do they interact?
Earth is a dynamic system of interacting spheres.
1. Geosphere - the earth and rock sphere
2. Hydrosphere - the sphere of water
3. Biosphere - the sphere of life, ranging from the hydrosphere, slightly into the atmosphere
4, Atomsphere - thin and tenuous sphere of gases, producing weather and climate
238
Where are new rock types mainly produced at?
Converging boundaries
239
Explain the rock cycle, beginning at magma.
Magma crystallizes to form igneous rock, igneous rock is weathered, transported, and deposited to form sediment, which is cemented to form sedimentary rock, sedimentary rock undergoes metamorphisis to form metamorphic rock. Metamorphic rock melts to form magma. Metamorphic rock can become sediment by weathering, as can sedimentary rock. Igneous rock can also undergo metamorphisis under heat and pressure to form metamorphic rock.
240
What are minerals? How many are there? How many are common in the earth's crust? How are they produced?
Minerals are inorganic substances formed by nature that combine together to form rocks. Their elemental composition, chemical structure, and bonding determine the properties that the mineral will have. There are 4700 known minerals, but only about 20 are predominant in the earth's crust.
241
What type of mineral is the most abundant?
Silicates
242
What are silicates? What is their structure, and elemental composition?
Silicates are composed of Silicon and Oxygen, covalently bonded to each other to form tetrahedrons (SiO4)4-. Because oxygen is an anion, and therefore negatively charged, metal cations such as Fe2+ and Mg2+ can ionically bond. This ionic bonding is weaker than the overall covalent bonding, which usually results in a spot of weakness along the mineral, which becomes the cleavage point.
243
What is the composition of a dark silicate?
Ferromagnesian - therefore with Fe and Mg within the silicate tetrahedra.
244
What are the four ferromagnesian silicates? Describe their bonding, and cleavage?
1. Olivine
- single tetrahedra, covalently bonded, with Fe2+ and Mg2+, no cleavage
2. Pyroxene
- single chains of tetrahedra, with metals between them, cleavage is 2 at 90 degrees
3. Amphibole
- double chains of tetrahedra, with metals between them, cleavage is 2 not at 90 degrees (60 and 120)
4. Biotite (black mica)
- sheets of tetrahedra with metals between them, cleavage is basal/platy
245
What are the four non-magnesian silicates? Describe them.
1. Muscovite (white mica)
- perfect basal cleavage, often used for muscovy window glass
2. Feldspar
- strongly bonded 3D network of silica tetrahedra
a. Orthoclase (K feldspar) with potassium, cleavage is 2 at 90 degrees.
b. Plagioclase (Ca/Na feldspar) with calcium in mafic rocks and sodium in felsic rocks, cleavage is 2 at 90 degrees.
3. Quartz
- very strong, purely covalent silica tetrahedra, has a hardness of 7, can form crystals with sufficient space in nature. (SiO2)
246
Name the two types of non-silicate minerals, and describe them.
1. Carbonates (CO3)2-
a. Calcite (CaCO3) - used in cement and limestone
b. Dolomite (MgCaCO3)
2. Evaporites
a. Halite (NaCl) - table salt
b. Gypsum - plaster and drywall
247
Name the metallic, non-silicate type of mineral.
Ores of metals
1. Hematite/Magnetite (Fe)
2. Sphalerite (Zn)
3. Pyrite/Chalcopyrite (Cu)
4. Galena (Pb)
248
Where are igneous rocks? Where does the name come from? Which types of minerals are in igneous rocks?
Igneous = fire
Igneous rock crystallizes from molten SILICATE magma, which is formed deep in the earth under high temperatures and pressures.
249
What are the two options for magma at the site of a volcano? What type of rock does each location of formation form? Typically what are the textures of this rock?
1. Intrusive - forms plutonic rock - texture tends to be PHANERITIC
2. Extrusive - forms volcanic rock - texture tends to be either PYROCLASTIC, APHANITIC, OR GLASSY, due to quick cooling, or quenching by air or water.
