Geo 1330 Exam 3 (Ch. 8, 9, 10, 11)
a principle of relative dating; a rock or fault is always younger than the rock through which it cuts
Cross-cutting relationship
Refers to the changes in the shape or position of a rock body in response to differential stress. General term for the process of folding, faulting, shearing, compression, or extension of rocks as the result of various natural forces.
Deformation
Describe a Modified Mercalli Intensity Scale.
Devised in 1931. Measures destructiveness of an Earthquake. Scale ranges from I to XII. Intensity I very weak, not felt by people Intensity XII total damage. A 12-point scale developed to evaluate earthquake intensity based on the amount of damage to various structures.
The location on Earth's surface that lies directly above the focus of an earthquake.
Epicenter
How does the focus (hypocenter) of an earthquake differ from the epicenter?
Epicenter The epicenter is the point on the surface of the earth that is directly above the hypocenter, which is also called the focus of an earthquake. The hypocenter is the starting point of fracturing rocks, and it is the actual point where earthquakes begins. Focus (Hypocenter) Hypocenters are found at a great depth below the surface. Vibrating waves move away from the hypocenter in various directions. The waves can travel to all places on the Earth and make the earth vibrate because of their great power. While the hypocenter is the origin of earthquakes
a unit of the geological time scale that is a subdivision of a period
Epoch
An __________ is time divided into periods. (A period of time)
Era
A break in a rock mass along which movement has occurred.
Fault
A break in rock mass along which movement has occured
Fault
Gradual displacement along a fault. Such activity occurs relatively smoothly and with little noticeable seismic activity.
Fault creep
A cliff created by movement along a fault. It represents the exposed surface of the fault prior to modification by weathering and erosion.
Fault scarp
The zone within Earth where rock displacement produces an earthquake.
Focus
a term for a linear arrangement of textural features often exhibited by metamorphic rocks
Foliation
The rock surface below Hanging wall
Footwall
Differential stress
Forces that are unequal or in different directions.
Small earthquakes, called ______________, often precede a major earthquake by days or, in some cases, by as much as several years
Foreshock
Sketch a seismogram showing the order of arrival of P-waves, S-waves and Surface Waves at a typical seismograph station.
Generally in the seismograpm station p waves can be reached first And later reaches the S waves and surface waves.
result from contact metamorphism of shale
Hornfel
An elongate, uplifted block of crust bounded by faults
Horst
the hot, watery solution that escapes from a mass of magma during the latter stages of crystallization; such solutions may alter the surrounding country rock and are frequently the source of significant ore deposits
Hydrothermal metamorphism
metamorphism that occurs when meteorites strike earth's surface
Impact metamorphism
2000 km
Using the time-travel graph below, how far away is the epicenter from a seismic station that records a time interval of 3 minutes between the first arrival of P waves and first arrival of S waves? 5 km 3300 km 2000 km 4000 km
The narrow zone of inclined seismic activity that extends from a trench downward into the asthenosphere.
Wadati-Benioff zones
Symmetrical fold
When limbs are mirror images of each other
What are the characteristics of an anticline versus a syncline in terms of the relative ages of strata, directions that strata dip relative to the fold axis, and outcrop patterns where strata are repeated on opposite sides of the fold axis?
When the beds are bent upwards, the resulting fold is called anticline. This fold is convex upwards. Naturally ,in such fold, the older beds occur towards the concave side and limb dips away from the axis of fold on either side. Syncline is just opposite to anticline in its nature. When the beds are bent downwards, the resulting fold is called syncline. This fold is convex downwards. Naturally, in such fold, the younger beds occur towards the concave side and limb dips towards to the axis of fold on either side.
Home Y
Which of these two identical homes would suffer the most damage if an earthquake occurred along the active fault? Home X Home Y Both homes would suffer the same amount of damage since they are both the same distance from the fault Neither home would experience any damage because this type of fault does not generate earthquakes
Energy is stored in rocks adjacent to the site of a future earthquake as ___________. Elastic strain Plastic flow energy Thermal energy Plastic strain
a
Seismic gaps are... Unusually quiet zones along known active faults Slices of land bounded by active, strike-slip faults on all sides Inactive faults cutting across high ridges and water gaps Segments of active faults with creep rates of up to 2 cm/yr
a
What fundamental concept states that in a horizontal sequence of conformable sedimentary strata, each higher bed is younger than the bed below it? a.) Law of superposition b.) Principle of lateral continuity c.) Principle of cross-cutting relationships d.) Principle of original horizontality
a
What metamorphic rock forms by contact metamorphism of mudstones and shales? Hornfels Marble Gneiss Schist
a
What platy, parallel, mineral grains are the most visual aspect of foliated metamorphic rocks? Micas Feldspars Calcite Quartz
a
Which of the Following would exhibit sheared and mechanically fragmented rocks? a. Fault movements at shallow depths b. Hydrothermal metamorphism at a mid-ocean ridge c. Heating of shale and mudstone near an igneous intrusion d. Burial metamorphism of volcanic rocks
a
Which of the following best characterizes an angular unconformity? a.) Tilted strata lie below the unconformity; bedding in younger strata above is parallel to the unconformity. b.) Horizontal lava flows lie below the unconformity and horizontal, sedimentary strata lie above. c.) The discordant boundary between older strata and an intrusive body of granite. d.) Tilted strata lie above the unconformity with loose, unconsolidated soil below.
