18.1 Types and Causes of Natural Hazards
6 min read•july 30, 2024
Natural hazards come in various forms, from earthquakes to hurricanes. They're classified as geological, hydro-meteorological, or biological, each with unique characteristics and potential secondary effects. Understanding these types helps us prepare for and mitigate their impacts.
The causes of natural hazards are complex, involving geological, meteorological, and hydrological processes. Human activities like and can worsen their effects. Climate change is also altering the frequency and of many hazards, making them more unpredictable.
Natural hazard classification
Types of natural hazards
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- originate from internal earth processes (, , )
- Earthquakes occur when stored elastic strain energy is suddenly released along a fault plane, causing seismic waves that shake the ground
- Tsunamis are generated by the displacement of a large volume of water, typically due to earthquakes, submarine landslides, or volcanic eruptions in oceanic regions
- Volcanic eruptions happen when magma rises through the Earth's crust and is expelled onto the surface, often accompanied by ash, gases, and lava flows
- Landslides involve the downslope movement of soil, rock, or debris, triggered by factors such as heavy rainfall, earthquakes, or human activities that destabilize slopes
- are caused by atmospheric, hydrological, or oceanographic processes
- (hurricanes, typhoons) form over warm ocean waters and are characterized by low-pressure centers, strong winds, and heavy rainfall
- Floods occur when water overflows onto normally dry land, often due to heavy rainfall, rapid , or the failure of man-made structures (dams, levees)
- Droughts are prolonged periods of low precipitation leading to water scarcity and increased wildfire risk
- Heatwaves are extended periods of excessively hot weather that can cause heat-related health impacts
- Storm surges are abnormal rises in sea level generated by strong winds and low atmospheric pressure during storms, which can cause coastal flooding
- are caused by exposure to living organisms and their toxic substances or vector-borne diseases
- are widespread occurrences of an infectious disease in a community at a particular time
- are epidemics that spread over multiple countries or continents
- Insect or are outbreaks of pests or diseases that can damage crops, livestock, or human health (locusts, rodents)
Hazard characteristics and secondary effects
- Natural hazards can be classified based on their frequency, duration, and area of extent
- Rapid-onset hazards occur suddenly with little warning (earthquakes, flash floods, tornadoes)
- Slow-onset hazards develop gradually over an extended period (droughts, sea-level rise)
- Some natural hazards can trigger secondary hazards, creating a cascade of impacts
- Earthquakes can cause landslides, tsunamis, or damage to infrastructure leading to technological hazards (dam failures, chemical spills)
- Hurricanes can cause flooding, storm surges, and tornadoes, leading to extensive damage and loss of life
- Volcanic eruptions can trigger lahars (volcanic mudflows), wildfires, or create ash clouds that disrupt air travel and cause respiratory issues
Processes behind natural hazards
Geological processes
- Plate tectonics involve the movement and interaction of Earth's lithospheric plates, leading to geological hazards
- Convergent plate boundaries, where plates collide, can cause earthquakes, volcanic eruptions, and mountain building
- Divergent plate boundaries, where plates pull apart, can create rift valleys, submarine ridges, and volcanic activity
- Transform plate boundaries, where plates slide past each other, are characterized by shallow earthquakes and offset landforms (San Andreas Fault)
- Seismic activity is the result of sudden movements within the Earth's crust or along plate boundaries
- Elastic strain energy accumulates in rocks due to tectonic forces and is released suddenly during an
- The focus is the point within the Earth where an earthquake originates, while the epicenter is the point on the surface directly above the focus
- Seismic waves radiate outward from the focus, causing ground shaking and potential damage to structures
Meteorological and hydrological processes
- Meteorological processes in the atmosphere, such as air pressure differences, wind patterns, and moisture content, can lead to various weather-related hazards
- Tropical cyclones form when warm, moist air rises over warm ocean waters, creating a low-pressure system that draws in more air and generates strong winds
- Severe thunderstorms develop when unstable atmospheric conditions allow warm, moist air to rise rapidly, leading to the formation of tall cumulonimbus clouds
- , fast-moving air currents in the upper atmosphere, can influence the path and intensity of weather systems
- Hydrological processes involve the movement and distribution of water on Earth's surface and can contribute to hazards
- The describes the continuous movement of water through evaporation, transpiration, condensation, precipitation, and runoff
