Modules 9-12 Flashcards
(155 cards)
1
Q
Uniformitarianism
A
Processes active in the environment today have operated since the beginning of earth’s history
2
Q
Relative Time
A
Sequences based on the relative position of rocks above/below each other
3
Q
Relative Dating
A
Can determine the order of events based on relative position of rocks
4
Q
Principle of Superposition
A
In undisturbed strata of sediment or rock, the bottom later is oldest, the top layer is youngest
5
Q
Principle of Original Horizontality
A
Sediments are deposited in horizontal layers; tilting and deformation happen later
6
Q
Principle of Lateral Continuity
A
Layers initially extend in all directions; later events (e.g. erosion, faulting) can separate layers
7
Q
Principle of Cross-Cutting
A
Intrusions, erosion, or faults are younger than the rock they cut through
8
Q
Principle of Faunal Succession
A
Some fossil species occur in unique time intervals, age of rock may be determined from those fossils
9
Q
Absolute Time
A
The actual time elapsed (usually in millions of years, for geologic time), most commonly measured using radiometric dating
10
Q
Radiometric Dating
A
Some isotopes of some elements cannot stay together indefinitely; they undergo radioactive decay, determine age by measuring the amount of “parent” atoms relative to the amount of “daughter” atoms
11
Q
Radioactive Decay
A
The nucleus of a “parent atom” decays to “daughter atoms” (releasing radioactive energy in the process)
12
Q
Half-Life
A
The time needed for half of the parent atoms to decay
13
Q
Geologic Time Scale
A
Summary timeline of Earth’s hsitory
14
Q
Eon
A
The largest unit of geologic time, divided into eras, then periods, then epoch
15
Q
Priscoan Eon
A
Began with Earth’s formation, part of the Precambrian supereon
16
Q
Archaean Eon
A
Single-celled organisms developed, part of the Precambrian supereon
17
Q
Proterozoic Eon
A
Current geologic eon (last 540 million years; roughly 12% of Earth’s history), began with Cambrian explosion: the appearance of abundant animal fossils
18
Q
Paleozoic Era
A
(“old life”) the appearance of fish, amphibians, reptiles, vascular plants. Part of the Phanerozoic eon
19
Q
Mesozoic Era
A
(“middle life”) dominated by dinosaurs and conifers; earliest birds, mammals, and flowering plants. Part of the Phanerozoic eon
20
Q
Cenozoic Era
A
(“recent life”) age of mammals. Part of the Phanerozoic eon
21
Q
Quaternary Period
A
Last 25 million years. Glacial and interglacial periods; anatomically modern humans. Divided into Pleistocene epoch and Holocene/Anthropocene epoch
22
Q
Rock
A
Assemblage of minerals bound together
23
Q
Mineral
A
Naturally occurring, inorganic substance with specific chemical formula, physical properties, and crystalline structure
24
Q
Crystalline Structure
A
Atoms arranged in a repeating pattern, often visible to the naked eye
25
Mineralogy
Study of the composition, properties, & classification of minerals
26
Silicate Minerals
Contain silicon (Si) and oxygen (O). Makeup 95% of the earth's crust. Rocks formed from silicates are usually strong and relatively resistant to weathering and erosion
27
Quartz
Made of silica (SiO₂); the second most common mineral in Earth's crust. Color is often transparent or white, can be many colors. Common in granite rock, gneiss rock, and beach or desert sand. Common silicate mineral
28
Feldspar
Most common class of mineral in the earth's crust. Contain aluminum, potassium, sodium, or calcium. Color is usually pink, cream, or grey. Common silicate mineral
29
Mica
Family of minerals that breaks into flakes and sheets. Shiny, partly transparent; clear, silvery-grey, green, brown, or black. Common silicate mineral
30
Mafic Minerals
Contain magnesium or iron, plus Silicon (Si) and Oxygen (O). Usually dark-colored. Common silicate mineral
31
Carbonate Minerals
Contain carbonate CO₃ (Carbon and 3 Oxygen atoms) bonded with another element. Commonly a cream or grey color; sometimes clear
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Oxide Minerals
Contain Oxygen bonded with a metallic element, like iron, copper, or titanium
33
Sulfate Minerals
Contain sulfate SO₄ (Sulfur and 4 Oxygen atoms) combined with some other element
34
Sulfide Minerals
Metallic element and sulfur atom. Commonly form in veins of ore
35
Salt Minerals
E.g., halite (NaCl, table salt); fluorite (CaF₂, calcium fluoride)
36
Chemical Composition
