4B1 Tectonics and Internal Earth Processes

Question 1

What are the 4 layers of the Earth?

Answer 1

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

Question 2

What is the lithosphere?

Answer 2

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

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

Question 3

Define:

plate tectonics theory

Answer 3

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 4

What is the average thickness of the lithosphere?

Answer 4

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 5

What are two primary driving forces of plate motion?

Answer 5

1. Slab pull
2. Ridge push

Slab pull is caused by the sinking of a dense plate into the mantle; ridge push results from gravitational forces at mid-ocean ridges.

Question 6

Fill in the blank:

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

Answer 6

convection

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

Question 7

What is slab pull?

Answer 7

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 8

What is ridge push?

Answer 8

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 9

What are the three main types of plate boundaries?

Answer 9

1. Convergent
2. Divergent
3. Transform

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

Question 10

What happens at a convergent boundary?

Answer 10

Two plates collide, and one may subduct beneath the other.

Convergent boundaries can form mountain ranges, trenches, or volcanic arcs, depending on the plates involved.

Question 11

Fill in the blank:

A ________ boundary occurs when two tectonic plates move apart.

Answer 11

divergent

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

Question 12

What happens at a transform boundary?

Answer 12

Two plates slide past each other horizontally.

Transform boundaries are associated with strike-slip faults, such as the San Andreas Fault in California.

Question 13

True or False:

Subduction occurs at divergent boundaries.

Answer 13

False

Subduction occurs at convergent boundaries where one plate sinks beneath another.

Question 14

What geological feature provides evidence for seafloor spreading?

Answer 14

Mid-ocean ridges

These ridges form where magma rises to create new crust, pushing older crust outward.

Question 15

Fill in the blank:

The presence of ________ fossils on separate continents supports the idea of continental drift.

Answer 15

identical

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

Question 16

How does seismic activity provide evidence for plate tectonics?

Answer 16

Earthquakes happen at plate boundaries, showing plate interaction.

The distribution of seismic activity aligns with the edges of tectonic plates.

Question 17

True or False:

Volcanoes only occur at convergent plate boundaries.

Answer 17

False

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

Question 18

Which type of plate boundary is the San Andreas Fault?

Answer 18

Transform

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

Question 19

What is formed when two continental plates collide?

Answer 19

Mountain ranges

The Himalayas are an example of mountains formed at a convergent boundary between two continental plates.

Question 20

True or False:

Tectonic plates are made only of continental crust.

Answer 20

False

Plates can consist of both oceanic and continental crust, or just one type.

Question 21

Fill in the blank:

The ________ is the name of the supercontinent that existed about 300 million years ago.

Answer 21

Pangaea

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

Question 22

What is crustal deformation?

Answer 22

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 23

What are the three types of stress that cause deformation?

Answer 23

1. Compression
2. Tension
3. Shear

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

Question 24

Fill in the blank:

Deformation typically occurs in Earth’s _________.

Answer 24

lithosphere

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

Question 25

What is **folding**?

Answer 25

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

Question 26

What is **faulting**?

Answer 26

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

Question 27

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

Answer 27

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

Question 28

# Fill in the blank: \_\_\_\_\_\_\_\_ deformation results in **permanent** changes to the shape of rocks.

Answer 28

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

Question 29

What is **brittle deformation**?

Answer 29

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

Question 30

What **type** of plate boundary is associated with trenches?

Answer 30

Convergent ## Footnote 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 31

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

Answer 31

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

Question 32

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

Answer 32

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

Question 33

How are earthquakes **related** to deformation?

Answer 33

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

Question 34

What are **seismic waves**?

Answer 34

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

Question 35

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

Answer 35

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 36

Where are most earthquakes **located**?

Answer 36

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

Question 37

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

Answer 37

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

Question 38

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

Answer 38

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

Question 39

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

Answer 39

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 40

What is the **moment magnitude scale**?

Answer 40

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 41

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

Answer 41

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

Question 42

What are **P-waves**?

Answer 42

Primary waves that are the **fastest** seismic waves. ## Footnote P-waves travel through *both* solids and liquids, causing particles to move back and forth.