- Soil moisture and groundwater levels can influence the occurrence and severity of floods and droughts
- Snowmelt in mountainous regions can contribute to spring flooding and alter the timing and of peak river flows
Human impact on hazards
Land-use changes and infrastructure development
- Human activities can exacerbate the frequency and intensity of some natural hazards by altering the natural environment and increasing
- Deforestation reduces the capacity of vegetation to intercept rainfall and stabilize slopes, increasing the likelihood of landslides and flash floods
- Urbanization can increase the area of impervious surfaces (roads, buildings), leading to higher surface runoff and increased risk in cities
- Agricultural practices, such as overgrazing or monocropping, can degrade soil quality and increase erosion, making land more susceptible to hazards
- The construction of infrastructure can provide protection against some hazards but may also create new risks
- Dams and levees can regulate river flow and prevent flooding, but their failure can lead to catastrophic floods downstream
- Coastal defenses (, ) can protect against storm surges and erosion, but may also alter sediment transport and beach dynamics
- Buildings and bridges designed without proper hazard-resistant features can collapse during earthquakes or strong winds
Population growth and vulnerability
- Population growth and migration can increase the number of people exposed to natural hazards
- Coastal areas are attractive for settlement and tourism but are exposed to hazards like hurricanes, tsunamis, and sea-level rise
- Floodplains provide fertile soil for agriculture but are prone to river flooding
- Seismically active regions near plate boundaries are often densely populated (Japan, California), putting many people at risk from earthquakes
- Inadequate , building codes, and risk reduction measures can increase the vulnerability of communities to the impacts of natural hazards
- Informal settlements and substandard housing are more likely to suffer damage during hazard events
- Lack of and evacuation plans can hinder timely response and lead to higher casualties
- Limited access to resources and services (healthcare, insurance) can make it harder for communities to recover from disasters
Climate change and hazards
Impacts on hydro-meteorological hazards
- Climate change is expected to alter the frequency, intensity, and distribution of various natural hazards, particularly those related to hydro-meteorological processes
- Rising global temperatures are likely to increase the frequency and severity of heatwaves and droughts, leading to increased water scarcity, wildfire risk, and heat-related health impacts
- Changes in precipitation patterns, such as more frequent and intense extreme rainfall events, can increase the risk of flooding and landslides in some regions
- Sea-level rise, resulting from thermal expansion of the oceans and melting of land-based ice, can increase the risk of coastal flooding, storm surges, and coastal erosion, particularly in low-lying areas and small island states
- The impacts of climate change on tropical cyclones remain uncertain and may vary regionally
- Warmer ocean temperatures may increase the intensity of tropical cyclones, but changes in atmospheric circulation patterns could also influence their frequency and tracks
- Rising sea levels can exacerbate heights and coastal flooding during cyclones
Indirect effects on geological hazards
- Climate change may have indirect effects on geological hazards through various mechanisms
- Increased frequency and intensity of rainfall events can raise the risk of landslides by saturating soils and destabilizing slopes
- Melting of glaciers and permafrost in high-altitude and high-latitude regions can increase the risk of and landslides as previously frozen ground thaws and weakens
- Changes in the distribution of water and ice mass on Earth's surface due to melting glaciers and ice sheets may alter the stress patterns in the Earth's crust, potentially influencing earthquake frequency or volcanic activity, although these effects are not yet well understood
- The impacts of climate change on natural hazards will vary regionally and will interact with other factors such as population growth, urbanization, and land-use changes
- Adaptive risk reduction strategies, such as improved land-use planning, hazard-resistant infrastructure, and early warning systems, will be necessary to build resilience to the changing hazard landscape
- International cooperation and support will be crucial to help vulnerable communities and developing nations cope with the increasing impacts of climate change on natural hazards
Key Terms to Review (35)
Animal plagues: Animal plagues are widespread outbreaks of infectious diseases that significantly impact animal populations, leading to high mortality rates and economic losses in livestock and wildlife. These diseases can arise from various sources, including pathogens, environmental factors, and human activities, and often result in severe consequences for agricultural industries and ecosystems.
