ESC 1000 EXAM 2
_____(uranium, carbon 14) Cannot be used for the radioactive isotope dating in______?
Carbon 14 cannot be used for the radioactive isotope dating in Igneous rocks or Metamorphic rocks
What is the order of arrangement and the characteristics of each interior region? Earth's Interior regions
Compositional Regions- rock compositional differences 1. crush: ocean=basalt or continents = granite 2. mantle = peridotite. 3. core = Iron with some nickel Physical Regions - seismic wave travel differences caused by changes in temp. and pressure with depth. 1. Lithosphere=brittle rocks 2. Asthenosphere=plastic rocks 3. Outer core = liquid 4. Inner core = solid
_____ regions of the earth's interior is made up of ____
Core=iro Mantle=peridotite ocean crust=basalt continental crust =granite
____ proposed the concept of ____ (3)
Cuvier proposed the concept of Catastrophism Hutton proposed concept of Uniformitarianism and Cross cutting relationships Smith proposed the concept of Faunal Succession Steno proposed original horizontality and superposition
What is the distinction between an earthquake and fault creep in relation to the elastic rebound? (Istanbull) "bending of a meter stick and it snapping back into place" Elastic Rebound: (h.f Reid) 1. friction locks up the fault blocks allowing strain/stress to accumulate in the rocks. 2. accumulated stress overcomes the friction, movement occurs along the fault, deformed rocks "snap back" and generate vibrations with or without surface displacement.
Earthquake: vibrations caused by the release of energy initiated by movement along a fault. Fault Creep: Gradual movement of a slipping fault. Many weak earthquakes. Not enough elastic rebound stress can accumulate for a strong quake. a bunch of little quakes release energy. the longer u go without a quake the bigger it will be when it happens to release a lot of energy.
___ are the speed, amplitude and motion characteristics of ___ (P,S,L) waves
Fastest compression and extension, low amplitude is the speed amplitude and motion characteristics of P-Wave, Intermed. speed, whipping motion, low amplitude = s wave slowest whipping and rolling high amplitude = L wave
What is the distinction between an earthquake's focus and epicenter?
Focus: point where the initial fault [movement occurred] (hypercenter) Epicenter: Point on the Earth's surface vertically [above the focus]
who is responsible for establishing the theories and ideas concerning seismic activity?
G. Mercalli Scale: Mercalli: compared damage to the strength Uses Roman Numerals. how the damage left behind compares to the strength. Richter Scale: Charles Richter, uses Arabic numbers 1-10 Magnitude - A measure of the amount of energy released by an earthquake. A logarithmic 32 fold scale-including both frequency and amplitude. 32x32=1024
Elastic Rebound Theory
H.F Reid Friction locks up fault blocks allowing strain/stress to accumulate. Accumulated stress overcomes friction movement occurs along the fault deformed rocks snap back and generate vibrations with or without surface displacement.
___ conceptualized the idea of ____
H.F reid conceptualized the idea of elastic rebound theory
What are the absolute dates found on the Geologic Time Scale as indicated in class?
IGN = billion of years Era: Precambrian Eon {1. Hadean 2. Archean 3. Proterozoic} Phanerozoic Eon {4. Paleozoic= before dinos 5. Mesozoic= during dinos 6. Cenozoic= event extinction of dinos}
3 noted laws of geology reconstructed to the geological sequence of events diagram ex: Cenozoic = age of the mammals = sabretooth cats, snakes, no dino. mesozoic = age of reptiles = dinos, rodents, no saber tooth cats.
Law of Superposition(Nic Steno): an undisturbed sequence of rock layers that the bottom is the oldest and the top is the youngest Law of Original Horizontality (nic steno)(sed rock lava flow): rock layers originally deposited as flat layers-present non-horizontal (folded rock layers) have been moved into that now non horizontal position Law of Cross-Cutting Relationships (Hutton): any cross cutting body is.... younger and occured after the top layer and does intersect...... is older than occured before the oldest bottom layer does not intersect. = The oldest rock layer does Not Cross cut. The youngest rock layer IS Cross cut. Principle of Faunal (and floral) Succession = fossil succession: If the rock layers on the bottom are older (superposition) than the fossils in the rock layers near the bottom must also be older. There are recognizable assemblages of fossils (not randomly mixed) Geologic time units. Ex. Age of the Reptiles+animals who ruled that time.
