Geology Study Guide: Final Exam
Earthquake the vibration of Earth produce by the rapid release of energy. elastic rebound theory States that our plates/fault lines are elastic that can bend and build up strain until is no longer can hold, and then there is a sudden release of energy (the earthquake). The build up of energy takes tens to hundreds of years, but an earthquake takes seconds to a few minutes. The buildup of strain and the release of energy describe how an earthquake works.
epicenter above the Earth’s surface, hypocenter is below the Earth’s surface focus Where an Earthquake begins (also called hypocenter)
geothermal gradient increase in temperature as you go deeper into the Earth, it’s hotter towards the core.
intensity measure of the severity of damage. Measured by Mercalli Scale Love wave (Lwave) waves that move back/forth (surface waves)
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Magnitude the amount of energy that is released as the rock breaks (ground movement). Measured by the Richter Scale. If you want to learn more check out What is humanistic psychology?
Modified Mercalli Scale measurements of the amount of intensity of an earthquake Pwave – primary waves that are the first to arrive. Fastest waves and travel through solids, liquids, and gasses. (Body Wave)
Rayleigh wave (Rwave) waves that move up and down (surface wave) Richter Magnitude Scale logarithmic scale used to measure the magnitude of an Earth quake. Measured in thousands.
Seismograph instrument that records seismic waves
Seismology the study of seismic activity within the Earth
Seismicity the occurrence or frequency of earthquakes in a region. Swave – second waves to arrive. They travel only through solids. (Body Wave) Swave shadow zone an area where the S waves are not received. Through this we know that the inner core is liquid.
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Tsunami seismic sea waves, usually happens after an earthquake
Causes of earthquakes
Sudden slip along a fault (most common), sudden motion along newly formed crustal fault, a sudden change in mineral structure, movement of magma in a volcano, volcanic eruption, giant landslide, meteorite impact, nuclear detonation.
It takes a minimum of 3 seismographs to measure an earthquake.
Branch of science concerned with earthquakes/seismic waves and related phenomenon. Types of seismic waves
Body Waves occur below the Earth’s surface. S waves(back/forth motion) and P Waves (pushpull, compress and expand motion).
Surface Waves waves on Earth’s surface. L waves (move back and forth) and R waves (move up and down).
Intensity vs. magnitude
Intensity measured by Mercalli Scale and measures the severity/damage of the earthquake Don't forget about the age old question of What is geography?
Magnitude measured by the Richter Scale and measures the amount of energy released as the rocks break (amount of ground motion)
Earthquakes are linked to tectonic plate boundaries.
Most occur in the Ring of Fire or the CircumPacific Belt (subduction zone) Hazards
Ground shaking, Roads collapsing, bridges topple, masonry (bricks) walls break apart Liquefaction: waves liquefy waterfilled sediments (quicksand/quickclay/sand volcanoes) Prediction
Short range predictions NO.
Long range predictionsKINDA By:
Reoccurrence Interval (average time between seismic events), historical records, geological evidence that requires radiometric dating.
Seismic Gap segments of a fault zone that have not had a recent seismic occurrence. Mitigation
Lessening the intensity or severity of an Earthquake.
Anchor bolt/ Cable, Cross Beams, Rollers/Springs to lessen the impact of earthquakes. Safety measures.
Anticline a fold that looks like an A. Beds dip away from each other. Oldest rocks of anticline are in the middle.
Basin double plunging syncline.
Compressional stress form folds, pushing together of rocks (convergent) continental accretion adding to continental material by plates running into each other deformation rocks being deformed due to stress. 3 types (Compressional, Tensional, Shear) If you want to learn more check out What is patriarchy?
dip the angle/direction that a bed is tilted. The maximum angle of an inclined plane. dome double plunging anticline
fault crack or a fracture of the Earth. Brittle deformation
fold Layers that are bent by slow plastic flow. Formed by compression, meaning it has been shortened. Ductile Deformation
footwall wall of fault that resembles a wall you could climb. Don't forget about the age old question of What is endothermy?
