Question 1

Volcanic activity associated with subduction zones is more gentle and less explosive than volcanic activity associated with hot spots and midocean ridges.

Accepted Answer

Volcanic activity associated with subduction zones can result in explosive events such as stratovolcano eruptions and pyroclastic flows. Hot spots and midocean ridges, on the other hand, tend to produce more gentle eruptions such as shield volcanoes and fissure eruptions.

Question 2

P waves travel more quickly than S waves.

Accepted Answer

P waves, also known as primary waves, are longitudinal waves that travel faster than S waves, or secondary waves, which are transverse waves. This is because P waves can travel through both solid and liquid material, whereas S waves can only travel through solid material.

Question 3

Deep Earthquakes (below 100km or 60mi) are usually associated with oceanic ridges.

Accepted Answer

Deep earthquakes are typically associated with subduction zones where one tectonic plate is forced under another, not with mid-ocean ridges where plates are moving apart.

Question 4

The midocean ridges and rises are spreading centers where new oceanic crust is created.

Accepted Answer

The midocean ridges and rises are areas where tectonic plates are moving apart, allowing magma to rise up and solidify, creating new oceanic crust.

Question 5

The continental landmasses are less dense than the mantle and are buoyed up by depressing the underlying mantle.

Accepted Answer

The continental crust is less dense than the mantle and therefore floats on top of it, creating continental landmasses. This is due to a process known as isostasy, which involves the depression of the underlying mantle to counteract the weight of the continental crust.

Question 6

Shear waves do not pass through a solid-liquid boundary between Earth's layers. Compressional waves can pass this type of boundary.

Accepted Answer

This statement is true. Shear waves are transverse waves that propagate only through solid materials, while compressional waves are longitudinal waves that can pass through both solid and liquid materials. Therefore, only compressional waves can travel through a solid-liquid boundary between Earth's layers.

Question 7

The thickness of deep-sea sediments increases with distance from a spreading center.

Accepted Answer

This is known as the "age-depth relationship" and occurs because sediments accumulate over time on the ocean floor, with the thickest sediments found furthest from spreading centers where the seafloor is older.

Question 8

The refraction and shadow patterns of seismic P-waves and S-waves indicate the dimensions and properties of Earth's layers.

Accepted Answer

This statement is true. Seismic waves, including P-waves and S-waves, travel through Earth's layers and change speed and direction as they encounter different materials. This causes the waves to refract and create shadow zones, which can be detected by seismic sensors. By studying the pattern of refraction and shadow zones, scientists can infer the dimensions and properties of Earth's layers.

Question 9

The largest lithospheric plate is the Pacific plate.

Accepted Answer

The Pacific plate is indeed the largest lithospheric plate, covering an area of approximately 103 million square kilometers.

Question 10

The North Atlantic Ocean was the first modern ocean to open during the breakup of Pangaea.

Accepted Answer

The Atlantic Ocean was not the first modern ocean to open; it was the Red Sea and the Indian Ocean that began to form earlier as Pangaea broke apart.

Question 11

The edge of an active continental margin bordered by a deep-sea trench is wide and shallow with deep deposits of land-derived sediments.

Accepted Answer

The edge of an active continental margin is characterized by a narrow and steep continental shelf, a relatively deep slope, and a deep-sea trench. The sediment deposits along this margin are mostly from oceanic processes such as biogenic and volcanic activity, rather than land-derived sediments.

Question 12

Earth's inner core is liquid whereas its outer core is solid.

Accepted Answer

Earth's outer core is actually liquid, while the inner core is solid due to the high pressure and temperature at its center.

Question 13

Isostatic columns of crustal material produce equal pressures deep within the mantle.

Accepted Answer

Isostatic columns of crustal material are in a state of isostasy, where the forces created by the weight of the material are balanced with the buoyancy forces caused by the displacement of the underlying mantle material. This results in a state of equilibrium, where the pressure deep within the mantle is equalized below the column. Therefore, the statement is true.

Question 14

The deep mantle below the asthenosphere is called the mesosphere.

Accepted Answer

The deep mantle below the asthenosphere is called the mesosphere.

Question 15

P waves travel only along the Surface of the Earth.

Accepted Answer

P waves, also known as primary waves, can travel through the Earth's interior, including its core, and do not solely travel along the surface. However, they can also travel along the surface as Love waves.

Question 16

The age of the seamounts from Hawaii to Midway Island increases in age from east to west.

Accepted Answer

This is known as the Emperor seamount chain and is a result of the Pacific Plate moving over a hotspot. As the plate moves, new volcanoes are formed, and the older ones move further away from the hotspot, resulting in a linear progression of increasing age from east (Hawaii) to west (Midway Island).

Question 17

The San Andreas fault is an example of a transform fault.

Accepted Answer

The San Andreas fault is a well-known transform fault located in California, USA. Transform faults are characterized by horizontal movement along the fault plane, as the tectonic plates move past each other in opposite directions.

Question 18

Epicenters are points on Earth's surface directly above a hot spot.

Accepted Answer

Epicenters are actually points on Earth's surface directly above the focus or hypocenter of an earthquake, not above a hot spot. Hot spots are regions of volcanic activity that occur away from tectonic plate boundaries, often in the middle of tectonic plates.

Question 19

Oceanic-type crust is more dense than continental-type crust.

Accepted Answer

Oceanic crust is composed mainly of basaltic rock, which is denser than the granitic rock that makes up continental crust.

Question 20

The steeper profile of the Mid-Atlantic Ridge compared to the East Pacific Rise indicates that the Mid-Atlantic Ridge is the faster spreading center.

Accepted Answer

The steeper profile of the Mid-Atlantic Ridge compared to the East Pacific Rise actually indicates that the Mid-Atlantic Ridge is a slower spreading center. Faster spreading centers like the East Pacific Rise tend to have smoother, less steep profiles.

Quiz 2: Earth Structure and Plate Tectonics

Volcanic activity associated with subduction zones is more gentle and less explosive than volcanic activity associated with hot spots and midocean ridges.

P waves travel more quickly than S waves.

Deep Earthquakes (below 100km or 60mi) are usually associated with oceanic ridges.

The midocean ridges and rises are spreading centers where new oceanic crust is created.

The continental landmasses are less dense than the mantle and are buoyed up by depressing the underlying mantle.

Shear waves do not pass through a solid-liquid boundary between Earth's layers. Compressional waves can pass this type of boundary.

The thickness of deep-sea sediments increases with distance from a spreading center.

The refraction and shadow patterns of seismic P-waves and S-waves indicate the dimensions and properties of Earth's layers.

The largest lithospheric plate is the Pacific plate.

The North Atlantic Ocean was the first modern ocean to open during the breakup of Pangaea.

The edge of an active continental margin bordered by a deep-sea trench is wide and shallow with deep deposits of land-derived sediments.

Earth's inner core is liquid whereas its outer core is solid.

Isostatic columns of crustal material produce equal pressures deep within the mantle.

The deep mantle below the asthenosphere is called the mesosphere.

P waves travel only along the Surface of the Earth.

The age of the seamounts from Hawaii to Midway Island increases in age from east to west.

The San Andreas fault is an example of a transform fault.

Epicenters are points on Earth's surface directly above a hot spot.

Oceanic-type crust is more dense than continental-type crust.

The steeper profile of the Mid-Atlantic Ridge compared to the East Pacific Rise indicates that the Mid-Atlantic Ridge is the faster spreading center.