Biological hazards: Biological hazards are biological substances that pose a threat to the health of living organisms, primarily humans, and can include pathogens like bacteria, viruses, fungi, and parasites. These hazards can result from natural events, leading to outbreaks of diseases that affect populations, thus intertwining with the study of natural hazards and their causes.
Breakwaters: Breakwaters are structures built along coastlines to protect harbors, shorelines, and boats from the effects of waves and erosion. They act as barriers, absorbing and deflecting wave energy, thus reducing the impact of storm surges and high waves on coastal areas. These structures play a significant role in mitigating natural hazards related to coastal processes, safeguarding infrastructure and ecosystems from damage.
Deforestation: Deforestation is the large-scale removal of trees from forested areas, resulting in the permanent destruction of forest habitats. This process often leads to significant ecological and environmental impacts, influencing climate patterns, biodiversity, and land use dynamics.
Drought: Drought is an extended period of abnormally low rainfall relative to the statistical multi-year average for a region, leading to water shortages and various environmental and socio-economic impacts. It can severely affect agriculture, water supply, and natural ecosystems, making it a critical concern in discussions about natural hazards.
Early warning systems: Early warning systems are organized methods and technologies designed to detect potential hazards and alert communities in advance to minimize risks and enhance safety. These systems integrate monitoring, data collection, and communication to provide timely information about natural hazards like earthquakes, tsunamis, or volcanic eruptions, enabling effective preparedness and response measures.
Earthquake: An earthquake is the sudden release of energy in the Earth's crust that creates seismic waves, resulting in ground shaking and often leading to significant damage. This natural hazard occurs primarily due to tectonic plate movements, volcanic activity, or human-induced processes. Understanding earthquakes involves recognizing their types, causes, and the associated risks, which are critical when studying major natural disasters and their impacts on societies.
Epidemics: Epidemics refer to the rapid spread of infectious diseases within a specific population or geographic area, often exceeding what is normally expected in that community. They can have significant social, economic, and health impacts, as outbreaks may strain healthcare systems and disrupt daily life. Understanding epidemics is crucial in identifying their causes and implementing effective control measures during natural hazards that create favorable conditions for disease transmission.
Flood: A flood is an overflow of water onto normally dry land, often resulting from excessive rainfall, rapid snowmelt, or the failure of dams or levees. Floods can cause significant damage to property, infrastructure, and ecosystems, and they are a major type of natural hazard that can affect communities worldwide. Understanding the causes and impacts of floods is crucial in assessing their role as a natural hazard.
Geological hazards: Geological hazards are natural events or processes that result from geological processes and can pose significant threats to life, property, and the environment. These hazards include phenomena like earthquakes, landslides, volcanic eruptions, and tsunamis, which are often driven by tectonic activity or volcanic processes. Understanding geological hazards is crucial for risk assessment and disaster management efforts in vulnerable regions.
Glacial lake outburst floods: Glacial lake outburst floods are sudden releases of water from a glacial lake, often caused by the failure of a dam made of ice or sediment. These floods can be catastrophic, leading to significant downstream impacts, such as erosion, flooding of communities, and destruction of infrastructure. Understanding these floods is crucial as they are considered a type of natural hazard, linked to climate change and glacial retreat.
