Natural Hazards and People

Hazard or Disaster?

A natural hazard is a natural event that could hurt people or damage the things they need. Earthquakes, volcanic eruptions, tropical cyclones, floods, droughts, heat waves and wildfires are all hazards.

A disaster is what happens when a hazard seriously disrupts a community and the community cannot cope on its own. A strong earthquake in an empty desert is a hazard, but it may not be a disaster. The same quake under a crowded city with weak buildings could be.

The United Nations office for disaster risk reduction, UNDRR, puts it this way. It says disasters come from hazards meeting people and places that are exposed and vulnerable. That is why many experts avoid the phrase "natural disaster." The hazard is natural. How much harm it does depends a great deal on people.

Where Hazards Cluster

Hazards are not spread evenly across the map. Each kind has its own pattern.

Earthquakes and volcanoes

Most earthquakes and volcanoes happen near the edges of tectonic plates, the huge slabs that make up Earth's outer shell. The busiest zone is the Ring of Fire, a horseshoe of deep ocean trenches and volcanoes around the Pacific Ocean. It runs from New Zealand past Indonesia, the Philippines and Japan, around to Alaska and down the west coast of the Americas. A second belt crosses southern Europe and Asia, from the Mediterranean through Iran to the Himalayas.

Tropical cyclones

A tropical cyclone is a huge spinning storm that forms over warm ocean water. It is one kind of storm with three local names, as the World Meteorological Organization explains:

• Hurricane in the North Atlantic and the eastern North Pacific.
• Typhoon in the western North Pacific, near Japan, China and the Philippines.
• Cyclone in the Indian Ocean and around Australia, affecting India, Bangladesh, Madagascar and northern Australia.

Cyclones bring strong winds, heavy rain and storm surge, a rise of seawater pushed onto the coast. Surge is often the deadliest part. Regional weather centers give each storm a name from a list so that warnings are easy to follow.

Floods, droughts and wildfires

Floods are most common on flat floodplains beside rivers and on deltas, where big rivers meet the sea. These places have rich soil, so many people farm and live there. The Ganges-Brahmaputra delta in Bangladesh and India is one of the most crowded. Droughts hit hardest in dry belts like the Sahel, the strip of land south of the Sahara, where rainfall changes a lot from year to year. Wildfires burn most often where a wet season grows plants and a long dry season dries them out, as in parts of Australia, California, the Mediterranean and the African savanna.

The Three Parts of Risk

Geographers break disaster risk into parts. A simple way to remember it is:

Risk = Hazard × Exposure × Vulnerability

• Hazard: the event itself, such as how strong the shaking is or how high the water rises.
• Exposure: the people, homes, roads and farms in the hazard's path.
• Vulnerability: how easily those people and things are harmed. Weak buildings, poverty, no warning system and poor roads all raise vulnerability.

The "×" is a reminder that if any part is close to zero, the risk is small. A huge storm over open ocean has almost no exposure. A town with strong buildings and good warnings has low vulnerability. UNDRR also lists capacity: the skills and resources a community has to prepare and recover. More capacity means less risk.

Two Earthquakes, Two Outcomes

In early 2010, two strong earthquakes struck the Americas just six weeks apart. Comparing them shows why risk depends on more than the hazard.

The Chile earthquake released roughly 500 times more energy, yet far fewer people died. Here are three reasons:

• Buildings. Chile has strict building codes, shaped by many past earthquakes, including the strongest one ever recorded, in 1960 (USGS, 2011). In Port-au-Prince, many concrete buildings were not built to resist shaking, and many collapsed.
• Where the shaking was. Haiti's earthquake was shallow and very close to a crowded capital. Chile's was centered offshore.
• Money and services. The World Bank calls Haiti the poorest country in Latin America and the Caribbean. It had fewer hospitals, rescue teams and supplies.

Each death in both countries was a person with a family. Comparing the two is not about blame. It helps show which choices save lives.

Making Places Safer

People cannot stop most hazards, but they can lower exposure and vulnerability.

• Warning systems. Satellites, weather radar and sensors spot many hazards early. Japan's Earthquake Early Warning system can give seconds of notice, enough to slow trains and stop elevators. U.S. tsunami warning centers watch the Pacific and the Atlantic. The UN's Early Warnings for All plan aims to cover every person on Earth by the end of 2027.
• Building codes. Rules about how to build, such as using steel bars in concrete or tying roofs down, help buildings survive shaking and wind.
• Land-use planning. Towns can keep new homes off floodplains, steep slopes and low coasts, and leave space for rivers to spread out.
• Nature. Wetlands and mangrove forests can soak up floodwater and soften storm surge.

In 2015, UN member states agreed on the Sendai Framework, a plan running to 2030. Its aim is to cut disaster deaths and losses by reducing risk before disasters happen, not just responding afterward.

A Changing Climate

Earth's climate is warming, and scientists have studied how that affects hazards. The Intergovernmental Panel on Climate Change (IPCC) states its findings with care, saying how sure it is about each one. In its 2021 report, it found that:

• Hot extremes, such as heat waves, have become more frequent and more intense across most land areas since the 1950s.
• Heavy rainfall has become more frequent and intense over most land areas where there is enough data.
• Some regions have seen more drought and more fire weather, the hot, dry, windy conditions that help fires spread.
• The share of tropical cyclones that become major storms has likely grown, but scientists are much less sure whether the total number of cyclones has changed.
• Global sea level rose about 20 cm from 1901 to 2018, which lets storm surge reach farther inland.

Climate change does not cause earthquakes or eruptions, and not every trend is the same everywhere. Growing cities on coasts and floodplains also raise exposure, so losses can rise even where a hazard has not changed.

Getting Ready at Home

Being prepared is something kids can help with, and it makes emergencies less frightening. Ready.gov, a U.S. government site, suggests a few steps for families:

1. Learn your local hazards. Ask an adult which hazards affect your area: floods, storms, earthquakes, wildfires or something else.
2. Make a plan. Pick a meeting place and one contact person, ideally someone out of town, whom everyone in the family will call or text.
3. Build a kit. Pack water, food that keeps, a flashlight, spare batteries, a first aid kit and copies of important papers.
4. Practice. Know safe moves for each hazard. In an earthquake, drop, cover and hold on. Never walk or drive through floodwater: turn around, don't drown. On a coast, if the ground shakes hard, move to high ground.

Emergency workers, teachers and neighbors practice for these events too. Most of the time, warnings and plans work.

Links to Earlier Units

• Landforms and Water: mountains, rivers and deltas, where many hazards happen.
• Climate and Biomes: wet and dry seasons that shape floods, droughts and fires.
• Cities and Urbanization: why fast-growing cities can raise exposure.
• Countries and Borders: why warnings and help often cross borders.

Game: Risk Sorter

Each round shows one fact about a place. Decide which part of risk it describes: the hazard, the exposure or the vulnerability. Every answer comes from this page.

Quiz: Natural Hazards and People

Ten questions. Choose one answer for each, then check your score. You can try as many times as you like.

Credits

Written by Marco for Jugami's World Geography course. The two world maps and the risk diagram are original SVG illustrations made for this page. The maps use public-domain land outlines from Natural Earth. The hazard zones on them are simplified drawings based on the USGS, WMO and NOAA sources below, not exact boundaries.