Question 1

As early as the 1700s, scientists and observers noticed a remarkable coincidence of shape of the Atlantic coasts of Africa and .

Accepted Answer

The Atlantic coasts of Africa and South America appear to fit together like pieces of a jigsaw puzzle, which was an early observation that contributed to the development of the theory of continental drift.

Question 2

Japan is located along the " Pacific Ring of Fire " and experiences many earthquakes. The majority of  the earthquakes around Japan occur .

Accepted Answer

The majority of earthquakes around Japan occur on the east side of the island where the Pacific Plate subducts beneath the North American and Philippine Sea Plates, which is part of the Pacific Ring of Fire.

Question 3

Scientists believe the breakup of Pangaea occurred about .

Accepted Answer

The breakup of Pangaea is estimated to have begun around 200 million years ago during the early Mesozoic era.

Question 4

If two oceanic plates collide and one is older and cooler (and therefore, denser) than the other, what will happen?

Accepted Answer

When two oceanic plates collide, the older, cooler, and denser plate will subduct beneath the other, leading to the formation of a deep oceanic trench.

Question 5

What is the primary reason for the inside of Earth being hot?

Accepted Answer

The primary reason for Earth's internal heat is the decay of radioactive elements, which generates heat in the inner layers.

Question 6

Why was Alfred Wegener's idea of continental drift dismissed?

Accepted Answer

At the time, the scientific community believed in a solid mantle, which seemed to contradict Wegener's idea of continents drifting over it.

Question 7

Buoyancy is the ability of an object to float in a fluid by .

Accepted Answer

Buoyancy occurs when an object displaces a volume of fluid equal to its own weight, allowing it to float.

Question 8

California's San Andreas fault is which type of plate boundary?

Accepted Answer

The San Andreas fault is a transform plate boundary where two tectonic plates slide past each other horizontally.

Question 9

The accounts for 83 percent of Earth's volume.

Accepted Answer

The mantle is the largest layer of Earth, making up about 83 percent of its volume.

Question 10

The rigid outer layer of Earth that comprises the continental crust, oceanic crust, and the uppermost mantle is called the .

Accepted Answer

The lithosphere is the rigid outer layer of Earth that comprises the continental crust, oceanic crust, and the uppermost mantle.

Question 11

Earlier than 200 million years ago, the continents were joined into one supercontinent called .

Accepted Answer

Pangaea was a supercontinent that existed during the late Paleozoic and early Mesozoic eras, about 335 million to 175 million years ago. It was formed from the collision of all the major landmasses on Earth at the time.

Question 12

The youngest seafloor rocks are found .

Accepted Answer

The youngest seafloor rocks are found near the rift valleys of mid-ocean ridges where new crust is formed by volcanic activity.

Question 13

What are the primary elements in Earth's continental crust?

Accepted Answer

The primary elements in Earth's continental crust are oxygen, silicon, and aluminum, which are the most abundant elements in the crust.

Question 14

A "mystery" in our understanding of plate tectonics has been, until recently, the nature of the power source capable of moving the plates and the continents embedded within them. Recent evidence indicates the power source to be .

Accepted Answer

Convection currents within Earth's mantle are the primary force driving the movement of tectonic plates. These currents are caused by the heat from the Earth's core, which creates a cycle of rising and sinking material in the mantle, pushing and pulling the plates along.

Question 15

About how many kilometers (miles) is it from the center of Earth to the outer edge of the outer core?

Accepted Answer

The answer of About how many kilometers (miles) is it...

Question 16

The mid-ocean ridges are .

Accepted Answer

Mid-ocean ridges are divergent plate boundaries where tectonic plates move apart, allowing magma to rise and create new oceanic crust.

Question 17

A cross section of Earth reveals a layered structure that has different thicknesses and densities. How do geologists know this?

Accepted Answer

Geologists use seismic waves generated by earthquakes to study Earth's interior. The waves travel at different speeds through different materials, allowing scientists to infer the structure and composition of Earth's layers.

Question 18

The hot, partially melted, slowly flowing layer of Earth is called the .

Accepted Answer

The asthenosphere is the hot, partially melted, and slowly flowing layer of the Earth located beneath the lithosphere.

Question 19

One cubic meter of which of these would weigh the most?

Accepted Answer

The mantle is composed of dense materials like peridotite, which is denser than ocean water, granite, or basaltic rock, making it the heaviest per cubic meter.

Question 20

Roughly how fast do most lithospheric plates move?

Accepted Answer

Most lithospheric plates move at a rate of about 5 centimeters per year, which is consistent with the typical speed of tectonic plate movement.

Quiz 2: Plate Tectonics