Assignment 9,10,11 (Geol 10113 Argenbright)

definition of a monocline:

A large steplike fold in otherwise flat-lying sedimentary rocks

How does a seismograph work?

A seismograph works by suspending a weight from bedrock, which remains motionless during an earthquake. A rotating drum that is affixed to the moving bedrock moves as the rock moves, recording the relative displacement between the stationary weight and the rotating drum. A seismograph can measure P waves, S waves, and surface waves.

Why are short-range earthquake predictions often unsuccessful?

Animal behavior is unreliable. Foreshocks do not occur before every earthquake.

What is thought to produce Earth's magnetic field?

As iron-rich fluid in the liquid outer core rises, the fluid is twisted by Earth's rotation. The flow of this electrically charged material generates a geodynamo.

What causes an earthquake such as the one that occurred in San Francisco in 1906?

As plates move, stress builds up at the boundary. When the boundary eventually snaps, energy is released as an earthquake.

What is the relative movement along a strike-slip fault?

Both blocks of rock move horizontally past each other. The dominant displacement is parallel to the strike of the fault.

Which statement(s) correctly describe(s) brittle deformation and ductile deformation?

Brittle deformation describes a rock breaking as a result of stress, whereas ductile deformation describes a rock bending or folding as a result of stress. Both types of deformation are permanent.

How do continental crust and oceanic crust differ?

Continental crust is thicker than oceanic crust; continental crust is less dense than oceanic crust; the oldest continental crust is older than the oldest oceanic crust; plus the continental crust is composed of a variety of rock types, whereas oceanic crust is composed of basalt and gabbro.

What is rock deformation, and how might a rock body change during deformation?

Deformation is a rock's reaction to stress, which can cause a rock to change its shape or position.

How was layering produced during the formation of Earth?

During its formation, Earth was so hot that iron, nickel, and other dense elements such as uranium melted and quickly sank to the center of Earth, producing its core. Meanwhile, less dense oxygen-seeking elements such as silicon and aluminum rose to create Earth's primitive crust.

What is meant by elastic rebound?

Elastic rebound refers to how the slippage along a fault (i.e., earthquake) allows the deformed rock to regain its original shape in a new location.

What characteristics do faults that experience fault creep exhibit?

Fault creep tends to produce slow, gradual displacements of rock blocks with little seismic shaking.

How are joints different from faults?

Faults are breaks within rock where appreciable displacement has occurred; joints are breaks within rock where no appreciable displacement has occurred.

Where do the youngest rocks in an eroded basin outcrop?

In top view, the youngest rocks of a basin are in the middle of the basin. The youngest rocks of a basin are on top of all the other rock layers.

Which type of fault tends to produce the most destructive earthquakes?

Megathrust fault

How do monoclines form?

Movement along a steep fault in basement rock pushes up a portion of the ductile rock layers above it.

Which layer of Earth forms at mid-ocean ridges?

Oceanic crust

How does triangulation determine the epicenter of an earthquake?

On a map, a circle is drawn around each of three recording stations, with the radius being the distance from the station to the epicenter of the earthquake. The epicenter is located where the three circles intersect.

What are the differences between P waves, S waves, and surface waves?

P waves are the fastest and have the lowest amplitudes; S waves are the second-fastest and have the second-lowest amplitudes; surface waves are the slowest and have the highest amplitudes.

Why do geologists believe the inner core is solid?

P waves refract at the boundary between the outer core and inner core.

Why do we believe Earth's outer core is a liquid?

P waves slow down and refract at the boundary between the mantle and the outer core. S waves do not travel through the outer core.

What data provided information about the existence of different zones within Earth?

P-wave and S-wave arrival times

Why does a shadow zone occur for P-waves?

P-waves refract as they go through the outer core

What happens to seismic waves that pass through the outer core?

S waves are bent around the outer core.

Which of the following statements about seismic wave ray paths is most accurate?

Seismic waves move along curved ray paths because the properties of materials in the Earth change.

How could you test whether the core of another planet were completely solid?

Set off a bomb to create seismic waves. If S waves arrive on the opposite side of the planet, then the core is solid.

At which types of plate boundaries do the three types of differential stress occur?

Shear stress occurs at transform boundaries, compressional stress occurs at convergent boundaries, and tensional stress occurs at divergent boundaries.

What is the Moho, and how is its depth determined?

The Moho is the boundary between the crust and the mantle. Its depth is determined by observing where refracted seismic waves and direct seismic waves cross over each other.

Why is the asthenosphere weaker than the lithosphere?

The asthenosphere is warmer and has a lower viscosity than the lithosphere.

If both earthquakes are of the same magnitude, why can an earthquake that occurs east of the Rockies produce damage over a larger area than the damage produced by an earthquake in California?

The bedrock in the eastern and central United States is more rigid than that in the western United States, which allows seismic waves to travel greater distances with less attenuation.

How are faults, hypocenters, and epicenters related?

The hypocenter is the exact point underground along a fault where the slippage of the two blocks of rock occurs. The epicenter is the point on Earth's surface that is directly above the hypocenter.

How do the positions of the magnetic poles change through time?

The magnetic north pole varies somewhat from the geographic North Pole while still remaining in the Northern Hemisphere. Additionally, periods of full magnetic reversals have occurred where magnetic north and magnetic south have switched places with each other. Both types of variation are caused by changes in the convection patterns within the outer core.

What is elastic deformation?

The temporary and reversible deformation of a rock caused by the gradual application of stress. During elastic deformation, the chemical bonds within the rock do not break.

describes Earth's mantle from top to bottom?

The upper mantle contains the lithospheric mantle, the asthenosphere, and the transition zone; the lower mantle is Earth's thickest layer and is made of perovskite; the D" is the lowest mantle layer that is rather weak.

What characteristic of seismic waves makes them useful for probing Earth's interior?

The velocities and directions of seismic waves reliably differ when they encounter different materials within Earth.

What does a reflected wave tell us about Earth's interior?

The wave has hit a boundary between two different Earth materials, causing it to reflect back to Earth's surface.

What is an earthquake, and how do earthquakes generally occur?

a sudden shaking of the ground that is caused by the rapid movement of one block of rock past another block of rock at a fault

Why do seismic waves travel along curved paths through the mantle?

because mineral phase changes in the upper mantle cause sudden increases in seismic velocity

reverse fault

compression

what are the four primary zones in Earth's interior?

crust, mantle, outer core, inner core

The Black Hills of South Dakota are a good example of which type of geologic structure?

dome

A monocline is a type of a

fold

What does the Modified Mercalli Intensity scale tell us about an earthquake?

how intense an earthquake feels

How do seismologists create long-range earthquake predictions?

identifying seismic gaps

Which type of earthquake destruction can cause houses to sink into the ground?

liquefaction

Earth's outer layer is composed of seven dominant plates. What is the name of this rigid outer layer?

lithosphere

The highest magnitude earthquakes typically occur

near subduction zones

Which type(s) of plate boundary is/are associated with Earth's largest earthquakes?

oceanic-continental convergent plate boundary ocean-oceanic convergent plate boundary

What type of plate interaction produces the San Andreas Fault?

plates sliding past one another

strike-slip fault

shear

Which type of seismic waves tend(s) to cause the greatest destruction to buildings?

surface waves

normal fault

tension

What information does a time-travel graph provide?

the distance from the earthquake to the recording station

Which of the following behaviors of seismic waves help scientists determine the location of layers in the Earth?

waves reflecting (bouncing) waves stopping (truncating) waves refracting (bending)