Every mineral has a specific chemical composition. However, in some cases, two or more different minerals may have the same particular combination of elements
37
Mineral Properties
Hardness, cleavage/fracture, color and streak, luster, magnetism, feel, odor or taste, and chemical reaction
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Luster
Surface sheen of a mineral
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Color
Most easily observable property of a mineral
40
Streak
Color of powdered form when scraped against a porcelain plate. Usually consistent for a specific mineral
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Hardness
Each mineral can scratch certain other minerals, but not vice versa
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Mohs Hardness Scale
The hardness of a mineral can be tested by trying to scratch it with a known object or known mineral
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Cleavage
The tendency of minerals to break along plane surfaces
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Fracture
When minerals do not break on a clean plane but break in some other characteristic way
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Magnetism
A few minerals are attracted to magnets and/or will attract a compass needle to them. E.g., magnetite, pyrrhotite
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Chemical Reactions
Certain carbonate minerals 'fizz' if they are exposed to acid. E.g., hydrochloric acid or acetic acid (vinegar))
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Fluoresence or Phosphorescence
Some minerals glow when exposed to black light, or after being exposed to sunlight
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Taste or Feel
E.g., halite (sodium chloride) is main component of table salt, e.g., sylvite has a bitter taste, e.g., bentonite (a volcanic clay) has a creamy feel
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Sound
E.g. phonolite has distinct sound when struck with a hammer
50
Igneous Rocks
Rocks formed directly from magma or lava (Ignis="fire")
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Sedimentary Rocks
Rocks that have formed from the deposition and compression of rock and mineral fragments or by precipitation of material in solution, Sedimentum= "settling" (Latin)
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Metamorphic Rocks
Rocks that have been created from transformation by heat and/or pressure from existing rocks
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The Rock Cycle
Describes transitions between the 3 types of rocks
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Magma
High-temperature molten rock, below surface
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Lava
Molten rock, that has spilled onto surface
56
Intrusive Igneous Rocks
Formed from magma that cools and solidifies slowly, below the surface
57
Extrusive Igneous Rocks
Formed from lava that has reached the surface, as lava flows or volcanic eruption; cools quickly
58
Igneous Rocks are Classified Based on:
Mineral composition and grain size
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Felsic Minerals
FELdspar and SIliCa; High in silica, aluminum, potassium, sodium; Low melting points, light-colored, and less dense
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Mafic Minerals
MAgnesium and FerrIC (Iron) compounds; High in magnesium and iron, with some silica; High melting point, dark-colored, and more dense
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Ultramafic Minerals
Very high in magnesium and iron
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Large Grain-size
Intrusive igneous rocks cool slowly
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Small Grain-size
Extrusive igneous rocks cool quickly
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Obsidian
An extrusive igneous rock that cools very quickly (by contact with cold seawater), resulting in glass-like rock with no visible grains
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Pumice
An extrusive igneous rock that has air pockets formed when gases escape from lava giving it a frothy texture; very lightweight; floats in water
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Pluton
Any body of intrusive igneous rock
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Batholith
Massive, irregular-shaped pluton, that melted and assimilated much of the rock structure it invaded