Fracture is any separation in a geologic formation, such as a joint or a fault that divides the rock into two or more pieces.
hanging wall fault wall that resembles a wall you could hang from. moves down in a tensional environment (normal fault)
isostatic rebound rebounding from where erosion is taking place joint fractures (cracks) where there is no rock offset (have not moved, just cracked similar to weathering) From in response to compression, tension, and shearing. monocline – folds that only have one limb (not anticline or syncline like) normal fault extension, hanging wall moves down
orogeny the process of mountain building
principle of isostasy mountains are uplifted from underneath the surface as their tops are weathered away.
reverse fault hanging wall moves up. Goes against gravity. Shortening shear stress sliding past each other, (transform)
stress the forces that deform rocks
Principle of Original Horizontality rocks are originally laid down horizontally. strike perpendicular. The intersection of a horizontal plane with an inclined plane strikeslip fault shear stress, hanging wall moves to the side
syncline a fold that looks like a smile. Beds dip inward/towards each other. The youngest rocks are in the middle
tensional stress moving away from each other, stretching/thinning (divergent exotic terrane crustal thickening happens when land from other plate boundaries collides with a continent.
thrust fault low angle (horizontal) reverse fault, hanging wall moves up
Evidence of tectonic activity
Geological processes of Uplift, Metamorphism, and Deformation
What is deformation?
General term that refers to all changes in he original form and/or size of a rock body 3 types of deformation
compressional, tensional, shear
Brittle vs. ductile
Brittle rocks that break into smaller pieces as a result of stress It’s breakable (faults/joints)
Ductile type of solidstate flow that produces a change in shape of an object without fracturing it’s bendable (folds, domes, basins)
Causes of continental deformation
Stress, weathering, erosion, subdution, plate tectonics
Isostasy Gravitational balance of mountains. As the top of mountains are weathered, there is a rebound effect that happens from underneath the surface and the mountains are uplifted.
Abrasion the “sandblasting” of rock by the particles in fast moving water eroding
alluvial fan build out at canyon mouths
alluvium general term for sediment deposited by moving water
bed load load at the bottom of the stream, consist of the biggest pieces of rocks/material. Requires a higher energy to move
braided stream more sediment available than water can transport, closer to mountains. delta where rivers end and enter into the ocean (standing water)
discharge – measure of the volume of water that passes any location of a certain stream at an interval (can always change)
dissolved load made up of small materials (ions) that can be dissolved and transported with lower energy
divide separates basins
floodplain an area of low-lying ground adjacent to a river, formed mainly of river sediments and subject to flooding.
fluvial sediment sediment in or deposited by a river system
gradient channel slope decreases as you go from headwaters to the mouth hydrologic cycle the cycle of water through Earth’s environments
meandering stream streams that transport much of their load in suspension in sweeping bends. More water than sediment, sweeping bends that resemble snakelike curves. natural levee form during floods. The coarsest sands are deposited first, then fine grains.
oxbow lake is a U-shaped body of water that forms when a wide meander from the main stem of a river is cut off, creating a free standing body of water.
point bar slowest flow on inner bend of river. It accumulates sand and deposition happens.
runoff – how the channel flow starts, sheet like flow of water from rain or other sources that covers the land surface
suspended load contains clay particles, medium sized particles in flow, requires a lower energy to move
sediment load amount of sediment carried by the water. Material moved by running water load.
Cut bank where the fastest flow happens, on the outer band of rivers. Channel will migrate towards cutbank.
Hydrologic cycle processes
Evaporation, Transpiration (plants release water as a vapor into the air), Precipitation, Sublimation, Infiltration (into the ground), Melting, Runoff
Streams/rivers are concentrated flows of water in channels. Stream are crucial for humans.
Permanent streams water flows all year, at or below water table, humid or temperate climates
Ephemeral streams dry up part of the year, above the water tables, dry climates
Begins from runoff, runoff becomes concentrated into a channel.
Channel roughness and slope decrease from headwaters to mouth. Discharge, channel size, and flow velocity increase from headwaters to mouth. 3 things running water does
Transports, deposits, erodes
Form when a stream enters standing water, they are not stationary and can move. Floods
A flood is when flow exceeds channel capacity.
Flood waters devastate property and ruin buildings. Flood risks can be calculated as probabilities (flood zones)
ConvectionDrives plate motion. Circulation due to change in temp when heated. How plate tectonics and seafloor spreading works.
convergent plate boundary plates coming together, subduction occurs. Volcanoes/Mountains form. Destroys crust.
divergent plate boundary plates moving away from each other, new crust forms (Basalt) Oceanic Ridges
hot spot mantle plume that occurs within a plate.
oceanic ridge formed form a divergent plate boundary, where new crust forms. paleomagnetism old iron deposits aid in information on where Paleomagnetic North was. Iron minerals archive the magnetic signal at formation.
