Lecture Quiz #7 Part 1 & 2
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Lecture Quiz #7 Part 1:
Chapter 9: Earthquakes and Earth’s Interior
1.
Describe
what is the principal cause of earthquakes?
The principal cause of earthquakes is the movement of tectonic plates in the Earth’s crust. Earthquakes occur when there is a sudden release of energy as a result of the movement or shifting of these plates. This energy release creates seismic waves that travel through the Earth and cause the ground to shake. 2.
Where do earthquakes principally occur?
Earthquakes principally occur in three large zones of the earth: 1) along the edges of tectonic plates, 2) along mid-ocean ridges, and 3) within plates. Additionally, they can occur at faults, which are cracks in the Earth’s crust where rocks on one side of the crack move past those on the other side.
3.
What are the principal destructive forces that can occur due to earthquakes?
Ground shaking
Landslides and rockfalls
Soil liquefaction
Tsunamis
Fire
Loss of infrastructure
Land subsidence
Flooding
Hazardous material releases
4.
How is the size of an earthquake determined?
The size of an earthquake is typically determined by its magnitude, which is a measure of the energy released during the earthquake. Seismologists use a variety of methods to determine the magnitude of an earthquake: seismic waves, satellite imagery, body wave magnitude, etc.
5.
What is the difference between an epicenter and hypocenter?
Epicenter: it the point on the Earth’s surface directly above the location where the earthquake occurred. In other words, it is the point where the seismic waves radiate outward from the earthquake source. Hypocenter: is the actual location within the Earth where the earthquake occurred, often several kilometers underground. It is the point where the rocks ruptured, and the seismic waves were generated.
6.
What is meant by elastic rebound?
Elastic rebound refers to the phenomenon where rocks on both sides of a fault plan will move past each other during an earthquake, storing energy as they deform, and then suddenly rebound back to their original position, releasing the stored energy as seismic waves. 7.
How is triangulation used to locate the source of an earthquake?
By calculating the distance from at least three seismograph stations to the epicenter. Each station records the time difference between the P and S waves’ arrival. 8.
Why are earthquakes more prevalent in the western U.S. than the eastern U.S.?
Earthquakes are more prevalent in the western U.S. due to the presence of tectonic plate boundaries, such as the San Andreas Fault, and the Pacific Ring of Fire, which causes more seismic activity. Additionally, the western U.S. has a different geology than the eastern U.S., with more fault lines and a thinner Earth’s crust, making it more prone to earthquakes. 9.
Major earthquakes are often followed by somewhat smaller events known as.
Aftershocks. . .. they are smaller earthquakes that occur in the days, weeks, or even months following a major earthquake. 10.
The mechanism by which rocks store and eventually release energy in the form of an earthquake is termed.
Elastic Strain Accumulation.
11.
The position on Earth's surface directly above the earthquake source is called the.
Epicenter.
12.
Primary of secondary waves have the highest velocities.
Primary waves (P-waves) have the highest velocities. P-waves, also known as compressional waves, travel through the Earth's crust at a speed of around 2-8 km/s, while secondary waves (S-waves) travel at a speed of around 1-5 km/s.
13.
The instrument that records earthquake events is termed a.
Seismograph.
14.
The distance between a seismological recording station and the earthquake source is determined from the.
Time difference between the arrival of P-waves and S-waves at the station, also known as the "time difference" or "travel time difference". By measuring the time difference between the arrival of these two types of waves, seismologists can calculate the distance from the station to the earthquake source, also known as the epicenter.
15.
The Richter magnitude of an earthquake is determined from the.
Amplitude of the seismic waves recorded on a seismograph. The Richter magnitude scale is a logarithmic scale that measures the magnitude of an earthquake based on the amplitude of the P-waves recorded on a seismograph. The higher the amplitude, the higher the Richter magnitude, and the more powerful the earthquake.
16.
Characterize tsunamis amplitude and wavelength?
Tsunami waves have a very large amplitude, typically ranging from 1 to 30 meters (3 to 100 feet) or more, and a long wavelength, typically ranging from 100 to 500 kilometers (62 to 310 miles). This means that tsunami waves have a much larger amplitude and longer wavelength than typical ocean waves, which allows them to travel at high speeds for long distances and cause devastating damage when they reach land.
17.
The amount of destruction caused by earthquake vibrations is affected by what various conditions.
Magnitude of the earthquake: The stronger the earthquake, the more intense the vibrations and the greater the potential for damage.
Distance from the epicenter: The closer a structure is to the epicenter of the earthquake, the more intense the vibrations will be.
Depth of the earthquake: Shallow earthquakes tend to cause more damage than deep earthquakes.
Type of soil: Soft or loose soil can amplify the vibrations, leading to greater damage.
Building design and construction: Poorly designed or constructed buildings are more susceptible to damage from earthquake vibrations.
Age and condition of the building: Older buildings or those in disrepair may be more vulnerable to damage.
Foundation type: Buildings with shallow foundations or those built on unstable soil may be more susceptible to damage.
Ground motion: The type and intensity of ground motion, such as horizontal or vertical movement, can affect the amount of destruction.
18.