250
Does flowing lava tend to be mafic or felsic? How about lava that violently erupts to form glassy textures or pyroclastic material?
Mafic = flowing, hot, runny
Felsic = more viscous, violently erupts
Viscosity is directly dependent on the silica content of the parent magma
251
What types of rocks are formed by felsic magma? How much silica does it contain, and what minerals form the rocks?
1. Granitic rock - phaneritic texture
2. Rhyolite - aphanitic texture
Minerals - quartz, biotite, orthoclase, Na-rich plagioclase
70% silica content, therefore very viscous
252
What type of rock does intermediate magma tend to produce? What percent of it is silica?
1. Diorite - phaneritic
2. Andesite - aphanitic
Minerals - amphibole, plagioclase
60% silica
253
What type of rock does mafic magma produce? What minerals are in the rock? What is it's silica content?
1. Gabbro - phaneritic
2. Basalt - aphanitic
Minerals - Ca-rich plagioclase, pyroxene
50% silica
254
What type of rock does ultramafic magma produce? What are the minerals in it? What percent of silica is it?
1. Peridotite
Minerals - pyroxene
40% silica content
255
Where is basalt found?
In the upper oceanic crust and on volcanic islands - the most abundant rock in the crust
256
Where is gabbro found?
In the lower oceanic crust
257
Where is peridotite found?
The main rock of the upper mantle
258
Name the four types of intrusive bodies, and their characteristics.
1. Dyke - discordant, tabular
2. Sill - concordant, tabulat
3. Laccolith - concordant, bulge
4. Batholith - discordant, bulge
259
What about Bowen's reaction series is continuous? What is discontinuous? How does it work?
Ferromagnesian silicates are discontinuous, non-ferromagnesian silicates are continues.
Bowen's reaction series states that heavier minerals have a higher melting point, and precipitate from the melt first. Lighter minerals precipitate from the melt last. This is how lighter rocks can be produced from mafic magma, as the mafic magma becomes felsic.
260
Out of olivine and pyroxene, which precipitates first?
Olivine, then pyroxene
261
Which mineral is left over after most of the magma melt has precipitated out?
Quartz - this is how granite can be formed from ORIGINALLY BASALTIC MAGMA
262
Why do volcanoes occur? What two things can lava do upon extrusion?
Gas builds up in the magma chamber, causing pressure that needs to be released. Lava can either flow down the side, or blow through the top.
263
What is extrusive, mafic magma also known as? What are its physical characteristics like?
Basaltic magma - it is hot and runny, and runs quietly downthe volcano before hardening
264
What is extrusive, felsic magma also known as? What are its physical characteristics?
Rhyolitic magma - it tends to be cooler and more viscous, tends to erupt violently and form pyroclastic material such as tuff and breccia
265
What are the two types of magma?
1. Pahoehoe - made of hotter, runnier, mafic magma which hardens to form a coiled, "ropy" texture
2. Aa - made of cooler, slower, felsic magma - tends to be "blocky" in texture
266
What are pillow lavas?
Pillow lavas resemble pillows and are formed underwater when magma either flows into the water, or exits through tube ends. The texture is typically GLASSY, from quenching or quick cooling by the water.
267
What is a Nuee Ardente? Where does the name comes from, and what is it also known as?
Nuee Ardente = glowing cloud - also known as a PYROCLASTIC FLOW
These are extremely destructive, and occur when a cloud of gas, hot ash, and magma races down a volcano - they can wipe out a whole city at once.
268
What is pyroclastic material, and what are some examples?
Pyroclastic material = fire fragments
Formed by magma ejected into the air. Can range from fine ash, to streamlined bombs, to large blocks.
269
What is a lahar?
A lahar is pyroclastic material, mixed with snow, mud, rain, and ice.
270
What is the most common type of volcano? What is it made up of?
