4B2 Plate Tectonics and System Interactions

Question 1

Define:

Earth’s structure

Answer 1

It refers to the organization of its layers.

Question 2

What are the 4 layers of the Earth?

Answer 2

1. The Inner Core
2. The Outer Core
3. The Mantle
4. The Crust

These layers vary in composition and state, with the crust being solid, the mantle semi-solid, and the core liquid (outer) and solid (inner).

Question 3

True or False:

The Earth’s crust is the thickest layer.

Answer 3

False

The crust is the thinnest layer, averaging 5–70 km in thickness, whereas the mantle is ~2,900 km thick, and the core (outer + inner) is ~3,500 km thick.

Question 4

What is the Earth’s crust made of?

Answer 4

Solid rock, including silicates like basalt and granite.

The crust is Earth’s outermost layer and is composed of continental (granite) and oceanic (basalt) rocks.

Question 5

Fill in the blank:

The mantle consists mostly of silicate minerals rich in ________ and ______.

Answer 5

magnesium; iron

The mantle is composed of semi-solid rock that is more viscous than the crust, extending to about 2,900 km deep.

Question 6

Which layer is the thickest?

Answer 6

The mantle.

The mantle makes up about 84% of Earth’s total volume.

Question 7

How does the temperature of the inner core compare to the outer core?

Answer 7

The inner core is hotter.

The inner core’s temperature can reach up to 5,500°C, hotter than the outer core, but it remains solid due to immense pressure.

Question 8

How deep does the Earth’s mantle extend?

Answer 8

2,900 km.

The mantle lies between the Earth’s crust and the outer core, extending to significant depths.

Question 9

Fill in the blank:

The Earth’s ______ _____ is primarily responsible for generating Earth’s magnetic field.

Answer 9

outer core

The movement of molten iron and nickel in the outer core generates the geodynamo effect, which creates Earth’s magnetic field.

Question 10

True or False:

The inner core is composed of solid iron and nickel.

Answer 10

True

The high pressure at the Earth’s center keeps the inner core solid, despite its extreme temperature.

Question 11

What is crustal deformation?

Answer 11

The bending, stretching, or compression of Earth’s crust.

Deformation can result from stress caused by plate movements, leading to features such as folds, faults, and fractures.

Question 12

What are the three types of stress that cause crustal deformation?

Answer 12

1. Compression
2. Tension
3. Shear

Compression squeezes rocks, tension stretches them, and shear stress causes sliding in opposite directions.

Question 13

Which layer of Earth is composed of liquid iron and nickel?

Answer 13

The outer core.

The outer core is liquid due to the high temperatures but remains in motion, generating Earth’s magnetic field.

Question 14

What is the lithosphere?

Answer 14

The rigid outer layer of Earth, including the crust and upper mantle.

The lithosphere is broken into tectonic plates that interact at boundaries.

Question 15

What is the average thickness of the lithosphere?

Answer 15

About 100 km.

Oceanic lithosphere ranges from 5–100 km in thickness, while continental lithosphere varies from 40 km to over 200 km in ancient regions.

Question 16

Fill in the blank:

The movement of tectonic plates is primarily driven by ________ currents in the mantle.

Answer 16

convection

Heat from Earth’s core causes mantle material to rise and sink, creating convection currents that drive plate motion.

Question 17

How does convection work in Earth’s mantle?

Answer 17

Hotter, less dense material rises, while cooler, denser material sinks.

This process drives tectonic plate movement and is crucial for Earth’s internal heat distribution.

Question 18

Define:

plate tectonics theory

Answer 18

It explains that Earth’s lithosphere is divided into plates that move over the asthenosphere.

This theory unifies ideas of continental drift and seafloor spreading, describing the motion of tectonic plates caused by forces within the Earth.

Question 19

What are two primary driving forces of plate motion?

Answer 19

1. Slab pull
2. Ridge push

Slab pull – Caused by the sinking of a dense plate into the mantle.

Ridge push – Results from gravitational forces at mid-ocean ridges.

Question 20

What is slab pull?

Answer 20

The force exerted by a sinking, subducting plate.

This force occurs as the dense oceanic plate sinks into the mantle at subduction zones, pulling the rest of the plate with it.

Question 21

What is ridge push?

