Geology Chapter 3 Flashcards

Questions and Answers

Which rock is older, the limestone (A) or the igneous sill (B)?

Limestone (correct)

Igneous sill

What type of unconformity is found at the location indicated by the arrow?

Disconformity

Angular unconformity (correct)

Paraconformity

Nonconformity

What type of unconformity is found at the location indicated by the arrow?

Angular unconformity

Nonconformity (correct)

Paraconformity

Disconformity

What is an index fossil?

An index fossil is a fossil that is used to define and identify a particular time period in the geological time scale. Signup and view all the answers

Which rocks are older, the lower gray muddy sandstone or the upper reddish sandstone?

Lower gray muddy sandstone Signup and view all the answers

What is stress (in geology)?

Force applied to a certain area. Signup and view all the answers

What is the geological structure shown in this image called?

Syncline. Signup and view all the answers

The hanging wall is on the __________ side of this fault.

right Signup and view all the answers

The hanging wall block moves up relative to the footwall block in reverse dip-slip faults.

True Signup and view all the answers

Match the images below with the type of fault.

Reverse Fault = Hanging wall moves up relative to the footwall. Strike-slip Fault = Blocks slide past each other horizontally. Normal Fault = Hanging wall moves down relative to the footwall. Signup and view all the answers

What type of stress would cause the fault pictured below?

Tension. Signup and view all the answers

What type of stress would cause the fault pictured below?

Shear. Signup and view all the answers

Which type of fault is best matched with the appropriate plate boundary?

Right-lateral strike-slip fault and transform boundary. Signup and view all the answers

What is the term used to refer to a horizontal line on an inclined fault surface (or any surface)?

Strike. Signup and view all the answers

What is the term used to refer to the inclination of an inclined fault surface (or any surface)?

Dip. Signup and view all the answers

What type of structure is the man standing in front of in this image?

Anticline. Signup and view all the answers

What type of structure is shown in this image?

Normal fault. Signup and view all the answers

What type of structure can be observed in this image?

Monocline. Signup and view all the answers

What kind of structure can be observed in this satellite image?

Left-lateral strike-slip fault. Signup and view all the answers

What type of stress would you expect to occur along a transform boundary?

Shear. Signup and view all the answers

What type of fault would occur as a result of compressive stress?

Reverse. Signup and view all the answers

You are exploring an area and find many reverse faults, synclines, and anticlines. Which of these tectonic settings would you hypothesize caused the deformation you see?

Continental collision. Signup and view all the answers

Ocean basins exist because ________________ (select all that apply).

Ocean crust is thinner than continental crust. Signup and view all the answers

Which of the following changes to the crust would act to increase regional elevations? (Choose all that apply.)

Decrease the density of the crust. Signup and view all the answers

If a region has extensive normal faulting, would you expect that region to have high regional elevation, high relief, or both?

High relief. Signup and view all the answers

If a region has extensive reverse faulting and folding, would you expect that region to have high regional elevation, high relief, or both?

Both. Signup and view all the answers

Currently, the most widely accepted hypothesis for the formation of the Rocky Mountains involves _________________.

Subduction of an ocean plate at a shallow angle under western North America. Signup and view all the answers

Match the relative dating principle with its definition.

Superposition = The layers of rock lie on top of one another in order from oldest at the bottom to youngest on top. Original Horizontality = Layers of rocks deposited from above in a gravity field, such as sediments and lava flows, originally were laid down horizontally. Lateral Continuity = Within the depositional basin in which they form, strata are continuous in all directions until they thin out at the edge of that basin. Cross-Cutting Relationships = Faults and igneous intrusions that cut across rocks are younger than the rocks they cut across. Inclusions = When one rock formation contains pieces or inclusions of another rock, the included rock is older than the host rock. Signup and view all the answers

Using the image shown below, how would you know which rock is older A or G? i.e., which of these relative dating principles would be most useful?

Principle of cross-cutting relationships. Signup and view all the answers

Match the type of unconformity with the correct description.

Disconformity = Where there is a break or stratigraphic absence between strata in an otherwise parallel sequence of strata. Nonconformity = Where sedimentary strata are deposited on crystalline (igneous or metamorphic) rocks. Angular Unconformity = Where sedimentary strata are deposited on a terrain developed on sedimentary strata that have been deformed by tilting, folding, and/or faulting so that they are no longer horizontal. Signup and view all the answers

Isotopes are atoms of the same element but have different numbers of __________.

Neutrons. Signup and view all the answers

Which of the following statements about the half-life of a radioactive isotope is true?