A composite cone - made up of pyroclastic material as well as lava flows - medium in size with a crater
271
Describe the three types of volcanoes, and their compositions.
1. Shield volcano - very large, ranging in hundreds of km, has a caldera at the top, much wider than it is tall - and made up of successive lava flows
2. Cinder cone - very small, with a crater, made mainly of pyroclastic material
3. Composite cone - medium sized, made of pyroclastic material and lava flows
272
What is the difference between a crater and a caldera? How is a caldera formed?
Crater
Caldera \> 1 km
Calderas are formed by the collapse of the underlying magma chamber as it empties
273
What leads the magma to the caldera or the crater?
A conduit or pipe
274
What are fissure eruptions? What do they form?
Fissure eruptions occur when magma flows out of fissures in the crust, plateaus are formed by the magma that flows from the fissure
275
Where do volcanoes tend to occur?
They tend to occur at convergent boundaries at subduction zones, where denser, oceanic lithosphere melts to form basaltic/gabbro rich mafic magma
276
What type of magma does melted oceanic lithosphere generate?
Basaltic magma
277
Around what geological structure do subduction zones and volcanoes tend to occur?
Around the Pacific Ring of Fire
278
What is a seamount?
A location in which and underwater volcano produces basaltic magma which flows out onto the sea floor
279
What is an intraplate volcano and what causes it?
An intraplate volcano occurs in the middle of a continent/lithospheric plate - it is caused by deep mantle plumes which protrude
280
What are the two types of weathering that forms sedimentary rock?
1. Mechanical
- frost wedging, sheeting, biological
2. Chemical
- hydrolysis, dissolution, oxidation
281
What is mechanical weathering also known as?
Disintegration
282
What is chemical weathering also known as?
Decomposition
283
What is the relationship between mechanical and chemical weathering?
They work together to enhance erosion - mechanical weathering increases surface area for chemical weathering to work on
284
Describe the types of mechanical weathering.
1. Frost wedging - water enters rock fractures as a liquid, it expands 9% as it freezes splitting the rock apart
2. Sheeting - occurs when material is unloaded from a batholith, allowing for rock expansion, as the rock expands slabs break off
3. Biological activity - vegetation grows roots in rock fractures - the roots grow and expand, splitting rock apart
285
Describe the three types of chemical weathering, and their effects on the rock.
1. Dissolution - CO2 + H2O ---\> H2CO3
- this carbonic acid dissolves some rocks, making them stable at surface conditions
2. Oxidation - ferromagnesian rocks have metals which react with oxygen in the atmosphere forming metal oxides, rust, and CLAY MATERIALS
3. Hydrolysis - occurs when K+ in orthoclase is replaced by hydrogen, because hydrogen is much smaller, it causes collapse of the mineral, forming clay
286
What type of rock does hydrolysis occur in?
Granitic rock, rich in orthoclase and potassium
287
What are the rates of weathering like for different rocks?
Rocks that form at low T/P are more stable at the surface - ex. quartz, biotite, etc. Rocks that form at high T/P are less stable at the surface - ex. olivine and pyroxene
288
In general, are light or dark silicates more stable at the surface?
Light, as they are formed nearest to surface conditions
289
What is the most weathering-resistant type of rock? Why?
Quartz, because it is the last mineral remaining in the magma melt, closest to surface temperature and pressure with strong, covalent bonds of silicate tetrahedra
290
Between marble and granite, which is more stable? Why? What is their common use?
Granite is more stable, predominantly formed of quartz, marble is soluble in carbonic acid and very susceptible to hydrolysis.
They are commonly used for headstones, however granite is the better choice.
291
How does climate effect the rate of rock weathering?
Tropical climates that are warm and wet tend to cause an increase in weathering rate, while polar climates tend to decrease the rate.
292
What is soil? What are the two main components of it?
Soil is the result of rock weathering (inorganic) with organic components.
