Tsunami & Volcano - PP 4

What is the definition of a tsunami?

A sea wave generated by a disturbance on the seabed that displaces the overlying water, releasing energy that travels through the ocean.

What is the main difference between an ordinary sea wave and a tsunami?

A tsunami is generated by the displacement of a large volume of water from a disturbance, such as an underwater earthquake, and involves substantial energy travelling through the ocean.

What are the 5 causes of tsunamis identified in the lecture?

Underwater earthquakes, landslides, volcanic eruptions, nuclear explosions, and impacts from objects from space.

What is the most common cause of tsunamis?

Earthquakes occurring in oceans and coastal settings.

What 3 factors are important when a tsunami reaches shore?

The amount of energy involved, the area affected, and the movement of the waves themselves.

What are the characteristics of a tsunami travelling through the deep ocean?

It can have a wavelength of 60 km or greater, a wave height of only a few feet or less, and can travel great distances at high speeds.

What happens when a tsunami enters shallow coastal waters?

The wave slows down considerably while its height increases, creating potentially devastating forces when it reaches shore.

What range of sizes can tsunamis have?

Tsunamis can range from micro-tsunamis to mega-tsunamis.

Do tsunamis arrive as a single wave or multiple waves?

Tsunamis usually arrive as multiple waves, with successive waves potentially becoming larger.

How far apart can successive tsunami waves arrive?

Approximately 15 minutes to several hours apart.

How does coastal topography affect tsunami damage?

The physical shape and elevation of the coastal area influence how far tsunami waters reach and the extent of damage.

What are the 3 categories of tsunamis based on their source?

Near-source, mid-source, and far-source tsunamis.

Where are tsunamis most common worldwide?

The Pacific Ocean. Tsunamis are less common in the Indian Ocean but can still be highly destructive.

What are the 3 major sources of tsunami risk along Canada's Pacific Coast?

Earthquakes in the Cascadia Subduction Zone, earthquakes elsewhere in the Pacific Ocean, and landslides.

How is coastal British Columbia divided for tsunami planning purposes?

Into five planning zones based on expected wave heights, run-up distances, and land subsidence.

Which tsunami planning zone has the highest hazard for the west coast of Vancouver Island?

Zone C.

What are the main sources of tsunami risk along Canada's Atlantic Coast?

Crustal earthquakes, large submarine landslides near the continental shelf, and submarine landslides occurring farther away.

What other Canadian regions are identified as having potential tsunami risks?

The Arctic Coast and interior waterways.

What caused the 1929 Grand Banks tsunami in Canada?

A magnitude 7.2 earthquake south of the Grand Banks triggered a massive submarine sediment movement, generating a tsunami.

Approximately how long after the 1929 Grand Banks earthquake did the tsunami begin arriving?

Approximately 2.5 hours later.

What are 6 major impacts of tsunamis?

Deaths and injuries, damage to buildings and infrastructure, agricultural destruction, damaged sewage systems, hazardous material releases, and economic losses.

What are 6 additional social and environmental impacts of tsunamis?

Homelessness, unemployment, hunger, disease outbreaks, environmental destruction, and soil contamination.

Why are public education and awareness important for tsunami mitigation?

Understanding tsunami hazards and knowing appropriate responses can save lives when tsunamis threaten coastal communities.

What are the 7 tsunami mitigation measures identified in the lecture?

Tsunami warning systems, hazard mapping and vulnerability assessments, managing development in at-risk areas, fire protection, tsunami shelters, protecting buildings and infrastructure, and public awareness.

How does managing development in tsunami-prone areas reduce risk?

It reduces exposure by limiting or controlling development in locations vulnerable to tsunami impacts.

Why is a tsunami more dangerous at high tide than at low tide?

High tide gives the tsunami a higher starting water level, allowing it to reach farther inland, particularly in low-lying coastal areas.

How does climate change increase potential tsunami impacts?

Rising sea levels increase the potential for tsunami flooding to extend farther inland, particularly in low-lying coastal regions.

What is the definition of a volcano?

A vent in the Earth's surface through which volcanic material erupts, or a mountain formed by the accumulation of eruptive materials.

What are the 3 main settings where volcanoes form?

Divergent plate boundaries, convergent plate boundaries, and hot spots.

How are volcanoes formed?

Volcanoes form through the accumulation of eruptive materials such as lava, ash, dust, and crusted-over ash flows around a vent connected to molten rock beneath Earth's surface.

What are the 8 types of volcanic formations identified in the lecture?

Cinder cone volcanoes, stratovolcanoes, shield volcanoes, lava domes, calderas, volcanic plugs, tuff cones, and lava plateaus.

What are cinder cone volcanoes?

The most common type of volcano, characterized by a symmetrical cone shape. They may occur independently or on the sides of larger volcanoes.

What are parasitic cones?

Secondary cinder cone volcanoes that form on the sides of stratovolcanoes or shield volcanoes.

What are stratovolcanoes?

Large volcanoes built from alternating layers of lava flows, ash, and blocks of unmelted rock, with vents connected to a magma reservoir below the surface.

What are shield volcanoes?

Volcanoes with eruptions that are generally not explosive, where liquid lava flows outward rather than erupting violently.

What are lava domes?

Masses of solid rock formed when thick, viscous lava slowly erupts from a volcanic vent.

What are the 2 main classifications of volcanic eruptions?

Non-explosive eruptions and explosive eruptions.

What are the main characteristics of lava flows?

