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Natural hazards are natural disasters caused by different reasons. Every year, lots of natural hazards happen and some of them are more dangerous than other natural hazards. Normally, we can’t do anything to stop a natural hazard and they happen from one minute to another one, without any advice. Natural hazards can be very powerful and destroy lands, cities, buildings, … They usually kill lots of people too and they can make irreparable damages in a land. Natural hazards still show human beings that Nature is very powerful and that there’s nothing we can do to stop it. In our magazine Earth Today we will take a look at some natural hazards. Let’s take a look at them!

EARTHQUAKES Earthquakes are one of the most known and feared natural hazards. Every earthquake supposes human victims: tens, hundreds or thousands but that’s not a number matter because at the end, there’re dead people anyways. Everyone knows that earthquakes shake the land where they happen and buildings start to tumble down like plastic toys and it destroys everything, creating the need to rebuild all the damage caused by the earthquake again.

But how do earthquakes exactly happen? There’re some pieces of territory, that under the ground have Catalan Pyrenees. The Pyrenees is a mountain region between the north of got tectonic areas that Spain and the south of France. This region is often shook by little release lots of energies earthquakes that move the ground and the mountains, but we can’t feel because of Earth’s moves them and scientists barely record the strength of those earthquakes. during all the time. But in fact, lots of little earthquakes happen everyday but we just can’t feel them because they’re of very little strength and that’s why there are more or less, 100 earthquakes per year. The strength of earthquakes are calculated by Richter degrees and there’s a classification with Richter degrees for every earthquake:


Richter degrees



Less than 2,0



Very little

We can’t feel this type of earthquakes. Usually we can’t feel them.










Very strong

8,0 or bigger


Sometimes we can feel them but they’re not dangerous. We feel them always but there aren’t big damages. It can damage old and notgood built buildings but the good-build ones don’t get damaged. It can destroy 100 miles away from the original place where the earthquake started. It destroys lots of buildings and areas. It is very dangerous and lots of people die.

There’re some lands like Lisbon or Japan that are located over tectonic areas, what makes them very vulnerable for earthquakes. But thanks to new technologies, scientists can anticipate some earthquakes and their strength; but anyways, us, the humans, we have demonstrated that we’re very vulnerable to natural hazards like earthquakes; it doesn’t matter how ready you’re, if a big earthquake comes everything tumbles down. We can’t do anything for avoiding or stopping earthquakes but in areas that usually suffer earthquakes, safer and good-build buildings can stand with earthquakes. Japan is a clear example of that technique. Everyone knows famous earthquakes. Let’s take a look at some of them: -


Lisbon; 1755. The 1st of November 1755 a very big earthquake happened in Lisbon. Between 60,000 and 100,000 people died because of that earthquake, becoming one of the worst earthquakes of all Earth’s story. Then, a tsunami and wildfires came, destroying the whole city. Some scientists say that Lisbon is destroyed every 400 years because of a tectonic area; the same that destroyed Lisbon in 1755. San Francisco; 1906. The 18th April of 1906, at morning a 7’8 Richter degrees earthquake shook the American city of San Francisco. Between 3,000 and 6,000



people died and 300,000 of the 400,000 San Francisco citizens became homeless. After the earthquake, some wildfires burn the city and they destroyed it. Pakistan, 2005. The 10th August of 2005 an earthquake shook Pakistan, causing more than 126,000 dead people and 2,000,000 homeless people. Sendai, 2011. The 11th March of 2011, one of the most recent earthquakes nowadays shook the land of Sendai, causing a few dead people. But the earthquake made a tsunami that killed lots of people (over 10,000 people) and it hit the nuclear power station of Fukushima, causing a very dangerous nuclear trouble. Meanwhile, Japan has already rebuild roads and buildings that the earthquake and the tsunami destroyed.

And the biggest earthquake of the story is this one: -

Valdivia (Chile); 1960. The 22nd May of 1960 a huge earthquake of 9’5 Richter degrees happened in the city of Valdivia, in Chile. It caused between 5,700 and 10,000 dead people but there were 4,000,000 that had problems after the earthquake (because their lost their homes, families…). The city of Valdivia was buried 4m under the water.

TSUNAMIS Tsunamis are a hydrological natural hazard. They’re huge water waves that come through the sea and when they shock on ground, tsunamis start to damage and drag everything. Tsunamis can be exactly caused by too many different reasons: submarine earthquakes, volcanic eruptions, after an earthquake (because of energy and moves matter) and different types of landslides. In the case of earthquakes, a 6.4 Richter degrees earthquake can make a dangerous tsunami (with 7m height waves) and a tsunami made by earthquakes of 7 Richter degrees are really dangerous.