Question 43

What are **S-waves**?

Answer 43

Secondary waves that are **slower** than P-waves. ## Footnote S-waves move through *solids* only, causing particles to move in a side-to-side motion.

Question 44

# Fill in the blank: \_\_\_\_\_ waves **cannot** travel through liquids.

Answer 44

S-waves ## Footnote S-waves are stopped by the Earth’s outer core, which is liquid, helping scientists study Earth’s interior.

Question 45

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

Answer 45

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 46

# True or False: Seismic waves travel **faster** through less dense materials.

Answer 46

False ## Footnote Seismic waves travel **slower** through less dense materials and faster through denser materials.

Question 47

What are **aftershocks**?

Answer 47

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

Question 48

What is a **seismograph**?

Answer 48

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 49

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

Answer 49

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

Question 50

What is a **volcano**?

Answer 50

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 51

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

Answer 51

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

Question 52

What **causes** volcanic eruptions?

Answer 52

**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 53

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

Answer 53

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

Question 54

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

Answer 54

* 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 55

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

Answer 55

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

Question 56

What is **magma**?

Answer 56

**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 57

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

Answer 57

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

Question 58

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

Answer 58

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

Question 59

What is a **hotspot**?

Answer 59

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 60

How do hot spots **form** volcanoes?

Answer 60

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 61

What is **pyroclastic flow**?

Answer 61

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 62

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

Answer 62

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

Question 63

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

Answer 63

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

Question 64

What is the Earth's **crust** made of?

Answer 64

Solid rock, including silicates like basalt and granite. ## Footnote The crust is Earth's **outermost** layer and is composed of continental (granite) and oceanic (basalt) rocks.

Question 65

# Fill in the blank: The mantle consists **mostly** of silicate minerals rich in \_\_\_\_\_\_\_\_ and \_\_\_\_\_\_.

Answer 65

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

Question 66

# True or False: The Earth's crust is the **thickest** layer.

Answer 66

False ## Footnote 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 67

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

Answer 67

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

Question 68

# True or False: The inner core is **composed** of solid iron and nickel.

Answer 68

True ## Footnote The high pressure at the Earth's center keeps the inner core solid, despite its extreme temperature.

Question 69

Which layer is the **thickest**?

Answer 69

The mantle. ## Footnote The **mantle** makes up about 84% of Earth's total volume.

Question 70

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

Answer 70

The inner core is **hotter**. ## Footnote 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 71

How **deep** does the Earth's mantle extend?

Answer 71

2,900 km ## Footnote The mantle lies between the Earth's crust and the outer core, extending to significant depths.

Question 72

# Fill in the blank: The Earth’s \_\_\_\_\_\_ \_\_\_\_\_ is primarily responsible for **generating** Earth's magnetic field.

Answer 72

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

Question 73

What is the **Van Allen radiation belt**?

Answer 73

A **layer of charged particles** trapped by Earth's magnetic field. ## Footnote These belts protect Earth from harmful solar and cosmic radiation by trapping and redirecting the particles.

Question 74

# True or False: Earth's magnetic field is strongest near the **equator**.

Answer 74

False ## Footnote The magnetic field is strongest at the **poles**, where the field lines converge.

Question 75

What is the **geodynamo**?

Answer 75

The **process** by which Earth's magnetic field is generated. ## Footnote The geodynamo arises from the convective movement of molten metal in the outer core, creating an electrical current.

Question 76

# Fill in the blank: The Earth's magnetic field helps **protect** us from harmful \_\_\_\_\_\_ \_\_\_\_\_\_\_\_.

Answer 76

solar radiation ## Footnote The magnetic field acts as a **shield**, deflecting harmful solar and cosmic radiation.

Question 77

What is a **geomagnetic reversal**?

Answer 77

A **reversal** of Earth's magnetic poles. ## Footnote Geomagnetic reversals have occurred throughout Earth's history, where the magnetic north and south poles *switch* places. These reversals leave fossil evidence with "magnetic stripes" in rock. This evidence helps support the theory of plate tectonics, as scientists can use the stripes to estimate the rate of movement of plates over time.