Natural Hazards | Science for ACT PDF Download

Introduction

Natural hazards are physical phenomena caused by atmospheric, water or tectonic processes that threaten people, property or the environment. They can occur within a short or long period of time.

What is the difference between natural hazards and natural disasters?

• The distinction between natural hazards and natural disasters is important to grasp. While natural hazards refer to potential threats posed by natural phenomena, natural disasters occur when these hazards reach a critical level and cause significant harm to society or the environment, overwhelming the community's resources.
• Natural hazards encompass various adverse effects, such as loss of life, injuries, and damage to infrastructure. When these effects surpass a predetermined threshold, a natural hazard escalates into a natural disaster. This threshold can be measured by criteria like the number of fatalities or the extent of economic losses.

Types of natural hazards include geophysical hazards like earthquakes, volcanic eruptions, and tsunamis; hydrological hazards such as floods; meteorological hazards like cyclones and storms; climatological hazards such as droughts and wildfires; and biological hazards including pandemics and epidemics.

The causes of natural hazards vary depending on their type:

• Geophysical hazards are triggered by tectonic processes.
• Hydrological hazards stem from factors like heavy rainfall, ice and snow melting, and storm surges. Deforestation and infrastructure modifications like dam breaches can exacerbate these hazards.

Meteorological hazards

• Meteorological hazards are triggered by extreme weather events, including heavy rain, strong winds, hail, and snowfall. These hazardous conditions can lead to various disruptions and damages. Notably, the impact of meteorological hazards has been intensified by climate change, which contributes to the frequency and severity of such events.

Climatological hazards

• Climatological hazards are characterized by prolonged periods of extreme heat or cold. These hazards pose significant risks to human health and the environment. With the ongoing rise in global temperatures due to climate change, the severity and frequency of climatological hazards have been exacerbated.

Biological hazards

• Biological hazards encompass various microorganisms such as bacteria, viruses, parasites, molds, and fungi, which pose threats to human health by causing diseases. Many biological hazards emerge from novel pathogens transmitted from animals to humans, leading to outbreaks and pandemics. A prominent example is the current Covid-19 pandemic, which highlights the substantial impact of biological hazards on global health and society.

Impacts of natural hazards

• Impacts of natural hazards can manifest in various dimensions, affecting societies, economies, and ecosystems. These consequences encompass loss of life, injuries, destruction of infrastructure, disruption of businesses, and harm to natural habitats. Moreover, natural hazards can trigger secondary hazards, compounding the initial damage. For example, flooding may trigger landslides, exacerbating the overall impact on affected areas.
• When comparing natural hazards, it's crucial to employ suitable metrics to gauge their severity and implications accurately. This comparative analysis enables stakeholders to prioritize mitigation efforts and devise effective response strategies. By assessing the relative risks posed by different hazards in a particular region, authorities can allocate resources efficiently and implement targeted measures to minimize vulnerabilities.
• Various measurement tools are utilized to assess the intensity of different natural hazards. For tectonic hazards, for instance, metrics such as the Moment Magnitude Scale (MMS), Mercalli scale, and the Volcanic Explosivity Index (VEI) are commonly employed. These scales provide standardized frameworks for quantifying the magnitude of hazards, facilitating informed decision-making and risk management initiatives.

Earthquake magnitude

Earthquake magnitude is measured based on the Moment Magnitude Scale (MMS), which quantifies the total seismic moment released by an earthquake. The scale ranges from 1 Mw to 10 Mw. We calculate it in terms of the distance the ground has moved along the slip and the force required to do so. The Moment Magnitude Scale is logarithmic, meaning that from one integer to the next, the amplitude of the ground motion is ten times greater, and the amount of energy released is 30 times greater.