Types of Natural Hazards (Tectonic, Weather, Biological)

Tectonic Hazards

Tectonic hazards are natural events caused by movements of the Earth's plates. These include earthquakes and volcanic eruptions, which mostly occur along plate boundaries where plates interact.

Earthquakes

Earthquakes happen when stress builds up along faults or plate boundaries and is suddenly released, causing the ground to shake. The energy spreads as seismic waves. The severity depends on the earthquake's magnitude and depth.

Most earthquakes occur at:

• Destructive boundaries – where plates move towards each other, causing one plate to be forced under another (subduction).
• Constructive boundaries – where plates move apart, creating new crust and causing small earthquakes.
• Conservative boundaries – where plates slide past each other, causing friction and earthquakes.

Volcanoes

Volcanoes form when magma from the mantle rises through cracks in the Earth's crust and erupts at the surface. Volcanoes are common at:

• Destructive boundaries – where subduction causes melting of the plate, forming magma.
• Constructive boundaries – where plates pull apart, allowing magma to rise.
• Hotspots – areas away from plate boundaries where magma rises through the crust.

Plate Boundaries

The Earth's lithosphere is divided into tectonic plates that move slowly. The main types of plate boundaries are:

• Destructive (Convergent): Plates move towards each other; one plate subducts, causing earthquakes and volcanoes.
• Constructive (Divergent): Plates move apart; magma rises to form new crust, causing volcanic activity and earthquakes.
• Conservative (Transform): Plates slide past each other; friction causes earthquakes but no volcanoes.
• Collision: Two continental plates collide, causing mountain building and earthquakes but no volcanoes. Collision boundaries cause the formation of mountain ranges such as the Himalayas.

Impacts and Examples

Tectonic hazards can cause severe damage to buildings, infrastructure, and lives. For example:

• The 2010 Haiti earthquake (magnitude 7.0) caused widespread destruction and loss of life due to poor building standards.
• The 1980 eruption of Mount St. Helens in the USA destroyed forests and caused ash clouds affecting air travel.

For instance, the 2011 Tōhoku earthquake in Japan (magnitude 9.0) triggered a tsunami and nuclear disaster, showing how tectonic hazards can have multiple effects.

Example: If an earthquake has a magnitude of 6.5 and occurs at a shallow depth, it is likely to cause more surface damage than a magnitude 7.0 earthquake at a depth of 100 km because seismic waves lose energy with depth.

Weather Hazards

Weather hazards are extreme weather events that can cause damage and danger to people and property. These include tropical storms, flooding, and storms common in the UK.

Tropical Storms

Tropical storms (also called hurricanes or cyclones) form over warm ocean waters near the equator where the sea temperature is above $26^\circ\mathrm{C}$. They develop when warm, moist air rises, creating low pressure and strong winds spiralling around the eye.

Tropical storms have:

• Very strong winds (up to $250\,\mathrm{km\,h^{-1}}$)
• Heavy rain causing flooding
• Storm surges that can flood coastal areas

Flooding

Flooding occurs when water overflows onto normally dry land. Causes include:

• Heavy rainfall saturating soil
• River overflow after prolonged rain
• Storm surges and coastal flooding

Flooding can damage homes, disrupt transport, and cause health problems.

Storms in the UK

The UK experiences storms caused by depressions (low pressure systems) moving in from the Atlantic. These bring strong winds and heavy rain, especially in autumn and winter.

Although less severe than tropical storms, UK storms can cause flooding, power cuts, and travel disruption.

Causes and Effects

Weather hazards result from atmospheric conditions:

• Tropical storms: Warm ocean water fuels the storm; Coriolis effect causes rotation.
• Flooding: Excess rainfall or storm surges cause water to overflow.
• UK storms: Rapid changes in air pressure bring strong winds and rain.

Example: A tropical storm with wind speeds of $150\,\mathrm{km\,h^{-1}}$ can cause roofs to be blown off and trees uprooted, leading to power outages and blocked roads.

Biological Hazards

Biological hazards are natural events caused by living organisms that can harm humans, animals, or plants. These include disease outbreaks and insect infestations.

Disease Outbreaks

Disease outbreaks occur when infectious diseases spread rapidly through populations. Causes include:

• Pathogens such as bacteria, viruses, or parasites
• Poor sanitation and crowded living conditions
• Global travel spreading diseases quickly

Examples include the Ebola outbreak in West Africa (2014–2016) and seasonal influenza.

Insect Infestations

Insect infestations happen when large numbers of insects damage crops, forests, or spread diseases. Causes include:

• Changes in climate allowing insects to survive in new areas
• Monoculture farming providing abundant food
• Lack of natural predators

Examples include locust swarms in East Africa and bark beetle outbreaks in forests.

For example, locust swarms can devastate crops, leading to food shortages.

Causes and Impacts

Biological hazards often result from natural cycles or human activities that disturb ecosystems. Impacts include:

• Health crises and loss of life from disease outbreaks
• Economic losses from damaged crops and livestock
• Food shortages and increased poverty

Example: The 2014 Ebola outbreak caused thousands of deaths and overwhelmed healthcare systems in affected countries.

Comparison of Hazard Types

Natural hazards vary in origin, frequency, distribution, and the vulnerability of people affected.

Differences in Origin

• Tectonic hazards: Caused by movements of the Earth's plates beneath the surface.
• Weather hazards: Caused by atmospheric and oceanic conditions, such as storms and rainfall.
• Biological hazards: Caused by living organisms like pathogens or insects.

Frequency and Distribution

• Tectonic hazards: Mostly occur along plate boundaries; some areas like the Pacific Ring of Fire are more prone.
• Weather hazards: Tropical storms occur in warm ocean regions; UK storms are seasonal; flooding can happen anywhere with heavy rain.
• Biological hazards: Can occur worldwide; outbreaks often linked to poor sanitation or climate conditions.

Human Vulnerability

Vulnerability depends on factors such as population density, building quality, preparedness, and healthcare. For example:

• Earthquakes cause more damage in poorer countries with weak buildings.
• Tropical storms affect coastal areas with dense populations.
• Disease outbreaks hit areas with limited medical resources hardest.

Examples

Hazard Type	Example	Location	Key Impact
Tectonic	2010 Haiti Earthquake	Haiti	Widespread destruction, thousands of deaths
Weather	Hurricane Katrina (2005)	USA (Gulf Coast)	Flooding, damage to homes, displacement
Biological	Ebola Outbreak (2014–2016)	West Africa	Thousands of deaths, overwhelmed health systems