7 - Tectonics and Internal Earth Processes

Question 1

Identify:

What theory explains Earth’s plate movement?

Answer 1

plate tectonics

This theory describes the movement of Earth’s tectonic plates, causing geological phenomena like earthquakes, volcanic eruptions, and mountain building.

Question 2

Define:

lithosphere

Answer 2

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

The lithosphere is divided into tectonic plates that float on the more fluid asthenosphere beneath.

Question 3

Define:

tectonic plate

Answer 3

A rigid section of Earth’s lithosphere moving on the asthenosphere.

These plates move due to mantle convection and interact at plate boundaries.

Question 4

Explain:

3 types of plate boundary interactions

Answer 4

1. Divergent Boundaries
2. Convergent Boundaries
3. Transform Boundaries

Divergent Boundaries: Plates move apart, creating new crust as magma rises to the surface (e.g., mid-ocean ridges).

Convergent Boundaries: Plates move toward each other, causing subduction or mountain formation.

Transform Boundaries: Plates slide past one another, often causing earthquakes.

Question 5

Explain:

What geological features form at convergent boundaries?

Answer 5

• Mountain Ranges
• Ocean Trenches
• Volcanic Arcs

Mountain Ranges: Formed when continental plates collide and compress.

Ocean Trenches: Formed as an oceanic plate is subducted beneath another plate, creating deep depressions.

Volcanic Arcs: Formed above subduction zones as one plate descends into the mantle, creating chains of volcanoes.

Question 6

Identify:

What geological feature forms at land-based divergent boundaries?

Answer 6

rift valleys

Rift valleys are formed when tectonic plates separate on land, such as in the East African Rift.

Question 7

Define:

transform boundary

Answer 7

Type of plate boundary where two tectonic plates slide past each other horizontally.

The San Andreas Fault in California is an example of a transform boundary, causing frequent earthquakes.

Question 8

Identify:

What geological feature is associated with transform boundaries?

Answer 8

strike-slip faults

These faults occur when plates slide horizontally past each other, often resulting in earthquakes.

Question 9

Explain:

How do earthquakes occur at transform boundaries?

Answer 9

Friction between sliding plates causes seismic energy release.

At transform boundaries, plates slide past each other, causing friction to build up. This energy is suddenly released along faults, making these areas prone to frequent earthquakes.

Question 10

Identify:

What is the primary driving force behind tectonic plate movement?

Answer 10

mantle convection

Mantle convection provides the necessary heat and motion to drive the movement of tectonic plates over the Earth’s surface.

Question 11

Define:

ridge push

Answer 11

The force from elevated mid-ocean ridges pushing plates away.

It occurs as the lithosphere at divergent boundaries is pushed upwards, creating a slope that moves plates outward.

Question 12

Identify:

What tectonic feature is associated with ridge push?

Answer 12

mid-ocean ridges

Mid-ocean ridges are where seafloor spreading occurs, and ridge push helps to drive plates apart at divergent boundaries.

Question 13

Identify:

What force pulls a subducting plate into the mantle?

Answer 13

slab pull

Slab pull occurs at convergent boundaries where one plate is subducted beneath another.

Question 14

Identify:

Where does slab pull primarily occur?

Answer 14

At convergent boundaries, particularly at subduction zones.

Subduction zones are areas where oceanic plates are pulled beneath continental plates, a process that generates significant tectonic forces.

Question 15

Explain:

How do tectonic plates influence the formation of mountain ranges?

Answer 15

Colliding plates push the crust upward.

Mountain ranges form at convergent boundaries where tectonic plates collide, compressing and uplifting the crust. The Himalayas are an example, created by the collision of the Indian and Eurasian Plates.

Question 16

Identify:

Which type of plate boundary is most likely to cause mountain building?

Answer 16

convergent boundaries

Convergent boundaries cause compressional stress, leading to the uplift of mountain ranges.

Question 17

Define:

convection currents

Answer 17

• Process that involves the movement of energy from one place to another.
• Also called convection heat transfer.

These currents transfer heat from the Earth’s core, causing mantle flow and driving plate movements.

Question 18

Define:

What is a fold in geology?

Answer 18

A bend in rock layers caused by compressional forces.

Folds form when rocks are subjected to stress, causing them to bend without breaking.

Question 19

Identify:

What fold arches upward with oldest layers at its core?

Answer 19

anticline

Anticlines are typically formed by compressional stress and are found in mountain ranges.

Question 20

Define:

syncline

Answer 20

A fold that sinks downward with youngest layers at its core.

Synclines are often found alongside anticlines in mountain ranges.

Question 21

Define:

fault

Answer 21

A crack in Earth’s crust where movement occurs.

Faults form when stress builds up in the crust, causing rocks to break and slide past each other.

Question 22

Explain:

3 main types of faults

Answer 22

1. Normal Fault
2. Reverse Fault
3. Strike-Slip Fault

Normal Fault: Forms when tension stretches the crust, causing the hanging wall to move downward.

