Volcanoes and Plate Tectonics

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Questions and Answers

What is the molten rock beneath the Earth's crust called?

Ash

Seismic waves

Lava

Magma (correct)

Volcanoes can only form at the Earth's surface.

False

What are the three types of seismic waves?

P-waves, S-waves, surface waves

The location where an earthquake starts is called the ______.

focus Signup and view all the answers

Match each type of wave with its description:

P-waves = Fastest seismic waves that move longitudinally S-waves = Slower waves that move transversely Surface waves = Slowest and most destructive waves Seismic waves = Energy waves released during an earthquake Signup and view all the answers

Where do hot spot volcanoes typically form?

Away from plate boundaries Signup and view all the answers

Most volcanoes are found at convergent plate boundaries.

True Signup and view all the answers

The area surrounding the Pacific Ocean known for its high volcanic activity is called the ______.

Pacific Ring of Fire Signup and view all the answers

Which type of plate boundary is characterized by plates moving away from each other?

Divergent boundaries Signup and view all the answers

Converging boundaries can create new crust.

False Signup and view all the answers

What is the process called when an oceanic plate is pushed under a continental plate?

Subduction Signup and view all the answers

______________ islands are formed when two oceanic plates collide and one undergoes subduction.

Island arc Signup and view all the answers

Which of the following statements about divergent boundaries is true?

They can lead to ocean ridges and rift valleys. Signup and view all the answers

Match the following boundary types with their characteristics:

Divergent = Plates move away from each other Transform = Plates slide past each other Converging = Plates collide together Subduction = Oceanic crust is pushed beneath continental crust Signup and view all the answers

Iceland is growing as a result of converging plate boundaries.

False Signup and view all the answers

What forms when continental plates collide?

Mountain ranges Signup and view all the answers

Study Notes

Volcanoes

Volcanoes form where extremely hot molten rock (magma) collects below weak spots in Earth's crust.
During eruptions, magma is forcefully pushed to the surface as lava.
Lava, at around 1200°C, cools and solidifies to create new rock.
Gas, ash, and solid rock are often released during volcanic eruptions.

Volcanoes at Plate Boundaries

Plate boundaries mark areas where Earth's crust is thinnest and weakest.
Divergent boundaries develop weaknesses in the crust as plates separate, allowing magma to rise.
Convergent boundaries also create weak spots as the subducting plate melts, causing magma to rise and form volcanoes.

Hot Spot Volcanoes

Hot spots are isolated, weak points in the crust, located away from plate boundaries.
The exact cause of hot spots remains unknown.
A hot spot creates a volcano/volcanic island directly above it.
As the tectonic plate moves over a hot spot, a chain of volcanoes develops, with older islands further away from the current hotspot. Examples include the Hawaiian Islands.

Earthquakes

Tectonic plates are usually held together by friction.
When external forces overcome friction, plates slip, releasing energy waves into the surrounding rock or water.
These energy waves are called seismic waves.

Types of Seismic Waves

Primary waves (P-waves): longitudinal; travel fastest.
Secondary waves (S-waves): transverse; travel slower than P-waves.
Surface waves: rolling motion; slowest, cause the most destruction.

Where Earthquakes Occur

Earthquakes are most frequent at plate boundaries, particularly convergent boundaries where plates collide.

Earthquake Focus and Epicenter

Focus: the starting point of the quake, located hundreds of kilometers underground.
Epicenter: the location directly above the focus, at the surface.

How Earthquakes Are Detected

Seismometers are used to detect earthquakes.
Early seismometers used a weighted pencil on a rotating drum, enabling the drum to move with the quake but not the pencil, allowing the movement to be recorded.
Later versions, like the Chinese seismometers, used a system of balls and dragons to detect the direction of movement.

Measuring Earthquake Magnitude

Earthquake severity is measured using the Richter scale, a logarithmic scale.
Each number on the scale represents a ten-fold increase in the earthquake's destructive power (e.g., magnitude 5.0 is ten times more destructive than magnitude 4.0).

Tectonic History of Australia

Australia's lithosphere is significantly thicker than other continents.
Australia does not sit on a plate boundary, which prevents continental rock from being destroyed.
Some of the rock in the Australian continent is very old and helps us understand its geological history and how the continent drifted from being part of the Pangea supercontinent.

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Description

Explore the fascinating world of volcanoes formed by tectonic activity. This quiz covers how volcanoes relate to plate boundaries and hot spots, including their formation, eruptions, and geological significance. Test your understanding of these powerful natural phenomena!