False Signup and view all the answers

If a rock starts off with 100 radioactive parent atoms, how many parent atoms will be left after 2 half-lives?

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Which of these is the comparison and correlation of strata within a region by examining the physical properties of the rock and its sequence with other strata?

Lithostratigraphic correlation. Signup and view all the answers

Organisms that lived for relatively short time periods are particularly useful for dating rocks, especially if they were distributed over a wide geographic area and so can be used to compare rocks from different regions. These organisms are known as ____________.

Index fossils. Signup and view all the answers

Which represents the longest interval of geological time?

An eon. Signup and view all the answers

What is the currently scientifically accepted age of the Earth?

4.54 billion years old. Signup and view all the answers

The block diagram above shows the various rock units that can be found in the Grand Canyon. Using the Principles of Relative Dating, put the rock units in order from oldest (1) to youngest (19).

1-H Vishnu, 2-G Zoroaster, 3-E Bass, 4-D Hakatai, 5-C Shinumo, 6-B Dox, 7-F, 8-A Cardenas, 9-R Tapeats, 10-Q Bright Angel, 11-P Muav, 12-O Temple Butte, 13-N Redwall, 14-M Supai, 15-L Hermit, 16-K Coconino, 17-J Toroweap, 18-I Kaibab, 19-S Coal Seam. Signup and view all the answers

You have measured the concentration of Uranium-235 and Lead-207 in the Vishnu Schist (Unit F on the Grand Canyon block diagram). U-235 is radioactive and decays into Pb-207. You have found 18 ppb (parts per billion) of U-235 and 72 ppb of Pb-207. Approximately how many half-lives of U-235 have passed since the Vishnu Schist formed?

2.5. Signup and view all the answers

You have measured the concentration of Uranium-235 and Lead-207 in the Vishnu Schist (Unit F on the Grand Canyon block diagram). You have found 18 ppb (parts per billion) of U-235 and 72 ppb of Pb-207. Using the chart and table above determine the numerical age of the Vishnu Schist.

1.775 million years old. Signup and view all the answers

You have measured the concentration of Potassium-40 and Argon-40 in the Cardenas Basalt (Unit A). You have found 65 ppb (parts per billion) of K-40 and 35 ppb of Ar-40. Using the chart and table above, determine the approximate numerical age of the Cardenas Basalt.

800 million years. Signup and view all the answers

During which of these time intervals did the supercontinent Pangea form?

Permian. Signup and view all the answers

During which of these time intervals do the oldest fossils come from?

Archean. Signup and view all the answers

During which of these time intervals did flowering plants appear?

Cretaceous. Signup and view all the answers

The most severe mass extinction in Earth's history occurred at the end of which of these time periods?

Permian. Signup and view all the answers

At the end of which of these time intervals did the non-avian dinosaurs go extinct?

Cretaceous. Signup and view all the answers

During which of these time intervals did modern humans appear?

Pleistocene. Signup and view all the answers

An earthquake occurs when ___________________.

There is a rupture and movement along a fault. Signup and view all the answers

Where do most earthquakes occur?

At plate boundaries. Signup and view all the answers

Which of these terms is defined as the point on the land surface directly above the location where the earthquake occurred?

Epicenter. Signup and view all the answers

Which of these terms is defined as the point within the Earth where the earthquake occurred?

Hypocenter. Signup and view all the answers

Which of these seismic waves travel through compression (like the compression of the coils of a spring, similar to the way sound travels)?

P-waves. Signup and view all the answers

Which of these seismic waves only travel along Earth's surface? (Select all that apply)

Rayleigh waves Signup and view all the answers

Indicate the order in which these seismic waves would arrive at a seismic station following an earthquake.

1st - P waves, 2nd - S waves, 3rd - Surface waves. Signup and view all the answers

Which scale would you use if you wanted to measure the amount of shaking felt by people and damage that occurred as a result of an earthquake?

Intensity scale. Signup and view all the answers

Which of these measurements will vary for a given earthquake depending on how far away from the epicenter you are?

Intensity. Signup and view all the answers

Which of the following conditions would increase the Moment Magnitude of an earthquake? (Select all that apply.)

Increase the rigidity of the rock Signup and view all the answers

How would the seismogram below change if the seismic station was farther from the earthquake epicenter? (Choose all that apply.)

The S-waves would arrive later. Signup and view all the answers

If a seismic station recorded the arrival of S waves from an earthquake 3 minutes after the arrival of P waves, how far is that station from the epicenter of the earthquake?