a
Which of the following describes radioactive decay by beta particle emission? a.) The atomic number of the daughter isotope is one more than the parent; the mass numbers are the same. b.) The mass number of the daughter isotope is one more than the parent and both isotopes have the same atomic number. c.) The daughter isotope has an atomic number two less than the parent and a mass number four less. d.) The daughter isotope has an atomic number one less than the parent and a mass number two less
a
Which of the following is a direct measure of the distance from a seismic receiving station to the focus of a distant earthquake? Time interval between the first P and first S-wave arrivals Magnitude of the ground motion of surface waves passing a receiving station Time elapsed between the first P-wave arrival and last aftershock The difference in the amplitude (height) of a P-wave relative to an S-wave
a
Which of the following refers to the process of fossilization where the pores of the original plant or bones of an animal are filled with precipitated mineral matter? Petrification Internal and external molds Carbonization Impression
a
Which one of the following is consistent with deformation by folding? Horizontal distance is shortened parallel to the direction of compressive stresses The crust is thinned parallel to the direction of compressive stresses The crust is stretched and elongated Shear stresses are the dominant causes of the deformation
a
Which one of the following statements regarding rock deformation and strength is correct? Rupture and plastic deformation occur when stresses exceed the elastic limit of a material Rocks undergo plastic deformation less readily as temperatures and pressures increase Elastic deformation is accomplished through internal flow of material When rocks are subjected to stress for long time periods, the amount of deformation gradually decreases and the rocks eventually return to their undeformed state
a
With regard to the illustration below, which of the following statements is correct? a.) Sill 'D' was intruded between beds 'C' and 'E' after deposition of 'E' b.) Dike 'F' was emplaced after development of the angular unconformity just below bed 'G' c.) Tilting of beds 'A' through 'E' occurred after deposition of beds 'G' through 'K' d.) Bed 'B' is younger than bed 'C' e.) Sill 'D' is younger than dike 'F'
a
In _____________ dating, rocks and structures are placed in their proper sequence or order. However, in ____________ dating, only the chronological order of events is determined
absolute, relative
a hard metamorphic form of coal that burns cleanly and hot
anthractie
A deeply eroded, structural basin would exhibit... Outcrops of the oldest strata in the center of the basin Outcrops of the youngest strata in the center of the basin Strata dipping outward (away) from the center of the basin Arch-like structure similar to an anticline
b
A thrust fault is best described as... a.) A steeply inclined, oblique-slip fault b.) A low-angle reverse fault c.) A vertical, normal fault d.) A near vertical, strike-slip fault
b
Amphibolite is a foliated metamorphic rock composed principally of hornblende and plagioclase. How does it form? By contact metamorphism of sandstone adjacent to a granitic batholith By regional metamorphism of volcanic rocks such as andesite and basalt By gouging and crushing of limestone along a fault By the impact of a meteor on interbedded sandstone and shale
b
An unconformity is a buried... a.) Fault or fracture with older rocks above and younger rocks below b.) Surface of erosion separating younger strata above and older strata below c.) Fault or fracture with younger strata above and older strata below d.) Surface of erosion with older strata above and younger strata below
b
Approximately how much more energy is released in a 6.5 Richter magnitude earthquake than in one with magnitude 5.5? 3000 times 30 times 300 times 3 times
b
During metamorphism, what is the major effect of chemically active fluids? Increase the pressures in deeply buried, regional-metamorphic zones Aid in the movement of dissolved silicate constituents and facilitate growth of the mineral grains Prevent partial melting so solid rocks can undergo very high temperature regional metamorphism Inhibit the formation of schistosity in hornfels and quartzite
b
In thrust faulting... Grabens develop on the footwall block The crust is shortened and the fault plane is inclined at an angle less than 45 degrees The crust is stretched and the fault plane is inclined at an angle greater than 45 degrees The hanging wall block slips downward relative to the footwall block
b
P waves... A. Propagate only in solids B. Are faster than S waves and surface waves C. Have higher amplitudes than do surface waves D. Produce the strongest ground shaking
b
The ____________ in California is the boundary between the North American and Pacific plates. Sierra Nevada frontal fault San Andreas strike-slip fault San Luis Obispo thrust fault San Francisco normal fault
b
The half-life of carbon-14 is about 6000 years. Assume that a sample of charcoal is formed by burning of living wood 15,000 years ago. How much of the original carbon-14 would remain today? a.) More than one-half b.) Between one-fourth and one-eighth c.) Between one-half and one-fourth d.) Between one-half and one-third
b
Which of the following best describes the conditions of contact metamorphism? Pressures are low, the rocks are shallow, and geothermal fluids are the source of metamorphic reactions Pressures are fairly low, the rock is in the upper part of the crust, and heat is supplied from a nearby magma body Heat is generated by shearing and mechanical movements along faults Occurs deep within a subduction zone where temperatures are moderate but pressures are high enough to cause intense deformation
b
Which of the following foundation materials is most stable during earthquake shaking? Unconsolidated, moist soil Bedrock Water saturated sand Clay and mud
b
Which of the following is an essential characteristic of an index fossil? a.) The organism lived only in specific, geographically restricted, environments such as lakes or estuaries b.) The specific life form only existed for a short range of geologic time c.) The specific life form spanned a large range of geologic time d.) The fossils occur in deep-water marine sediments, but the organism actually lived on beaches
b
Which of the following metamorphic rocks forms at the highest grade of regional metamorphism? Hornfel Granulite Schist Slate
b
Which of the following metamorphic rocks is characterized by the segregation of light- and dark-colored minerals into thin layers or bands? Garnet hornfels Gneiss Slate Quartzite
b
Which of the following refers to the investigative process by which geologists identify and match sedimentary strata and other rocks in one area with rocks of the same age at different locations? Relative dating Correlation Absolute dating Compaction
b
Which of the following terms describes the strong, parallel alignment of coarse mica flakes and/or of different mineral bands in a metamorphic rock? Rock cleavage Foliation Stress streaking Marbleizing
b
Which one of the following is not likely to be genetically associated with impact of an asteroid or large meteorite? Tektites Blueschists Coesite Impact crater
b
_________ refers to the tendency for a foundation material to lose its internal cohesion and fail mechanically during earthquake shaking. Slurrying Liquefaction Motion slip Seismoflowage
b
A syncline is... A fold in which the strata dips towards the hinge line A fold in which the strata dips away from the hinge line A fold with only one limb A fold that is bent upward in the form of an arch
b If it dips toward the hinge line, it is a fold axis.