Heatwave: A heatwave is an extended period of excessively hot weather, which may be accompanied by high humidity. This phenomenon is significant because it poses risks to human health, agricultural productivity, and environmental conditions. Heatwaves can result from various atmospheric conditions, including high-pressure systems that trap warm air, and they are increasingly linked to climate change.
Hurricane: A hurricane is a powerful tropical cyclone characterized by strong winds, heavy rainfall, and organized convection, typically forming over warm ocean waters. These storms can cause severe damage through high winds, storm surges, and flooding, making them one of the most dangerous natural hazards that impact coastal regions and inland areas.
Hydro-meteorological hazards: Hydro-meteorological hazards refer to natural disasters that are primarily caused by the interaction of water and atmospheric conditions. These hazards include phenomena such as floods, hurricanes, droughts, and landslides, which result from the variability in weather patterns, climate change, and geographic features. Understanding these hazards is crucial as they significantly impact ecosystems, human settlements, and economic activities.
Insect plagues: Insect plagues refer to severe outbreaks of insect populations that cause widespread damage to crops, ecosystems, and human health. These plagues can result from various environmental factors, including climate change, habitat disruption, and the introduction of invasive species, leading to ecological imbalances that can affect agriculture and biodiversity.
Intensity: Intensity refers to the strength or severity of a natural hazard, influencing its impact on people, property, and the environment. This concept is crucial in assessing the potential damage and risks associated with various hazards, such as earthquakes, hurricanes, or floods. Understanding intensity helps in emergency planning, risk assessment, and implementing effective mitigation strategies.
Jet streams: Jet streams are fast-flowing, narrow air currents found in the atmosphere, typically located near the tropopause, which is the boundary between the troposphere and the stratosphere. These high-altitude winds play a crucial role in influencing weather patterns, temperature distributions, and atmospheric circulation by transporting heat and moisture across long distances.
Land-use planning: Land-use planning is the process of evaluating how land resources are utilized and establishing guidelines to manage land development effectively. It involves balancing various needs, such as agriculture, housing, transportation, and environmental conservation, to promote sustainable growth while minimizing negative impacts on the environment. This practice is crucial for ensuring that land is used efficiently and responsibly, particularly in areas prone to natural hazards or with critical ecosystems.
Landslide: A landslide is a geological phenomenon that involves the movement of rock, earth, or debris down a slope due to gravity. This natural process is often triggered by various factors such as heavy rainfall, earthquakes, volcanic activity, or human activities, and it plays a significant role in shaping landscapes, particularly in areas with steep terrains and plate tectonics.
Magnitude: Magnitude refers to the size or intensity of a geological event, most commonly associated with earthquakes, but also applicable to volcanic eruptions and other natural phenomena. This concept is crucial for understanding the potential impacts and consequences of such events, as it helps to quantify the energy released and the resulting effects on the environment and human activities. Magnitude is often measured using various scales, which provide a standardized way to compare different events.
Pandemics: Pandemics are widespread outbreaks of infectious diseases that affect large populations across multiple countries or continents. They often result in significant health, social, and economic impacts, and can arise from various pathogens, including viruses and bacteria, that are capable of sustained human-to-human transmission.
Plate Tectonics: Plate tectonics is the scientific theory that explains the movement of Earth's lithosphere, which is divided into tectonic plates that float on the semi-fluid asthenosphere beneath them. This movement shapes the Earth's surface through various processes such as earthquakes, volcanic activity, mountain building, and ocean basin formation.
Risk Assessment: Risk assessment is the process of identifying, analyzing, and evaluating potential hazards and risks to determine their impact on people, property, and the environment. This systematic approach helps prioritize risks based on their likelihood and potential consequences, enabling informed decision-making for disaster preparedness and mitigation strategies. It is essential in understanding how natural hazards can lead to disasters, assessing the vulnerabilities in specific areas, and developing effective response plans.
Seawalls: Seawalls are coastal structures built to protect shorelines from erosion, storm surges, and high waves. They serve as a barrier between the ocean and the land, aiming to reduce the impact of natural hazards associated with coastal flooding and erosion. By absorbing and reflecting wave energy, seawalls play a critical role in preserving coastal infrastructure and habitats against the forces of nature.
