10.3 Volcanoes and Earthquakes

Question 1

What are Volcanoes?

Answer 1

-Volcanoes form where extremely hot, magma accumulates beneath weak spots in the Earth’s crust.
-Eruptions force magma, gas, ash, and rock to the surface.
-Magma becomes lava (~1200°C) upon reaching the surface.
-Lava cools and solidifies, forming new rock.

Question 2

What are Volcanoes at Divergent Plate Boundaries?

Answer 2

-Create weaknesses in the crust as separating plates thin the crust, allowing magma to find its way up
-Most volcanoes can be found at plate boundaries

Question 3

What are Volcanoes at Convergent Plate Boundaries?

Answer 3

-create weak spots as the subducting plate melts, magma rises to form volcanoes

Question 4

What are Hot Spots Volcanoes?

Answer 4

-Hot spots are weak points in the crust, away from plate boundaries, that form volcanoes or volcanic islands directly above them
-As plates move over hot spots, new volcanoes form, creating island chains (e.g., Hawaiian Islands).
-Hawaii, the current island above the hot spot, has an active volcano.

Question 5

What are Earthquakes?

Answer 5

-Tectonic plates are typically held together with friction
-When other forces overcome the friction forces, the plates slip, releasing waves of energy into the rock or water around it
-Earthquakes most commonly occur at plate boundaries, especially convergent boundaries

Question 6

What are the 3 Types of Waves?

Answer 6

-Primary waves (P-waves) move longitudinally (back and forth) that travel fast
-Secondary waves (S-waves) move transversely (up and down) and travel slower than P-waves
-Surface waves move in a rolling motion and are the slowest. They cause the most destruction

Question 7

How do Earthquakes Occur?

Answer 7

-Earthquakes happen at specific points where the earth slips, usually along fault line
-The location where the quake starts is called the focus
-The location directly above the focus at ground level is called the epicenter

Question 8

How to Detect Earthquakes?

Answer 8

-Seismometer: A weighted pencil stays stationary while a moving drum records earthquake motion.
-Chinese seismometer: Dragons drop balls into frogs’ mouths to indicate the direction of an earthquake.

Question 9

How is Earthquakes’ Severity Measured?

Answer 9

-Richter scale.
-A logarithmic scale: each number represents a 10-fold increase, each fold is 10 times severer than the previous one

Question 10

What is the Tectonic History of Australia?

Answer 10

-The lithosphere under Australia is 200km thick – thicker than most other continents.
The continent is does not sit on a plate boundary prevents continental rock from being destroyed