In this picture the importance of the coast’s ground incline can be appreciated. In the left picture, we can see that with a sloping ground, the wave heats harder and with a less sloping ground it doesn’t hit so bad.


This hazard is made of different waves, but there’re two important ones: a big one that lasts between 5 minutes and 1 hour and the little one that can go 880km far. While the big wave approaches to the coasts, it gets bigger and the damage is stronger too and the see tide goes quickly out. An important factor about tsunami’s damage is the incline of the coast’s ground; if the coast’s ground is more sloping, waves will be more dangerous and destructive. There have been lots of tsunamis through all Earth’s history, but let’s just take a brief look to the two most famous tsunamis of this decade. -


Indian Ocean tsunami. The 26th December of 2004 a big and important tsunami hit different countries and islands located in the Indian Ocean (India, Sri Lanka, Indonesia and Thailand). This tsunami was incredibly fast and in just a few hours it hit lots of lands and it destroyed lots of buildings and houses causing very important economical troubles for those countries. It caused more than 300,000 dead people, plus lots of disappeared people and because of the tsunami, rare diseases attacked people that died too. Sendai tsunami. It is one of the most recent and famous tsunamis, and one of the most terrible and dangerous of all the times. After the earthquake that Japan suffered, the 11th of March of 2011 a big alert of tsunami was created by the Japanese weather statements and the alert went through lots of countries: EEUU, Canada, Chile, Argentina, Russia, South-America countries… It was a terrible disaster, with waves of 10m height that paralyzed the whole Japanese country and killed thousands of people. The tsunami hit Fukushima nuclear station, causing one of the biggest nuclear accidents of the whole story.

TORNADOES A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. Tornadoes come in many shapes and sizes, but are typically in the form of a visible condensation funnel and is often encircled by a cloud of debris and dust.


There are several different scales for rating the strength of tornadoes, the Fujita scale.

Most tornadoes take on the appearance of a narrow funnel. Tornadoes may be obscured completely by rain or dust. Tornadoes can have a wide range of colors, depending on the environment in which they form. Lighting conditions are a major factor in the appearance of a tornado. Tornadoes normally rotate cyclonically in direction. Tornadoes emit widely on the acoustics spectrum and the sounds are caused by multiple mechanisms. Electromagnetics and lightning have little or nothing to do directly with what drives tornadoes. Most tornadoes follow a recognizable life cycle. When the mesocyclone approaches the ground, a visible condensation funnel appears to descend from the base of the storm, often from a rotating wall cloud. It then reaches mature stage and then it wraps around, the vortex begins to weaken, and become thin and rope-like. There are different types of tornadoes: -

Multiple vortexes: This type of tornado has two or more columns of spinning air rotating around a common center. Waterspout: It is a tornado over water. Landspout: It is a tornado not associated with a mesocyclone.


VOLCANOES A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from below the surface. Volcanoes are generally found where tectonic plates are diverging or converging. A volcanic eruption is a natural calamity that besides wrecking havoc on human life and property can cause a lot of environmental changes by contributing to acid rain and global warming. Though we cannot prevent the occurrence of such eruptions, we can reduce their devastating effects.

Volcanoes are notorious for their devastating effects, not only on human life but also on the global environment. Lava, emission of toxic gases, ash fall, lahars and landslides are some of the most dangerous hazards of volcanic eruptions.

Volcanoes are classified I different types: a) Active The volcanoes that erupt regularly are called active. There are about 500 active volcanoes in the world. b) Extinct Extinct volcanoes are those that scientists consider unlikely to erupt again, because the volcano no longer has a lava supply. One example is Zuidwal volcano in the Netherlands. c) Dormant Volcanoes may remain dormant for a long period of time. It is difficult to distinguish an extinct volcano from a dormant one. For example, Yellowstone has a repose period of around 700 years.

There are many different types of volcanic eruption and they vary in strength: a) The weakest volcanoes are  Hawaiian eruptions  Strombolian  Vulcanian



b) The strongest volcanoes are:  Phreatomagmatic eruptions  Phreatic eruption  Pelean eruptions  Plinian eruptions  Ultra Pilnian  Phreatic eruptions

Volcanoes have different materials: Lava: is only a part of the hazards created by volcanoes. Lava flows are usually slow and therefore, people can easily escape them. But, they can cause extensive economic loss by burning and crops. Gas: volcanic eruptions usually contain a number of harmful gases like carbon dioxide, sulfur dioxide, water vapor, etc. That can create a lot of changes in the Earth's atmosphere. Ash: volcanic ash mainly consists of small and sharp rock particles formed from the breakdown of magma. The explosive eruptions of volcanoes can throw such ash particles over a long distance.

ISSBN 338-89-1996 © Marc and Alice 2011

Joan Oró Publishers Ltd


Earth Today  

A Magazine on Natural Hazards

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