Volcanoes<br />5th grade, A Closer Look<br />MacMillian/McGraw-Hill<br />
Where are Volcanoes found? <br />volcano- opening in Earth's crust<br />most are located at plate boundaries<br />Ring of Fire surrounds Pacific Ocean <br />
Parts of Volcano<br />All volcanoes have at least one vent (opening).<br />Crater- cup-shaped depression may form around a vent<br />Magma chamber- where magma collects<br />Lava- when magma reaches Earth’s surface<br />
Caldera- a hole forms beneath the magma chamber, the magma leaks out and the chamber collapses inside itself. <br />Dike- Some magma hardens in vertical cracks <br />Sill- forms when magma hardens between horizontal layers of rock<br />Laccolith- when sills don’t spread horizontally, instead they push upward and form a dome shape <br />Batholith- largest/deepest underground magma formations. They are huge, irregularly shaped, reaches deep into crust. <br />
Types of Volcanoes<br />Shield volcanoes- <br />built by thin, fluid lava<br /> spread over large area<br /> broad base, gently sloped sides<br />Cinder-blockvolcanoes<br /><ul><li>Built by thick lava
form cone shape with narrow base and steep slopes</li></ul>Composite Volcanoes<br />Built by layers of ash and cinders, sandwiched between layers of hardened lava<br />
Eruption- outpouring of lava, ash, gases, or combination of these<br />
Volcanoes erupt when one plate is pushed under another plate.<br />Rocks push down, heat and melt.<br />Magma forms and pools in the magma chamber under the crust.<br />Cracks form above the chamber or pressure grows too great and magma rushes upward toward the Earth’s surface. <br />
Active, Dormant, Extinct <br />Active volcanoes- currently erupting or have recently erupted<br />Dormant volcanoes- doesn’t erupt for a long time<br />Extinct volcanoes- dead/stopped erupting long ago<br />
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