What are the differences between burial and regional metamorphism? Which is more extensive? Where does each type occur? Describe the stresses associated with burial versus regional metamorphism.
burial - sedimentary rocks are buried even deeper regional - when temp. and pressures increase beyond range of burial metamorphism; occurs under places with high temp and ressure over large areas regional is more extensive
A graben is characterized by... A hanging wall block that has moved up between two reverse faults A footwall block that has moved up between two normal faults A hanging wall block that has moved down between two normal faults A footwall block that has moved down between two reverse faults
c
Brittle deformation would be favored over ductile deformation in which of the following conditions? High confining pressures Warmer temperatures Cooler temperatures Greater depths
c
In which setting would regional metamorphism be most likely? At shallow depths adjacent to an igneous intrusion At shallow depths along major transform faults in the continental crust At great depths in the crust where two continents are colliding At shallow depths beneath the seafloor where water pressures are immense
c
Normal and reverse faults are characterized mainly by... Strike slip Horizontal slip Dip slip Basal slip
c
Sandstone strata and a mass of granite are observed to be in contact. Which of the following statements is correct geologically? a.) The sandstone is younger if the granite contains sandstone inclusions b.) The sandstone is younger if it shows evidence of contact metamorphism from the granite c.) The granite is older if the sandstone contains pebbles of the granite d.) The granite is older if it contains inclusions of sandstone
c
The proportion of parent to daughter isotopes in a radioactive decay process is 40% parent and 60% daughter. How many half-lives have elapsed since the material was 100% parent atoms? a.) Less than 1 b.) More than 3 c.) Between 1 and 2 d.) Between 2 and 3
c
What is the minimum number of seismograph stations needed in order to determine the location of an earthquake epicenter? One Two Three Four
c
What metamorphic rock is thought to form by partial melting and in situ crystallization of the melted portion? Blueschist Eclogite Migmatite Amphibolite
c
Which of the following metamorphic rocks forms from the metamorphism of limestone or dolostone? Migmatite Amphibolite Marble Quartzite
c
Which of the following observations would not bear directly on working out the sequence of geologic events in an area? a.) Inclusions of sandstone in a granite pluton b.) A well-exposed basaltic dike cross-cutting sandstone c.) The feldspar and quartz contents of a granite d.) An unconformity between a granite and sandstone
c
Which of the following statements is true for anticlines but not for synclines? The limbs dip or are inclined towards the fold axis (hinge line) Plunging folds can only be anticlines, but not synclines After erosion, strata become older towards the fold axis (hinge line) of an anticline, but not a syncline After erosion, the youngest strata are exposed along the fold axis (hinge line) of an anticline
c
Which one of the following statements concerning foci and epicenters is correct? The focus and epicenter are the same point at the location of fault slippage The fault first slips at the epicenter and afterwards breaks at the focus The epicenter is at the surface directly above the focus where the earthquake initiates The earthquake starts at the epicenter and the rupture extends down to the focus
c
Which one of the following statements is correct? P waves travel through solids; S waves do not. P and S waves travel through liquids, but P waves do not travel through solids. S waves travel through solids while P waves travel through both solids and liquids. P and S waves travel through liquids, but S waves do not travel through solids.
c
Describe the global distribution of earthquakes. Where do most earthquakes occur? Intermediate and deep earthquakes primarily occur along which of the three types of plate boundaries?
In globally most of the earthquakes occur at Pacific Ocean plate and Himalayan regions due to active plate boundaries. This means seismically active. Pacific Ocean is an example of active margin. But in Atlantic Ocean is passive margin, this means there is no seismically active, so there is less chances to get earthquakes. Three types of plate boundaries are to produce deep and intermediate earthquakes Convergent plate boundaries-In these regions deeper earthquakes occur. Divergent boundaries-In these regions shallow and intermediate earthquakes occur. Transform boundaries-In these regions shallow earthquakes occur.
Where are we on the Geologic Time Scale? Where on the time scale is the origin of earth represented and what is the age (in millions of years)? What is the age (in millions of years) assigned to the time line marking the boundary between the Precambrian and Phanerozoic Eons? What percentage of earth history falls into the Precambrian? Which Eon contains most of earth's fossils? Is more known about the Precambrian or Phanerozoic Eon? Why
In the Geological time we are on Halocene epoch. Precambrian on the time scale is the origin of earth represented and 4600 is the age (in millions of years). 540 is the age (in millions of years) assigned to the time line marking the boundary between the Precambrian and Phanerozoic Eons. Phanerozic Eon contains most of earth's fossils. We known more about Phanerozoic Eon because of life abundance. 88 percentage of earth history falls into the Precambria
What are inclusions? If a sedimentary rock layer contains inclusions of an adjacent igneous rock, what can we say about the relative ages of these rock units?
Inclusion are the foreign rock materials which are trapped in Rocks of different composition Inclusion are always older than the rocks containing them
fragment of rock unit enclosed in another rock unit
Inclusions
a mineral that is a good indicator of the metamorphic environment in which it formed; used to distinguish different zones of regional metamorphism
Index mineral
A measure of the degree of earthquake shaking at a given locale based on the amount of damage.
Intensity
What are isotopes? Distinguish between a parent and daughter isotope. Which one is more stable? Can a parent isotope decay into a daughter isotope of the same element?
Isotopes are atoms with the same number of protons but different number of neutrons is known as isotopes. Daughter isotopes are more stable. The daughter isotopes are the results of the radioactive disintegration of the parent isotope. But these two has different physical and chemical nuclear properties. Ex. Radium is product of uranium disintegration. I think, it does not a parent isotope decay into a daughter isotope of the same element
What does the moment magnitude of an earthquake measure?
It measures how big the earthquake is or how much energy released during an earthquake
A fracture in rock along which there has been no movement
Joint
A remnant or an outlier of a thrust sheet that was isolated by erosion
Klippe
Define each of the following: Principle of Superposition, Principle of Original Horizontality, and Principle of Cross-cutting Relationships. How are each of these principles applied to relative dating?
Law of Superposition: In an undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below (Figure 9.2). Principle of Original Horizontality: • Layers of sediment are generally deposited in a horizontal position • If resulting sedimentary rock is folded or faulted, then the deformation occurred after formation Principle of Cross-cutting Relationships (Figure 9.4): • If a fault cuts rocks or a magma intrudes rocks... - The fault/magma are younger than the rocks - Faulting and intrusion occurred after the sediments were deposited and lithified Inclusions (Figure 9.5) • Inclusions are fragments of a rock unit enclosed in another rock unit • The rock unit that supplied the inclusions must be older than the rock containing the inclusions
The transformation of a stable soil into a fluid that is often unable to support buildings or other structures.
