Question 1

What is the outermost layer of the Earth called?

Accepted Answer

The outermost layer is called the crust (or lithosphere when combined with the upper mantle).

Question 2

What causes tectonic plates to move?

Accepted Answer

Tectonic plates move due to convection currents in the mantle caused by heat from Earth's core.

Question 3

Name the three types of plate boundaries.

Accepted Answer

Convergent (plates collide), divergent (plates move apart), and transform (plates slide past each other).

Question 4

What landform is created when two continental plates collide?

Accepted Answer

Mountain ranges are formed when two continental plates collide (e.g., the Himalayas).

Question 5

What happens at a divergent boundary?

Accepted Answer

At divergent boundaries, plates move apart and new crust is formed as magma rises to fill the gap.

Question 6

What occurs at a transform boundary?

Accepted Answer

At transform boundaries, plates slide horizontally past each other, causing earthquakes. The San Andreas Fault in California is a well-known example.

Question 7

What is subduction?

Accepted Answer

Subduction occurs at convergent boundaries when a denser oceanic plate slides beneath a lighter continental plate, sinking into the mantle. This can form trenches and volcanic arcs.

Question 8

Where do most earthquakes and volcanoes occur?

Accepted Answer

Most earthquakes and volcanoes occur along plate boundaries, especially around the Pacific Plate — a region called the "Ring of Fire."

Question 9

What is an earthquake?

Accepted Answer

An earthquake is a sudden shaking of the ground caused by the release of energy from rocks that break or slip along a fault.

Question 10

What is a fault?

Accepted Answer

A fault is a crack or fracture in Earth's crust along which rocks can move. Movement along faults causes earthquakes.

Question 11

What is the difference between the focus and the epicenter of an earthquake?

Accepted Answer

The focus (hypocenter) is the underground point where the earthquake originates. The epicenter is the point on Earth's surface directly above the focus.

Question 12

What scale is used to measure earthquake magnitude, and what does it mean?

Accepted Answer

The Richter scale (or moment magnitude scale) measures earthquake magnitude. Each whole number increase represents about 10× more shaking and ~31.6× more energy released.

Question 13

What are seismic waves, and what are the two main types?

Accepted Answer

Seismic waves are energy waves released by an earthquake. Primary waves (P-waves) compress rock and travel through solids and liquids; Secondary waves (S-waves) shake rock side-to-side and only travel through solids.

Question 14

How do volcanoes form at convergent plate boundaries?

Accepted Answer

When an oceanic plate subducts beneath a continental plate, the sinking plate melts in the mantle. The resulting magma rises through the crust, forming a volcano.

Question 15

What is the difference between magma and lava?

Accepted Answer

Magma is molten rock beneath Earth's surface. Once it erupts and reaches the surface, it is called lava.

Question 16

What are hot spots, and give one example?

Accepted Answer

Hot spots are areas where unusually hot mantle material rises and melts through the crust, forming volcanoes not at plate boundaries. The Hawaiian Islands were formed by a hot spot.

Question 17

Why do some volcanic eruptions produce lava flows while others produce explosive ash clouds?

Accepted Answer

Lava composition matters: low-silica (basaltic) magma is runny and flows easily; high-silica (rhyolitic) magma is thick, traps gases, and leads to explosive eruptions.

Question 18

Explain why the Himalayas are still growing taller each year.

Accepted Answer

The Indian Plate and Eurasian Plate are both continental plates that continue to converge. Since neither plate subducts, the collision keeps pushing rock upward, slowly increasing the height of the Himalayas.

Question 19

A geologist finds identical fossils and rock layers on the east coast of South America and the west coast of Africa. What does this evidence suggest?

Accepted Answer

It supports the theory of continental drift — these continents were once joined together as part of the supercontinent Pangaea and have since separated through plate movement.

Question 20

Why can scientists use seismic wave data to learn about Earth's interior layers?

Accepted Answer

P-waves travel through solids and liquids while S-waves only travel through solids. By tracking how these waves bend and stop at different depths, scientists can infer the composition and state (solid/liquid) of Earth's layers.

Plate Tectonics Answer Key

Prior Knowledge Questions

Activity A – Plate Boundaries

Activity B – Earthquakes

Activity C – Volcanoes

Assessment Questions

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