_____ regions of the earth's interior will be made up of rocks that behave _____(spongey, brittle) because of the temperature and pressure conditions
Lithosphere regions of the earths interior will be made up of rocks that behave brittle because of the temperature and pressure conditions
What is the difference between magnitude and intensity? (The Mercalli and Richter Scales)
Mercalli measures damage compared to strength Richter measures amount of energy released by an earthquake (local and moment)
What are the characteristics of the three seismic waves discussed? P-primary S-secondary L-surface
P-wave/Primary: fastest with low amplitude and compress and exstension S-wave/secondary: Intermed with low amplitude and side to side whipping motion L-wave/Surface: Slowest with high amplitude and whipping and rolling motion
How is a seismic shadow zone created?
P-waves refracting upon changing from liquid to solid making shadow zones
What is the Radioactive decay of uranium to lead?
Rdiactivity- breaking apart (decay) of unstable isotopes of elements at a constant rate. Loss of protons (atomic # changes) now not the original element. Radioactive--------------------to--------stable Parent Isotope Uranium ----> to ----> daughter isotope or Uranium----------to---------lead
What is the fundamental difference between 'relative' and 'absolute' dating methods?
Relative dating: Determination of the chronological sequence of events. Formation, oldest on bottom/1st and newest on top last. Absolute dating: The Quantitative Age of an Event is Determined. -More accurate -(uses atomic number and radioactivity established half life decay ratio) -Absolute Age = # of half life X the rate or speed the isotope decays
How do ranges of absolute dates be obtained for sedimentary rock layers?
Sedimentary rocks are made up of multiple rocks there for multiple dates. Can not be directly dated Fragments originate from rocks of multiple ages Absolute dates for sedimentary rock layers= 1.superposition of sedimentary with dated igneous rock layers. 2.Cross cutting of sedimentary with dated igneous intrusions (plutons)
What information can be derived from seismographs and/or time distance graphs?
Seismographs: instrument that measures the amount of ground motion produced by seismic waves Provides= 1. amplitude 2. duration/frequency (length of time the ground shook) both 1 and 2 measure strength with combination Time-distance graph: Travel the longer distance is how much time between intervals. Seismograph and Time - Distance Travel Graph both provide the time the earthquake occured at the epicenter and the distance of the seismograph recording station from the epicenter. And epicenter location.
The ___ scale is designated by _______ numerals.
The Mercalli scale is designated by Roman numerals The Richter Scale is designated by Arabic numerals.
The difference in the amount of energy released by a _____ magnitude quake compared to a magnitude quake is ___ times.
The difference in the amount of energy released by a 32 times (6-7) magnitude quake is 32x32 compared to a magnitude quake is 1024 times 6-8
What is the concept of Half-life?
The time required for 1/2 of the original amount of parent isotope to decay. 100% to 50% or 1to1 to 25% or 3to1
What do the theories of catastrophism and uniformitarianism entail?
Theory of Catastrophism: Global acting violent focus , acted over a short period of time. (Georges Cuvier) multiple extinction events wiped out animals Principle of Uniformitarianism: The ancient Earth was shaped by the same natural processes we observe today, but over great lengths of time. (James Hutton) The present is the key to understanding the past.
The characteristics and specific examples of each plate boundary
Transform Relative motion: Moves in opposite directions with no gap Expression/landform: Fault Zone Examples: san andreas - shallow focus 100km Seismic Activity: Shallow focus Elastic rebound stress, no quakes in soft asthenos, originates in hard 100km thick lithosphere. Cannot have elastic rebound stress in soft asenosphere Volcanic activity: none no vol. along san andreas, no gap between plates to allow lava form aesthno to reach surface Future outlook: Island of the Coast of Oregon, not falling into sea, parts of california and mexico west of the san andreas fault moving northward Divergent: Moves opposite directions Relative Motion: oceanic ridge=mid atlantic ridge/iceland Expressions/landforms: oceanic ridge and cont rift valleys Examples: Mid Atlantic ridge/iceland and East African Rv Seismic activity: shallow focus - originates in hard 100km thick lithosphere plate cannot have elastic rebound stress in soft asthenosphere Volcanic Activity: Basalt shield vol. room for lava to come up to the surface Future outlook: Africa splits apart along the East African R.V Convergent: come together then dive under then break off Relative motion ^ Examples HImalaya A. Mts Seismic activity: Deep focus earthquake on subduction plate Volcanic activity: composite andesitic volcano
What is the Geologic Time Scale? Eras: Eons:
Uses dates and events to separate eras on the geological time scale. Eon is like a month short, Era could be millions or billions of years. Eras: 1. Hadean 2. Archean 3. Proterozoic 4. Paleozoic= before dinos 5. Mesozoic= during dinos 6. Cenozoic= event extinction of dinos Eons: 1. Precambrian=billions of years ago 2 Phanerozoic= millions of years ago
what is used to draw boundaries between different plates of the earths lithosphere?
