Presentation on theme: "Chapter 18 Page 498. 18.1 Zones of Volcanism Volcanism = describes all the processes associated with the discharge of magma, hot fluids and gases."— Presentation transcript:
Chapter 18 Page 498
18.1 Zones of Volcanism Volcanism = describes all the processes associated with the discharge of magma, hot fluids and gases.
Ring of Fire Active volcanoes that create a “ring” pattern in the pacific ocean Typically volcanoes from convergent and divergent boundaries.
Convergent Volcanoes Volcanoes that form from plates colliding or subducting. Land volcanoes tend to be explosive
Divergent Volcanism 2/3rds of volcanism underwater The ocean ridges that form tend to release giant pillow lava. Tend to be non-Explosive and large
Hot Spots Volcano that forms NOT at a plate boundary. Magma rises from HOT WEAK areas of the mantle We can also measure the rate and direction the plates are moving by these
Anatomy of a Volcano Conduit = tube Vent = opening Crater = depression around the vent Side vent = smaller opening Ash cloud = small cloud of ash
Calderas Large crater that may have formed from a large explosion. Sometimes forms into a lake
Now complete the worksheet on labeling a volcano
18.2 Explosive Eruptions Tephra = is the erupted material from the volcano. Can be solidified lava OR pieces of crust Classified by size: Less than 2 mm is called ASH Largest is called BLOCKS
Explosion effects Ash can rise into atmosphere hurting: Airplanes Change in weather (Block sun’s rays therefore lower temps) Death/disease Food chain instability
Proclastic Flows Clouds of ash and other tephra Travels at speeds of 125 mph Mixed with hot gases up to temps of 700*C Can kill thousands AFTER the explosion
Volcanic Gases The more dissolved gases in the magma, the more explosive the magma is! CO2, SO2, HSO4, H2O vapor This will mix in the air to form ACID RAIN which changes the acidity or PH of the surround water supplies. They may also increase in temperature due to bubbling magma underneath
Types of Volcanoes 1. Shield Volcanoes 2. Cinder Cones 3. Composite Volcanoes All three depend on 2 factors: All three depend on 2 factors: 1.Type of material that forms it 2.Type of eruption
Shield Volcano Broad, gently sloping, circular base Largest type Nonexplosive eruption which leaves layers of lava.
Cinder Cone Formed from eruptions that eject small pieces of magma from the air. The small pieces pile back around the vent causing the cinder cone shape. Small and steep
Composite Volcanoes Violent eruptions Formed by layers of hardened chunks of lava from the eruptions alternating between explosions and oozing of lava Cone shaped with concave slopes (larger than cinder)