ES

Lecture 1: Natural Disasters: Overview, Characteristics, and Global Impact

General Overview of Natural Disasters in the US

  • Hurricane Tracks (Blue Lines):

    • Concentrated on the East and Southern Coasts of the US.

    • Display a characteristic U-turn pattern.

    • No significant hurricane activity on the West Coast.

  • Tornadoes (Red Dots):

    • Primarily found in the middle of the US, particularly the Great Plains, also known as "Tornado Alley."

    • Can occur throughout the Eastern Half of the US, but are rare on the West Coast.

  • Earthquake Hazard (Red/Green Colors):

    • Concentrated on the West Coast, Alaska, and Hawaii due to their location near plate boundaries.

    • Some hazard in the interior of the US, notably the New Madrid Fault Zone.

  • Volcanoes and Fires:

    • Volcanoes are found on the West Coast, especially the Pacific Northwest.

    • Fires are also prevalent in these Western regions (e.g., California).

  • Bimodal Distribution of Disasters in the US:

    • Weather-type disasters (hurricanes, tornadoes, floods): Concentrated in the Eastern Half and Southern/East Coasts of the US.

    • Geologic-type disasters (earthquakes, volcanoes, fires): Concentrated in the Western Half of the US, including Alaska and Hawaii.

  • Anomalies and Rarities:

    • Earthquakes and tornadoes can happen on the East/West Coasts respectively, but are exceedingly rare.

    • New Madrid Fault Zone: Located in the central US (e.g., Missouri, Arkansas, Tennessee). Approximately 500,000,000 years ago, North America attempted to rift apart here. Although it didn't complete, faults remain and can be reactivated. Major earthquakes occurred here 200 years ago, powerful enough to temporarily reverse the flow of the Mississippi River. These faults pose a recurring threat even without an active plate boundary.

  • Population Centers (Black Dots):

    • Concentrated on the East and West Coasts, with sparse population in the middle of the US.

    • Population is especially dense on the East Coast, even though California is the most populous state.

Global Deadliest Natural Disasters

  • Top Disasters by Death Toll:

    • China floods (multiple events): Most significant cause of death was secondary starvation due to crop failure, not direct drowning. Death tolls in the millions (e.g., event in 1931 killing 3,700,000 million, and another in 1887 killing 900,000 to 2,000,000).

    • China earthquakes: One in the 16th century (Shaanxi, 1556) killed nearly a million people (830,000), an unheard-of number for single earthquakes today. Another (Tangshan, 1976) killed at least half a million. These high death tolls reflect poor construction and high population density.

    • Bangladesh cyclones: Cyclones (hurricanes in the Indian Ocean) are frequent and deadly, causing hundreds of thousands of deaths (e.g., 1970 event, 300,000 to 500,000 deaths).

    • Other significant events include tsunamis (e.g., 2004 Indian Ocean) and additional earthquakes in Turkey, Indonesia, Syria, and Iran.

  • Key Learnings from Deadliest Disasters:

    • Primary Causes of Death: Floods, earthquakes, and cyclones/hurricanes are the three deadliest disaster types.

    • Geographic Concentration: Most severe events historically occurred in Asia and the Middle East (Eastern Hemisphere), with Haiti as a notable outlier.

    • Contributing Factors for High Death Tolls:

      • Population Density & Numbers: Extremely high populations in affected regions.

      • Poor Building Infrastructure: Lack of earthquake codes and robust construction (e.g., homes made of silt collapsing in China).

      • Lack of Evacuation Systems: Many developing nations lack sophisticated early warning and evacuation protocols found in Western nations.

Global Costliest Natural Disasters

  • Top Disasters by Economic Damage:

    • Japan: The 2011 earthquake and tsunami is the costliest natural disaster in recorded human history, causing immense economic damage and bringing the nation "to its knees." Japan repeatedly ranks high due to its advanced infrastructure and industrialization.

    • United States: Frequently experiences high costs from hurricanes (e.g., Katrina, Ian), floods, and other weather events, as well as some earthquakes. Major property losses occur despite lower death tolls.

    • Europe and China: Also experience significant economic losses, especially industrialized areas.

  • Key Learnings from Costliest Disasters:

    • Affected Nations: Industrialized nations (USA, Japan, Europe, parts of China) bear the highest economic losses.

    • Reason for High Costs: They have significantly more valuable property and infrastructure to lose.

    • Lower Death Tolls (Generally):

      • Strict Building Codes: Enforced construction standards (e.g., in California, chances of dying in an earthquake are near zero due to well-made buildings).

      • Effective Evacuation Plans: Sophisticated warning systems and organized evacuations minimize loss of life (e.g., for hurricanes on the US East Coast).

    • Dominant Costly Events: Hurricanes, floods, and earthquakes cause the most economic damage.

  • Trend in Economic Losses:

    • Economic losses have been growing commensurate with global population growth (e.g., population increased from 1 billion in 1800 to 8 billion today).

    • Dominated by flood and extreme weather events (hurricanes), with earthquakes also contributing significantly.

Are Natural Disasters Increasing?

  • General Answer: No, with the possible exception of weather-type disasters (linked to climate change).

  • Reasons for the Perception of Increase:

    • More People: Global population growth means more individuals are in harm's way.

    • Increased Vulnerability: Growing populations in developing nations often reside in areas susceptible to disasters and lack the capacity to cope.

