7th Grade Science · 80% of the world’s earthquakes occur along plate boundaries. • If you follow the locations of active volcanoes and the sites where earthquakes occur you can

Mythology• Myths are society’s

oldest stories that

explain different

aspects of life and

the natural world.

They usually

reflected ancient

religious beliefs.

How would you explain these?

Madame Pele

The Hawaiian Islands

What causes the Hawaiian Islands?

Is there a plate boundary in the middle of the Pacific?

Fixed Hot Spot

Hawai’ian Volcanoes 101https://www.youtube.com/watch?v=i4W2CW4G_Do

A baby island…

What is a volcano?

• A volcano is a

weak spot in the

crust where

magma has come

to the surface.

http://alaskadestination.com/alaska-volcano-images/

What are some of the things that can happen during an explosive eruption ?

• Explosion breaks lava into fragments of different sizes.

a. volcanic ash

b. cinders

c. bombs http://www.gc.maricopa.edu/earthsci/imagearchive/bombs.htm

• Pyroclastic flow: a mixture of hot gases, ash, cinders, and bombs.

http://www.volcano.si.edu/volcanoes/region15/peru/ubinas/3110ubi7.jpg

What is pahoehoe?• Pahoehoe is

lava that flows

easily and

hardens into a

rippled surface.

http://seismo.berkeley.edu/~manga/EPS214/rope.jpg

What is A’a?• A’a flows

slowly and

hardens into

rough chunks.

http://www.decadevolcano.net/photos/keywords/a_a_lava.htm

http://www.livingwilderness.com/hawaii/hawaii-pahoehoe-flow.html

http://volcanoes.usgs.gov/hazards/lava/index.php

http://www.earlham.edu/~bestan/Graphics/aa1.jpg

http://stevekluge.com/geoscience/images/

What is the life cycle of a volcano?

• Active: one that is

erupting or

showing signs of

erupting

• Dormant:

scientists expect

eruption in the

future

• Extinct: unlikely to

erupt again.

http://maps.unomaha.edu/Peterson/funda/Pictures/Japan-2/Japan_files/image001.jpg

Mt Fuji in Japan

How many active volcanoes are there?• There are about 600 active volcanoes on land

and more under the ocean where it is hard for scientists to observe or map them.

What causes a volcano to erupt?• Dissolved gases are trapped in magma. As the

magma rises, the pressure decreases, and the gases expand causing bubbles that increase in size as they rise to the top. The bubbles push the magma from the chamber into the pipe until it comes out a vent.

Are earthquakes and volcanoes related?

• When a volcano erupts,

the pressure of the

rising magma forcing

its way through the

crust to the surface will

often trigger earthquake

activity.

• Scientists have been

able to demonstrate

this link and also know

what type of earthquake

to look for.

Are earthquakes and volcanoes related?

• Scientists have observed that 75% of the world’s volcanoes and

80% of the world’s earthquakes occur along plate boundaries.

• If you follow the locations of active volcanoes and the sites where

earthquakes occur you can begin to see the boundaries of the

tectonic plates lining up around the globe. This supports the theory

because true earthquakes only occur around these areas.

What kind of landforms are made by volcanoes?

Mauna Kea is a shield volcano.

http://cimss.ssec.wisc.edu/sage/geology/lesson3/concepts.html

Diamond Head is a tuff coneTuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption.

Lava Pillow

Lava Tube, Volcano National Park, Hawai’i

http://www.traveltohawaiireviewed.com/bigisland/Attraction/Thurston_Lava_Tube.html

Lava tube from above

San Francisco Peaks - the remnants of the only stratovolcano

A cinder cone - Sunset Crater, AZ

http://cimss.ssec.wisc.edu/sage/geology/lesson3/concepts.html

San Francisco Peaks volcanic field

Superstition Mountains -resurgent dome

Mount St. Helens in Washington State is an active composite volcano.

http://www.worldbook.com/wb/Students?content_spotlight/volcanoes/how_kinds

Crater Lake caldera in Oregon.

http://www.swisseduc.ch/stromboli/glossary/caldera-en.html

Formation of a caldera

Lava plateau in Colorado.

http://www.photos-of-the-year.com/contest/08/potm/showphoto.php?photo=1459

Ship Rock, New Mexico is a volcanic neck or plume.

http://www.scienceclarified.com/landforms/Ocean-Basins-to-Volcanoes/Volcano.html

Half Dome Mountains in Yosemite national Park, CA

http://www.answers.com/topic/batholith

Devil’s Peak - columnar joints in Wyoming

Hot Springs

National Park in

Arkansas

http://www.viewpoints.com/Hot-Springs-National-Park-review-11871

Castle Geyser in

Yellowstone National Park in

Wyoming

http://geology.about.com/library/bl/images/blgeyser.htm

Yellowstone Volcano