Download Slide 1

Volcanoes
Volcano facts
How many eruptions?
15,110 volcanoes in last
10,000 years
 The highest peak?
6,887 m, Ojos del Salado
(Chile)

The biggest eruption?
2,500 km3,Yellowstone, 2.2
Ma (USA)
 First volcanologist?
79 AD - Pliny the Younger
 Total deaths
238,000 (1600-1982)

History

The word Volcano is derived from the name of the
ancient Roman island of Vulcano. The Romans believed
that Vulcan, the god of Fire and the maker of weapons,
used the volcano on that island to forge his weapons.
Definition of a Volcano

1. An opening in the crust of the Earth from which
magma and gases escape to the surface.

2. The mountain that is formed from volcanic
processes.
Volcano Classification

Active- are either currently erupting or have erupted
recently. Over 500 volcanoes are in this group.

Dormant- are not currently erupting but are considered
likely to do so. Mt. St Helens was dormant for 123 years
before it erupted in 1980.

Extinct- or dead volcanoes have not erupted in recent
history and are not likely to erupt.
Anatomy of a Volcano

A volcano is a mountain formed of lava and/or
pyroclastic material (hot fragment of preexisting
rocks that are blown from the vent of a volcano).

A crater is the depression at the summit of a
volcano or that which is produced by a meteorite
impact.

A conduit, or pipe, carries gas-rich magma to
the surface.
Anatomy of a Volcano
Types of Volcanoes

The three main volcanic types are
 shield volcanoes,
 cinder cones
 composite cones

***On the next few slides please draw each type of
volcano in your notes***
Shield Volcanoes

Shield volcanoes are broad, gently sloping
volcanoes built from fluid basaltic lavas.
Cinder Cones

Cinder cones are small volcanoes built
primarily of pyroclastic material ejected
from a single vent.
 Steep slope
 Small is size
 Occur in groups
Cinder Cones
Composite Cones

Composite cones are volcanoes
composed of both lava flows and
pyroclastic material.
 Most are located in the Ring of Fire
 (Ex
Mt. Rainer)
Large in Size
 Most Violent Eruptions

Composite Cones
Mt. Rainer
Washington State
Mount St. Helens Before and
After the May 18, 1980, Eruption
Washington State
Factors Affecting Eruptions




Composition of the Magma
Temperature of the Magma
Dissolved Gasses
Viscosity- is the measure of a material's resistance
to flow.


Temperature- hotter magma’s are less viscous
Composition- Silica Content


High Silica- high viscosity
Low Silica – low viscosity
There Are Three Major Volcanic Zones
 Subduction
Zones
 Mid-oceanic ridges
 Hot spots
There are Two Different Types of Lava




Pahoehoe lava (resembles braids in ropes)
Aa lava (rough, jagged blocks)
Pyroclastic materials is the name given to
particles produced in volcanic eruptions
Pyroclastic Avalanche-
Pahoehoe (Ropy) Lava Flow Fast Moving
Pahoehoe Lava
Slow-Moving Aa Flow
Aa Lava
Intrusive Activity
Plutons- intrusive igneous rock bodies which are
classified by shape, size, and their relationship to other
surrounding rocks.
-Batholiths-LARGEST plutons, irregularly shaped, coarsegrained igneous rocks.
-Laccoliths-mushroom-shaped pluton with a round top
and flat bottom. Relatively small
-Sills-when magma intrudes parallel to rock layers
-Dikes-a pluton that cuts across pre-existing rock layers
*MANY PLUTONS ARE FORMED DUE TO
MOUNTAIN-BUILDING PROCESSES

Mt. Saint Helens Erupting
Mount Saint Helens photographs 10-26-04
1980 Eruption
Pompeii- Italy
https://www.youtube.com/watch?v=QScagfQC5-w
Santorini Greece
Old Faithful- Yellowstone
Sunset Crater – Flagstaff Arizona
Kilauea Hawaii- Most active volcano
Popocateptl- Mexico
Mt Erebus Volcano- Antarctica

One of the worlds
most active
volcanoes
Please write down this link in your
notes!!!

http://www.cotf.edu/ete/modules/volcanoes/volcano.html