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Sill
Magma spread between pre-existing strata, forming horizontal layers
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Dike
Magma cut across pre-existing strata of rock, forming a vertical wall
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Laccolith
Magma filled underground chamber, pushed overlying strata up forming a lens-shaped body of rock
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Lithification
Process of cementation, compaction, and hardening that turns loose sediment into rock
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Clastic Sedimentary Rock
Made from fragments or clasts of rocks which are compacted and cemented together
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Chemical Sedimentary Rocks
Formed from dissolved minerals that are transported in solution and then recrystallize out as rocks
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Organic Sedimentary Rocks
Contain deposits of plant or animal remains
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Compaction
As layers of clastic sediment accumulate, lower layers are compressed by the weight of upper layers; amount of pore space decreases, as air and water are expelled
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Cementation
Dissolved minerals precipitate out of solution, recrystallizing in pore spaces and forming a natural cement that holds the clasts together
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Clasts
Fragments of rock or mineral; size determines how far they are transported before being deposited (large clasts settle out first)
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Evaporites
Rocks that form as water evaporates, leaving salts behind; e.g., halite (table salt), gypsum, epsomite
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Contact Metamorphism
Intruding magma heats and transforms (but doesn't completely melt) adjacent rock
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Regional Metaphorism
Tectonic activity creates intense pressure, altering the mineral structure
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Rock Cycle: Below Surface
Heat and pressure
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Rock Cycle: Above Surface
The exposed rock is weathered, transported, and deposited as sediment
83
Burial and Pressure
Compression and cementation, forming sedimentary rock
84
How to Tell Rock Types Apart: Igneous
Grains interlock, minerals look fused or crystallized together
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How to Tell Rock Types Apart: Clastic Sedimentary
Grains touch but don't interlock, held together by cement
86
How to Tell Rock Types Apart: Chemical Sedimentary
Interlocking grains, the difference from igneous in the types of minerals
87
How to Tell Rock Types Apart: Foliated Metamorphic
Twisted, folded, or swirled, or breaks into-thin layers
88
How to Tell Rock Types Apart: Non-Foliated Metamorphic
Harder to ID: often based on mineral groupings
89
Seismic Tomography
Image earth's interior using earthquake waves
90
Inner Core
Solid (due to high pressure, in spite of high temp), mostly iron and nickel
91
Outer Core
LIquid (slightly lower pressure allows melting at high temp), mostly iron, with a little nickel
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Earth's Magnetism
Caused by the flow of liquid outer core around the solid inner core
93
Polar Wandering
The slow, erratic movement of magnetic poles, relative to the rotation axis
94
Lower Mantle
Solid, rigid rock- due to pressure
95
Upper Mantle
Solid, but not completely rigid
96
Asthenosphere
Plastic rock (solid, but deforms and flows like dough), some molten hot-spots (syrupy consistency)
97
Uppermost Mantle
Solid and rigid; part of lithosphere, less then 100 km thick
98
Crust
Outermost layer of earth
99
Oceanic Crust
Denser than continental crust, mostly basaltic rock
100
Continental Crust
Less dense than oceanic crust, more granitic rock, with some basaltic rock
101
Lithosphere
Outer shell of rigid rock, includes all of the crust, plus the uppermost mantle. Thicker under continents, thinner under oceans
102
Lithosphere/Asthenosphere Boundary
Based on rigid vs. plastic consistency. The rigid ____ moves around atop ____ is plastic
103
Crust/Uppermost Mantle Boundary
Based on a sharp change in density. The ___ is less dense than the ____.