Reverse Fault: Occurs under compression, pushing the hanging wall upward relative to the footwall.

Strike-Slip Fault: Results from shear stress, where blocks slide past each other horizontally.

Question 23

Explain:

2 characteristics of normal faults

Answer 23

1. Vertical Movement
2. Hanging Wall and Footwall

Vertical Movement: In a normal fault, the movement is primarily vertical.

Hanging Wall and Footwall: The block of rock above the fault plane is called the hanging wall, and the block below is called the footwall. In a normal fault, the hanging wall moves downward relative to the footwall.

Normal faults typically form at divergent boundaries where plates pull apart.

Question 24

Explain:

2 characteristics of reverse faults

Answer 24

1. Compressional Forces
2. Hanging Wall Moves Up

Compressional Forces: Reverse faults are formed by compressional forces, meaning forces that push or squeeze the Earth’s crust together.

Hanging Wall Moves Up: In a reverse fault, the hanging wall (the block of rock above the fault plane) moves upward relative to the footwall (the block of rock below the fault plane).

Reverse faults form under compressional stress, usually at convergent boundaries.

Question 25

# Explain: What causes **strike-slip faults**?

Answer 25

Formed by **shear stress**, where plates slide past each other horizontally.

Question 26

# Identify: What **type of stress** is associated with **reverse faults**?

Answer 26

compressional stress ## Footnote *Compressional stress* causes the plates to push together, resulting in reverse faults.

Question 27

# Identify: What is the **main cause** of **mountain building**?

Answer 27

**Tectonic plate processes**, particularly at **convergent boundaries**. ## Footnote Mountain ranges like the **Himalayas** formed by the collision of two continental plates.

Question 28

# Define: What is **rifting**?

Answer 28

The process of **pulling** apart a tectonic plate to form a rift valley. ## Footnote Rifting typically occurs at *divergent boundaries*, where plates move away from each other.

Question 29

# Identify: What is an **example** of a **rift valley** formed by rifting?

Answer 29

The East African Rift Valley ## Footnote The *East African Rift* is an active divergent boundary where tectonic plates are pulling apart.

Question 30

# Describe: How do **normal faults** contribute to **rifting**?

Answer 30

It **stretches** the crust, forming rift valleys. ## Footnote *Normal faults* occur in regions under tension, where divergent boundaries stretch the crust, creating rift valleys as the land separates.

Question 31

# Define: What is **seafloor spreading**?

Answer 31

The **process** of forming new ocean crust at **mid-ocean ridges**. ## Footnote This occurs at divergent boundaries where tectonic plates separate, and magma rises to form new crust.

Question 32

# Identify: What **process** pulls oceanic crust down at **convergent boundaries**?

Answer 32

subduction ## Footnote **Subduction** occurs when oceanic plates, which are denser than continental plates, are forced beneath them at convergent boundaries. This process creates ocean trenches and contributes to volcanic activity and mountain formation.

Question 33

# Define ocean trench

Answer 33

* Long, narrow, and incredibly deep **depression** on the ocean floor. * Formed at **subduction zones**, where two of Earth's tectonic plates collide. * The **denser plate** is forced beneath the **lighter plate**, bending downwards into the Earth's mantle. This process creates the deep, V-shaped trench. ## Footnote *Ocean trenches*, such as the *Mariana Trench*, are formed at convergent boundaries where subduction occurs.

Question 34

# Explain: What is the **difference** between *oceanic crust* and *continental crust*?

Answer 34

* **Oceanic crust** is thinner and denser, composed mainly of **basalt**. * **Continental crust** is thicker and lighter, made mostly of **granite**.

Question 35

# Explain: How does **ridge push** influence **seafloor spreading**?

Answer 35

It pushes **new oceanic crust** from the ridge, aiding **seafloor spreading**. ## Footnote This process helps push oceanic plates outward, contributing to the expansion of ocean basins.

Question 36

# Define: continental drift

Answer 36

The **theory** that continents **drifted apart** over millions of years. ## Footnote Proposed by *Alfred Wegener*, it suggests continents were once part of a supercontinent called Pangaea.

Question 37

# Enumerate: 3 pieces of evidence supporting the **continental drift theory**

Answer 37

1. Fossil Similarities Across Continents 1. Continental Fit 1. Geological Similarities ## Footnote **Fossil Similarities Across Continents**: Identical fossils found on distant continents suggest they were once connected. **Continental Fit**: Continents, like South America and Africa, fit together like puzzle pieces. **Geological Similarities**: Similar rock formations and mountain ranges on different continents indicate a shared history.

Question 38

# Explain: How does **continental drift** relate to **seafloor spreading**?

Answer 38

**Seafloor spreading** moves **continents apart**. ## Footnote As new crust forms at mid-ocean ridges, it moves continents apart, supporting the idea that continents have drifted over time.

Question 39

# True or False: **Continental drift** was **widely accepted** when first proposed.

Answer 39

False ## Footnote It was rejected **initially** because Wegener couldn't explain the mechanism behind the movement of continents.