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Volcanic Hazards and Their Impact

Class Session Overview

  • Date: June 21

  • Topic: Volcanic Hazards

  • Content Review: Finishing off Module Four

    • Previous Topic: Introduction to Volcanoes and types of magma/lava

    • Today's Focus: The hazards associated with volcanic eruptions

Announcements and Reminders

  • Forklift Assignment:

    • Due Date: Wednesday, the tenth

    • Purpose: Reviewing materials from Module Four prior to the exam.

  • Exam:

    • Date: In-class on Friday, the tenth (following fall break)

    • Review to be discussed in class on Friday.

    • Content: Covers Modules One through Four (up to today's class).

  • Project One:

    • Unlock Time: Available at 02:00 today

    • Type: Creative writing assignment based on volcanic hazards.

    • Purpose: Develop creative work regarding stratovolcanoes and their hazards.

    • Resources: Lecture 10 page on Canvas with video resources on human hazards.

    • Tips: Can adapt a song for the assignment or choose other creative formats (comic books, children's books, etc.).

  • Due Date: October 14

Exam Structure and Lab Schedule

  • Exams: No labs on the day of the exam (Friday). The Tuesday group will resume labs on the fourteenth.

Schedule for Today

  • Focus on:

    • Types of volcanic hazards

    • Monitoring techniques for volcanoes

    • Case Studies: Mount Saint Helens, Mount Vesuvius, Kilauea

Types of Volcanic Hazards

Primary Hazard: Lava Flows

  • Definition:

    • Lava and magma are the same; termed 'lava' when reaching the surface.

    • Types of Lava: Basaltic (Mafic), Andesitic, Rhyolitic.

  • Characteristics:

    • Basaltic Lava:

    • Hottest and flows farthest.

    • Creates shield volcanoes and allows gas escape.

    • Andesitic & Rhyolitic Lava:

    • Stickier; doesn’t flow far.

    • Presents less immediate risk since you can outrun it.

  • Heat Concerns: Lava is approximately 2,200°F, enough to cause burns and destroy infrastructure.

    • Example:

      • Lava flow from La Palma, Canary Islands in 2021 destroyed homes and infrastructure, highlighting the risk to communities.

Pyroclastic Flows

  • Definition:

    • A cloud of ash, gas, and volcanic rock bits.

    • Temperature: Up to 1,300°F, speeds exceeding 60 mph.

  • Destructiveness:

    • Can knock down trees/buildings and travel long distances (up to 20 km).

    • Example: Mount Pinatubo eruption in 1991.

  • Impacts: Often fatal due to speed, heat, and asphyxiation risks.

Ash Fall

  • Characteristics:

    • Smallest volcanic particles (<2 mm), able to travel vast distances.

  • Dangers:

    • Risk to aircraft engines as ash can melt and clog them.

    • Impacts buildings (collapse risk) and agriculture (crop destruction).

    • Health risks, respiratory issues due to inhalation.

Gas Emissions

  • Common Gases:

    • Water vapor, carbon dioxide, sulfur dioxide.

  • Effects:

    • Can lead to acid rain, suffocate animals in valleys, and impact air quality.

  • Historical Example: Eruption of IFAOFA (2010) disrupted air travel due to ash clouds.

Lahars

  • Definition:

    • A mixture of volcanic debris, water, and mud, creating dangerous flows down slopes.

  • Formation Conditions:

    • Can occur during eruptions (flash melting of snow) or after heavy rainfall.

  • Hazards: Fast-moving and may bury communities, much like a concrete river.

    • Example: Eruption of Nevada del Ruiz in 1985, leading to mass casualties.

Landslides

  • Causes:

    • Triggered by earthquakes or structural weaknesses in the volcano.

  • Risks: Can occur with volcanic eruptions and lead to substantial debris flows.

    • Historical context: Largest landslide in British Columbia due to volcanism.

Monitoring Volcanoes

Assessment Techniques

  • Seismic Activity:

    • Monitoring earthquakes using seismometers to identify magma movement.

    • Increase in frequency and shallow depth indicates magma nearing the surface.

  • Gas Composition:

    • Gas measurements correlate with volcanic activity.

    • Increase in gas emissions denotes magma approaching surface.

  • Ground Deformation:

    • GPS tracking can show bulging and changes in surface shape, indicating volcanic activity.

    • Tilt meters can measure subtle shifts in volcano angle due to magma movements.

Case Studies

Mount Saint Helens (1980)

  • Sequence of Events:

    • Notable for the lateral blast due to a sequence of earthquakes and a bulging side caused by magma.

    • Outcome: Extensive destruction on May 18, 1980, due to lateral eruption.

Mount Vesuvius (AD 79)

  • Historical Context:

    • Known for pyroclastic flows that destroyed Pompeii.

  • Importance: Understanding past eruptions aids in resilience and preparedness for future events.

Ongoing Monitoring and Preparedness

  • USGS Alerts:

    • Green: Normal behavior

    • Yellow: Advisory (elevated activity)

    • Orange: Watch (escalated activity)

    • Red: Eruptive event imminent.

Summary of Volcanic Hazards

  • Primary dangers come from pyroclastic flows and lahars.

  • Understanding signs of volcanic activity can save lives through timely evacuations.

Final Notes

  • Reminder about the due dates for assignments and upcoming exams.

  • Encourage students to engage with creative writing and examination preparations.

  • Preparation discussions for next class focusing on specific volcanic case studies and implications of past eruptions.