104
Isostasy
The equilibrium state of the lithosphere floating on the asthenosphere
105
Mid-Ocean Ridge
Forms from upwelling magma, two sides of seafloor spread laterally apart
106
Subduction Zone
Ocean crust sinks under some other crust
107
Seafloor Spreading
As plates diverge, new oceanic crust will be continually added at the mid-ocean ridge
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Theory of Plate Tectonics
Encompasses continental drift, sea-floor spreading, and movement of crustal plates
109
Divergent Plate Boundary
Plates spread apart; magma rises, forming new crust. Continental crust is uplifted and stretched; forms rift valley and block mountains
110
Convergent Plate Boundary
Plates collide, crust destroyed, mountain building
111
Transform Plate Boundary
Plate move past each other, crust neither formed nor destroyed
112
Continental Shields
Large, ancient, low-lying expanses of crustal rock that form the core of continental landmasses
113
Orogenic Belts
Regions of current or former mountain-building along margins of continental shields
114
Orogenesis
Process of mountain building along a n active continental margin, via volcanism and tectonic activity
115
Volcanism
Extrusion of magma at earth's surface
116
Tectonic Activity
Bending (folding) and breaking (faulting) of the lithosphere, usually causing metamorphism
117
Orogeny
A mountain-building episode (over millions of years)
118
Active Continental Margins
Where two plates converge; tectonically active
119
Passive Continental Margins
Where continental crust and oceanic crust are on the same plate
120
Geomorphology
The study of the formation and evolution of earth's landforms and landscapes, through endogenic and exogenic processes
121
Landform
A single, typical unit that forms part of the general topography. E.g., a hill, a mountain, a valley, a dune
122
Landscape
A collection of landforms (often the same type of landforms). E.g., mountain chain, series of ridges and valleys, a string of dunes
123
Endogenic Processes
Driven by internal forces of heat and convection in the earth; raise continental surfaces up
124
Exogenic Processes
Driven by external forces like rivers, waves, ice, and wind; Usually lower continental surfaces
125
The Geologic Cycle
Includes interactions among the hydrologic cycle, the rock cycle, and the tectonic cycle
126
Hydrologic Cycle
Movement of water; drives weathering, erosion, transportation, and deposition of rocks and minerals
127
Tectonic Cycle
Recycling and renewal of earth's crust; the crust is destroyed at subduction zones, new crust is created at the rift zones and by upwelling
128
Rocks are subjected to 3 types of stress, which are expressed at the surface in different ways. The three types are:
Tension(or extension), Compression, and Shear
129
Whether a rock breaks depends on:
Composition of the rock and the amount of stress
130
Folding
Bending and deformation of beds (or layers) of rocks resulting from compressional forces
131
Monocline
Landform in which deformation results in beds that are inclined in a single direction, in a step-like bend; Occurs because of relatively small amount of compression
132
Anticline
Folded rock layer in arch- or ridge-like structure; Layers slope downward from central axis
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Syncline
Folded rock layers in rough- or valley-like structures; Layers slope upward from central axis
134
Symmetrical Folds
Axial plane is vertical
135
Asymmetrical Folds
Beds in one limb dip more steeply than those in the others
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Overturned Folds
Both limbs dip in same direction but one limb has been tilted beyond vertical
137
Four Combinations of Anticlines and Synclines
Anticlinal valley, anticlinal ridge, synclinal valley, and synclinal ridge
138
Identifying ridge of valley is based on:
Surface topography
139
Identifying an anticline or syncline requires:
Looking at the layers of rock, not just the surface topography
140
Plunging Folds
The axis (ridge of trough) of the fold dips (or plunges) downward at an angle
141
Hogsback Ridges
Sharp ridge formed from edge of gently tipped, resistant rock that overlies softer rock; the softer rock erodes, forming a steep cliff
142
Fault
A fracture in crustal rock, involving slippage of rock on one side of the fracture relative to the other side; Results when rock is stressed beyond its ability to remain a solid unit
143
The Resulting Fault of Compression Stress
Reverse or thrust fault
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The Resulting Fault of Tension Stress
Normal or tension fault
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The Resulting fault of Shear Stress
Strike-slip or transform fault
146
Reverse (Thrust) Faults
Caused by compression; causes shortening of crust as one block rides over the other; hanging wall is thrust up above the footwall; exposed part of hanging wall will typically erode.
147
Normal (Tension) Fault
Causee by tension (pulling); causes lengthening of crust as blocks pull outward; hanging wall is thrown down relative to the footwall.
148
Fault Scrap
Cliff formed by faulting
149
Overthrust Fault
A reverse/thrust fault in which the fault plane is nearly horizontal
150
Horst or Graben Landscape
Blocky landscape resulting from multiple normal faults acting in concert; often occurs in rift-zones with tension stresses on landscape
151
Horst
Upward-faulted block
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Graben
Downward-faulted block
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Strike-Slip Fault (Transform Fault)
Caused by lateral shearing; movement is lateral; horizontal layers are not displaced on opposite sides of fault
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Left Strike-Slip Fault
Opposite side shifts to left
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Right Strike-Slip Fault
Opposite side shifts to right