Pangaea continents were all once connected as a supercontinent. It was not the only super continent in history.
plate tectonic theory Plate tectonics helps to explain: earthquakes, volcanic eruptions , formation of mountains, location of continents, location of ocean basins. Theory that the Earth’s outer crust is made up of plates (oceanic and continental).
seafloorspreading Evidence lies in magnetism in the sea floor. Convection is the mechanism.
transform fault horizontal motion of faults created by transform plate boundary. Most transform faults connect ocean ridge segments.
transform plate boundary plates slide past each other, creates fault valleys.
2 types of lithosphere
Who is Alfred Wegener?
Gave us the idea of Pangea and continental drift.
3 types of plate boundaries and characteristics of each
Convergentsubduction occurs, oceanic trenches, volcano arcs form (continentocean) mountain arcs form(continentcontinent), volcanic island arcs (oceanocean) DivergentBasalt forms, oceanic ridges, continental rift valleys, volcanic activity, earthquakes
Transformcreates fault valleys, earthquakes are common
Process of convection
Circulation of heat from Earth’s core that drives plate motion.
carbonate minerals minerals that contain carbon (CO3)2 Derived from shells and marine organisms precipitated from sea water. ex: limestone
cleavage tendency to break along planes of weak bonding that produces shiny surfaces. Hardness resistance to abrasion/scratching. Measured by Mons Scale of Relative Hardness. Diamond=hardest Talc=weakest
luster – appearance in light (metallic or nonmetallic)
mineral natural occurring, inorganic, solid, crystalline structure with a definite chemical composition. Building blocks of rocks. Divided into classes based on chemical composition.
silica tetrahedron SiO4 (shape of silicates) 4 oxygen to one silica Silicate mineral that is composed of silica and oxygen
Physical Properties of minerals:
Luster, Color, Streak (color of a mineral in powder form), hardness, cleavage, fracture (absence of cleavage), specific gravity (ratio of weight of mineral to water)
Others: magnetism, reaction to HCL acid, malleability, double refraction, taste, smell, elasticity.
Classification of Minerals:
Done by composition. Minerals can be separated by the principle anion or anionic group. Earth’s majority of minerals are Silicates/Carbonates.
aphanitic texture not grainy/crystallized. Rapid coolingno time for crystals to form. (Rhyolite, Andestite, Basalt)
felsic composition high amounts of silica, lighter color
igneous rock – cooling/crystallizing of lava or magma.
lava –extrusive flow from volcano
mafic composition rich in iron/magnesium, darker color
magma – intrusive flow from volcano, underground
phaneritic texture grainy crystals, formed intrusive with lots of time to cool (Granite, Diorite, Gabbro)
plutonic (intrusive) rock magma cools/crystalizes underground
viscosity the resistance to flow. Low viscosity: runny lava/mafic magma High viscosity: thick, stiff flow of lava/felsic magma
volcanic (extrusive) rock lava flows coming out of volcano hardening or pyroclastic debris (fire rock ejected from volcano or volcanic ash)
Lava vs. magma
Lava is found at Earth’s surface, magma occurs beneath the surface How are igneous rocks classified?
We classify igneous rocks by texture/composition
Extrusive vs. intrusive
Lava flow (extrusive) stream or mound of cooled lava melt
Pyroclastic debris fire rock ejected form volcano, volcanic ash, or volcanic rock Plutons (intrusive) magma chamber that cools underground
Felsic (highest amounts of silica), Intermediate, Mafic, Ultramafic (highest amounts of iron/magnesium)
Aphanetic no grains/crystals, extrusive no time to cool
Phaneritic grains/crystals, intrusive lots of time to cool
Porphyritic mixes of sizes/crystals, extrusive complex cooling history Chapter 5:
aa – Hawaiian word that is describing Basalt that solidifies with a jagged, sharp, angular texture.
basalt plateau when a volcano erupts, basalt is formed and the area around the volcano can become a basalt plateau
cinder cone smallest volcano type, conical piles of tephra (pyroclastic debris) circumPacific belt Ring of fire where the most volcanoes are due to the tectonic boundaries creating subduction zones
composite volcano (stratovolcano) largest volcano, steep slopes, cone shaped crater a dip in a volcano, volcano crater
pahoehoe –Hawaiian word describing Basalt with a glassy, ropy skin texture shield volcano –slightly dome shaped, lateral flow of basaltic lava (not very high) volcano – An erupting vent through which molted rock surfaces
Where does igneous activity occur?