Liquefaction
An estimate of the total amount of energy released during an earthquake, based on seismic records.
Magnitude
metamorphic rock formed from limestone or dolostone
Marble
Non-Foliated Metamorphic Rocks:
Marble, quartzite, hornfel, anthracite, fault breccia
How is the Richter magnitude determined?
Measure size of earthquake on basis of ground motion, not destruction. Measuring maximum amplitude of p or s wave on seismic wave pattern.
is made of once nearly spherical pebbles that have been heated and flattened into elongated by differential stress
Metaconglomerate
a group of associated minerals that are used to establish the pressures and temperatures at which rocks undergo metamorphism
Metamorphic facies
the changes in mineral composition and texture of a rock subjected to high temperatures and pressures within earth
Metamorphism
substantial chemical changes due to active fluids
Metasomatism
a rock exhibiting both igneous and metamorphic rock characteristics; such rocks may form when light-colored silicate minerals melt and they crystallize, while the dark silicate minerals remain solid
Migmatite
form when light colored silicate minerals melt and then crystalize, while the dark silicate minerals remain solid
Migmatite
A more precise measure of earthquake magnitude than the Richter scale that is derived from the amount of displacement that occurs along a fault zone.
Moment magnitude
A one-limbed flexure in strata are usually flat-lying or very gently dipping on both sides on this.
Monocline
younger sedimentary rocks lie on older igneous or metamorphic rocks
Nonconformity
metamorphic rocks that do not exhibit foliation have a _______________ texture.
Nonfoliated
A fault in which the rock above the fault plane has moved down relative to the rock below
Normal fault
_______________ dating uses the number of years that have passed since an event occurred.
Numerical (absolute)
An asymmetrical fold is said to be _____________ if one or both limbs are tilted beyond the vertical
Overturned
Describe the particle motions for P-waves, S-waves and surface waves.
P waves: These are compressional waves; these are longitudinal in nature (Particles move in longitudinal or vertical motion) It is also known as primary waves and these waves can travel in both solid and liquid materials S waves: These are shear waves, these are transverse in nature (particles move in transverse or horizontal motion) It is also known as secondary waves and these waves can travel only solids. Both P waves and S waves are known as body waves. Surface waves: These waves travel slowly than body waves These are mainly two types 1) Rayleigh waves-particles move in ripple motion like water on the earth surface 2) Love waves -These are horizontal polarized shear waves
the systematic study of fossils and the history of life on earth
Paleontology
Studyies the history of past seismic activity. Used to predict probabilities of future earthquakes.
Paleoseismology
the rock from which a metamorphic rock formed
Parent rock
a basic unit of the geologic time scale that is a subdivision of an era; may be divided into smaller units called epochs
Period
a metamorphic rock composed mainly of fine crystals of muscovite, chlorite, or both
Phyllite
Some folds are inclined at an angle known as this
Plunging fold
all geologic time prior to the Phanerozoic eon; a term encompassing both the Archean and proterozoic eons
Precambrian
A type of seismic wave that involves alternating compression and expansion of the material through which it passes.
Primary (P) waves
in any undeformed sequence of sedimentary rocks, each bed is older than the one above and younger than the one below
Principle of superposition
the eon following the Archean and before the Phanerozoic. Extends between 2500 and 542 million years ago
Proterozoic eon
A metamorphic rock formed from quartz sandstone.
Quartzite
the spontaneous decay of certain unstable atomic nuclei
Radioactivity
What is radioactivity? What types of atoms undergo radioactive decay?
Radioactivity is the process of emitting radiation from nucleus of an unstable Atom Atoms with unstable nucleus , like uranium thorium will undergo decay
Describe the principles behind carbon-14 dating. What types of materials can be dated using carbon-14? Is carbon-14 useful for dating most geological samples? Why or why not?
Radiocarbon dating is a method to determine the ages of some materials with carbon isotopes C-12,C-13 and C-14 Of these C-14 is radioactive. Since it has a half life of only 5730 years. It can be used to date events of recent geological history but it does not date the most geological samples due very less half life than geological samples half life. Radiocarbon (C-14) is produced in the atmosphere by cosmic ray bombardment of nitrogen -14.
the procedure of calculating the absolute ages of rocks and minerals that contain certain radioactive isotopes
Radiometric dating
metamorphism associated with large-scale mountain building
Regional metamorphism
Distinguish between relative and absolute (numerical) dating.
Relative dating - Determine sequence or order that geologic events and processes occurred - No actual dates attached, just the order Absolute dating - Determine actual ages of rocks and events - Utilizes isotopes and radiometric dating
A fault which the material above the fault plane moves up in relation to the material below
Reverse fault
Charles Richter (1935) devised a procedure to measure the size of an earthquake on the basis of ground motion rather than the amount of destruction
Richter scale
the tendency of rocks to split along parallel, closely spaced surfaces; these surfaces are often highly inclined to the bedding planes in the rock
Rock cleavage
medium-to coarse-grained metamorphic rocks having foliated texture, in which platy minerals dominate
Schist
A seismic wave that involves oscillation perpendicular to the direction of propagation.
Secondary (S) waves
A segment of an active fault zone that has not experienced a major earthquake over a span when most other segments have. Such segments are probable sites for future major earthquakes.
Seismic gaps
What are seismic gaps and what do they say about future major earthquakes?
Seismic gaps along a fault: Segments where fault is locked. Strain not released along these segments, build up. Fault slips within segment, and enormous strain build up released as major EQ
The energy released from the area of fault slippage travels outward as intense vibrations called ____________. These cause the ground around the area of fault slippage to shake violently, producing an earthquake.
Seismic waves
The record made by a seismograph.
Seismogram
Explain how seismologists locate the epicenter of an earthquake?