Volcanic - Global distribution of volcanoes Seismic - Global distribution of earthquake activity Geographic features/landform - oceanic ridges and deep sea trenches, continental rift valleys (ex. East African RIft Valley), Many fault zones (ex. San Andreas), Many folded metamorphic mt. ranges (ex. Himilayas)
What are the factors that can limit the use of radioactive isotope dating?
can be done on only some materials. It is not useful for determining the age of sedimentary rocks. For this, geologists date a nearby igneous rock. Igneous rocks- starts when the radioactive elements in the lava crystalize with the solidifying lava. -Must use uranium -Cannot use Carbon 14 -Decay of the isotope starts at the same time the igneous rocks are formed. radiometric techniques are applied to metamorphic rocks, the results normally tell us the date of metamorphism, not the date when the parent rock formed. Metamorphic rocks-starts when the radioactive elements crystalize with the metamorphic index minerals in the metamorphic rock. Decay of isotope starts at the same time the meta. Index minerals are formed. _must use uranium - cannot use carbon 14 Fossils - most fossils are petrified replicas = no original carbon 14 and cannot be dated Original fossil material can only be dated with carbon 14. Uranium cannot date.
What are polar reversals?
changes in the polarity of the magnetic field
Uranium 23.8 is used for? Carbon 14 is used for?
dating very old events Useful for dating very young events
Who established noted principles and theories? Theory of Catastrophism: Principle of Uniformitarianism:
George Cuvier- James Hutton- but popularized by -Charles Lyellfyi-
What is the classification of earthquakes by depth of the focus? Depth of Foci;
(shallow, Deep) : surface to 100km is where earthquakes happen. Earthquakes do not happen past 101-700km
What are the laws of Superposition: Original Horizontality: Crosscutting relationships: Principal Faunal (floral) Succession: Who were they established by?
1) Super position:(Nicolas Steno)In an undisturbed sequence of rock layers that -rock layers on the bottom were deposited 1st. Being oldest. -rock layers on the top were deposited last. Being youngest. -applies to sedimentary rocks and lava flow layers -may or may not apply to plutons 2) Original Horizontality:(Nicolas Steno) rock layers were originally deposited as flat layers -present day non-horizontal (folded) rock layers have been secondarily moved into that now non-horizontal position. ie. originally flat then folded. -applies to sedimentary rocks and lava flows -may or may not apply to plutons 3) Law of Cross-Cutting Relationships:(James Hutton) any cross-cutting body (such as plutons or faults) -are younger than/occured after the youngest (topmost) rock layer that it does intersect -is older than/occured before the oldest (bottommost) rock layer it that does not intersect -1 Deposition of Rock layer a -2 Deposition of Rock layer b -3 Intrusion of Pluton C into rock Layers a and b vol extends to surface , pluton cross cuts rock layers a and b rock layers a and b have contact metamorphism -4 Erosion of volcano and the top layer b -5 deposition of rock layer D -6 deposition of rock layer E 4) Faunal Succession: = fossil succession (William Smith) If the rock layers on the bottom are older (superposition) than the fossils in the rock layers near the bottom must also be older.
How an earthquake can cause damage?
1. Ground motion destruction 2. Displacement 3. Fires (hard to put out when lines are busted. ex 1906 fires lasted 3 days) 4. Landslides (sides of mountains fall off) (lahoga San francisco california) (san andres is horizontal so won't fall in sea) 5. Liquefaction (mud turns to quicksand then solidifies 6. Seismic wave Tsunami
What is the depth of astheno/lithosphere boundary?
100km
What are the significant events used to separate eras on the geologic time scale?
65 mill Phanerozoic=Cenozoic=sed rocks with age of the mammal fossils (no dinos) 245 mill Phanerozoic=mesozoic=sed rocks with age of the reptile/dinosaur fossils (no large mammals) (no exclusively paleozoic trilobite fossils) 570 mill Precambrian=paleozoic = sed rocks with "hard body" paleozoic fossils. 1st hard body fossil found after cambrien explosion. 4.6 bill Precambrian=proterozoic=hidden life precambrian=archean precambrian=hadean=1st hard rock crust found and started geological time.
What are the names of scientist responsible for some of the discussed theories?
Alfred Wagner: continental drift/pangea Harry Hess: suggested ocean floor is moving (Polar Reversal) Plate tectonics Theory : suggest the lithosphere is divided into numerous plates which are in motion relative to one another.=mathews, vine and wilson (wegner and Hess)
How does the speed of seismic waves change when passing through the earth's interior region?
Asthenosphere= slower through sand and soft rock Lithosphere=faster through asphalt