Transcript The causes of valcanoes

The causes of volcanoes
Even though things can appear very calm on the
surface of the Earth, underneath the materials are
very hot. This is called magma. When at times magma
works it's way up towards the surface of the ground, it
can break through. This is what is happening when a
volcano erupts.
The effects of volcanoes
Mount Pinatubo's devastating explosion on June 15, 1991 resulted
in an incredible surge of sulfer dioxide gas into the stratosphere
where it combined with water to form sulfuric acid. The new
aerosol deteriorated the Earth's ozone layer by altering the
chlorine and nitrogen compounds, and it also lowered the Earth's
surface temperature.
Causes of earthquakes
An Earthquake is a sudden tremor or movement of the earth's crust, which originates naturally at or below the surface.
The word natural is important here, since it excludes shock waves caused by French nuclear tests, man made explosions
and landslides caused by building work.
There are two main causes of earthquakes.
Firstly, they can be linked to explosive volcanic eruptions; they are in fact very common in areas of volcanic activity
where they either proceed or accompany eruptions.
Secondly, they can be triggered by Tectonic activity associated with plate margins and faults. The majority of
earthquakes world wide are of this type.
Terminology
Effect of earthquakes
Most earthquake-related deaths are caused by the collapse of structures and the construction practices play a
tremendous role in the death toll of an earthquake. In southern Italy in 1909 more than 100,000 people perished in an
earthquake that struck the region. Almost half of the people living in the region of Messina were killed due to the easily
collapsible structures that dominated the villages of the region. A larger earthquake that struck San Francisco three
years earlier had killed fewer people (about 700) because building construction practices were different type
(predominantly wood). Survival rates in the San Francisco earthquake was about 98%, that in the Messina earthquake
was between 33% and 45%) (Zebrowski, 1997). Building practices can make all the difference in earthquakes, even a
moderate rupture beneath a city with structures unprepared for shaking can produce tens of thousands of casualties.
Causes of volcanoes
The earth has “plates” and when two plates hit each other, one goes under and becomes “molten” which means it gets so hot, the ground turns into
liquid. The molten stuff finds a hole in the ground and comes out the top. All of the continents used to be just one big piece of land, but the land
broke up and floated away and created the 7 continents we have now. This was called continental drift. If you look at South America, it looks like it
could fit like a puzzle piece into Africa.
Because of the way the ground broke, it created plates. Even though the ground is heavy, the plates continue to move and that can cause earthquakes
and volcanoes. When two plates hit each other, one can go under and become "molten” which means it gets so hot, the ground turns into liquid. The
molten stuff finds a hole in the ground and comes out the top. When the molten stuff is in the volcano it is called magma. When it explodes, it is
called lava.
Volcanoes explode because of the gas buildup. When the gas builds up a lot, the gas and lava, which is hot rocks, blows out the top, it’s a lot like the
way a soda explodes. The lava can get up to 1600 degrees - a lot hotter than an oven. After the lava cools, it turns into rock. One of the types of rock is
obsidian, which is shiny and black. Volcanoes can also occur on other planets. Not all volcanoes explode, some are inactive and some are dormant.
The lava can kill people, but there can be other problems. If there’s heavy rains on the ash it creates a thick mud that has trapped people and animals.
When all the trees and plants are destroyed by the lava, the animals have nothing to eat.
Lots of volcanoes happen in the “Ring of Fire” which is from California to Asia. There are large tectonic plates in the Ring of Fire and lots of
earthquakes happen here too.
cool videos of volcanoes:
http://www.volcanoworld.org/vwdocs/movies/movie.html
http://www.volcanoworld.org/vwdocs/eruption_scale.html
http://yahooligans.yahoo.com/content/science/brainpop/movie?id=volcanoes
sources:
http://www.nsf.gov/nstw_questions/eart/quest083.htm
http://www.geosc.psu.edu/~jrogie/ans11-3.html
http://www.volcanoworld.org/
http://pubs.usgs.gov/publications/msh/contents.html
http://pubs.usgs.gov/publications/msh/continuing.html
http://www.volcanoes.com/
http://www.geology.sdsu.edu/how_volcanoes_work/Home.html
landslides
Landslides occur and can cause damage in all 50 States. Severe storms,
earthquakes, volcanic activity, coastal wave attack, and wildfires can cause
widespread slope instability. Landslide danger may be high even as emergency
personnel are providing rescue and recovery services.
To address landslide hazards, several questions must be considered: Where and
when will landslides occur? How big will the landslides be? How fast and how
far will they move? What areas will the landslides affect or damage? How
frequently do landslides occur in a given area?