Category: Others/ Misc

Presentation Description

No description available


Presentation Transcript

Volcanoes : 



Volcanoes Evidence that we live in an active planet The gods of the underworld Millions of people live near active volcanoes The greatest geological hazard

Mount Saint Helens- after: 

Mount Saint Helens- after



Future hazard: 

Future hazard Population near big, recently active volcanoes Seattle Mexico City Quito Indonesia Japan


Lava Molten rock that flows on the surface Basaltic Lava low silica, fluid, low gas, not explosive Andesitic Lava high silica viscous gas-rich explosive

Types of volcanoes: 

Types of volcanoes 1. Shield Volcanoes Hawaii, Iceland Basaltic 2. Stratovolcanoes (or composite) Mt. Saint Helens, Pinatubo, etc Andesitic Explosive

Shield Volcanoes: 

Shield Volcanoes Huge broad cones Gentle slopes Made from lava flows Basaltic Form at hotspots Not very dangerous Predictable


Stratovolcanoes (composite) Andesitic lava Rich in dissolved gases Violent eruptions alternate with lava flows Steep-sided cones Very dangerous Unpredictable

Pyroclastic Flows: 

Pyroclastic Flows Product of explosive eruptions Hot ash shot up into the atmosphere Ash column collapses Pyroclastic flow can travel 60 mi/hr Ash can fall 100’s of miles away Ash may affect global climate

Mt. Saint Helens before: 

Mt. Saint Helens before

Phreatic (vapor) eruption: 

Phreatic (vapor) eruption



Mt. St. HelensPyroclasticEruption: 

Mt. St. Helens Pyroclastic Eruption

After the eruption: 

After the eruption

Lahars (mudflows): 

Lahars (mudflows)

Lahars (mudflows): 

Lahars (mudflows) Very destructive Kill as many people as the eruption itself Loose ash forms mud avalanches Glaciers on top of volcano melt Rain

Inside a volcanoe: 

Inside a volcanoe


Pyroclastic eruption

Volcanic landscape: A Caldera (Crater Lake): 

Volcanic landscape: A Caldera (Crater Lake)

Crater lake formation(caldera): 

Crater lake formation (caldera) 1. Early eruptions from composite cone 2. Great eruption empties the magma chamber 3. Summit collapses 4. Caldera fills with water


Plate Tectonic Settings of Volcanism


Plate tectonic settings of volcanoes

authorStream Live Help