Inorganic component = regolith
Organic component = humus
293
What are the five factors in soil formation?
1. Parent soil - the type of bedrock and sediment determines the rate of soil formation and its fertility - parent rock maintains many of the mineral properties
2. Time - the more time that passes, typically the more soil that is produced
3. Climate - soil forms fast in greater amounts in the tropics, and slower and in lesser quantities in polar regions
4. Plants and animals - both plants and animals decompose to humus, releasing nutrients into the soil, and increasing the soil's water retention
5. Topography - sleep slopes erode easily and do not hold moisture or vegetation
294
What are the letters that represent a soil profile? What is each layer comprised of?
O = the organic layer, with lots of humus
A = a mix of organic matter and minerals
E = eluviation layer - transportation from upper layers to lower layers, leaching of ions in solution
B = accumulation of oxides and clays (in wet climates)
C = regolith and parent material
295
How does rain cause soil erosion?
Causes soil to be eroded into rills, then gullies, and then streams
296
What are some ways that soil is eroded? What are the consequences of soil erosion?
Rain, deforestation, farming, wind, etc.
Consequences = decreased lake holding capacity causing flooding, lack of fertile soil for food production, vegetation reduction
297
What does the word sedimentary mean? What percentage of the rock on earth is sedimentary?
Sedimentary = to settle - contains high levels of quartz and clay minerals
75%
298
What is the formation of sedimentary rock from sediment known as?
Diagenesis and lithification
299
Describe the two types of diagenesis and lithification in the formation of sedimentary rocks?
1. Compaction - pressure on sediment forces grains close together, expelling water whcih binds the grains together
2. Cementation - fluid with ions (the cement) coats the sediment grains, causing them to stick together
300
What is clastic sedimentary rock also known as? Describe the types and where they're formed.
Detrital rock
1. Conglomerate - solidified gravel formed in flowing rivers, landslides or in wave actions with rounded rocks (breccia if angular), close to the source.
2. Sandstone - made up of sand grains and quartz, if it is well-sorted the grains are of the same size, if not = poorly sorted
3. Arkose - sandstone with a large amount of feldspar
4. Shale - made up mostly of silt and clay, deposited in quiet waters, and floodplanes
301
Describe shale.
Shale is made up of silt and clay grains that are packed very closely together, formed in quiet waters. It is impermeable to water, and makes GOOD CAP ROCK for oil and gas. Also used for pottery, tiles, etc.
302
Describe the different types of limestone.
Limestone is formed with CALCITE
1. Micrite - formed in sea water
2. Fossiliferous limestone - formed in coral reefs
3. Chalk - formed by dead plankton on deep sea floors
4. Coquina - formed in shallow waters and at beachy shorelines of shells and fossils, loosely cemented together
5. Travertine - formed in karst and cave environments
303
What are the other types of chemical sedimentary rocks? (Non-limestone, mostly inorganic)
1. Dolostone (replaces Ca with Mg in limestone)
2. Chert - formed from microorganisms that use silica
3. Coal (ORGANIC) - formed in ancient swamps from the remains of animals and vegetation
4. Evaporites - formed in ancient sea basins - ex. Halite and Gypsum
304
Describe the four types of sedimentary structures.
1. Strata - strata is layered by different deposition events
(ex. CROSS-BEDDING, GRADED BEDDING)
2. Mudcracks - cracks in the mud formed by evaporation
3. Ripple marks - reveal the location of ancient seas and wind over loose sediment
4. Fossils - mainly found in sedimentary rock
305
What is graded bedding?
Graded bedding is the settling of particles with the coarser, larger ones on the bottom and smaller, finer pieces on the top. Occurs in TURBIDITIES after deposition by turbidity currents.
306
What are the four controlling factors that produce metamorphic rock?