At plate boundaries. MidOcean Ridges, convergent (subduction zones), divergent, hot spots
Types of volcanoes and eruption styles; Explosive vs. nonexplosive eruption styles Quiescent produce lava flows
Explosive blow up (ash clouds and debris thrown)
Shield Volcano quiescent basaltic lava flow
Cinder Cone lava shoots straight up into the air, not much of a flow (andesitic or felsic lava)
Stratovolcano felsic or rhyolitic lava, explosive volcano
chemical weathering –weathering through an alteration of chemical composition erosion –removal of weathered materials
mechanical weathering – mechanically alerting the size of materials parent material original rock material
regolith –layers of weathering products on Earth’s surface.
soil –organic bearing regolith that supports plant life (organic means having living organisms)
soil horizon distinct layers of soil that differ in texture, structure, composition and color. Orange Apes Eat Boston Crème (Donuts) order from top soil to bottom weathering physical/chemical process that alters rocks and minerals.
Relationship between chemical can mechanical weathering
Weathering is an essential part of the rock cycle. It is responsible for the formation of soil.
Mechanical weathering pieces keep composition and increase surface area. The more surface area available the more chemical weathering can happen.
Greater surface area=more effective weathering
What is soil and how does it form?
Soil is organic bearing regolith that supports plant life, meaning it houses living organisms. Soil is formed from weathered material (broken down rock). It is formed from the top down.
Factors that control soil formation
Climate and Soil climate is the most important factor of soil formation. Chemical processes operate faster where there is warm and wet climate. Tropics will have the thickest amount of soil, where deserts/artic will have the least.
Parent Material chemically stable rock will have less soil formation (like quarts) Organic activity humus comes form organic activity (microorganisms/plant root nutrients)
Relief/Slope if there is a slope, soil will be less likely to form there bc of gravity Time more time=more erosion/weathering=more soil
biochemical sedimentary rocks rocks that are formed from sediment derived from biological processes.
carbonate rock Clacite, made of calcium carbonate. The larger grouping of rocks that we refer to as Limestone.
chemical sedimentary rock rocks made by chemical processes or the precipitation of ions in a solution
detrital sedimentary rock rock that derives from weathering of preexisting rock. Clastic texture (composed of clasts)
fossil tangible remains and traces of ancient life. Usually found only in sediments and sedimentary rocks. Important for determining depositional environments. Lithification sediment becomes sedimentary rock by compaction, cementation, or both Sediment any solid that settles to a bottom of a liquid
sedimentary rock –products of mechanical and chemical weathering
What is sediment?
Any solid that settles to the bottom of a liquid.
Types of sediment
Detrital/Chemical or Biochemical
How are the different types of sedimentary rocks formed?
Detritalforms from weathering of preexisting rock
Chemical Form from the precipitation of ions in solution (limestone, rock salt) Biochemicalrock derived from biological processes/organisms (shells) Classification of sedimentary rocks
Detrital rocks are classified by grain size. The biggest pieces of rocks (grains) you will find will be the closest to where they came from (parent material)
Chemical/Biochemical sedimentary rocks are classified by composition/texture
contact (thermal) metamorphism metamorphism due to contact with or proximity to an igneous intrusion
foliated texture any planar arrangement of mineral grains or structural features within a rock (driven by compressional stress)
heat the most common/important agent of metamorphism. Sources of heat include: Lava, Magma, Deep burialgeothermal gradient
metamorphic rock added heat/pressure to sedimentary rocks. They are some of the oldest rocks on Earth
metamorphismthe transitions of one rock into another by temperatures and or pressures unlike those in which it formed.
nonfoliated texture metamorphic rocks that lack foliation
Agents of metamorphism
The agents of metamorphism include: Heat/Pressure (increase with depth: confining pressure is equal on all sides, differential pressure is not the same amount of pressure on
all sides), and Chemically active fluids (that come from a plume underground, the fluids will be hot.)
Causes of metamorphism
Temperature/pressure (main causes) and Chemically active fluids (small scale) Metamorphic Textures
Foliated (slate, phylite, schist, gneiss) or Nonfoliated (marble, quartzite, anthracite)