Seismologists can locate the epicenter with help of seismograph station. You can find epicentre through seismograms,that means from the seismograms the time interval between the arrival of the P waves and S waves with the three different seismic stations.It can be calculated with the help of the travel time graph,the distance between the recording station and the epicentre is determined.
The study of earthquake waves, _______________, dates back almost 2000 years to the Chinese.
Seismology
Stress that causes two adjacent parts of a body to slide past one another.
Shear
Metamorphic facies
Slate
a type of foliation that is characteristic of slates, in which there is a parallel arrangement of fine-grained metamorphic minerals
Slaty cleavage
An irreversible change in the shape and size of a rock body caused by stress
Strain
The force per unit area acting on any surface within a solid
Stress
The compass direction of the line of intersection created by a dipping bed or fault and a horizontal surface. This is always perpendicular to the direction of dip.
Strike
A fault along which movement occurs horizontally
Strike-slip fault
Seismic waves that travel along the outer layer of Earth.
Surface wave
A linear downfold in sedimentary strata
Syncline (opposite of anticline)
What are four factors that determine how a rock deforms?
Temperature, pressure, rock type, time
What is a formation? What are the different ways (criteria) by which rocks can be grouped into formations?
The most basic local unit of stratigraphy is the formation • A particular rock unit is grouped into a formation based on a distinctive appearance and/or other characteristics: - Lithology (rock type) - Color - Sedimentary structures - Certain depositional patterns
Why is the Mercalli Scale subject to uncertainty in determining the size of an earthquake? Roman numerals, upon which this scale is based, are hard to use in mathematical equations. The Mercalli scale is directly related to the amount of energy released by the earthquake, which cannot be accurately measured with seismographs. The Mercalli Scale is based on the amount of damage from an earthquake, which depends on many factors such as the strength of buildings, type of foundation, distance from the epicenter, and duration of shaking. The Mercalli Scale does not take into account the amount of damage from an earthquake, and therefore is not representative of the strength of ground shaking.
c
____________ was struck by three, major earthquakes during the winter and spring months of the years 1811-1812. Nome, Alaska Los Angeles, California New Madrid, Missouri Charleston, South Carolina
c
What are some of the problems associated with using the Mercalli scale to measure the strength of earthquakes?
This Scale is okay if we are the considering about the amount of damage caused by the the quake in any location, it's more applicable to the urban areas or the human residing areas are and it's least useful for the remote locations. Where as the Richter Scale is designed for easier comparison of earthquake magnitudes, regardless of the location.
A low-angle reverse fault
Thrust fault
A high-pressure metamorphism resulting from the crushing and shearing of rock during tectonic movement, mostly along faults. It is generally localized along fault planes (areas of detachment where rocks slide past one another). It produces sheared, highly deformed rocks called mylonites.
cataclastic metamorphism
Name two common platy minerals that produce foliation in metamorphic rocks. Can non-platy minerals exhibit foliation (think metaconglomerate)?
chlorite and mica; yes
What is the difference between differential stress and confining pressure?
confining pressure - Pressure applied equally on all surfaces of a body. differential stress - stress applied unequally and predominates in one direction
Approximately how often do locked segments of the San Andreas Fault (California) break, resulting in major earthquakes? Once every six hundred years Once every fifteen years Once every ten thousand years Once every hundred and fifty years
d
In a ___________ fault, the hanging wall block moves up with respect to the footwall block. Normal Strike-slip Abnormal Reverse
d
Jointing in rocks is characterized by... Closely spaced, parallel faults along which the blocks have moved in opposite directions Structures formed where normal and reverse faults intersect The hinge lines connecting two limbs of an anticline or syncline Roughly parallel fractures separating blocks that show no displacement
d
The ________ is directly related to the Richter earthquake-magnitude rating. A. Average of the highest and lowest Mercalli intensity ratings B. Distance between the receiving station and the epicenter C. Time interval between the first P-wave arrival and the first P wave reflected from the crust-mantle discontinuity D. Amplitude of the seismic waves
d
The radioactive isotopes uranium-238, uranium-235, and thorium-232 eventually decay to different, stable, daughter isotopes of ___________. a.) Iron b.) Argon c.) Strontium d.) Lead
d
What is the source of natural carbon-14? a.) Nuclear fission of the heavy, radioactive elements uranium and thorium b.) Fusion of hydrogen and helium in the Sun and eruption of solar flares c.) Leakage of radioactive gases from the liquid, outer core d.) Cosmic ray collisions and neutron-capture involving atmospheric nitrogen
d
What term describes the zone of contact metamorphism surrounding an intrusive magma body? Schistosity Migmatite Metasomatism Aureole
d
What type of foliation results from the parallel alignment of abundant, coarse-grained mica flakes in a metamorphic rock? Gneissic banding Slaty cleavage Phyllitic structure Schistosity
d
Which low-grade metamorphic rock, composed of extremely fine-sized mica and other mineral grains, typically exhibits well-developed rock cleavage? Marble Hornfels Quartzite Slate
d
Which of the following denotes the divisions of the geologic time scale in correct order of decreasing lengths of time beginning with the longest time interval and ending with the shortest? a.) Eon, era, epoch, period b.) Era, period, epoch, eon c.) Eon, epoch, period, era d.) Eon, era, period, epoch
d
Which of the following is the best method for determining the probability of future earthquakes for a particular area? Compare the phase of the Moon relative to the time of month Keep track of the frequency of volcanic eruptions in other parts of the world Watch for any changes in the behavior of animals Paleoseismology; history of past earthquake activity in the area
d
Which of the following metamorphic rocks forms at very high pressures but moderately low temperatures associated with subduction of oceanic crust and sediments? Mylonite Migmatite Marble Blueschist
d
Which of the following metamorphic rocks typically forms by metamorphism of a sandstone? Marble Slate Amphibolite Quartzite
d
Which of the following refers to the idea or concept that ancient life forms succeed one another in a definite, evolutionary pattern and that the contained assemblage of fossils can determine geologic ages of strata? Principle of cross correlation Law of fossil regression Law of correlative indexing Principle of faunal succession
d
Which one of the following best describes the geology of the Black Hills region in South Dakota? An eroded syncline with older, sedimentary strata in the axial region and younger, metamorphic rocks around the margins A basin filled with folded, sedimentary rocks and thick coal beds A large graben deeply eroded by Pleistocene glaciers An elongate dome cored by Proterozoic igneous and metamorphic rocks
d
Which one of the following statements is true regarding tsunamis? Tsunamis travel faster in shallow water and slower in deeper water. The wave heights of tsunamis decrease and wavelengths increase as they move into shallower water. Tsunamis are started by gravitational pull of the Moon on Earth. In the deep ocean, tsunami wavelengths are longer and wave heights smaller compared to tsunami waves in shallow water close to shore.