    • High-Risk Land Use: People build in dangerous areas:

      • Near active volcanoes (e.g., Big Island of Hawaii).

      • On river floodplains (convenient for water, flat land, transport, but prone to flooding).

      • On coasts vulnerable to hurricanes (East/South Coasts of US).

      • On eroding cliffs (e.g., California coastal homes).

      • Examples: New Orleans (built below sea level, vulnerable to hurricanes like Katrina); homes on actively collapsing cliffs.

    • Government Failure to Respond/Adapt: Common in developing nations where governments may not prioritize disaster preparedness.

    • Instantaneous Media Coverage: Modern technology provides immediate, global reporting of events, making them seem more frequent or widespread than in the past.

  • Philosophical Perspective: The Earth is a living planet that has been releasing energy (earthquakes, volcanic eruptions, tsunamis, floods) for billions of years and will continue to do so. Humans often build in the path of this natural energy release, transforming natural events into "natural disasters" or even "man-made disasters."

Characteristics of Natural Disasters

  • 1. Type of Event:

    • Primarily categorized into two groups:

      • A. Geological/Tectonic (Fewer Examples):

        • Earthquakes (e.g., Alaska earthquake in a courtroom).

        • Volcanic Eruptions (e.g., Mount Unzen, Japan; pyroclastic flows are the most dangerous part).

        • Landslides/Rockfalls (e.g., Lake Superior cliff collapse).

        • Tsunamis (e.g., 2011 Japan tsunami, 2004 Indian Ocean tsunami).

      • B. Atmospheric/Weather (More Examples):

        • Hurricanes/Cyclones/Typhoons (e.g., Hurricane Katrina, Hurricane Milton; largest storm systems on Earth).

        • Tornadoes (powerful, but often not very large in cloud diameter).

        • Floods (most common atmospheric event).

        • Droughts.

        • Wildfires (can sometimes form "fire tornadoes").

        • Blizzards.

        • Hailstorms.

        • Thunderstorms/Lightning (e.g., Chicago lightning strike).

        • Avalanches (triggered by weather but gravity-driven).

        • Sandstorms/Dust Devils.

        • Cold Waves/Heat Waves.

        • Waterspouts (tornadoes over water, generally short-lived and less dangerous than land tornadoes).

        • El Niño/La Niña (can influence rain/drought patterns).

    • Other Categories:

      • Impact Events: Collisions with space objects (e.g., Chelyabinsk meteor, Russia, 2013). These have their own category but can include geological and atmospheric elements. They can affect the entire Earth and have long-lasting repercussions (e.g., dinosaur extinction 65 million years ago).

  • 2. Magnitude:

    • Definition: The size of an event; how much energy the event is releasing.

    • Measurement: Typically measured on specific scales for different event types.

      • Earthquakes: Richter scale (and others, like Moment Magnitude).

      • Hurricanes: Measures wind speed and intensity (e.g., Saffir-Simpson Hurricane Wind Scale).

      • Volcanic Eruptions: Measures ash volume and area covered (e.g., Volcanic Explosivity Index - VEI).

  • 3. Frequency:

    • Definition: How often an event of a specific size occurs. Calculated as the rac{ ext{number of events}}{ ext{time period}} .

    • Recurrence Interval: The time between same-sized events. It is the reciprocal of frequency.

    • Example (San Andreas Fault):

      • A magnitude 7.8 earthquake on the Southern San Andreas Fault (a major fault running through California) has a frequency of approximately one quake every 200 years.

      • Its recurrence interval is about 200 years.

      • The last such event occurred over 300 years ago, meaning it is currently considered "overdue."

    • Relationship to Magnitude: Higher magnitude events are less frequent, while lower magnitude events are more frequent (e.g., magnitude 2 earthquakes occur millions of times a year globally).

  • 4. Duration:

    • Definition: How long the event takes to occur.

    • Examples:

      • Earthquakes: Seconds to minutes.

      • Volcanic Eruptions: Days to weeks or months.

      • Floods: Hours.

      • Hurricanes: Days (up to a week).

      • Tornadoes: Minutes (rarely hours).

      • Meteorite Impact: Instantaneous (but repercussions can last millions of years).

  • 5. Aerial Extent:

    • Definition: How far, in terms of area, the event reaches or affects.

    • Examples:

      • Magnitude 7.8 earthquake on Southern San Andreas Fault: Affects several counties (Southern California and Northern Mexico).

      • Hurricane: Affects several states.

      • Tornado: Affects a city or a smaller local area.

      • Indian Ocean Tsunami (2004): Affected the entire Indian Ocean basin, particularly Sumatra, Indonesia, and coastal countries of India, Sri Lanka, and Eastern Africa.

      • Large Asteroid Impact: Can affect the entire Earth.

Relationship Between Magnitude, Frequency, Energy Release, and Recurrence Interval

  • General Relationship: The higher the magnitude of an event, the less frequent it is.

  • High Magnitude Event:

    • Energy Released: Very high.

    • Recurrence Interval: High (meaning a very long time must be waited for another such event).

  • Small Magnitude Event:

    • Energy Released: Low.

    • Recurrence Interval: Low (meaning it does not take a long time for another such event to occur).

  • This inverse relationship is a fundamental concept for understanding natural disasters throughout the semester.