Lava usually moves slowly, its path can be roughly predicted, and it is rarely a direct threat to human life.

What secondary hazards can occur when lava contacts snow or forests?

Contact with snow can produce flooding and debris flows, while contact with forests can cause wildfires.

Define pyroclastic flows.

Fast-moving, hot avalanches of volcanic rock, ash, and gas that travel down the slopes of volcanoes and can extend for kilometres.

How fast can pyroclastic flows travel?

Approximately 48 km/h to more than 145 km/h, making them particularly dangerous near volcanoes.

What are pyroclastic surges?

Turbulent, low-density clouds of volcanic materials that can accompany explosive activity and create serious hazards near a volcano.

What are phreatic explosions?

Steam explosions associated with volcanic activity that can release toxic gases, such as carbon dioxide and hydrogen sulphide, and dangerous falling rocks or particles.

Define a lahar.

A volcanic mudflow or debris flow consisting of hot or cold mixtures of water and volcanic debris.

How do lahars form, and where are they particularly dangerous?

They form when volcanic materials interact with water, ice, snow, or wet sediments and are particularly dangerous near volcanoes.

How are volcanic gases released?

They escape by bubbling out of lava or passing through soil and volcanic vents.

What are the 6 common volcanic gases identified in the lecture?

Water vapour, carbon dioxide, sulphur dioxide, hydrogen, hydrogen sulphide, and carbon monoxide.

Why can volcanic gases be dangerous?

Some volcanic gases are irritating or poisonous and can threaten the health and safety of nearby populations.

Define tephra.

Rock fragments and other volcanic materials ejected from a volcano during an eruption.

What are larger fragments of tephra called?

Lapilli, bombs, and blocks.

What are the physical characteristics of volcanic ash?

Volcanic ash is hard, abrasive, slightly corrosive, electrically charged, and does not dissolve in water.

How far can volcanic ash travel from an eruption?

Volcanic ash can affect regions thousands of kilometres from the source volcano.

Why is volcanic ash dangerous to aircraft?

It can abrade aircraft surfaces, contaminate openings, and enter jet engines, where it can melt and cause severe damage.

What damage can volcanic ash cause to buildings, transportation, and agriculture?

It can reduce visibility, make surfaces slippery, cause roofs to collapse, and damage crops and wild plants.

How can volcanic ash affect infrastructure and water supplies?

It can clog ventilation systems, corrode metal, contaminate water supplies, and irritate or damage eyes.

What health and recovery problems can volcanic ash cause?

It can threaten people with respiratory problems and require expensive, time-consuming cleanup.

What causes volcanic earthquakes?

The movement of magma or other fluids underground, often producing earthquakes too small to detect without instruments.

Why are volcanic earthquakes important for monitoring and forecasting eruptions?

Significant seismic activity often occurs before volcanic eruptions, making earthquake monitoring valuable for identifying possible upcoming activity.

How can volcanic activity generate tsunamis?

Submarine volcanic eruptions or volcanic landslides entering large bodies of water can displace water and generate tsunamis.

Are submarine earthquakes or volcanic eruptions a more frequent cause of tsunamis?

Submarine earthquakes are a more frequent cause of tsunamis than volcanic activity.

What major extinction event is linked to volcanic activity in the lecture?

Earth's largest extinction event, approximately 250 million years ago, when about 90% of marine species and 75% of land-dwelling species disappeared over approximately 60,000 years.

What are 3 major historical volcanic eruptions identified in the lecture?

Mount Vesuvius in Italy (A.D. 79), Krakatoa in Indonesia (1883), and Mount Pinatubo in the Philippines (1991).

What were the major impacts of the 1980 Mount St. Helens eruption?

It killed 57 people and caused debris avalanches, flooding, mudflows, damage to buildings and transportation infrastructure, and destruction of forests, wildlife, and crops.

How did the Mount St. Helens eruption affect infrastructure and the economy?

Ash caused electrical transformer failures and power outages, water and sewage facilities were damaged, and estimated economic losses reached approximately US$2–3 billion.

What are Canada's 5 potentially active volcanic areas?

The Garibaldi Volcanic Belt, Wells Gray–Clearwater volcanic field, Northern Cordilleran volcanic province, Anahim Volcanic Belt, and Wrangell Volcanic Belt.

Where are Canada's potentially active volcanic areas located?

In British Columbia and the Yukon Territory.

What does the lecture state about Canada's volcanic eruption history?

At least 49 eruptions occurred in British Columbia and Yukon during the past 10,000 years, and the lecture identifies Lava Fork in northwestern B.C. as the site of the most recent eruption, approximately 150 years ago.

Which American volcano is identified as posing the greatest hazard to Canada, and why?

Mount Baker in Washington, because it is approximately 23 km south of the Canadian border and close to population centres in southwestern British Columbia.

What are the 6 main mitigation measures for volcanic hazards?

Learning from past eruptions, establishing detection and monitoring systems, preparedness and evacuation planning, land-use planning, improved communications, and public awareness and education.

How does studying previous eruptions and monitoring volcanic activity reduce risk?

Historical eruption patterns and monitoring data help identify volcanic hazards and possible warning signs, supporting better preparation.

How do evacuation planning and land-use planning reduce volcanic risks?

Evacuation planning prepares populations to leave dangerous areas, while land-use planning can reduce exposure by managing development in areas threatened by volcanic hazards.

Why are communication systems and public education important for volcanic mitigation?

They help inform communities about volcanic risks, warning information, and appropriate protective actions before and during an eruption.