Volcanoes
What is Magma? dr evil
Magma Magma: Liquid rock under Earth’s surface
Magma forms when… The temperature rises above the melting point of the rock The pressure is lower, which lowers the melting point of rock The addition of water lowers the melting point of the rock
Volcano 101 video The video says that volcanoes are “both creators and destroys”. What does this mean? What are examples of this? volcanoes 101
Volcanism Volcanism: the movement of magma onto Earth’s surface
Volcanism Lava: magma on top of Earth’s surface
In your packet: Explain the difference between magma and lava.
Volcanism Volcano: an opening in earth’s surface through which magma and gases are expelled
Major Volcanic Zones Most volcanoes form along convergent or divergent plate boundaries
Volcanoes at Divergent Boundaries Divergent boundaries: mid-ocean ridges The largest amount of lava rises at divergent boundaries Most are unnoticed by humans because it happens underwater
Iceland Iceland: the only place on Earth where a divergent boundary is above sea level
Convergent Boundaries Volcanoes at Convergent boundaries: Volcanic mountain chains or volcanic island arcs Examples: Japan, Alaska Aleutian Islands, Mount Saint Helens The ring of fire is mostly made up of convergent boundaries
Draw triangles on your map on page 1 to represent volcanoes on plate boundaries
The Ring of Fire The Ring of fire: an area surrounding the Pacific Ocean where a large number of volcanoes and earthquakes occur.
What about Hawaii?
Hot Spots Hot spots: areas on Earth’s surface where magma is close to the surface Also called mantle plumes
Hot Spots Hawaii and Yellowstone are examples of hot spots http://education.sdsc.edu/optiputer/flash/hotSpots.htm Hawaii and Yellowstone are examples of hot spots The PLATE moves NOT the hot spot!!! Yellowstone
Studying volcanoes Volcano Hazards: https://www.youtube.com/watch?v=6X64IhvYYlw
Types of Magma Mafic magma: rich in iron and magnesium and forms dark colored rock Example: Oceanic crust Produces: runny, quiet eruptions
Types of Magma Felsic magma: rich in silicate materials and forms light colored rock Example: continental crust Produces: thick, explosive eruptions Magma with more dissolved gases is more explosive
Types of Eruptions The flow of magma or lava depends on the viscosity of the magma Viscosity: how much a fluid resists flowing High Viscosity= lava that moves very slowly Low Viscosity= lava that moves quickly https://www.youtube.com/watch?v=DVQw0svRHZA High Viscosity Low Viscosity
Quiet Eruptions https://www.youtube.com/watch?v=488BkTUsMa4 Quiet eruptions: mafic magma flows out slowly and has a high viscosity Examples: Hawaii
More explosive because it has more dissolved gases in it Explosive Eruptions Explosive Eruptions: Felsic magma that is thicker and has a low viscosity More explosive because it has more dissolved gases in it http://www.youtube.com/watch?v=3XTVZmAtu0s
Types of Lava pahoe 2014 1. Pahoehoe lava: mafic lava that flows slowly and forms a wrinkled crust lava flows
Lava Flows 2. Aa lava: mafic lava that flows faster and has a chunky texture Aa lava flow
Lava Flows 3. Blocky Lava: cooled lava at surface breaks into large chunks
Types of pyroclastic materials 4. Pyroclastic Material: Escaping gases send molten and solid rock into the air pyroclastic flow
Types of Pyroclastic Material Classified by particle size Ash: less than 2mm diameter
Cont. Types of Pyroclastic Material Volcanic bombs: molten rock larger than 64 mm in diameter Volcanic blocks: solid rock that can be larger than a house
BOOM! Volcanic eruptions can be more powerful than atomic bombs!! Marum Crater