Answer 21

The gravity-driven force on the raised lithosphere at mid-ocean ridges.

Newly formed, warm crust at ridges is less dense and slides away due to gravity, pushing older crust outward.

Question 22

What are the three main types of plate boundaries?

Answer 22

1. Convergent
2. Divergent
3. Transform

These boundaries describe the interactions between tectonic plates, such as collision, separation, and lateral sliding.

Question 23

Fill in the blank:

A ________ boundary occurs when two tectonic plates move apart.

Answer 23

divergent

Divergent boundaries often create mid-ocean ridges or rift valleys.

Question 24

What type of plate boundary is associated with trenches?

Answer 24

Convergent

Trenches form at subduction zones, where one tectonic plate is forced beneath another, typically involving an oceanic plate descending into the mantle, creating deep underwater depressions.

Question 25

What happens at a **convergent boundary**?

Answer 25

**Two plates collide**, and one may subduct beneath the other. ## Footnote Convergent boundaries can form *mountain ranges*, *trenches*, or *volcanic arcs*, depending on the plates involved.

Question 26

What happens at a **transform boundary**?

Answer 26

Two plates **slide** past each other horizontally. ## Footnote *Transform boundaries* are associated with strike-slip faults, such as the San Andreas Fault in California.

Question 27

# True or False: Subduction occurs at **divergent boundaries**.

Answer 27

False ## Footnote **Subduction** occurs at **convergent** boundaries where one plate sinks beneath another.

Question 28

What geological feature provides evidence for **seafloor spreading**?

Answer 28

Mid-ocean ridges ## Footnote These **ridges** form where magma rises to create new crust, pushing older crust outward.

Question 29

Which type of plate boundary is the **San Andreas Fault**?

Answer 29

Transform ## Footnote The *San Andreas Fault* is an example of a strike-slip fault where the Pacific Plate slides past the North American Plate.

Question 30

What is formed when two **continental plates collide**?

Answer 30

Mountain ranges ## Footnote The **Himalayas** are an example of mountains formed at a convergent boundary between two continental plates.

Question 31

# True or False: Tectonic plates are made **only** of continental crust.

Answer 31

False ## Footnote Plates can consist of **both** oceanic and continental crust, or just one type.

Question 32

# Fill in the blank: The **supercontinent** that existed about 300 million years ago is known as _________.

Answer 32

Pangaea ## Footnote **Pangaea** eventually split apart due to tectonic plate movements, forming the continents we know today.

Question 33

# Fill in the blank: Deformation typically **occurs** in Earth's \_\_\_\_\_\_\_\_\_.

Answer 33

lithosphere ## Footnote The **lithosphere** is rigid and can deform under tectonic forces, leading to geological features.

Question 34

# True or False: Faulting occurs **without** breaking the rock.

Answer 34

False ## Footnote Faulting involves the **breaking** of rocks, often leading to earthquakes.

Question 35

What is **brittle deformation**?

Answer 35

**Breaking** of rocks under stress. ## Footnote Brittle deformation typically occurs near Earth's surface where temperatures and pressures are lower.

Question 36

What is **folding**?

Answer 36

**Bending** of rock layers. ## Footnote Folds often form in sedimentary rocks and create features like anticlines and synclines.

Question 37

What is **faulting**?

Answer 37

**Breaking** of rock layers with movement. ## Footnote Faults are classified as normal, reverse, or strike-slip based on the direction of movement.

Question 38

# Fill in the blank: \_\_\_\_\_\_\_ deformation causes **permanent changes** to rock shape.

Answer 38

Plastic ## Footnote *Plastic deformation* occurs under high pressure and temperature, causing rocks to bend rather than break.

Question 39

# True or False: Trenches can form at **transform boundaries**.

Answer 39

False ## Footnote Trenches are exclusive to **convergent** boundaries where subduction occurs.

Question 40

# Fill in the blank: The **presence** of \_\_\_\_\_\_\_\_ fossils on separate continents **supports continental drift**.

Answer 40

identical ## Footnote Fossils of species like *Mesosaurus* found on continents now separated by oceans suggest they were once connected.

Question 41

List **types of supporting evidence** used in plate tectonics.

