VOLCANOES

CAUSE AND EFFECTSVOLCANOESGroup MembersPutu Agastya (03)I Putu Agi Karasugi(04)Cintya Meriasti(13)Dandy Christopher(14)DEFINITIONA volcano is simply a rupture (opening or vent) on the earth's surface (crust) through which molten magma (extremely hot mixture of gases, lava, ash and other burning substances) escape on to the earth's surface. These volcanoes can erupt and pose many hazards. An erupting volcano can produce sulfuric acid and poisonous ash and trigger tsunamis, flash floods, earthquakes, mudflows and rockfalls.DANDY CHRISTOPHER (14)Scientists have categorized volcanoes into three main categories: active, dormant, and extinct. An active volcano is one which has recently erupted and there is a possibility that it may erupt soon. A dormant volcano is one which has not erupted in a long time but there is a possibility it can erupt in the future. An extinct volcano is one which has erupted thousands of years ago and theres no possibility of eruption.DANDY CHRISTOPHER (14)Cinder ConesCinder cones are circular or oval cones made up of small fragments of lava from a single vent that have been blown into the air, cooled and fallen around the vent.

Composite VolcanoesComposite volcanoes are steep-sided volcanoes composed of many layers of volcanic rocks, usually made from high-viscosity lava, ash and rock debris.

Shield VolcanoesShield volcanoes are volcanoes shaped like a bowl or shield in the middle with long gentle slopes made by basaltic lava flows. Basalt lava flows from these volcanoes are called flood basalts.Volcanoes are grouped into three types: cinder cones, composite volcanoes, shield volcanoes and lava volcanoes. DANDY CHRISTOPHER (14)Cinder Cone Volcanoes

DANDY CHRISTOPHER (14)Composite Volcanoes

DANDY CHRISTOPHER (14)Shield Volcanoes

DANDY CHRISTOPHER (14)CausesVolcanoes are formed when magma from within the Earth's upper mantle works its way to the surface. At the surface, it erupts to form lava flows and ash deposits. Over time as the volcano continues to erupt, it will get bigger and bigger.

Putu Agastya (03)Volcanoes erupt because of density and pressure. The lower density of the magma relative to the surrounding rocks causes it to rise (like air bubbles in soda). It will rise to the surface or to a depth that is determined by the density of the magma and the weight of the rocks above it. As the magma rises, bubbles start to form from the gas dissolved in the magma. The gas bubbles exert tremendous pressure. This pressure helps to bring the magma to the surface and forces it in the air, sometimes to great heights.Putu Agastya (03)ERUPTION PROCESS

Putu Agastya (03)UNDERSEA ERUPTION

Putu Agastya (03)EFFECTSUnlike other natural disasters such as floods, wild fires and earthquakes, volcanoes can have some positive effects, even though they can be very disastrous.Negative effects can include:Eruptions occurring close to human settlements may spill and destroy lives and buildings. People often have to be evacuated. Ash discharged very high into the stratosphere can have negative consequences on the ozone layer.Landscapes and natural sceneries can be destroyed.Ash and mud can mix with rain and melting snow, forming lahars. Lahars are mudflows flowing at very fast pace.

Cintya Meriasti (13)And the positive effects:Different types of erupting volcanoes provide extraordinary scenery, so beautiful and natural that they attract tourists to the area, bringing in some economic value.Places close to volcanic activities tend to have higher potential for geothermal energy, which can be an advantage to the towns and cities.Some ash and lava breakdown become soils that are rich in nutrients, and become good areas for crop planting activities.

Cintya Meriasti (13)Mt. Rabaul aftermath

Cintya Meriasti (13)Building destroyed by lava

Cintya Meriasti (13)Mount St. Helens, Post-Eruption

Cintya Meriasti (13)Conclusion In conclusion,volcanoesare cracks in the Earths crusts where magma has reached the surface and turned into lava. There are about 500 volcanoes spread out all over the world. Although volcanoes are most known for the destruction they can do, there are some cases where volcanoes have helped create lands such as the beautiful Hawaiian Islands. There is no experience that is more impressive than seeing one of these spectacular volcanoes, and they are sure to leave lasting impressions on people of any age.Volcanologists look for clues that will help them predict when a volcano will erupt. Thanks for their dangerous work, many lives can be saved from what volcanologists discover.I Putu Agi Karasugi (04)Who wrote the text? We wrote the text togetherWho is the text likely to be for? The text is likely for the students and people who wants to know more about volcanoesThe purpose of writing the text The purpose is to give the idea about volcano and to expand their knowledgeThe advantages of using the expressions of cause and effect are such as:

They can relate a happening event to the source reasonsThey can give more detailed explanation about an eventEase people to read an event. They can find the cause and learn the effects quicklyTHANK YOU