Most of our knowledge about Earth's interior comes from.
Analyzing seismic waves, which help us understand the composition and structure of the Earth’s layers. Lecture Quiz #7 Part 2: Chapter 11: Crustal Deformation and Mountain Building
1.
Describe for me the difference between Confining Pressure, Compressional Stress, Tensional (Extensional) Stress and Shear Stress.
Confining Pressure:
* Force applied equally in all directions
* Squeezes material in all directions, causing compression
Compressional Stress:
* Force applied inward, causing material to compress
* Pushes material together, resulting in shorter length
Tensional (Extensional) Stress:
* Force applied outward, causing material to stretch
* Pulls material apart, resulting in longer length
Shear Stress:
* Force applied parallel to a surface, causing material to deform by sliding or rotating
* Can cause material to change shape, without changing volume
2.
What is the difference between a Normal Fault, a Reverse Fault and a strike-slip lateral fault?
Normal Fault:
* Occurs when the hanging wall drops down relative to the footwall
* Results in extension and stretching of the Earth's crust
* Typically forms in areas where the crust is being pulled apart, such as at mid-ocean ridges
Reverse Fault:
* Occurs when the hanging wall moves up relative to the footwall
* Results in compression and shortening of the Earth's crust
* Typically forms in areas where the crust is being squeezed together, such as at subduction zones
Strike-slip Lateral Fault:
* Occurs when rocks on either side of the fault move horizontally past each other
* No net vertical movement; rocks simply move sideways
* Typically forms in areas where tectonic plates are sliding past each other, such as at transform faults.
3.
What is an anticline? A syncline?
An anticline is a type of fold where the rocks are bent upwards into a convex shape, with the youngest rocks at the top. Imagine a inverted arch shape.
A syncline, on the other hand, is a fold where the rocks are bent downwards into a concave shape, with the youngest rocks at the bottom. Think of a U-shape.
4.
What is a large
down-warped
area called (miles across)?
A basin, which is a depression in the Earth's surface that is formed by subsidence, tectonic activity, or erosion. It can be filled with sediments, water, or other materials, and can range in size from small, localized depressions to vast regions like ocean basins.
5.
What is a thrust fault?
A thrust fault is a type of fault where one rock layer is pushed up and over another rock layer, resulting in a compressional force and a reverse sense of motion. This means that the older rocks are pushed on top of younger rocks, which is opposite to the normal stratigraphic order. Thrust faults typically occur when two tectonic plates are colliding or compressing against each other,
causing the rocks to be pushed together and deformed. 1.
What stress force is responsible?
Compressive stress force.
6.
What type of faults occur from extensional forces?
Extensional forces lead to the formation of normal faults. In a normal fault, the hanging wall (upper side) moves down relative to the footwall (lower side), creating a linear valley or rift. This occurs when the extensional force stretches and thins the Earth's crust, causing it to break and create a fault. Normal faults are typically found in areas undergoing extension, such as rifts, basins, and divergent plate boundaries.
7.
Describe the difference between a “horst” and a “grabben”.
Horst: A horst is a block of the Earth's crust that has been uplifted along a normal fault, resulting in a raised relief feature. The horst is bounded by two normal faults, and the rocks on the horst are typically older than the rocks in the surrounding area.
Graben: A graben, on the other hand, is a down-dropped block of the Earth's crust that forms between two normal faults. The graben is lower in elevation than the surrounding area, and the rocks within the graben are typically younger than the rocks on the
horst.
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8.
How do you define a right lateral strike-slip fault?
A right lateral strike-slip fault is a type of fault where the rocks on the opposite side of the fault move to the right relative to the observer's position. In other words, if you are standing on one side of the fault, the rocks on the other side will move to your right. This type of fault is also known as a dextral strike-slip fault. It's important to note that the term "right" refers to the direction of movement, not the orientation of the fault itself.
9.
Large circular down-warped structures are called.
Basins.
10.
What do the Appalachian Mountains represent?
The Appalachian Mountains represent a classic example of a Paleozoic fold mountain range. They were formed during the Paleozoic Era, about 480-250 million years ago, as a result of the collision of the North American and African plates. The Appalachians were once as tall as the Himalayas but have since eroded over time. Today, they represent a mature, weathered mountain range with a rich geologic history.
11.
What is meant by the term isostatic rebound?
Isostatic rebound refers to the gradual rise of the Earth's crust after the melting of large ice sheets or glaciers. When a region is covered by a thick ice sheet, the weight of the ice presses down on the underlying rocks, causing the crust to deform and sink. When the ice melts, the weight is removed, and the crust begins to rebound, slowly rising upwards due to the redistribution of the
Earth's mantle beneath it. 12.
A transform fault is.
A transform fault is a type of fault that occurs when two tectonic plates are sliding horizontally past each other, without creating or destroying any crust. Unlike convergent or divergent faults, transform faults do not involve plate convergence or divergence, but rather lateral movement along a fault zone. 13.
A good example of a present-day, passive continental margin is the.
Atlantic coast of North America.
14.
A(n) ___is a thick accumulation of sediments and small, tectonic blocks formed of material scraped off a descending, lithospheric plate.
A trench.