d
_____________ in layered sedimentary rocks are evidence for horizontal compression and shortening. Normal faults Strike-slip faults Horsts and grabens Tight folds
d
What is the difference between differential stress and confining pressure? Which of these two stresses is most likely to produce foliation in a metamorphic rock?
differential stress - forces are unequal in different directions confining pressure - squeezes rock equally in all directions differential stress is most likely to produce foliation in a metamorphic rock
Define an unconformity? What do unconformities represent in terms of rock units and geologic time? How do unconformities form? Be able to sketch and describe the following: Angular unconformity, disconformity and nonconformity.
erosional surfaces or intervals of missing strata within a rock sequence. Types of Unconformities • Angular unconformity • Nonconformity • Disconformity
Along oblique-slip faults, both blocks have horizontal but not vertical components of movement. True False
f
Foliated metamorphic rocks are composed largely of equidimensional grains of minerals such as quartz and calcite. True False
f
For shallow-focus earthquakes, surface-wave amplitudes are usually smaller than P and S-wave amplitudes. true false
f
Most sedimentary rocks are readily dated by radiometric methods. True False
f
Composed of fragments produced by rocks fracturing during faulting
fault breccia
Archaeon eon
first eon of the Precambrian time; precedes the proterozoic extends between 4.5 to 2.5 billion years
Do folds reflect brittle or ductile deformation?
folds are ductile deformatiom.. These are result from external forces.
What are migmatites? How do migmatites form? Do they represent low or high temperatures?
forms at temperatures exceeding 700 degrees C where gneiss partially melts felsic minerals melt, mafic minerals remain solid silica-rich liquid invades partially melted rock softened rock contorts and deforms
What is the Principle of Fossil Succession? How is this principle useful for correlating rocks from one exposure to another? What are the criteria for a good index fossil?
fossil organisms succeed one another in a definite and determinable order Geographically widespread fossil that is limited to a short span of geologic time.
What type of geothermal gradient is associated with contact metamorphism?
geothermal gradients are high
What are index minerals? How are index minerals used in mapping metamorphic terrain?
good indicators of the metamorphic conditions under which they were formed (only present for short amount of time)
What are the agents of metamorphism?
heat pressure chemically active fluids
What are the agents of metamorphism?
heat, pressure (stress), and chemically active fluids.
an imaginary axis that layer is bent around.
hinge line
Chemical reactions between the heated seawater and basalt result in metamorphism of the basalt. It can also occur on continents where crustal rocks are metamorphosed by invading, hot fluids associated with igneous intrusions.
hydrothermal metamorphism
used in geology to determine the degree of metamorphism a rock has experienced. Depending on the original composition of and the pressure and temperature experienced by the protolith (parent rock), chemical reactions between minerals in the solid state produce new minerals.
index minerals
Seismographs are...
instruments that measure the vibrations in the ground
What is meant by the correlation of rock units? Identify different criteria (e.g. lithology, sedimentary structures, color, fossils, etc.) that can be used to correlate rocks from one exposure to another.
matching a particular rock layer (formation) in one exposure with its counterpart at a different locality
How does metamorphism affect the isotopic date of a mineral? If the whole-rock age of a metamorphic rock is older than its mineral age as determined by radiometric dating, then what might each of these ages represent (see my power point slides)?
metamorphism is change in the form of rock on increasing temperature and pressure.by this process sedimentary rock converted into metamorphic rock. the isotopic age obtained from the individual rock represent the time at which the mineral crstallize first in the magma. Isotopic method is used to determine the crstallization age of the igneous rock. There is no change in the lattice site in crystal structure before and after the crystallization. Metamorphism after the process of diagenesis. In the low grade metamorphism the temperature is about 150- 200 degree celcius. Metamorphic events have a important role in the isotopic dating of rock metamorphic event can cause the escape the daughter isotopes into the surrounding matrix. after the metamorphic event daughter isotopes again accumulate in the mineral. If a heating of rock occured then there will be presence of daughter nuclei in the surrounding matrix. and there is no metamorphism then mineral age will be coincide with age of whole rock and they give the temperature of initial crystallization of the rock. whole rock provide the initial age at which the rock formation takes place. If a whole age rock is older than its mineral age it will represent the the rock crystallize first then the isotopic mineral formation takes place.
a rock composed of two intermingled but distinguishable components, typically a granitic rock within a metamorphic host rock.
migmatites
How do migmatites form?
migmatites are found in high-grade metamorphic terrains where a sequence from high-grade metamorphic rocks through migmatites to granite bodies is often seen in the field. The granite component is thought to form by partial melting of the rock during extreme metamorphism.