Answer 41

1. Ages of crustal rocks 1. Hot-spot volcanoes 1. Distribution of rocks and fossils 1. Continental shapes ## Footnote **Ages of crustal rocks** - Older rocks are farther from ridges. **Hot-spot volcanoes** - Fixed volcanoes show plate movement. **Distribution of rocks and fossils** - Similar rocks/fossils found on different continents. **Continental shapes** - Matching coastlines suggest past connection.

Question 42

How does **seismic activity** provide evidence for plate tectonics?

Answer 42

Earthquakes happen at **plate boundaries**, showing plate interaction. ## Footnote The distribution of seismic activity **aligns** with the edges of tectonic plates.

Question 43

How are earthquakes **related** to deformation?

Answer 43

They **release energy** when rocks shift. ## Footnote **Earthquakes** usually happen at plate boundaries where stress accumulates.

Question 44

# Fill in the blank: The **point** on Earth’s surface directly above the earthquake’s focus is called the \_\_\_\_\_\_\_\_\_\_.

Answer 44

epicenter ## Footnote The **epicenter** is the point on Earth's surface directly above the earthquake’s focus (hypocenter), where seismic waves typically cause the greatest shaking and damage.

Question 45

# True or False: Aftershocks are usually **stronger** than the main earthquake.

Answer 45

False ## Footnote Aftershocks are smaller, but they can still cause *significant* damage.

Question 46

Where are most earthquakes **located**?

Answer 46

Along **tectonic plate** boundaries. ## Footnote **Earthquakes** frequently occur in regions where plates collide, pull apart, or slide past each other.

Question 47

# True or False: Earthquakes are **equally** distributed around the world.

Answer 47

False ## Footnote Earthquakes are **concentrated** along plate boundaries, forming the *Ring of Fire* around the Pacific Ocean.

Question 48

What are **aftershocks**?

Answer 48

**Smaller tremors** that occur **after** the main earthquake. ## Footnote Aftershocks happen as the Earth *adjusts* to the new position of the tectonic plates.

Question 49

# Fill in the blank: The \_\_\_\_\_ \_\_\_ \_\_\_\_\_ is a **major area** in the Pacific Ocean with many earthquakes and volcanoes.

Answer 49

Ring of Fire ## Footnote This **region** encircles the Pacific plate and is home to **75%** of the world's active volcanoes.

Question 50

What is the **measure of energy released** during an earthquake?

Answer 50

Magnitude ## Footnote **Magnitude** is commonly measured using the Richter scale or moment magnitude scale (Mw).

Question 51

# True or False: The Richter scale measures the **damage** caused by an earthquake.

Answer 51

False ## Footnote The Richter scale measures the earthquake's **size**, not the damage. The damage is often measured by the Modified Mercalli Intensity scale.

Question 52

What is a **seismograph**?

Answer 52

An instrument used to **detect** and **record** seismic waves. ## Footnote Seismographs measure the *ground motion* caused by earthquakes and provide data about their intensity and duration.

Question 53

What is the **moment magnitude scale**?

Answer 53

A scale that measures the **total energy released** by an earthquake. ## Footnote It is more **accurate** than the Richter scale for large earthquakes, considering the fault size and slip.

Question 54

# Fill in the blank: A magnitude 7 earthquake is \_\_\_\_\_ times **more powerful** than a magnitude 6.

Answer 54

32 ## Footnote Each whole number increase on the magnitude scale represents a **32-fold** increase in energy release.

Question 55

What are **seismic waves**?

Answer 55

**Waves of energy** that travel through Earth’s layers. ## Footnote They are generated by **earthquakes** and provide insight into Earth’s internal structure.

Question 56

What wave causes the **most damage** during an earthquake?

Answer 56

Surface waves ## Footnote *Surface waves*, including Love and Rayleigh waves, move slower than P-waves and S-waves but have larger amplitudes, causing intense ground motion that leads to significant structural damage.

Question 57

What is a **volcano**?

Answer 57

A **rupture** in Earth's crust where molten lava, gas, and ash escape. ## Footnote Volcanic eruptions occur when magma from Earth's mantle reaches the surface, forming lava, ash, and gases.

Question 58

What **causes** volcanic eruptions?

Answer 58

**Pressure** from magma forces its way through Earth's crust. ## Footnote *Magma* rises due to pressure from tectonic plate movements or hot spots, leading to eruptions.

