Volcanoes Wh at do we know about them?

1. Volcanoes What do we 
know about 
them?

2. The earth is made up of 3 different Layers The inner Core The core of the earth is in 2 parts, the solid inner core and the molten liquid outer core. The inner core of the earth is mostly made of iron and nickle. The Outer core is super heated lava found 3000 miles below the earths surface. The outer core

3. The mantel the mantel is super heated rock which represents 85% of the weight of the earth! This is about 1,800 miles thick. The crust The crust is what separates us from the mantel. Is is around 18 miles thick, this is the part that we live on. The Earth's rocky outer crust solidified billions of 
years ago, soon after the Earth formed. This crust 
is not a solid shell; it is broken up into huge, thick 
plates that drift atop the soft, underlying mantle.

4. Tectonic Plates The plates are made of rock and drift all over the 
globe; they move both horizontally (sideways) and 
vertically (up and down). Over long periods of time, the 
plates also change in size as their margins are added 
to, crushed together, or pushed back into the Earth's 
mantle. These plates are from 50 to 250 miles (80 to 
400 km) thick. The area encircling the Pacific Ocean 
is called the "Ring of Fire," because 
its edges mark a circle of high 
volcanic and seismic activity 
(earthquakes). Most of the active 
volcanoes on Earth are located on this 
circumference. On the edge of the 
Pacific Ocean, the edge of the 
Pacific Continental Plate is expanding 
in the seabed, and is hitting the 
North American Plate, the Nazca 
Plate, the Eurasian Plate, and other 
plates, causing the margins of the 
plates to collide, buckle, and 
compress, causing earthquakes and 
volcanoes.

5. What do the plates have to do with volcanoes? Most volcanoes are formed by the movement of tectonic plates on the 
surface of the earth. The tectonic plates are in constant motion, albeit very slow motion. 
They sometimes move toward each other, other times they’ll move 
apart, and still other times one will sink while the other rises above it.

6. When a tectonic plate sinks, it sinks down into the 
mantle and becomes very hot. So hot, in fact, that the 
rock melts. This molten rock will gradually make its way 
up to the surface of the earth through a series of 
cracks. When it reaches the surface of the earth, we 
refer to it as lava. As layer upon layer of lava builds up, 
a volcano is formed. What do we call lava 
when it is under the 
surface? Answer A: Magma!

7. There are many factors that determine what kind of lava flow 
will occur and what type of volcano it will be. The amount of gas 
trapped in the lava, the kinds of minerals making up the lava, 
and how much pressure can be trapped in the area all affect 
the eruption and formation of the volcano.

9. Definitions Crater - Mouth of a volcano - surrounds a volcanic vent. Conduit - An underground passage magma travels through. Summit - Highest point; apex Throat - Entrance of a volcano. The part of the conduit that 
ejects lava and volcanic ash. Ash - Fragments of lava or rock smaller than 2 mm in size 
that are blasted into the air by volcanic explosions. Ash Cloud - A cloud of ash formed by volcanic explosions. Magma - Molten rock beneath Earth's surface. Parasitic Cone - A small cone-shaped volcano formed by an 
accumulation of volcanic debris. Sill - A flat piece of rock formed when magma hardens in a 
crack in a volcano. Vent - An opening in Earth's surface through which volcanic 
materials escape. Flank - The side of a volcano. Lava - Molten rock that erupts from a volcano that 
solidifies as it cools.

10. Did you know? The name "volcano" has its origin from the name of 
Vulcan, a god of fire in Roman mythology.

11. Where is the ring of fire?

12. There are several types of volcanoes and these come in 3 different forms.

13. Active volcanoes are volcanoes that have erupted in recent history or are continually erupting. Here are some examples of active volcanoes. Kilauea Volcano on the island of Hawaii 
(the Big Island) is widely considered to 
be the most active volcano on Earth. 
Over the course of its most recent 
eruption which began in January of 1983, 
the volcano has expelled enough lava to 
pave a road around the planet three 
times over. Mount Etna, on the Italian island of Sicily, 
has been erupting more or less continuously 
for the past 2,000 years though its overall 
history stretches back approximately 300,000 
years. Though somewhat less famous (or 
infamous) than neighboring Mount Vesuvius, 
Mount Etna greatly outclasses the latter peak 
as it rises 2.5 times its height. In addition, 
most of Etna’s more spectacular eruptions and 
associated geological events occurred in 
prehistory. The volcano erupted in every year 
from 200 through 2008 and its recent 
eruption occurred in April of 2010.

14. The Sakurajima volcano is located on what 
was formerly an island in southern Japan’s 
Kagoshima Bay. The island is now connected 
to the mainland via a low-lying peninsula 
created by lava flows during the mountain’s 
immense eruption of 1914. Sakurajima 
stands 3,665 feet (1,117m) above sea level 
and has been erupting more or less 
continuously since 1955. The Chaitén volcano in southern Chile began 
erupting on May 2 of 2008, an event that 
caught scientists by surprise as the mountain’s 
last eruption was estimated to have occurred 
about 9,500 years ago. Though the mountain 
is still in an eruptive state, the initial stages 
were marked by the expulsion of voluminous 
ash clouds shot through by incandescent bolts 
of lightning.

15. Extinct Volcanoes Extinct volcanoes are those that scientists consider unlikely to erupt again, 
because the volcano no longer has a lava supply. Edinburgh Castle is built on an extinct volcano.

16. Dormant Volcanoes It is difficult to distinguish an extinct volcano from a dormant one. 
Volcanoes are often considered to be extinct if there are no written 
records of its activity. Nevertheless, volcanoes may remain dormant for a 
long period of time. Vesuvius was described by Roman writers as having been covered with 
gardens and vineyards before its famous eruption of AD 79, which 
destroyed the towns of Herculaneum and Pompeii. Before its catastrophic 
eruption of 1991, Pinatubo was an inconspicuous volcano, unknown to most 
people in the surrounding areas. Vesuvius, AD 79 Pinatubo, 1991

17. Video Footage Use the following link to access National Geographic Site and view the video footage on volcanoes. Look out for the under water eruption footage. http://video.nationalgeographic.com/video/player/environment/environment-natural-
disasters/volcanoes/volcano-lava.html