Tectonic Hazards: Plate Boundaries and Natural Disasters

• A natural hazard poses a threat to life and property, arising from events like earthquakes, volcanoes, tropical cyclones, floods, and droughts.
• Predicting natural hazards is difficult, despite knowing the areas are at risk.
• Earthquakes are the most unpredictable natural hazard.

Tectonic Hazards

• The Earth’s crust consists of seven major plates and several smaller ones.
• Convection currents in the magma, driven by the Earth's core heat, cause plate movement.
• Plate boundaries, where plates meet, are zones of significant tectonic activity, causing earthquakes and volcanoes.

Types of Plate Boundaries

• Constructive/Divergent: Plates move apart, magma rises to fill the gap, forming new crust, shield volcanoes, and rift valleys; small earthquakes can occur.
• Destructive/Convergent: Plates collide, the oceanic plate subducts, forming ocean trenches and high mountains; friction causes rocks to melt, leading to volcanoes and earthquakes.
• Composite volcanoes consist of alternating layers of lava and ash, typically found at destructive plate boundaries, known for steep slopes, narrow bases and explosive eruptions due to high magma viscosity.
• Continental plates colliding compress sediments, forming fold mountains and triggering earthquakes but no volcanic activity due to the absence of oceanic plate subduction
• When two oceanic plates converge, the older, denser plate is subducted, resulting in magma rising to form island arcs, such as the Japanese islands.
• Conservative/Transform: Plates slide past each other at different speeds, leading to pressure build-up and earthquakes like the San Andreas fault.
• A seismometer is used to measure an earthquake's magnitude on the Richter scale.
• Earthquake focus: the underground point where an earthquake starts, with the epicenter being the surface point directly above it.
• Liquefaction: the process which can occur during an earthquake in saturated sediments, causing the ground to behave like liquid.

Factors Affecting Earthquake Impact

• Magnitude of the earthquake
• Epicenter location
• Time of day or year
• Relief of the area (mountainous vs. coastal)
• Severity of aftershocks
• Level of human settlement development
• Population density
• Building strength

Impacts of Earthquakes

• Infrastructure damage
• Fires from gas pipes
• Tsunamis
• Landslides
• Habitat loss
• Water-borne diseases
• Financial losses

Management Strategies (3Ps)

• Prediction: Monitor tremors, study epicenters, create hazard maps, and observe animal behavior.
• Preparation/Protection: Build earthquake-proof structures, use smart meters for gas, plan land use carefully, conduct disaster drills.

During and After an Earthquake

• Emergency services evacuate people, rescue survivors, and put out fires, sometimes with military assistance.
• Repair airports quickly, establish temporary camps, and provide medical teams.
• International aid agencies provide essential supplies.
• Restoration of services like water, electricity, and communication begins.

Volcanic Eruptions

• Volcanoes are formed from magma erupting through a crack, building up solidified lava and ash over time.

Impacts of Volcanic Eruptions

• Pyroclastic flows: fast-moving clouds of hot gas and ash that kill people and cause extensive damage.
• Gases: Carbon dioxide can suffocate; hydrogen sulfide and sulfur dioxide can be toxic.
• Water vapor: Causes torrential rain.
• Volcanic bombs and ash: Kill people, bury settlements, and collapse buildings.
• Ash clouds: Damage aircraft engines.
• Lahars: Mudflows from melted snow.

Beneficial Impacts of Eruptions

• Fertile soils
• Mineral veins
• Geothermal energy for electricity
• Tourist attractions

Volcano Prediction

• Monitor tremors with seismometers
• Use heat-seeking cameras via satellite
• Track temperature increases around the crater
• Monitor steam and gas emissions
• Analyze hot spring chemistry

Volcano Preparation and Protection

• Monitor volcanoes
• Educate locals
• Create hazard maps, diversion channels, and lava barriers
• Spray water on lava
• Drop concrete slabs on lava flows
• Reinforce buildings
• Train emergency services for evacuation

Climatic Hazards: Tropical Cyclones

• Tropical cyclones are storms forming over warm tropical oceans, marked by strong winds and heavy rain, lasting 24-48 hours.
• Forming between 5° and 20° latitude north and south of the Equator.
• Hurricanes occur in the Atlantic and eastern Pacific, cyclones in the Indian Ocean and Australia, and typhoons in the western Pacific.
• Tropical cyclones need 27°C water down to 60m depth, forming between May-Nov (Northern Hemisphere) and Nov-May (Southern Hemisphere).
• Warm water fuels tropical cyclones; rising moist air creates low pressure, drawing in high-pressure air, the Earth's rotation causes swirling, forming the eye.
• Eye: low pressure, calm sinking air, Eye wall: dense cloudy area with maximum wind speed.
• Spiral rain band: Bands of clouds and heavy rain surrounding the eye.
• A tropical cyclone can be up to 800 km in diameter and up to 20 km in height, typically lasts about a week, rotating anticlockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
• The Saffir-Simson scale categorizes hurricanes, with Category 1 having wind speeds of 119-153 km/h and Category 5 exceeding 252 km/h.

Impacts of Tropical Cyclones

• Flooding: Coastal storm surges.
• Landslides: Saturated loose material.
• Infrastructure damage and power outages
• Economic losses, including tourism
• Water-related diseases
• Loss of life
• Habitat loss

Managing Tropical Cyclones

• Monitoring via satellite images and issuing warnings through media
• Evacuating low-lying areas
• Stockpiling supplies
• Constructing cyclone shelters, embankments, and stilts
• Preserving mangrove swamps
• Using cyclone-proof building methods
• Post-storm search and rescue, restoring water, power, and sanitation

Flooding

• Flooding: rivers breaking banks after rainfall or snowmelt
• Physical causes of flooding include prolonged heavy rain or rapid snowmelt that saturate the ground.
• Human activities can increase flood risk, including deforestation and urbanization.
• Deforestation and urbanization prevent infiltration, which causes more water to overload river channels.

Impacts of Flooding

• Loss of life, livestock, and crops
• Infrastructure damage
• Homelessness and injuries
• Water contamination
• Food shortage
• Health issues
• Economic downturn

Managing Flooding

• Monitoring rainfall, river discharge, and drainage basins is important.
• Hard engineering flood management involves building dams, embankments, basins, and overflow channels.
• Soft engineering flood management techniques include allowing rivers to flood in washlands, planting trees and enforcing land-use planning.

Drought

• Drought is a prolonged period of abnormally dry weather.
• Droughts common in tropics, like savannas and monsoonal regions.
• Lack of rain, coupled with high pressure, as well as El Niño and La Niña oscillations can cause extreme drought conditions.
• El Niño warms Pacific waters near South America, disrupting storm patterns, and leading to droughts in Australia and the Philippines.
• La Niña cools waters, causing droughts in parts of Americas.
• Warmer temperatures due to climate change can reduce global rainfall.
• Human activities, such as deforestation and building dams, can also cause drought.

Drought: Impacts

• Water sources drying up
• Wetland loss
• Death of plants and animals
• Reduced crop yields
• Malnutrition and starvation
• Increased soil erosion and desertification
• Air quality decrease
• Wildfires
• Migration

Managing Drought

• Monitoring precipitation and temperatures, and managing water supplies .
• Increase water supplies and store government supplies.
• Government stockpiles include water, food, and medicine.
• Increased awareness of drought conditions is key aspect to conservation.
• Agricultural improvements and water conservation are key preparing for droughts.

Explore tectonic hazards arising from earthquakes, volcanoes and plate movement. The Earth's crust is made up of major and minor plates. Plate boundaries are zones of tectonic activity which result in earthquakes and volcanoes.