Seismic Activity: Seismic activity refers to the frequency, type, and size of earthquakes that occur in a specific area over a given time period. This activity is closely linked to tectonic processes, as the movement of tectonic plates generates stress along fault lines, leading to earthquakes and other seismic events. Understanding seismic activity is essential for assessing the potential for erosion and mass wasting events, analyzing tectonic and structural landforms, and evaluating natural hazards.
Snowmelt: Snowmelt refers to the process of melting snow, which occurs when temperatures rise, leading to the transformation of solid snow into liquid water. This phenomenon plays a significant role in hydrology, as it contributes to river flow, groundwater recharge, and influences both natural ecosystems and human activities. Understanding snowmelt is essential in the context of water resource management, as it can lead to flooding and other natural hazards when large volumes of water are released rapidly.
Soil Saturation: Soil saturation refers to the condition in which all the pores in the soil are filled with water, leaving no space for air. This state is crucial for understanding how water interacts with soil, influencing various processes such as erosion and mass wasting, as well as the occurrence and impact of natural hazards. When soil is fully saturated, it can lead to increased weight and reduced stability, making slopes more prone to landslides and other forms of mass wasting, while also affecting how water moves through the environment during events like flooding or heavy rainfall.
Storm surge: A storm surge is an abnormal rise in sea level generated by a storm, primarily due to the wind's push and the low atmospheric pressure associated with hurricanes and other severe weather systems. This phenomenon can lead to catastrophic flooding in coastal areas, causing significant damage to infrastructure and ecosystems. Understanding storm surges is crucial for predicting their impact on communities during severe weather events.
Topography: Topography refers to the arrangement of natural and artificial physical features of an area, including its elevation, terrain, and the configuration of the land's surface. Understanding topography is crucial because it influences various environmental processes, such as soil formation, landform development, species distribution, and the assessment of natural hazards and risks.
Tropical cyclones: Tropical cyclones are intense circular storms that originate over warm tropical oceans and are characterized by low atmospheric pressure, high winds, and heavy rain. These storms play a significant role in the Earth's climate system and are influenced by various physical processes, making them essential to understanding how climate change impacts weather patterns and natural hazards.
Tsunami: A tsunami is a series of ocean waves generated by large disturbances, often caused by underwater earthquakes, volcanic eruptions, or landslides. These waves can travel across entire ocean basins and cause massive destruction when they reach coastal areas. Tsunamis are closely linked to geological processes and can be associated with different types of plate boundaries, contributing to their classification as significant natural hazards and notable disasters.
Urbanization: Urbanization is the process through which rural areas transform into urban ones, characterized by an increase in population density and the growth of cities. This phenomenon significantly impacts various aspects of the environment, economy, and social structures, influencing how societies function and interact with natural systems.
Volcanic eruptions: Volcanic eruptions are geological events where magma from beneath the Earth's crust escapes to the surface, often resulting in explosive blasts or the flow of lava. These eruptions can reshape landscapes, create new landforms, and impact climate and ecosystems. The activity associated with volcanic eruptions is closely linked to tectonic movements and can lead to various natural hazards that pose risks to human life and infrastructure.
Vulnerability: Vulnerability refers to the susceptibility of a community, environment, or system to suffer harm from natural hazards. This term encompasses the social, economic, and physical factors that influence how individuals and populations respond to these hazards. Understanding vulnerability helps identify areas that are at greater risk and can lead to better preparedness and response strategies during natural disasters.
Water cycle: The water cycle is the continuous movement of water within the Earth and atmosphere, involving processes like evaporation, condensation, precipitation, and infiltration. This cycle plays a critical role in Earth's systems by connecting the hydrosphere, atmosphere, lithosphere, and biosphere, ultimately affecting climate, weather patterns, and ecosystems.