1. Parent rock - the metamorphic rock maintains the majority of the composition of the parent rock
2. Heat - heat drives chemical reactions
- produced from PLUTONIC INTRUSIONS, as well as by the geothermal gradient
3. Pressure - two types, confining and directed
4. Chemically acitve fluids - water can be important as it often has a high concentration of ions - also, water is released upon heating through evaporation whivh causes rock dehydration
307
What are the two types of pressure involved in the formation of metamorphic rock? How do they work, and what rock texture does it cause?
1. Confining pressure - occurs in all directions and increases with depth (ex. swimming pool water pressure)
2. Directed pressure - occurs at convergent boundaries of colliding lithospheric plates
Causes a foliated rock texture
308
What is metamorphic grade, and what causes it mainly? Name the rocks from low to high grade.
Metamorphic grade is the intensity of metamorphism - increases with TEMPERATURE
Low grade - chlorite, muscovite, biotite, garnet, staurolite, sillimanite - High grade
309
What is contact metamorphism also known as? What kind of pressure occurs? What kind of heat change occurs? Give an exampe of a type of rock it produces.
Thermal metamorphism, occurs above intrusions into cooler parent rock - causes recrystallization, but NOT reorientation of crystals (ex. no foliation). Only pressure that occurs is confining pressure.
ex. Sandstone is baked into granite
ex. Limestone is baked into marble
310
What is the effect of contact metamorphism surrounding the intrusion?
An aureole = a golden halo
Decreases with distance (temperature) away from the intrusion
311
What is regional metamorphism? Where does it occur? What kind of heat/pressure is present? Give an example of a rock it produces.
Regional metamorphism occurs at convergent plate boundaries in the CORES OF MOUNTAIN BELTS where directed pressure is most intense, near subduction zones. It involves directed pressure, and the only heat present is due to the geothermal gradient. It casues both recrystallization and reorientation of crystals into a foliated rock.
Ex. shale
312
What are the grades of shale metamorphism, and where do they occur?
1. Slate (lowest grade, farthest from the core)
- slaty cleavage, very fine partings
2. Phyllite
- wavy partings
3. Schist
- mica and chlorite schist with schistose texture (ex. mica on the outside, amphibole in the centre)
4. Gneiss
- highest level of foliation found in mountain roots
- light and dark mineral segregation
313
What are the four ways in which geological time is deciphered?
1. Superposition
2. Original horizontality
3. Cross-cutting relations
4. Inclusions
314
What is the principle of superposition?
States that every rock is older than the rock above it and newer than the rock below it.
315
What is the Original horizontality theory?
States that sediment is deposited horizontally, therefore any rock that has sediment that is not completely horizontal has undergone some sort of change
316
What does the Cross-cutting relations theory state?
That a **fault** is newer than the rock it cuts, and a **rock** must be younger than the rock it cuts
317
What do inclusions tell us about the age of a rock?
The intrusive rock must be older than the rock it intrudes
318
What is an unconformity? What are the two causes of unconformities.
An unconformity is a gap in a rock's geological time - missing rocks are typically due to NONDEPOSITION or EROSION within rock sequences.
319
What are the three types of unconformities? Describe them.
1. Angular Unconformity - flat strata, resting on tilted strata
2. Nonconformity - occurs when sediment is deposited onto igneous rock or metamorphic rock
3. Disconformity - layers of horizontal, parallel strata, with a change in sediment that is often difficult to recognize
320
What is used to determine correlation between rocks in different outcrops?
Fossil succesion, using a fossil index.
Fossil succession - animals evolved at different times in earth's history
Fossil index - some fossilized organisms are widespread around the world and are known to have existed at a certain time
321
How is radioactive dating used? What is the definition of a half-life?
With radiometric methods - parent, radioactive isotopes decay to daughter atoms.
Half-life = the amount of time it takes for an original sample to decay to half of its amount
Comparing the amount left to the half-life allows for the amount of time since formation to be deduced
322
How was the age of the earth determined?
Using radiometric measures
323
What is carbon dating, and how does it work?
