Volcanoes

By: Brianna Petrilla

A topic that we have discussed in our class that really interests me is

volcanoes. Volcanoes are an amazing phenomenon. They are one of the most

fascinating natural occurrences on planet earth, in my opinion. They are all over

the world, some are even here in Utah. Not only are they on land, they are even

under the deep ocean waters as well. “There are about 550 active volcanos in the

world. On Average, about 15 of them will erupt this week, 55 this year, and

perhaps 160 this decade” (Darrel Hess, 2014, p.418). They are as beautiful as they

are dangerous though. Volcanoes can be extremely deadly and destructive.

Volcanoes affect our lives dramatically. Volcanoes can kill mass numbers of

people who live near them. Communities build up around many volcanoes, this is

dangerous. You may think the volcano you built your house near won’t erupt in

your lifetime, well there’s always a chance it could erupt. Avoid the danger by not

building your home near volcanoes. “A volcano is considered active if it has

erupted at least once within historical history and is considered likely to do so

again” (Darrel Hess, 2014, p.418). Throughout history there have been many tragic

events involving volcanic eruptions. Some examples of how extremely dangerous

volcanoes can be are; Tambora located in Indonesia killing 92,000 in 1815, Mount

Pelee located in Martinique killing 29,025 in 1902, Ruiz located in Columbia

killing 25,000 in 1985, (infoplease, 2007) and so many more devastating volcanic

disasters.

http://volcanoes.usgs.gov/Imgs/Jpg/Ruiz/30410135_071_caption.html

The

aftermath of

the eruption

of Ruiz,

located in

Columbia in

1985.

Lahars Flow (Volcanic mud

flow consisting of ash and

pyroclastic deposits)

“Most volcanoes that form on large bodies of land occur where two tectonic

plates come together, and one of them is forced to subduct below the other one into

the hot mantle.” (Schmidlkofer) The pressure and heat increases causing the rock

to turn into magma. This magma in the subduction zone gets pushed to the surface,

which causes volcanoes to form.

There are four main types of volcanoes; Shield Volcanoes, Stratovolcanoes

(or Composite), Lava Domes, and Pyroclastic Cones (or Cinder Cones). These

different types of volcanos are all very unique looking and come in various

different shapes and sizes.

Shield Volcanoes are very interesting. “Their name derives from their low-

angle profile, which resembles the personal shields carried by warriors.”

(Smithsonian Institution) “Some shield volcanos are massive and very high, but

http://www.angelfire.com/sc3/popocatepetl/page2.html

This is how a volcano is

created.

they are never steep sided” (Darrel Hess, 2014, p.422). They are formed by the

constant buildup of lava flow. The lava flow comes from the fissure vent system.

Shield Volcanoes can dramatically vary in size. Some Shield Volcanos around the

world include; Mauna Loa (Hawaii), Mauna Kea (Hawaii), Darwin (Galápagos

Islands), Fernandina (Galápagos Islands), Alcedo (Galápagos Islands), Belknap

(Oregon), Newberry (Oregon), Medicine Lake (California), and the list goes on

and on.

That’s the Shield Volcano, Mauna

Loa, located in Hawaii. Fissure Vent

http://commons.wikimedia.org/wiki/File:Mauna_Kea_from_Mauna_Loa_Observatory,_Hawaii_-_20100913.jpg

https://www.flickr.com/photos/djdude101e/7355007102/

http://www.geographic.org/photos/volcanoes/volca

no_photos_24.html

This is the Shield

Volcano,

Fernandina,

located in the

Galápagos Islands.

