Geology Exam 2
Tsunami are typically about _________ high in the open ocean, and 6 to 15 m high on reaching shallow water.
1 m
If Alaska and California are ignored, the list of 10 largest U.S. earthquakes shows ____________.
10 events affecting at least 10 different states
Tsunami wavelengths can be as great as _________.
780 km
Over _________ of volcanism is associated with the edges of tectonic plates.
90%
During the 1990s, hundreds of trees were killed at Mammoth Mountain, California, by the diffuse emission of _________ gas.
CO2
The point below the surface of Earth where a fault first ruptures underground is known as the epicenter.
False
The relation between distance and damage from an earthquake is obvious: it is always the case that tthe closer to the hypocenter/epicenter, the greater the damage.
False
The types of rock or sediment on which a structure's foundation sits has no influence on whether the structure will be damaged by shaking from an earthquake.
False
The ongoing collision between Asia and the subcontinent of India is resulting in __________.
great earthquakes over a very large area
Seismic S-waves disappear at the core-mantle boundary, resulting in the S-wave shadow zones, because:
They cannot travel in the liquid outer core.
Modern tsunami warning systems primarily use __________.
sea surface buoys and ocean bottom pressure sensors
Detailed mapping of the ocean bottom around the Hawaiian Islands revealed a previously unrecognized tsunami source. What did geologists discover on the seafloor in this area?
slumps and debris avalanches formed by volcanic flank collapse
Earthquake-related tsunami are created by sub sea fault movements with pronounced vertical offsets of the seafloor. Such movements occur most commonly along __________________.
subduction zones
Earthquakes are most commonly caused by ______________.
sudden earth movements along faults
The frequency of a wave is __________________.
the number of waves passing a given point per unit time
Magma at great depth does not contain gas bubbles because the high pressure at depth keeps gas dissolved in solution.
True
Major southern California faults, such as the Imperial, San Jacinto system, Elsinore, and Laguna Salada, also appear to be part of the San Andreas Plate boundary fault system carrying peninsular California to the northwest.
True
Most of the subduction-zone earthquakes of today occur around the rim of the Pacific Ocean or the northeastern Indian Ocean.
True
Moving into the core, P wave velocities gradually increase until a positive jump is reached at about a 5,150-km depth, suggesting that the inner core is solid.
True
Passing through the mantle below the asthenosphere, the seismic wave velocities vary but generally increase until about 2,900-km depth where P waves slow markedly and S waves disappear at the core-mantle boundary zone.
True
The shaking produced by Rayleigh waves causes both vertical and horizontal movement.
True
Typically fewer than 20 major and great earthquakes (magnitudes of 7 and higher) each year account for more than 90 percent of the energy released by earthquakes.
True
Which of the following statements is true regarding tsunami and volcanoes?
Volcanic eruptions can result in tsunami as they explode, collapse, or send debris into the water.
In the 1989 Loma Prieta quake, the Marina District building collapses were extensive, and numerous destructive fires broke out, due to all but which one of the following?
Widespread looting and arson
A caldera collapse occurs ________________.
after the magma chamber is mostly empty
The 17 January 1994 Northridge earthquake in Los Angeles was generated on a _______ thrust fault.
blind
The Toba eruption 74,000 years ago may have __________.
caused a great reduction in the worldwide human population
Pyroclastic debris is __________.
chucks of magma and rocks blown into the air by gas in a volcanic eruption
A well-formed conical volcano located above an active subduction zone that has not erupted in 12,000 years is __________.
considered active
In 1964, 12 people were killed during a tsunami at Crescent City, California. All of these fatalities were caused by the _______ wave, which was the highest in the series.
fifth
Tsunami arrive as a series of several waves separated by periods typically in the _________ range.
10- to 60-minute
Most tsunami travel at speeds of _________ miles per hour.
420 to 480
The intensity of an earthquake is influenced by all but which of the following?
The current air pressure
In 1883, __________ exploded and the resulting tsunami killed 36,000 people on Java and Sumatra.
