1.
What is the Lehmann Discontinuity?
Correct Answer
B. Seismic boundary
Explanation
The Lehmann Discontinuity is a seismic boundary within the Earth's interior, specifically located near the core-mantle boundary. It represents a zone where seismic waves experience changes in velocity, indicating a transition between different layers of the Earth.
2.
Where is the Lehmann Discontinuity located?
Correct Answer
B. Upper mantle
Explanation
The Lehmann Discontinuity is located in the upper mantle of the Earth’s interior. It is an abrupt increase of P-wave and S-wave velocities at a depth of 220 km beneath the Earth’s surface. It appears beneath continents, but not usually beneath oceans and does not readily appear in globally averaged studies. So, the correct answer is B. Upper mantle.
3.
What type of seismic waves are often associated with the Lehmann Discontinuity?
Correct Answer
A. P-waves
Explanation
The correct answer is A. P-waves. The Lehmann Discontinuity, named after seismologist Inge Lehmann, is an abrupt increase of P-wave and S-wave velocities at a depth of 220 km beneath the Earth’s surface. It appears beneath continents but not usually beneath oceans and does not readily appear in globally averaged studies. So, P-waves are often associated with the Lehmann Discontinuity.
4.
What is the significance of the Lehmann Discontinuity in terms of Earth's structure?
Correct Answer
D. Marks the boundary between the inner and outer core
Explanation
The Lehmann Discontinuity is significant in terms of Earth’s structure as it marks the boundary between the inner and outer core. This discontinuity was theorized by seismologist Inge Lehmann and is defined by an increase in seismic wave velocity from the outer to the inner core and by seismic wave reflection off the solid inner core. So, the correct answer is D. Marks the boundary between the inner and outer core.
5.
How is the Lehmann Discontinuity detected?
Correct Answer
A. Seismic wave analysis
Explanation
The Lehmann Discontinuity is primarily detected through the analysis of seismic waves generated by earthquakes. Changes in the behavior of seismic waves as they travel through the Earth's interior help scientists identify the presence and characteristics of the Lehmann Discontinuity.
6.
Which type of seismic wave can travel through both solids and liquids?
Correct Answer
A. P-wave
Explanation
P-waves or primary waves can travel through both solids and liquids, as they are compression waves that propagate by compressing and expanding the material they pass through.
7.
Which layer of the Earth's interior is responsible for generating Earth's magnetic field?
Correct Answer
C. Outer core
Explanation
The outer core, which is in a liquid state, contains molten iron and nickel. The movement of this liquid metal creates Earth's magnetic field through the process of convection.
8.
Which of the following tectonic plate boundaries is characterized by plates moving away from each other?
Correct Answer
B. Divergent boundary
Explanation
A divergent boundary occurs when tectonic plates move away from each other. This movement creates a gap where new crust is formed as magma rises from the mantle. Divergent boundaries often occur along mid-ocean ridges.
9.
What type of seismic wave causes the most damage during an earthquake?
Correct Answer
A. Rayleigh wave
Explanation
Rayleigh waves are surface waves that move in a rolling motion, causing the ground to shake in an elliptical pattern. They have a complex motion and can produce vertical and horizontal ground displacements. Rayleigh waves often result in the most significant ground shaking and can cause considerable damage to structures during an earthquake. While all seismic waves (P-waves, S-waves, Love waves, and Rayleigh waves) contribute to the overall impact of an earthquake, surface waves like the Rayleigh wave tend to have a more pronounced effect on the Earth's surface and structures.
10.
Which tectonic plate boundary involves the collision of two plates?
Correct Answer
A. Convergent boundary
Explanation
A convergent boundary occurs when two tectonic plates collide. Depending on the types of plates involved, it can result in the formation of mountains, volcanic activity, or subduction zones.
11.
What is the minimum number of seismic stations needed to determine the location of an earthquake epicenter?
Correct Answer
C. 3
Explanation
At least three seismic stations are required to determine the location of an earthquake epicenter. By analyzing the time difference between the arrival of P-waves and S-waves at each station, the epicenter can be triangulated.
12.
Which layer of the Earth's interior is the thickest?
Correct Answer
B. Mantle
Explanation
The mantle is the thickest layer of the Earth's interior, extending from the base of the crust to the top of the outer core. It constitutes about 84% of the Earth's total volume and is primarily composed of solid rock.
13.
Which tectonic plate boundary is responsible for the formation of volcanoes?
Correct Answer
A. Convergent boundary
Explanation
Volcanoes are primarily formed at convergent plate boundaries. When an oceanic plate collides with a continental plate, the denser oceanic plate is forced beneath the continental plate in a process called subduction. This subduction triggers volcanic activity.
14.
What type of seismic wave arrives at a seismic station first during an earthquake?
Correct Answer
C. P-wave
Explanation
P-waves or primary waves are the fastest seismic waves and arrive at a seismic station first during an earthquake. They are compressional waves that travel through solids, liquids, and gases.
15.
Which tectonic boundary is responsible for the majority of earthquakes worldwide?
Correct Answer
D. Subduction zone
Explanation
Subduction zones, which occur at convergent plate boundaries, are responsible for the majority of the world's earthquakes. These zones are characterized by one tectonic plate being forced beneath another, creating intense seismic activity.