Volcanic Rock

“Basalt”

Consists of

Layers of

Solidified Lava

Flows

Stratovolcanoes (or Composite) are what most people picture when they hear

the word volcanoes. They look like towering, somewhat triangular peaks. Stratovolcanoes are made of stratified layers of thick, sticky, lava flows and

fragmental material. “These mountains build up steep sides by having layers of

ejected pyroclastics (ash and cinders) from explosive eruptions alternate with lava

flows from nonexplosive eruptions” (Darrel Hess, 2014, p.423). Stratovolcanoes

are formed from multiple eruptions from flank and summit vents. Compound

stratovolcanoes are able to form when the focus of the eruption moves, which

causes more than one volcano to form. Some examples of Stratovolcanoes are;

Santa Maria (Guatemala), Mount Jefferson (Oregon), Mount Baker (Washington),

Kamen (Russia), Mombacho (Nicaragua), and there are many more.

http://www.fitpacking.com/2009/NCNP.cfm

The

Stratovolcano,

Mount Baker,

located on

Northern

Cascades in

Washington.

Stratovolcanoes are steep-sided

symmetrical cones

--------------------------------

-

Lava Domes are created when thick, sticky magma is pushed out of the vent

and builds up around it. Lava domes have very steep edges. They can form during

single eruption, or even from occasional lava extrusion. Some Lava Domes are;

Soufrière Hills (Montserrat), Soufrière St. Vincent (Windward), El Chichón

(Mexico), Ceboruco (Mexico), Mount Unzen (Japan), and there a lot more.

http://demiseofcomplexsocieties.blogspot.com/2

011/12/explosive-eruption.html

This is the Lava Dome volcano,

El Chichón, located in Francisco

León, north-western Chiapas,

Mexico.

https://readtiger.com/wkp/en/Mount_Jefferson_(Oregon)

This is the

Stratovolcano,

Mount

Jefferson,

located in the

Cascade Range

of Oregon.

Eruption Cloud

Fissures Eruption Column

Crater

Steep slopes of

solidified and

pyroclastics.

Pyroclastic Cones (or Cinder Cones) are one of the most plentiful forms of

volcanoes. They have a cone like appearance which is probably why they are also

called Cinder Cones. Pyroclastic Cones name is made of the Greek word pyro

(which means fire) and klastos (which means broken). (Smithsonian Institution)

The name makes sense since these volcanoes are made of fragmental material.

They are formed from a single volcanic explosion, where the materials released

during the explosion build up around the vent. Some Pyroclastic Cones are;

Bárcena (Mexico), Crater Lake (Oregon), Cerro Negro (Nicaragua), San Quintin

Volcanic Field (Mexico), and many, many more.

http://www.japan-guide.com/e/e4452.html

This is the Lava Dome volcano,

Mount Unzen, located on the

island of Kyūshū, Japan

4,9

00

fe

et

http://oregon365minblog.blogspot.co

m/2011/04/oregons-volcanoes.html

The Pyroclastic Cone volcano,

Crater Lake, located in southern

Oregon.

http://www.summitpost.org/cerro-negro/785143

The Pyroclastic Cone

volcano, Cerro Negro,

located in the Cordillera

de los Maribios

mountain range in

Nicaragua.

Cone

Crater

Composed of ash/pyroclastic cinder-size pieces

Works Cited

http://volcanoes.usgs.gov/Imgs/Jpg/Ruiz/30410135_071_c

aption.html

http://www.angelfire.com/sc3/popocatepetl/page2.html

http://commons.wikimedia.org/wiki/File:Mauna_Kea_fro

m_Mauna_Loa_Observatory,_Hawaii_-_20100913.jpg

https://www.flickr.com/photos/djdude101e/7355007102/

http://www.geographic.org/photos/volcanoes/volcano_pho

tos_24.html

http://www.fitpacking.com/2009/NCNP.cfm

https://readtiger.com/wkp/en/Mount_Jefferson_(Oregon)

http://demiseofcomplexsocieties.blogspot.com/2011/12/exp

losive-eruption.html

http://www.japan-guide.com/e/e4452.html

http://oregon365minblog.blogspot.com/2011/04/oregons-

volcanoes.html

http://www.summitpost.org/cerro-negro/785143

http://www.infoplease.com/ipa/A0197833.html

The Internal Processes . (2014). In D. Hess, McKnight's

Physical Geography: A Landscape Appreciation Eleventh

Edition (pp. 400-431). Upper Saddle River: Pearson.