Krakatau
Which state listed below is most likely to have a magnitude 9 or larger earthquake in the next several hundred years?
Washington
The seismic-gap method of earthquake forecasting works by identifying __________.
segments along a fault that not moved for the longest amount of time
A _________ is an oscillating wave that sloshes back and forth within an enclosed body of water such as a sea, bay, lake, or swimming pool.
seiche
__________ are steep-sided, symmetrical volcanic peaks built of alternating layers of pyroclastic debris capped by high-viscosity andesitic to rhyolitic lava flows that solidify to form protective caps.
stratovolcanoes
________ faults are commonly found at areas of plate convergence where subduction or continental collision occurs.
Reverse
The 1946 April Fool's Day tsunami at Hilo, Hawaii, was caused by an earthquake near ________.
Alaska
Which state accounts for the greatest percentage of all U.S. earthquakes of magnitude 3.5 and above?
Alaska
Why are low-latitudes the most dangerous latitudes to have a large volcanic eruption occur?
Ash and gases from low-latitude eruptions are spread around Earth to the greatest degree.
Seafloor spreading generates __________ magma
Basaltic
Aftershocks occur before the mainshock in an earthquake sequence.
False
It is virtually impossible for small ships at sea to survive a passing tsunami.
False
During the summer of 1783, the greatest lava eruption of historic times poured forth at _________, accompanied by the release of an enormous volume of gases that enshrouded much of northern Europe in a "dry fog" or blue haze rich in SO2 (one of the visible components of today's urban smog).
Laki, Iceland
Seismic waves cannot travel through ______________.
Liquids (the mantle)
The largest historic tsunami wave run-up ever recorded was caused by a massive rockfall into the water at ________________.
Lituya Bay, Alaska
On 8 May 1902, a massive eruption of __________ killed 30,000 people in the town of St. Pierre.
Mont Pelée, Martinique,
A genuine success story of advance warning before a large eruption occurred in the Philippines in 1991 before the climactic eruption of _________________.
Mt. Pinatubo
__________ eruptions are the most violent types of explosive eruptions.
Plinian-type
Read the article found at https://eos.org/features/the-wicked-problem-of-earthquake-hazard-in-developing-countries?utm_source=eos&utm_medium=email&utm_campaign=EosBuzz030918 (Links to an external site.)Links to an external site. List three reasons why reducing earthquake risk in developing countries is a difficult problem. What are the recommendations given in this article for Bangladesh and its large urban centers?
Reducing earthquake risk in developing countries is a difficult problem due to limited resources, uncertainties in our ability to assess hazards, and increased migration. The article suggests more earthquake awareness, fixing building codes, and a lot of money to fix these problems that need immediate attention.
Define resonance and explain why it is important to building damage in an earthquake.
Resonance is the oscillation caused by seismic waves. During an earthquake, every building responds differently to the waves. If the frequency of the oscillation is close to the "natural frequency" of the building, the resonance could cause severe damage.
____________ in the Aegean Sea underwent an explosive series of eruptions around 1628 bce that buried the Bronze Age city of Akrotiri on Thera to depths of 70 meters.
Santorini
Which of the following represents evidence for major fault movement on the Seattle Fault zone about 1,100 years ago?
Several tsunami deposits have been recognized in the sediment layers of the area. The former shoreline at Restoration Point was uplifted 7 meters above the high-tide line in a single event. The same date appears in the ages of six major rock avalanches in the Olympic Mountains. Numerous large landslides occurred at this time, including some that carried trees in growth position to the bottom of Lake Washington. All of these choices are correct.
The Great Basin region between the eastern Sierra Nevada in California and the Wasatch Mountains in Utah ______________________ in response to plate-tectonic forces.
has expanded in an east-west direction
The best course of action to take if you suspect a tsunami is headed your way is to __________.
head to higher ground and stay there
As minerals form in magma kept at a constant temperature, what happens to the viscosity of that magma?
it increases
Violent causes of death from volcanic eruptions include _______________.
lahars tsunami pyroclastic flows poison gases Correct! All of these choices are correct.
