SLIDE 1
D Y N A M I C E A R T H H T T P : / / W W W . Y O U T U B E . C O M / W A T C H ? V = U Z P 1 D N Y B G F C
Volcanoes D Y N A M I C E A R T H H T T P : / / W W W . Y O U T U - - PowerPoint PPT Presentation
Volcanoes D Y N A M I C E A R T H H T T P : / / W W W . Y O U T U - - PowerPoint PPT Presentation
Volcanoes D Y N A M I C E A R T H H T T P : / / W W W . Y O U T U B E . C O M / W A T C H ? V = U Z P 1 D N Y B G F C What is a volcano? Magma (melted rock inside Earth) bubbles up to Earths surface Lava (magma on surface) exits
SLIDE 2
SLIDE 3
Craters and Caldera
Crater: bowl shaped depression at top of
the volcano surrounding the vent (less than 1 km in diameter)
Caldera: large bowl shaped depression that
forms when summit collapses into magma chamber (volcano collapses)
EX: Crater Lake (Oregon)
SLIDE 4
Types of Volcanoes: Shield Volcano
Shape: large; gentle slope; broad circular base Lava Type: thin, basaltic lava Eruption Type: non-explosive Example: Hawaiian volcanoes
SLIDE 5
Types of Volcanoes: Cinder-Cone Volcano
Shape: small with steep sides Lava Type: thick magma with water and silica Eruption Type: explosive! Example: Izalco volcano; El Salvador
SLIDE 6
Types of Volcanoes: Composite or Strato-Volcano
Shape: medium sized; medium steepness Lava Type: alternating layers of basaltic thin lava
and explosive thick lava
Eruption Type: most explosive!!, has alternating
non-explosive and explosive eruptions
Example: Mt. St Helens; Mt. Ranier (Washington)
SLIDE 7
SLIDE 8
Tephra
Rock fragments thrown into air during
volcanic eruptions;
Classified by size:
- Dust
- Ash
- Lapilli “little stones”
- Blocks (large & angular)
- Volcanic Bombs (large & rounded; cool in air
- r on contact with ground)
SLIDE 9
Pyroclastic Flow
Cloud of gas, ash, and tephra that comes
from explosive eruption
Travels nearly 200 km/hr 700 degrees Celsius Mount Pele on island of Martinique in 1902 killed
more than 29,000 people
SLIDE 10
SLIDE 11
Where do most volcanic eruptions occur?
80% at convergent plate boundaries Ring of Fire: largest ring of volcanic activity
around Pacific Plate
15% at divergent plate boundaries (Mid Atlantic
Ridge)
5% form away from plate boundaries near hot spots Hot spots: stationary plumes of magma that push
up a volcanic island of seamount
SLIDE 12
SLIDE 13