Download Magma

Volcanoes
What is Magma?
• dr evil
Magma
• Magma: Liquid rock under Earth’s surface
Magma forms when…
1. The temperature rises above the melting point of
the rock
2. The pressure is lower, which lowers the melting
point of rock
3. 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
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
https://www.youtube.com/watch?v=488BkTUsMa4
Quiet Eruptions
• Quiet eruptions: mafic magma flows out slowly and
has a high viscosity
• Examples: Hawaii
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.co
m/watch?v=3XTVZmAt
u0s
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