Hurricane

Hurricane Katrina

Hurricane Katrina, which happened in 2005, was the most costly hurricane in the history of the US. It is the sixth strongest Atlantic hurricane recorded. It formed over the Bahamas on August 23rd. While it crossed Florida it was just a category 1 hurricane, but still caused some deaths until strengthening in the Gulf of Mexico. The storm weakened before making its second landfall as Category 3 on the morning of Monday, August 29 in southeast Louisiana. The most severe loss of life and property damage happened in New Orleans. At least 1,836 people lost their lives in the actual hurricane and in the subsequent floods, making it the deadliest U.S. hurricane since the 1928 Okeechobee Hurricane.

Landslide

A landslide includes a wide range of ground movement.

Landslides are caused when the stability of a slope changes from a stable to an unstable condition. A change in the stability of a slope can be caused by a number of factors, acting together or alone.

Types of landslide include :

• Debris flow - slope material that becomes saturated with water.


• Earth flow - downslope, viscous flows of saturated, fine-grained materials


• Debris avalanche - chaotic movement of rocks soil and debris mixed with water or ice (or both).


• Sturzstrom - Often very large, these slides are unusually mobile, flowing very far over a low angle, flat, or even slightly uphill terrain.

Earthquakes are among the most deadly natural hazards. There are around 100 earthquakes each year of a size that could cause serious damage.

Seismology is the study of earthquakes and seismic waves. The seismograph records the seismic waves generated by earthquakes, allowing the seismologist to determine where, and how deep, a particular earthquake is. Also, the seismic waves from earthquakes can be used to image the deep interior of the Earth, providing vital clues to the internal structure of our planet.

Movements within the Earth’s crust cause stress to build up at points of weakness, and rocks to deform. When the stress finally exceeds the strength of the rock, the rock fractures along a fault, often at a zone of existing weakness within the rock. The stored energy is suddenly released as an earthquake.

Floods

Flooding is a natural event. It occurs when there is heavy rainfall that fills rivers and streams above their normal capacity, or if there are very high river or coastal tides that cause levels to rise or surge. The excess water that gathers cannot be restrained by normal boundaries such as a river embankment.

This means lowere laying areas are most at risk. Floods can also occur when rainwater collects on the ground and cannot find a drain.

Volcanoes

Deep inside Earth, between the molten iron core and the thin crust at the surface, there is the mantle, a large layer of rock that is largely solid, but flows like plastic. When, for various reasons, rock from the mantle melts, it sometimes moves to the Earth’s surface through weak spots in the crust, releasing heat, gasses, and rock.This is a volcanic eruption.

Avalanches

Avalanches occur in the snow. They can reach speeds of 80 mph in just 5 seconds. Avalanches are most common during and in the 24 hours right after a storm that dumps 12 inches (30 centimeters) or more of fresh snow.

These factors affect whether and how a slope avalanches:

• Storminess


• temperature


• wind


• slope steepness


• orientation (the direction it faces)


• terrain


• vegetation


• general snowpack conditions

It is unusual for a victim of an avalanche to escape.

Introduction

A natural disaster is the effect of a natural hazard that effects the environment.
For example:

• flood
• volcanic eruption
• landslide
• earthquake
• avalanche