1,3(a)Most earthquakes and volcanoes occur at the plate boundaries where two plates collide and diverge. The ways for classifying volcanoes are shown below, and the ritcher scale is used for earthquakes.
1,2(b)There are four main types of volcanoes. They are cinder cone, composite, shield, and lava dome.
A cinder cone is made when lava with lots of pressure is blown into the air, as the globs fall they cool into cinders that form a cone around the vent. Paricutin in Mexico is an example of this.
Composite volcanoes are formed from alternating layers of lava, ash, and cinder. they are steep sided and are the largest of volcanoes. Mt st helents is an example of this.
Shield volcanoes are large, flat volcanoes formed when fluid lava pools outward over an area. Hawiian volcanoes are an example of this.
Lava domes are fomed when the lava is too fluid to really go anywhere so it piles up inside the cone, this eventually builds pressure to form a violent ezplosion, Mt Pelee is an example.
1,4(c) Volcanoes have an impact on the atmosphere by blowing ash into the air, which blocks light. They can poison the water and affect the temperature (both heating and cooling)
bibliography
1 Principal types of volcanoes,USGS,http://pubs.usgs.gov/gip/volc/types.html,2/6/97
2 Types of volcanoes, Oregon State University, http://volcano.oregonstate.edu/vwdocs/vwlessons/lessons/lesson6.html
3 eathquake measurement, Geography.info, http://www.geography.info/earthquakes/10/earthquake_measurement.html, 2006
4 How volcanoes affect the climate, scientific american, http://www.scientificamerican.com/article.cfm?id=how-do-volcanoes-affect-w, 10/4/05
Pics
http://www.solcomhouse.com/images/volcanotyypki.jpg
http://comp.uark.edu/~sboss/tectonic14.gif
http://www.istockphoto.com/file_thumbview_approve/5743532/2/istockphoto_5743532-destruction-and-aftermath-of-earthquake-or-natural-disaster.jpg
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