<p> Volcano Notes Outline Name ______Date______Period____</p><p>Volcanism : Any activity that includes the movement of magma towards or onto Earth’s surface</p><p>Volcano: A vent or fissure in Earth’s surface through which magma and gases are expelled</p><p>Formed by: 1. Subduction 2. Rifting 3. Hotspots</p><p>Magma: Liquid rock produced under the Earth’s surface. Made up of molten rock, minerals and dissolved gases</p><p>Lava: Magma that flows onto the Earth’s surface. Loses some of the gases and has more minerals than magma.</p><p>What is magma? Made up of molten rock, minerals and dissolved gases from the upper layers of the mantle </p><p>What factors affect the formation of magma? </p><p>Temperature -- temps need to be between 800˚C and 1200˚C</p><p>Pressure – as pressure decreases, the temperature at which a substance melts also decreases</p><p>Water content of the rocks – rocks melt at lower temperature in the presence of water</p><p>Composition of the rocks – different types of rock melt at different temperatures</p><p>What is Viscosity?</p><p>A substance’s resistance to flow is called its viscosity.</p><p>Ex: cold syrup is more viscous than hot syrup (cold syrup does not flow easily)</p><p>Gases in Magma</p><p>Most important: Water vapor, carbon dioxide, and sulfur</p><p>Also has: hydrogen (which can combine with oxygen to form steam)</p><p>Amount of gas determines type of eruption</p><p>Large amt of gases = more explosive eruptions Volcano Notes Outline Name ______Date______Period____</p><p>Three types of magma Compositio Source Viscosity Gas Silica Explosive Location n Material Conten Conten of t t Magma Basaltic Upper Low 1 – 2 % About Least Both mantle 50% oceanic and continenta l crust Andesitic Oceanic Intermediat 3 – 4 % About Intermediat Continent crust and e 60% e al margins oceanic – sediments subductio n zones</p><p>Rhyolitic Continent High 4 – 6 % About greatest Continent al crust 70% al crust</p><p>Lava Fragments: </p><p>Tephra: solid fragments of lava produced by explosive eruptions</p><p>Smallest pieces: ash</p><p>Larger pieces: lapilli</p><p>Largest pieces: blocks (solid), bombs (liquid then harden)</p><p>Volcanic Hazards</p><p>Pyroclastic Flows – clouds of ash, dust, and gases (AKA – Nuee Ardente – “Glowing Cloud”)</p><p>Move at speeds of up to 200 km/h</p><p>Denser than surrounding air – so it stays close to ground Volcano Notes Outline Name ______Date______Period____ Poisonous</p><p>Superheated (5X the temperature of boiling water-~7000C)</p><p>Lahar – heated snow covered mountaintop – snow melts  super fast mudslide – more dangerous than nuee ardente (more common)</p><p>Lava Flows – obviously dangerous due to heat – but can be diverted or chilled Ash – threat of suffocation</p><p>Poisonous gases – kill due to toxicity – but the most common and dangerous is CO2 (drives away oxygen)</p><p>Types of Volcanoes</p><p>Type of Volcano depends on:</p><p>Type of material that forms it and type of eruptions that occur</p><p>*We will focus on (3) most common</p><p>Shield Volcano (Mauna Loa)</p><p>Mountain with broad, gently sloping sides</p><p>Generally non-explosive</p><p>Cinder-Cone Volcano (Izalco – El Salvador)</p><p>Material that is ejected high into the air – piles back up around the vent</p><p>Steep sides, but generally small in size</p><p>Water and silica laden magmas, and full of gas – somewhat explosive</p><p>Composite Volcano (Mount St. Helens)</p><p>Large amounts of water, silica, and gases</p><p>VERY LARGE – Due to their large size – pose the greatest threat</p><p>These can blow their tops completely off forming a CALDERA – Crater Lake Oregon Volcano Notes Outline Name ______Date______Period____</p><p>Living vs. Dead Volcanoes</p><p>Active Volcano: A volcano that is erupting. Also, a volcano that is not presently erupting, but that has erupted within historical time and is considered likely to do so in the future.</p><p>Dormant Volcano: Literally, "sleeping." The term is used to describe a volcano which is presently inactive but which may erupt again. Most of the major Cascade volcanoes are believed to be dormant rather than extinct. </p><p>Extinct Volcano: A volcano that is not presently erupting and is not likely to do so for a very long time in the future </p><p>Volcano Predictions</p><p>Tectonic Activity</p><p>The volcanic mountain will “rumble” prior to an eruption</p><p>Magma is working its way up the vent or volcanic pipe, and pushes stuff around during its ascent</p><p>Topographic “Bulges”</p><p>The magma can push up/out on the land as it rises</p><p>Gas emissions – volcanic “burps” of sulfur, water vapor, and carbon dioxide</p><p>Temperature Spike – the temperature around and inside the volcano will rise</p><p>~Questionable~: Animals will bug out of the area – </p>