The presence of water ________ the melting point of rock.
lowers
Earthquakes in Hawaii are mostly related to ________________.
movement of volcanic magma beneath the ground
Which of following correctly lists the order in which the minerals form in a cooling magma from the first to the last to form?
olivine, pyroxene, amphibole, biotite mica, and quartz
If basaltic lava reaches the sea or a lake, it cools rapidly into ____________ lava.
pillows
Spreading centers are an ideal location for volcanism because ______________.
the oceanic plates pull apart causing hot asthenosphere rock to rise and undergo decompression melting to form magma that continues to rise they sit above the high-temperature asthenosphere the asthenosphere rock has low percentages of SiO2 Correct! All of these choices are correct.
What is the cause of volcanism at Italy's Vesuvius, Stromboli, Vulcano, and Etna?
the subduction of Mediterranean seafloor beneath Europe
Active volcanoes today in Oregon and Washington, including Mt. St. Helens, result from _________________.
the subduction of the Juan de Fuca Plate beneath North America
The Richter scale is set up so that for approximately every _______ increase in the energy of the seismic waves, the Richter magnitude increases one number, e.g., from 4 to 5.
thirty-fold
Transform faults have mostly vertical displacement rather than horizontal displacement.
False
Seismic P-waves travel slower than S-waves.
False
The higher the viscosity of magma, the more fluid is its behavior.
False
Which of the following statements about tsunami in the deep ocean are true?
They are always "feeling" the bottom.
A building's period of swaying is determined, in part, by the material used to build it.
True
For magnitudes above about 6, the bigger earthquake magnitude generally means that more people in a larger area and for a longer time will experience the intense shaking.
True
The Rio Grande Rift in New Mexico, Colorado, westernmost Texas, and Mexico is one of the major continental rifts in the world where the continental crust is being heated and stretched from below.
True
The deadliest earthquake in history occurred in 1556 when about 830,000 Chinese were killed in and near Xi'an on the banks of the mighty Huang River.
True
The moment magnitude is more accurate than the classical Richter scale because it is tied directly to physical parameters such as fault-rupture area, fault slip, and energy release, and because other earthquake scales use indirect measures such as how much a seismograph needle moves.
True
The most dangerous volcanoes tend to be in the same general plate-tectonic settings as the largest earthquakes in the world.
True
__________ melting occurs when a rock melts due to a lowering of pressure.
deconmpression
Mt. Rainier, Washington, is number one on the danger list of many U.S. volcanologists because of its __________.
great height active hot-water spring systems, which have weakened the mountain internally extensive glacial cap frequent earthquakes Correct! All of these choices are correct.
Several geologic phenomena are being studied as signs of an impending volcanic eruption. These include seismic waves, ______________, and the release of gases.
ground deformation
With compressional forces, the hanging wall moves upward relative to the footwall; this type of fault is referred to as a __________ fault.
reverse
The New Madrid earthquakes are apparently related to an old buried ____________.
rift zone
The Lisbon earthquakes of 1755 are historically significant because ______________.
they changed the prevailing philosophies of the era, producing a more pessimistic view of the world
Using the S-P timing method, epicenters can be located using seismograms from a minimum of ______ recording stations.
three
Why does the magma from some volcanoes flow smoothly and relatively peacefully, while the magma from other volcanoes blasts forth violently and deals death over wide areas?
variations in the temperature, water and gas content, and viscosity of magmas differences in the chemical and mineral makeup of magmas Both of these choices are correct.
The three 'Vs' of volcanology are __________________.
viscosity, volatiles, and volume
Geologists have shown that the east coast of the United States faces a serious tsunami threat from ________.
volcanic flank collapse in the Canary Islands
Liquefaction occurs when seismic waves cause __________.
water to be injected into sediment causing the grains to lose cohesion and behave like a fluid
The greatest earthquakes in the world occur _____________.
where plates collide with each other
A shield volcano has a great ___________.
width compared to its height