Describe hydrothermal metamorphism. What types of reactions occur? Where does hydrothermal metamorphism occur?
occurs along mid-ocean ridges where heated seawater percolates through hot, fractured basalt crustal rocks on continents can react with invading, hot fluids associated with igneous intrusions
Describe contact metamorphism. Where does it occur?
occurs at high temperatures, adjacent to magma chambers; restricted to a small area round the margins of a magmatic intrusion
In what tectonic environment do blueschists and eclogites form?
progressive metamorphism of basalt blueschist - very high pressures, relatively low temperatures eclogites - extremely high pressures, moderate-high temperatures
In what tectonic environment do blueschists and eclogites form?
progressive metamorphism of basalt blueschist - very high pressures, relatively low temperatures eclogites - extremely high pressures, moderate-high temperatures
Fossil
remains or traces of organisms preserved from geologic past
What is cataclastic metamorphism? Where does it occur? What is the difference between a fault breccia and mylonite?
results form the crushing and shearing of rock during tectonic movement occurs along fault planes
Rank the following metamorphic rocks in order of increasing grade of metamorphism: schist, granulite, phyllite, slate, gneiss.
slate phyllite schist gneiss granulite
Identify the parent rock for each of the following metamorphic rocks: slate, quartzite, marble, greenstone, and anthracite.
slate ---> shale quartzite ---> sandstone marble ---> limestone greenstone ---> basalt anthracite ---> bituminous coal
Rank the following metamorphic rocks in order of increasing grade of metamorphism: a) schist b) granulite c) phyllite d) slate e) gneiss.
slate, phyllite, schist, gneiss, granulite (d, c, a, e, b)
Foliated metamorphic rocks:
slate, phyllite, schist, gneiss, migmatite
Calcite is the main mineral constituent of the sedimentary rock limestone and of the metamorphic rock marble. True False
t
Following a major earthquake, aftershocks diminish in magnitude but may still be powerful enough to destroy or further damage weakened buildings. true false
t
Hydrothermal metamorphism involves chemical reactions between hot fluids and surrounding rocks such as occurs beneath mid-ocean ridges True False
t
Some large earthquakes are preceded by smaller magnitude foreshocks. true false
t
T or F. A disconformity is an erosional unconformity with parallel beds or strata above and below.
t
T or F. Rapid burial and possession of hard parts are necessary conditions for the preservation of plant or animal remains as fossils.
t
T or F. The term Paleozoic describes the era of ancient life forms.
t
The Richter earthquake magnitude scale is based on the total amount of energy released by the earthquake. True False
t
The oldest, sedimentary rock strata are exposed along the hinge line (fold axis) of deeply eroded anticlines. True False
t
What metamorphic rock is a typical product of hydrothermal metamorphism?
talc and other clay minerals
What is a contact metamorphic aureole?
the area surrounding the intrusion where the contact metamorphism effects are present
Phanerozoic eon
the part of geologic time represented by rocks containing abundant fossil evidence. The eon extends from the end of the Proterozoic eon (540 million years ago) to the present
Describe Carbon-14 dating.
the radioactive isotope of carbon is produced continuously in the atmosphere and used in dating events from the very recent geologic past (the last few tens of thousands of years)
What is Half-life?
the time required for half of the atoms in a radioactive substance to decay
What is the age of the Earth accepted by most scientists today? 6.4 billion years 4.5 million years 4.5 billion years 4500 billion years
4.5 billion years
Fold
A bent layer or series of layers that were originally horizontal and subsequently deformed.
Adjustments that follow a major earthquake often generate smaller earthquakes called __________________.
Aftershock
A medium-grade, nonfoliated metamorphic rock for which the parent rock is mafic.
Amphibolite
WEAKLY-OR-NON-FOLIATED metamorphic rocks:
Amphibolite, metaconglomerate, greenstone
What types of rocks can be effectively dated using isotopic dating techniques? Why is isotopic dating not useful for most sedimentary rocks? How can the approximate ages of these sedimentary rocks be determined?
Any rock containing radio active minerals can be dated using dating techniques. sedimentary rocks are the accumulation of detritus . so if they contain any radioactive mineral it only represent the age of the rock from which it has eroded. Fossils assemblages can be used to know the ages of sedimentary rocks
How does increasing the confining pressure affect the way a rock deforms?
At high pressure material are less prone to fracture because the pressure of the surroundings tends to hinder the formation of fracture. Where at the low confining stress material will tend to behave brittle and fractures out. Rock deformation experiments have also been carried out and resulted the following result by increasing confined pressure or Pconf has an effect of increasing the value of yield stress and the rock has an overall increase in its strength, keeping the all other variables being constant.
a zone or halo of contact metamorphism found in the country rock surrounding an igneous intrusion
Aureole
Folds are also described by their _________________, which is a surface that connects all the hinge lines of the folded strata
Axial plane
A circular downfolded structure
Basin
Visualize five, horizontal, sedimentary strata exposed in a cliff or canyon wall identified by consecutive numbers, 1 being the lowest bed and 5 being the highest. Which of the following statements concerning the strata are true? a.) Bed 5 is the oldest b.) Beds 1 and 3 are older than bed 4 c.) Bed 4 is older than bed 2 d.) Bed 3 is older than both beds 2 and 4
Beds 1 and 3 are older than bed 4
The elastic limit (strength) of a rock that surpassed, it either bends or breaks. Rocks that break into smaller pieces exhibit this.
Brittle deformation
How does a building's structure, distance from epicenter and nature of the soil and bedrock affect the amount of damage caused by an earthquake?
To reduce the damage during earthquake The buildings should be firmly tight together without being left in separate parts Epicenter is where the intensity of an earthquake is more so if we are away from epicenter we can have less damage Hard rocks will offer greater resistance to seismic waves than loose and unconsolidated soils and rocks
A major strike-slip fault that cuts through the lithosphere and accommodates motion between two plates
Transform fault
Describe a Tsunami.
Tsunamis also called seismic sea waves: -Destructive waves that are often inappropriately called "tidal waves" Result from vertical displacement along a fault located on the ocean floor or a large undersea landslide triggered by an earthquake.
What causes tsunamis? Describe the changes to tsunami waves as they approach the shoreline in terms of wave velocity, wave height, the spacing between waves, and amount of destruction.
Tsunamis are underwater earthquakes A sudden slip in the oceanic crust will generate a tsunami . As rhe wave approach shoreline it's velocity decreases wave height increases and spacing between waves or wavelength also decreases
Discuss the difference between ductile and brittle deformation.
Brittle materials have some a elastic behavior but only a small region of ductile behavior before they fracture. Here low temperature, low confining pressure and high strain rate are the factors of brittle materials. Ductile materials have a small region of elastic behavior and large region of ductile behavior before they fracture this represents the ductile nature of materials. Here high temperature, high confining pressure and low strain rate are the factors of ductile materials.
low-grade metamorphism that occurs in the lowest layers of very thick accumulations of sedimentary strata
Burial metamorphism
results from the crushing and shearing of rock during tectonic movement; generally along fault planes; might produce sheared, highly deformed rocks called mylonites
Cataclastic metamorphism
Name two common platy minerals that produce foliation in metamorphic rocks. Can non-platy minerals exhibit foliation (think metaconglomerate)?
