[Natural]

Disasters

Types of DisastersThe earth’s weather is very mysterious. There is a lot of change in it. Here is a list of the top 3 most commonly occurring natural disasters:

Hurricanes are a cyclonic storm system that formsover the oceans. It is caused by evaporated water thatcomes off of the ocean and becomes a storm.The Coriolis Effect causes the storms to spin, and a hurricane is declared when this spinning massof storm attains a wind speed greater than 74 mph.

An earthquake is a result of movement in the earths crust. This shakes the ground violently andcauses extreme damage.

Tornadoes are violent,rotating columns of air which can blow at speeds between 50 and 300 mph, and possibly higher.

Volcanoes and Tsunamis

This report is focusing on the 4th and 5th most commonly occurring natural disasters; volcanoes and tsunamis.

What is a volcano?A volcano is a rupture on the crust of a planetary mass object, such as the Earth, which allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.Earth's volcanoes occur because the planet's crust is broken into 17 major, rigid tectonic plates that float on a hotter, softer layer in the Earth's mantle. Therefore, on Earth, volcanoes are generally found where tectonic plates are diverging or converging. Volcanoes can form where there is stretching and thinning of the earth crust's interior plates. Volcanoes are usually not created where two tectonic plates slide past one another.Erupting volcanoes can pose many hazards, not only in the immediate vicinity of the eruption. One such hazard is that volcanic ash can be a threat to aircraft furthermore people because of overwhelming heat and suffocation.

What is a tsunami?Tsunamis are giant waves caused by earthquakes or volcanic eruptions under the sea. Out in the depths of the ocean, tsunami waves do not dramatically increase in height. But as the waves travel inland, they build up to higher and higher heights as the depth of the ocean decreases. The speed of tsunami waves depends on ocean depth rather than the distance from the source of the wave. Tsunami waves may travel as fast as jet planes over deep waters, only slowing down when reaching shallow waters. While tsunamis are often referred to as tidal waves, this name is discouraged by oceanographers because tides have little to do with these giant waves.

PicturesHere are some more pictures of volcanoes and tsunamis.

Interesting facts [all natural disasters]

Over 2.6 billion people have been affected by natural disasters in the past decade.

The number of natural disasters has quadrupled in the past 30 years.

There have been over 3,400 floods worldwide since 1980. More than 2,600 severe storms have occurred in the last 30

years. The greatest famine in history killed around 45 million people in

China between 1958 and 1962. In 2010, Haiti suffered the deadliest earthquake in almost 500

years, killing over 316,000 people. The total cost of damage caused by natural disasters in the 1990s

reached over $650 billion. Does anyone know what many scientists believe is causing a

dramatic increase of natural disasters?

Thank-you for listening

To end my presentation, I would like to share a fact with you: recently, scientists discovered a new theory as to how a recent tsunami occurred.