Question 59

# Fill in the blank: Volcanic mountains **form** when \_\_\_\_\_\_\_ builds up.

Answer 59

magma ## Footnote Volcanic mountains are often **found** at convergent and divergent plate boundaries.

Question 60

What is a **hotspot**?

Answer 60

A **volcanic region** fed by mantle plumes beneath a tectonic plate. ## Footnote Examples include the *Hawaiian Islands*, which formed as the Pacific Plate moved over a hotspot.

Question 61

How do hot spots **form** volcanoes?

Answer 61

By magma **rising** from deep within the Earth. ## Footnote As tectonic plates move over hot spots, a series of volcanoes can form, like the Hawaiian chain.

Question 62

# True or False: Volcanoes **only** occur at convergent plate boundaries.

Answer 62

False ## Footnote Volcanoes **also** occur at divergent boundaries (e.g., mid-ocean ridges) and hotspots.

Question 63

# Fill in the blank: The **largest type** of volcano is a \_\_\_\_\_\_\_ volcano.

Answer 63

shield ## Footnote *Shield volcanoes* can cover large areas with lava flows, making them the largest by volume and area.

Question 64

# True or False: Composite volcanoes have **gentle eruptions**.

Answer 64

False ## Footnote *Composite volcanoes* tend to have **explosive** eruptions due to the thick, viscous magma that traps gas.

Question 65

What is the **difference** between a shield and a composite volcano?

Answer 65

* **Shield** volcanoes have **gentle** slopes. * **Composite** volcanoes are steeper and more **explosive**. ## Footnote Shield volcanoes produce fluid lava, while composite volcanoes alternate between lava flows and explosive eruptions.

Question 66

What is **magma**?

Answer 66

**Molten** rock beneath Earth's surface. ## Footnote When magma reaches the surface, it is called lava, and its composition affects the type of eruption.

Question 67

What is magma called when it **reaches** Earth's surface?

Answer 67

Lava ## Footnote **Lava** cools and solidifies, forming rocks such as basalt or andesite.

Question 68

# True or False: Lava that is **high in silica** tends to flow **more quickly**.

Answer 68

False ## Footnote **Lava** high in silica is more viscous, causing it to flow **slowly** and often form steeper volcanic cones.

Question 69

What is **pyroclastic flow**?

Answer 69

A **fast-moving mixture** of hot gas, ash, and volcanic material. ## Footnote *Pyroclastic flows* are *extremely dangerous*, as they travel quickly and can reach temperatures of over **1,000°C.**

Question 70

# True or False: Volcanic eruptions **always lead** to significant damage.

Answer 70

False ## Footnote While **eruptions** can be catastrophic, many eruptions, especially from shield volcanoes, are non-explosive and cause *minimal damage*.

Question 71

# Fill in the blank: Volcanic \_\_\_\_\_ is **fine rock** and **mineral debris** ejected during an eruption.

Answer 71

ash ## Footnote **Ash** can cause health problems, disrupt air travel, and damage buildings and crops.

Question 72

What are the **characteristics** of a tsunami?

Answer 72

**Large ocean waves** from underwater disturbances. ## Footnote Often caused by earthquakes or landslides, **tsunamis** travel fast and can lead to severe coastal flooding.

Question 73

# True or False: Earthquakes can be predicted with **exact** timing and location.

Answer 73

False ## Footnote While scientists can *identify high-risk zones*, no technology can precisely predict when an earthquake will occur.

Question 74

What is an **earthquake-resistant building**?

Answer 74

A **structure** designed to withstand seismic forces and reduce damage. ## Footnote These buildings use *shock absorbers*, *flexible materials*, and *reinforced frameworks*.

Question 75

Why are **elevated buildings** used in tsunami-prone areas?

Answer 75

To **reduce damage** by allowing water to pass beneath them. ## Footnote Stilt-based designs *minimize* resistance against strong waves and prevent total destruction.

Question 76

List **three** tsunami defense structures.

Answer 76

1. Seawalls 2. Breakwaters 3. Floodgates ## Footnote **Seawalls** – Barriers that block or slow tsunami waves. **Breakwaters** – Offshore structures that reduce wave energy. **Floodgates** – Systems that control water flow to prevent inland flooding.