2000km. Signup and view all the answers

The 2010 Haiti earthquake had a rupture area estimated to be 30 km long and 11 km wide, and a displacement on the fault of 4 m. Use the Moment Magnitude calculator linked here to estimate the Moment Magnitude of the Haiti earthquake.

7.01. Signup and view all the answers

The March 11, 2011 earthquake off the coast of Japan had a Moment Magnitude of 9.1. The dimensions of the rupture area during the earthquake are estimated to have been 300 km long and 150 km wide. Use the Moment Magnitude calculator linked here to estimate the amount of displacement on the fault that must have occurred.

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Which of the areas indicated on the map have a 2% Probability of exceeding shaking equivalent to 80% of gravity in the next 50 years? (Choose all that apply.)

A Signup and view all the answers

The figure below shows varying seismic hazard within the Seattle region. What is the most likely cause for the variability in shaking intensity expected in different areas?

Sediment/rock type. Signup and view all the answers

Investigate the recent earthquake near Palu, Indonesia. What is the tectonic setting that caused this earthquake?

Strike-slip faulting at shallow depths within the interior of the Molucca Sea microplate. Signup and view all the answers

Investigate the recent earthquake near Palu, Indonesia. What is the highest Intensity of shaking that was predicted for this earthquake by the Shakemap model?

IX. Signup and view all the answers

Investigate the recent earthquake near Palu, Indonesia. What is the highest Intensity of shaking that was reported for this earthquake by people using the Did You Feel It feature?

IX. Signup and view all the answers

Investigate the recent earthquake near Palu, Indonesia. How many people were estimated to have experienced violent shaking (Intensity IX) according to the PAGER model?

501,000. Signup and view all the answers

Investigate the recent earthquake near Palu, Indonesia. How many shaking-related fatalities were most likely to have occurred as a result of this earthquake according to the PAGER model?

1,000-10,000. Signup and view all the answers

In a reverse fault, the hanging wall moves UP relative to the footwall.

True Signup and view all the answers

What type of fault is shown here? Sangre de Cristo Fault San Luis Valley

Normal fault. Signup and view all the answers

Stream offset by the San Andreas Fault! What type of fault is this?

Right-lateral strike-slip fault. Signup and view all the answers

A Normal Fault is a result of what kind of stress?

Tension. Signup and view all the answers

What type of structure is shown in this image? Rabbit Valley, western Colorado

Normal fault. Signup and view all the answers

What type of structure is shown in this image? Mosaic Canyon

Normal fault. Signup and view all the answers

What type of structure is shown in this image? Mojave Preserve

Reverse fault. Signup and view all the answers

What type of structure is shown in this image? Mexican Hat

Monocline. Signup and view all the answers

What type of structure is shown in this image? Sheep Mountain

Anticline. Signup and view all the answers

In general, which type of faults would you predict to find at a convergent plate boundary?

Reverse. Signup and view all the answers

In general, which type of faults would you predict to find at a divergent plate boundary?

Normal. Signup and view all the answers

At which type of plate boundary setting would you predict most folding to occur?

Convergent. Signup and view all the answers

Let's make some predictions: We will define elevation as the height above the liquid surface (difference between block height and block root). If we increase the block thickness, __________.

elevation will increase. Signup and view all the answers

If we increase the density of the block, __________.

elevation will decrease. Signup and view all the answers

If we increase the density of the liquid, __________.

elevation will increase. Signup and view all the answers

Why do we have ocean basins?

Ocean crust is denser than continental crust. Signup and view all the answers

Predict: which of the following processes would increase regional elevation?

Heat the crust. Signup and view all the answers

Ways to Increase Regional Elevation

Shorten/thicken crust, add surface material, add magma at depth, heat crust or mantle. Signup and view all the answers

Ways to Decrease Regional Elevation

Structurally thin crust, erode material, cool crust or mantle. Signup and view all the answers

How Faulting Can Form Mountains (Relief)

Thrust faulting (Denali), normal faulting (Death Valley). Signup and view all the answers

How could the Rocky Mountains have formed?

The prevailing hypothesis for the Rockies' birth, called flat-slab subduction, says that the Pacific oceanic plate dove underneath the North American plate at an unusually shallow angle. Signup and view all the answers

How are rock types related to elevation in Colorado?

Igneous and metamorphic rocks are located at high elevation. Signup and view all the answers

What must have happened at some time after the igneous and metamorphic rocks formed?

They became uplifted relative to the surrounding rocks. Signup and view all the answers

According to isostasy, thicker crust gives us _____ elevation.