Works only on matter that was once living (carbon-based). Living organisms take in both C12 and C14 while living from the environment. C12 is consistently present in living things. C14 is constantly decaying to N14, and is taken in from the environment only when the organism is alive. Therefore, when alive an organism has a ratio of C14/C12 that is constant. When the organism dies, C14 decays to N14, and the ratio of C14/C12 decreases.
C14 has a half-life of 5730 years. Therefore, using this half-life and the ratio of C14/C12, the time since the organism has died can be deduced.
324
How far back can carbon dating be used to detect the amount of time since an organism has died?
~50,000 years
325
What is crustal deformation? What materials may be yielded from crustal deformation?
Rocks can become deformed to produce strctures that can
a) PRODUCE ENERGY
b) OIL RESERVES
326
What three types of stress cause rock deformation?
1. Compressional stress - shortens rock, squeezes rock together
2. Tensional stress - pulling rock apart, lengthens it
3. Shear stress - causes sideways slip of the crust
327
What is strain?
The result of stress
ex. stress = force, strain = result
328
What is elastic deformation?
Occurs before elastic limit is reached - no permanent rock damage is done
329
What two types of deformation are the result of the elastic limit being reached?
1. Brittle deformation (strong rock) - occurs to crustal rock near the surface, fracturing
2. Ductile deformation (weak rock) - flowing which occurs higher temperatures and pressures, ex. rock sagging
If given enough time, all rocks will undergo ductile deformation due to gravity - all rock will flow eventually!
330
What are the two components used to uniquely define a rock in geological space?
1. Dip: AZIMUTH of a horizontal line on the surface of a plane - the angle the rock forms with the horizontal
2. Strike: perpendicular to the dip, horizontal
331
What type of pressure/stress causes folds in a rock? What is the anatomy of a fold?
Caused by compressional stress
- fold has two limbs on either side, as well as a fold axis, and an axial plane
- Anticline - the arch of a fold
- Syncline - the trough of a fold
332
Describe the different types of folds.
1. Overturned = the anticline is overturned in a fold
2. Plunging = when the fold axis is facing downwards in comparison to the horizontal
3. Symmetrical - limbs are mirror images
4. Asymmetrical - limbs are NOT mirror images
333
What is a monocline?
A gentle "step" inthe crust, often caused by and underlying fault
334
What is a dome rock deformation? What is a basin?
Dome = oldest strata on the inside, newest on the outside
Basin = oldest strata on the outside, newest on the inside
335
What is a joint rock deformation?
A fracture in which no displacement occurs - it is a parallel pattern of fractures, caused by the cooling of igneous rock
336
What type of stress causes joints? What material is often found between joints?
- tensional stress causes joints
- ores deposits are often found during joint fractures
337
What is a fault? What does the friction cause?
A type of rock deformation in which fracture and displacemet both occur. Friction causes the formation of a slickenslide.
338
What are the two types of dip-slip faults? What type of stress causes them?
Slippage along the dip of the fault plane
1. Normal = hanging wall moves down, due to tensional stress
2. Reverse = hanging wall moves up in comparison to the footwall, due to compressional stress
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What are the types of strike-slip faults?
A strike-slip fault is slippage along the strike of a fault
1. Left-lateral - left side of the fault moves down
2. Right-lateral - right side of the fault moves down
3. Transform faults - occurs at oceanic lithospheric paltes, breaking up oceanic ridges, allowing for them to spread through divergent boundaries, ddue to tensional stress
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What type of fault occurs along the Californian San Andreas Fault?
Strike slip transform faults
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What causes an earthquake?
Elastic rebound of the crust as stress builds up, causing slippage or crustal deformation
-DIP-SLIP OR STRIKE-SLIP crustal deformations both cause earthquakes
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What is the hypocentre of the earthquake? What is the epicentre? Where do seissmic waves propogate from?
Hypocentre = the location of the slippage, seissmic waves propogate from here
Epicentre = the spot on the surface of the crust, directly above the hypocentre
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Where do earthquakes typically occur?
