Tectonics Notes

Question 1

What is the Ring of Fire known for?

Answer 1

Contains ¾ of 550 historically active volcanoes

The Ring of Fire is a major area in the basin of the Pacific Ocean where a large number of earthquakes and volcanic eruptions occur.

Question 2

What are island arcs exemplified by?

Answer 2

Aleutian islands

Island arcs are typically formed by the subduction of one oceanic plate beneath another.

Question 3

What is an example of a submarine volcano?

Answer 3

Kick’em Jenny in Grenada

Submarine volcanoes are underwater volcanoes that can erupt and create new landforms.

Question 4

What percentage of tsunamis occur in the Pacific?

Answer 4

90%

The Pacific Ocean is the most active region for tsunami generation.

Question 5

What is the deepest earthquake recorded?

Answer 5

700 km below ground

This depth indicates the extreme conditions under which some earthquakes can occur.

Question 6

What event in Nevada in 1968 caused 30 minor earthquakes over 3 days?

Answer 6

Underground nuclear testing

Such tests can induce seismic activity in the surrounding area.

Question 7

What caused 2 earthquakes in Lancashire in 2011?

Answer 7

Fracking

Hydraulic fracturing can lead to induced seismicity.

Question 8

What is the Mohorovicic discontinuity?

Answer 8

The boundary between the crust and the mantle with a change in density

This discontinuity marks a significant transition in Earth’s structure.

Question 9

What is the P-wave shadow zone?

Answer 9

Between 105° and 145° from the source

This zone is where P-waves are not detected due to their refraction through the Earth’s core.

Question 10

What is the S-wave shadow zone?

Answer 10

After 105° from the source

S-waves cannot travel through liquid, creating this shadow zone.

Question 11

What is the population density of Tokyo?

Answer 11

6,200 per km²

Tokyo is one of the most densely populated cities in the world.

Question 12

What is the population density of Shirakawa in Gifu?

Answer 12

4.6 per km²

This indicates a much lower population density compared to urban areas like Tokyo.

Question 13

What was the magnitude of the Northridge earthquake in 1994?

Answer 13

6.6 magnitude

This earthquake resulted in 57 deaths and significant damage.

Question 14

What was the magnitude and time of the Bam earthquake in 2003?

Answer 14

6.6 magnitude, 5:26 a.m.

This earthquake resulted in 34,000 deaths.

Question 15

What was the magnitude of the Cairo earthquake in 1992?

Answer 15

5.8 magnitude

This earthquake resulted in 560 deaths.

Question 16

What are the characteristics of basaltic plates?

Answer 16

• 1,000-1,200°C
• 45-52% silica content

Basaltic plates are typically found in oceanic crust.

Question 17

What are the characteristics of andesitic plates?

Answer 17

• 800-1,000°C
• 52-66% silica content

Andesitic plates are commonly associated with volcanic arcs.

Question 18

What are the characteristics of rhyolitic plates?

Answer 18

• 650-800°C
• 66-75% silica content

Rhyolitic plates are often found in continental crust.

Question 19

List the classification of eruptions in ascending order of destructiveness.

Answer 19

• Icelandic
• Hawaiian
• Strombolian
• Vulcanian
• Vesuvian
• Pilinian

This classification helps in understanding the potential impact of volcanic eruptions.

Question 20

What tragic event occurred in Lake Nyos in August 1986?

Answer 20

1,700 deaths

A sudden release of carbon dioxide from the lake caused this disaster.

Question 21

What is a pyroclastic tsunami?

Answer 21

Krakatoa in 1883

This event was caused by a volcanic eruption that generated massive waves.

Question 22

What is a meteotsunami?

Answer 22

Hunga Tonga-Hunga Ha’apai in 2022

Meteotsunamis are caused by atmospheric conditions rather than seismic activity.

Question 23

What disaster occurred due to lahars from Nevado del Ruiz in 1985?

Answer 23

Destroyed Armero city

Lahars are volcanic mudflows that can be extremely destructive.

Question 24

What were the casualties of the Boxing Day Tsunami?

Answer 24

180,000-280,000 people

This tsunami was one of the deadliest natural disasters in recorded history.

Question 25

What successful predictions were made using the **seismic gap theory**?

Answer 25

* Kuril Island in 2006 * Kuril Island in 2007 ## Footnote The seismic gap theory helps in predicting potential earthquake occurrences.

Question 26

What is the basis for **land use zoning** in San Francisco-San Jose?

Answer 26

Based on stability of geological conditions and uses setbacks ## Footnote This zoning helps mitigate risks associated with earthquakes.

Question 27

What is the **time lag** of a tsunami from Ecuador to Japan?

Answer 27

20 hours ## Footnote This time lag is crucial for tsunami warning systems and preparedness.