Chlorite, Mica; Yes
Differential stress that squeezes a rock mass as if placed in a vise.
Compressional stress
stress that is applied uniformly in all directions
Confining pressure
rock layers that were deposited without interruption
Conformable
usually occurs where high temperatures are restricted to a small area, generally around the margins of an igneous intrusion. Geothermal gradients are high.
Contact Metamorphism
changes in rock caused by the heat from a nearby magma body
Contact metamorphism
What are the differences between burial and regional metamorphism?
Contact metamorphism is a type of metamorphism where rock minerals and texture are changed, mainly by heat, due to contact with magma. Regional metamorphism is a type of metamorphism where rock minerals and texture are changed by heat and pressure over a wide area or region.
Asymmetrical fold is when..
they are not mirror images of each other
What are fossils? Describe at least five different types of fossils.
traces or remains of prehistoric life now preserved in rock The remains of relatively recent organisms - teeth, bones, etc. - Entire animals, flesh included - Given enough time, remains may be petrified (literally "turned into stone") - Molds and casts - Carbonization
Describe how foliation is produced in a metamorphic rock (3 mechanisms)
1. preferred mineral orientation - perpendicular to stress 2. alternating mineral bands - compositional layers (light and dark) 3. mineral flattening - grains elongate and flatten
Describe how foliation is produced in a metamorphic rock (3 mechanisms).
1. preferred mineral orientation - perpendicular to stress 2. alternating mineral bands - compositional layers (light and dark) 3. mineral flattening - grains elongate and flatten
What goes up the chimney down but not down the chimney up?
An umbrella, while it is down it is furled and it is easy to get it up. But when it is unfurled it cannot.
an unconformity in which older strata dip at an angle different from that of the younger beds
Angular unconformity
A fold in sedimentary strata that resembles an arch.
Anticline
What type of stress is most likely to produce foliation in metamorphic rock?
Differential stress
forces that are unequal in different directions
Differential stress
The angle at which a rock layer or fault is inclined from the horizontal. The direction of this is at a right angle to the strike.
Dip
A fault in which the movement is parallel to the dip of the fault.
Dip-slip Fault
a type of unconformity in which the beds above and below are parallel
Disconformity
A roughly circular upfold structure.
Dome
A type of solid-state flow that produces a change in the size and shape of a rock body without fracturing. Occurs at depths where temperatures and confining pressures are high.
Ductile deformation
The vibration of Earth produced by the rapid release of energy: -Energy released radiates in all directions from its source, the hypocenter - Energy is in the form of waves - Sensitive instruments around the world record the event
Earthquake
The sudden release of stored strain in rocks that result in movement along a fault.
Elastic rebound
Know the stages of the Elastic Rebound Theory in explaining earthquakes.
Elastic rebound theory is the first theory to explain about earth quakes. It explain how the energy can spread during the earthquakes. In the rocks some amount of energy has been stored in a form of strain thus can leads to deformation to the rocks then rocks may exceed their elastic limit in a certain conditions then rocks rocks get faulting or slipping etc,finally causes earthquake waves through this energy.It is known as elastic rebound theory.
the largest time unit on the geological time scale, next in order of magnitude to era
Eon
Know how the Geologic Time Scale is subdivided in terms of eons, eras, periods, and epochs. Know the names of the eons and eras as listed in the table of terms above. Given an outline of the time scale, be able to place the names of eons and eras in the appropriate spaces. Know in general what divisions represent periods and epochs, but do not memorize the names.
Geologic Time Scale subdivided in terms of eons, eras, periods, and epochs by their events like years. Eonothem can be termed as eon is major divisions for geological time scale. It has following major divisions those are Phanerozoic,Proterozoic,Archean, Headen. Erathem can be termed as era,it has sub divisions of eon. Like plaeozoic,cenozoic,mesozoic. Periods shows divisions of era like Quaternary,Jurrasic,permian etc. Period has sub divisions like Eocene,Oligocene,pleistocene etc. Geological time scale can used represents geological history of earth and it's atmosphere, life and geological events.
Medium-to coarse-grained banded metamorphic rock in which granular and elongated minerals dominate
Gneiss
a texture of metamorphic rocks in which dark and light silicate minerals are separated, giving the rock a banded appearance
Gneissic texture
A valley formed by the downward displacement of a fault-bounded block.
Graben
A low-grade granoblastic rock produced by the metamorphism of mafic volcanic rock and containing abundant chlorite, which accounts for its greenish cast
Greenstone
the oldest eon
Hadean eon
What is meant by half-life? Do different parent-daughter isotopes (e.g. uranium 238 - lead 206, potassium 40 - argon 40, etc.) have different half-lives?
Half life is the time taken to decay half of the parent atom Yes different isotopes have different half life's, for eg uranium 238 to lead 206 have half life of 4.5 BY and potassium argon have 1.25BY
A tilted fault block in which the higher side is associated with mountainous topography and the lower side is a basin that dills with sediment
Half-graben
How geologists identify the rock surface immediately above the fault
Hanging wall
The type of stress that tends to pull a body apart
Tensional stress
What are the various ways by which future earthquakes may be predicted?
The earthquakes are majorly formed from the disturbances within the tectonic plates. We can not predict the movements of the plates directly. Seismic atudies warn us while the earthquake is occuring. So we need to observe the earthquake warly than any instrumrnt, today we are using. So we must observe the movements of tectonic plates. Tectonic plates slide past under one another slowly or abruptly. The slow motion or slow slip tectonic movements can be predicted by obervations taken from GPS( Global Posiotioning System). Then we can warn the govt and people how the earthquake will be? And equipment that are used to monitor the notion of tectonic plates are very much helpful to predic earthquake early. And the scientists can estimate earthquake intensity by observing the geological structures of the continental crust by advanced instruments.