At plate boundaries, often convergent
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How does a seissmograph work?
It has a weight with a pen on the end, and a paper scroll beneath it. At the time of an earthquake, the shaking causes the weight to move, "drawing" on the paper creating a seissmograph.
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What are the three different types of waves formed by an earthquake, and how fast do they each travel?
1. SURFACE WAVES - l waves, slowest, largest amplitude on a seissmograph
2. BODY WAVES
a) P waves - primary waves, the fastest, arriving first, undergoing push-pull wave actions (like a slinky!)
b) S waves - slower than P waves, they are shear, and travel perpendicular to the direction of oritentation
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How is the epicentre of an earthquake located?
Each wave (p, s, and l) travel at different speeds; their unqie velocities can be intersected to find the distance to the epicentre from one seissmograph. The distance forms the radius of a circle. The distance from the epicentre fromthree different seissmographs are used, and circles are formed using the distance as the radius. The location of the intersection is the epicentre of the earthquake.
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What is the primary focus of the Richter scale? How does it work? Is there a maximum?
Richter scale mainly measures the energy released by the earthquake.
It is exponential and limitless. Each sequential number is 10x the ampitude of the previous and releases 32x the energy. Therefore, two away, the amplitude of the wave is nearly 100x larger, and the energy is nearly 1000x larger.
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What was the highest recorded rating of an earthquake on the Richter scale to date?
8.9
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What is moment magnitude? What does it take into consideration, and which kind of earthquakes is it best for?
Moment magnitude is best for larger earthquakes. It takes rock strength, the size of the fault, and the displacement all into consideration.
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What was the highest rating on the Moment magnitude scale? How about the Tsunami on boxing day?
9.6 was the highest, 9.5 on boxing day
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What are the five ways by which earthquakes cause destruction?
1. Ground vibrations
- buildings have trouble withstanding horizontally propogating waves - sediment does not withstand it well, hard bedrock is better at withstanding it
2. Liquifaction
- normally soft sediment becomes unstable and turns to MUD, buildings sink, submerged rock emerges, etc.
3. Tsunamis
A seissmic sea wave may be caused following the rupture of the sea floor. Wave grows as it reaches towards the shoreline and the ocean floor becomes shallower
4. Landslides/Ground subsidence
- ground lowers, and landslides may occur if there are sedimentary hilly areas around
5. Fire
- often caused by rupture of electrical lines and broken gas lines, worsened by broken water lines
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How are earthquakes predicted in the short-term? How about in the long-term?
Short-term - not yet technology to predict them
Long-term - seissmic gaps = earthquake is overdue due to a lack of seissmic activity/buildup of strain
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How do seissmic waves propgate through the earth's interior?
Crust-mantle (Liquid) - p and s waves both accelerate
Mantle - core (Liquid) - p waves slow down, s waves disappear
Inner core (solid) - p waves accelerate once again
NOTE: all waves propogate from the epicentre
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How is the ocean floor mapped?
Through the use of multibeam sonar, and satellite imaging.
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What is the passive continental margin, and what three components is it made up of?
Passive continental margin = not associated with boundaries, volcanoes, or earthquakes
1. Continental shelf - approximately **130 m deep**, average of **80 km** wide a gentle slope, valuable for OIL and GAS, FISHING, and SAND/GRAVEL DEPOSITS.
2. Continental slope - approximately **20 km** wide, with a steeper slope than the continenta shelf. IT IS THE BOUNDARY BETWEEN OCEANIC AND CONTINENTAL LITHOSPHERE.
3. Continental rise - formed due to deposits of sediment, in GRADED BEDDING. Caused by turbidities from turbidity currents and deep sea fans.
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What is a submarine canyon and how is it caused? What does it do and where is it found?
