Ryan McCue Margo Moeller Lauren Ranalli Erin Moosbrugger

Ryan McCueMargo MoellerLauren Ranalli

Erin Moosbrugger

LR

What is a Volcano?

• A volcano is a hill or mountain formed from lava and rock

fragments ejected through a volcanic vent.

LR

Why do volcanoes erupt?

When rock inside the Earth becomes hot enough it melts. This molten rock, or magma, is less

dense than the surrounding solid rock. Just as an object that is less dense than water will

float on water, the relatively low density of the magma causes it to rise to the surface of the

Earth. If the magma contains water and dissolved gasses, when the magma reaches

the surface the water and dissolved gasses will suddenly expand into steam and gas, causing a violent eruption. This is like shaking a coke

can and then popping the tab.

LR

Types of Volcanoes

• COMPOSITE VOLCANOES are viscous. Eruptions produce gas, ash, and rock. The magma is sticky.

• SHIELD VOLCANOES are non-viscous. Eruptions produce lava. The magma is runny.

LR

How do volcanoes affect weather?

• Major volcanic eruptions can send ash into the atmosphere so heavy that it can actually block sunlight,

and thus make the temperature for the next few years cooler than

usual.

LR

Mt. St. Helens

8, 363 ft.RM

Early Days

• Mt. St. Helens is a stratovolcano in Washington State.

• It is in the Cascade mountain range, in which it is considered the youngest

• The earliest recorded eruption occurred in 1831.

• Yet Radiocarbon dating indicates at least a dozen eruptions before this beginning in approximately 2335 B.C.

RM

First major eruption

• Mt. St. Helens’, first major recorded eruption took place in 1980 and took the lives of 57 people

• Half of the casualties were cause by asphyxiation from ash

RM

First sign of trouble

• After 123 years of inactivity, on March 20, 1980 Mt. St Helens’ emitted an earthquake registering a 4.2 on the Richter scale

• This was soon followed by hundreds of smaller earthquakes

• 7 days later, a huge steam explosion came through the mountain’s ice cap.

RM

The Bulge

• In two months the volcano had pushed a 1 by ½ mile long bulge that pushed out over 400 feet.

• This bulge was filled with magma that, scientist said on May 18, could fill a balloon 18000 feet across.

RM

Aftermath

• The ensuing eruption left a yawning depression 625 meters deep, 2 kilometers wide and 2.7 kilometers long.

• It is open to the north from the side of the mountain that broke loose in a colossal earthquake-triggered avalanche that initiated the eruption on May 18.

RM

Diamond HeadO’hau, Hawaii

MM

The FACTS

• Diamond Head is…• An extinct volcano, when active was 3500 feet tall• An extinct volcano for 150,000 years.• Sinking b/c of erosion, reducing it to 761 feet• A large tuff cone which was formed by a short series of

explosive eruptions some 100,000 year ago.• Named Diamond Head b/c British sailors saw calcite crystals

and mistakenly thought they were diamonds.• A National Natural Landmark• A lookout post, b/c of the view the military constructed a trail

to the summit in the early 1900’s. During WWII the observation post was used to coordinate artillery fire from Fort Derusy in Waikki

• The hike is moderate ability and is 1.5 miles roundtrip, it takes approximately 2 hours.

MM

HALF WAY UP

MM

Diamond Head @ Sunset

MM

• Diamond Head is a peak, 761 feet high, (232m) along the rim of an extinct volcano, Southeast Oahu island, Hawaii. A prominent point in the Honolulu skyline, Diamond Head was designated a national natural landmark to protect its slopes from the commercial development along world-famous Waikiki Beach. U.S. Fort Ruger is at the northern end of the crater’s floor. The crater was the site of an ancient Hawaiian burial ground.

MM

EM

Mount Vesuvius• Composite Volcano (Stratovolcano)• Located on the Bay of Naples• Made by an outer broken cone: Mount Somma• Formed from the convergent boundary of the

African Plate and the Eurasian Plate• Composed of hardened lava (highly viscous),

volcanic ash and pumice

EM

History• Oldest rock found 300,000 years old• Destroyed settlements during the Bronze and

Stone Ages (Nola)• Had been inactive for hundreds of years before

79 AD• After Pompeii, erupted once every hundred

years until 1037 • 600 years of quiesence • 1631- an eruption killed 4000 people

EM

PompeiiPOMPEII

EM

79 AD-the Most Famous Eruption

•Commenced with an Earthquake

•Mountain’s top split and Vesuvius showered the land with ash and stones and pumice

•Nowhere for anyone to go (Pliny the Younger)

•Absolutely buried Pompeii and Herculaneum

em

Pompeii (cont.)

• Lasted 19 hours, ejected 1 cubic mile of ash• 10000 people killed• Found Pompeii after 1631 eruption• Ash preserved bodies and other artifacts

(bread)

EM

Vesuvius Today

• Last time Vesuvius erupted was MARCH 22, 1944

• Did more damage than the German air raid 2 years later

• 600,000 people living on the skirts of Vesuvius• Magma at a depth of 8 to 10 kilometers

EM

WE HOPE THAT YOU HAVE ENJOYED OUR

PRESENTATION AND THAT YOU HAVE LEARNED MUCH MORE ABOUT VOLCANOES!

THANK YOU FOR YOUR TIME AND ATTENTION!

LR

Work Cited• http://www.holoholo.org• http://gary.appenzeller.net• http://www.telsin.com• http://www.bartleby.com• http://www.hawaiiweb.com• http://members.tripod.com• http://volcano.und.nodak.edu• http://www.cotf.edu• http://www.vesuvioinrete.it• http://www.npr.org• Thomson and Turk. Earth Science and the Environment.• http://volcano.und.nodak.edu/vwdocs/msh/ov/ovb/ovbgh.html• Zeilinga de Boer, Jelle. Volcanoes in Human History.

MM & EM