Higher. Signup and view all the answers

According to isostasy, denser crust gives us _____ elevation.

Lower. Signup and view all the answers

Reverse or thrust faulting tends to increase ___________.

Both regional elevation and relief. Signup and view all the answers

Which of these best describes the order of events that must have happened to explain the sedimentary rocks we see at Red Rocks Amphitheater?

Rock A was deposited, then Rock B was deposited, then the rocks were tilted. Signup and view all the answers

Which Rock is older, the felsic igneous rock (A) or the mafic igneous rock (B)?

If inclusions (or clasts) are found in a formation, then the inclusions must be older than the formation that contains them. Signup and view all the answers

Normal faulting tends to increase __________.

Relief. Signup and view all the answers

If you crush a soda can, what type of stress are you applying?

Compression. Signup and view all the answers

Study Notes

Geology: Key Concepts and Terms

Stress in geology refers to the force applied to a specific area of rock.
Geological structures like synclines and anticlines represent the folding of rock layers under pressure.
In a fault, the hanging wall is on the right side during a right-lateral strike-slip fault.
In reverse dip-slip faults, the hanging wall block moves upward relative to the footwall.
Normal faults are results of tension stress, while reverse faults arise from compressive stress.
Strike-slip faults exhibit horizontal movement along the fault line and are categorized as right-lateral or left-lateral based on the movement direction.
Strike and dip are crucial terms for fault surfaces, where strike refers to a horizontal line on the inclined fault surface and dip denotes the angle of inclination.

Fault Types and Geological Structures

A reverse fault is identified by the upward movement of the hanging wall compared to the footwall.
Normal faults occur as a result of extensional forces, leading to the dropping of the hanging wall.
Structures like monoclines and anticlines are important in understanding tectonic forces and geological formations.
The hanging wall moves up in a reverse fault while it moves down in a normal fault.

Stress and Plate Boundaries

Tension stress is associated with normal faults, while shear stress is linked to strike-slip faults along transform boundaries.
The type of fault corresponds with the type of tectonic plate boundary: normal faults are found at divergent boundaries, whereas reverse faults are found at convergent boundaries.

Geological Time and Dating

Isotopes have varying neutron counts, impacting their stability and decay rates, which is crucial for dating rocks through techniques like radiometric dating.
The half-life of isotopes indicates the time it takes for half of the radioactive parent isotopes to decay into daughter isotopes.
Principles like superposition and cross-cutting relationships aid in determining the relative ages of rock layers.

Eons and Geological Events

The currently accepted age of the Earth is approximately 4.54 billion years.
Important geological events include the formation of Pangea during the Permian and significant mass extinctions at the end of this period.
Index fossils play a pivotal role in dating and correlating rock layers due to their widespread distribution and short geological lifespan.

Seismology and Earthquake Mechanisms

Earthquakes occur when there's a rupture along a fault, usually at plate boundaries.
Hypocenter is the point within the Earth where the earthquake originates, while the epicenter is the surface point above it.
P-waves (primary waves) travel through compression, while S-waves and surface waves (Love and Rayleigh waves) carry energy along the Earth's surface.
The Moment Magnitude scale measures the energy released during an earthquake, considering the area of the fault that slipped.

Earthquake Effects and Measurements

Factors like the rigidity of rocks and the amount of fault displacement directly affect the Moment Magnitude.
The intensity of an earthquake measures the shaking felt at various distances from the epicenter and can vary with distance.
Tools like ShakeMap predict shaking intensity and help estimate the impact on populations and structures.

Geological Features and Elevation

The elevation and relief of landforms are influenced by crust thickness and density, with thicker and less dense crust generally leading to higher elevations.
Processes like faulting and crustal thickening can lead to the formation of mountains.
The presence of dense oceanic crust leads to lower elevation compared to continental crust.

Insights into Geological Conservation

Methods to increase regional elevation include adding surface material, heating the crust, or shortening/thickening the crust.
Crustal cooling, eroding material, and structurally thinning crust contribute to decreased regional elevation.

Summary of Geological Principles

Relative dating principles guide the interpretation of geological history, with sedimentary rock layers displaying an ordered accumulation over time.
Understanding geological processes helps recognize the transformation of landscapes and predicts the occurrence of natural events like earthquakes.

Studying That Suits You

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Description

Test your knowledge on key geological terms and concepts in Chapter 3. This quiz will help you understand fundamental geology terminology, including stress, synclines, and fault structures. Perfect for students studying geology concepts!