Occurs at the continental slope. Submarine canyons are caused by ancient glaciation, when rivers flowed through the slope. Turbidity currents of sediment are caused by the canyons which form turbidity deposits. Turbidites currents form the continental rise.
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What is an active continental margin?
Active subduction zones, with an accretionary wedge formed of deformed sediment and fragments of oceanic plates.
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What is a deep ocean basin, and what percentage of the earth's surface does it make up? What three components make up a deep ocean basin?
Deep ocean basin makes up ~30% of the earth's surface
1. Deep ocean trenches - formed at subduction zones, most occur around the Pacific margin
2. Abyssal plains - some of the flattest areas of earth, hide rugged terrain with deposits of graded bedding strata from turbidity deposits
3. Seamounts - underwater volcanoes, common near OCEANIC RIDGES, form pillow lavas, cause sea floor spreading
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What is a coral reef? What is an atoll?
Coral reef - the skeletalremaisn of ancient corals, cemented by ALGAE SECRETIONS over thousands of years, up to **45 meters deep**, require warm water as well as sunlight
Atoll - formed around the remains of a seamount that becomes inactive - seamount sinks into the sea floor, and coral grows upwards to remain in the sun
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What is the longest topographic feature on earth?
The Mid-Ocean Ridge
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What is an oceanic ridge and what two components make it?
1. Rift valleys - rise **2-3 km** above the ocean floor
2. Transform faults - cut through the rift valleys
Magma protrudes through the fault, causing sea floor spreading
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Within what time period was paleomagnetism discovered?
During WWII
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What type of rock displays paleomagnetism?
Basaltic rock
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What is paleomagnetism?
Magnetic minerals in basalt point to the existing magnetic poles at the time of ROCK CRYSTALLIZATION
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What is polar wandering?
Over the past 500 million years the magnetic poles of the earth have been reversed - shows diverging paths, poles have only migrated a little bit, therefore it can be used as a reference to deduce how much the continents have shifted
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What is sea floor spreading? How quickly does it occur?
Sea floor spreading occurs at sea floor ridges, in which material in the mantle is upwelled, causing se floor to MOVE TOWARDS THE TRENCHES, which CONSUME sea floor. Typically occurs approximately 5 cm/year, although faster in some places than others
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What are geomagnetic reversals?
Due to frequent reversal of the earth's poles, the ocean floor has regions of basalt with different polarities. APPEARS LIKE A STRIPED MIRROR IMAGE, COMING OUT FROM THE OCEANIC RIDGE. Stripes get older further away from the ridge
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Which Canadian discovered the striped-mirror image of geomagnetic reversal?
Lawrence E. Morely
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Who came up with the theory that the earth's continents are cut up into 7 different tectonic plates?
J.T. Wilson
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How many lithospheric, tectonic plates are there?
7
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What are the three types of plate boundaries?
1. Divergent - cause sea floor spreading by the formation of ridges, which are formed by magma upwelling
2. Convergent - occurs at subduction zones, oceanic lithosphere is consumed
3. Transform faults - faults that cut across oceanic lithosphere, where plates slide past each other - cuts ridges, perpendicular to their direction
BETWEEN TWO CUTS OF A TRANSFORM FAULT = ACTIVE
BEYOND RIDGE SEGMENTS = INACTIVE
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Where does the epicentre of a deep earthquake tend to be? Where does the epicenter of a shallower one tend to be?
Deep = near subduction zones
Shallow = near trenches and oceanic ridges
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What evidence exists for J.T. Wilson's tectonic plate model of the lithosphere?
1. Earthquakes - tend to occur at plate boundaries
2. Ocean drilling - sea floor gets deeper and older away from oceanic ridges, maximum age = **180 million years old**, sea floor continuously moves away from ridges, towards deeper trenches
3. Hotspots - seamounts and volcanic islands form a chain on a palte continuously moving over a MANTLE PLUME
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What is the cause of the movement of lithospheric plates?
Convection in the asthenosphere, caused by unequal heat distribution
