test 4 notes
seismic gaps
Short, inactive segments along active faults
The tremendous amount of energy involved in thrusting two tectonic plates together results in __________ boundaries having the largest magnitude earthquakes.
convergent
Tectonic plates collide due to _______ motions, move away from each other due to _______ motions, and slide past one another at transform faults.
convergent; divergent
The triple junction in _____________ has created a rift valley with many topographic features including valleys, domed highlands, lakes, and volcanic peaks
Africa
In which of these scenarios will the plate subduct?
An older, colder oceanic plate that collides with a younger, warmer oceanic plate A warmer, younger oceanic plate that collides with an older continental plate
Where do most of the subduction-zone earthquakes of today occur?
Around the rim of the Pacific Ocean and in the northeast Indian Ocean
Which of the following describes the spreading center basin related to the northern end of the Gulf of California?
It continues from the Gulf of California in Mexico and finally stops at the end of the Salton Sea in the United States.
Which of the following statements accurately characterizes the earthquake activity in the Salton Trough?
It is one of the most earthquake-active areas in the United States.
What does the word slip refer to when used to describe earthquakes?
It means movement has occurred along a fault.
The seismic-gap method of forecasting earthquakes involves ______.
looking for segments along a fault that have not moved in a long time as compared to other segments
Most earthquakes along fracture zones occur on the ______ faults between the offset sections of spreading centers.
transform
Mantle heat that collects at ______ may cause doming and fracturing in a radial pattern. Gravity may then pull the dome apart and allow magma to well up into the three fracture zones.
triple junctions
Rifting
Gravity pulls an uplifted area apart.
A fault is
a place where Earth ruptures and two sides move past each other in earthquake-generating events
Rank the type of tectonic plate edge by the magnitude (strength) of the largest earthquakes that occur along it. (Place the boundary that experiences the greatest magnitude earthquakes at the top. Divergent or pull apart Convergent or push together Transform or slide past
1.) Convergent or push together 2.) Transform or slide past 3.) Divergent or pull apart
Order the stages involved in forming an ocean basin.
1.) centering 2.) doming 3.) rifting 4.) spreading
Spreading
New seafloor is formed.
tectonic triple junction
A point where three plate edges touch
Where do shallow earthquakes occur in subduction zones?
At the bend in the subduction plate In the upper portion of the down-going plate In the overriding plate
If two tectonic plates converge and no subduction occurs, which of the following is true?
Both of the plates must be continental crust. Rationale: Continent crust does not subduct because it is composed of low-density, high-buoyancy material.
Which plate boundary has the lowest earthquake frequency?
Divergent boundaries Rationale: The warm rocks located at divergent boundaries have a lower rigidity. They do not build up as much stress as rocks at other locations before deforming
Which of the following accurately characterize spreading center earthquakes?
Earthquakes can occur in swarms as magma migrates underground. Small and moderate-size earthquakes dominate.
Which of the following accurately describes the tectonic setting in the area of the Red Sea, Gulf of Aden, and the northeastern portion of Africa?
Magma beneath northeastern Africa has caused doming, which resulted in gravity-fueled pull-apart faulting and rifting.
Doming
Mantle heating causes melting, and that results in the surface of the Earth extending upward.
Which of the following accurately describe the tectonic boundaries of the Pacific plate?
Smaller earthquakes occur at its spreading centers. Slide-past motions dominate in the northeast Pacific and along its eastern border with California. The Pacific Plate subducts along its northern and western edges.
Why do the common earthquakes of the Salton Trough tend to occur in swarms?
The earthquakes are related to the forceful movement of magma beneath the crust.
Why is there a depth-related distribution in the power of earthquakes at a subduction zone?
The forces that cause earthquakes align differently with depth, and the rock's resistance to stress changes with depth.
What has been the effect of the triple junction located in the northeast Africa since its development about 25 million years ago?
The influx of seawater into a rift zone has created a sea between Africa and separated the land on the Arabian Plate. It has created steep escarpments and dramatic valleys in northeast Africa. It has created the Arabian plate by splitting it from northeast Africa.
Centering
The lithosphere moves over an especially hot region of the mantle.
Why do subduction zones result in earthquakes with the greatest magnitudes?
The process of subducting a tectonic slab or pushing two continents together requires incredible amounts of energy.
What is the reason divergent boundaries have fewer earthquakes than other boundaries?
The rocks located there are warmer, which prevents them from building up a lot of stored stress.
What is creating the down-dropped rift valleys in pull-part basins that have formed the Red Sea, Gulf of Aden, and the Great Rift Valley?
The triple junction of three spreading centers
Why is an ocean basin opening up north of the Gulf of California in the Salton Sea area of California?
There is a developing spreading-center segment of the rift that opened the Gulf of California.
Why are the interiors of subducting slabs the only places on the slab where powerful earthquakes can occur at great depth?
They are the only places left on the descending slabs still cold enough to resist the pressures before breaking in a rigid manner.
Most earthquakes that occur along fracture zones between segments of midocean ridge occur ______.
on the segments between offset sections of ridge crest