Transcript Volcanoes and Volcanism

Atwood Quarry, Port Clyde, ME
Chelsea Sonksen
Craters of the Moon NP
Will Junkin
Snake River, ID
Hannah O’Brien
Wildcat Mountain and Mt Washington
Kyle Migliorini
Rock Candy
1 Glass jar or drinking glass
1 Piece of cotton string
1 Pencil or stick
1 Paper clip
1 Food coloring (optional)
1 c Water
2 c Sugar
Additional sugar
Tie a short piece of cotton string to the middle of the pencil or stick. Attach a paper clip to the end of the
string for a weight.
Moisten the string very lightly, and roll in a bit of sugar (this will "attract" the sugar crystals from the
syrup to the string).
Place the pencil or stick over the top of the glass or jar with the string hanging down inside.
Heat the water to boiling, and dissolve the 2 cups of sugar into it.
For the biggest crystals FAST, heat the sugar-water solution a SECOND time, and dissolve as much
additional sugar as you can into it. Add a few drops of food coloring to the solution if desired.
Pour the solution into the prepared glass or jar and leave undisturbed for a couple of days.
Depending on how much sugar you were able to dissolve into the water, you should start to see crystals
growing in a few hours to a few days.
Source: Karen Mintzias
Just Recipes: http://www.melborponsti.com/index.htm
IGNEOUS PROCESSES AND IGNEOUS ROCKS
IGNEOUS COMPOSITIONS
ULTRAMAFIC ROCKS
MAFIC derived from Magnesium and Ferrum (iron).
Dominated by Fe-Mg silicates, olivine and pyroxene.
Contains very little silica < 40%.
No feldspars or quartz.
Form deep in the Earth’s surface.
Very dark in color and dense.
Found at converging continental
plate boundaries.
PERIDOTITE OR DUNITE
IGNEOUS PROCESSES AND IGNEOUS ROCKS
IGNEOUS COMPOSITIONS
MAFIC ROCKS
Silica content is 45-55%.
Contains dark plagioclase
feldspars, pyroxenes and
possibly olivine.
GABBRO - phaneritic
BASALT - aphanitic
SCORIA - aphanitic and
porous (vesicular).
BASALT is major constituent in
oceanic crust.
IGNEOUS PROCESSES AND IGNEOUS ROCKS
IGNEOUS COMPOSITIONS
INTERMEDIATE ROCKS
Silica content is 55-65%.
Contains dark plagioclase
feldspars, pyroxenes,
biotite and hornblende.
Very little if any quartz.
Lighter color than mafic rocks.
ANDESITE - aphanitic
2nd most abundant volcanic
rock in Earth’s crust.
DIORITE - phaneritic
IGNEOUS PROCESSES AND IGNEOUS ROCKS
IGNEOUS COMPOSITIONS
FELSIC ROCKS
Felsic comes from Feldspar and Silica.
Silica content is >65%.
Rich in orthoclase, muscovite
and quartz.
Lighter color than intermediate
rocks.
Wide variety in texture in felsic rocks.
PHANERITIC TEXTURE
GRANITE
APHANITIC TEXTURE
RHYOLITE
FELSITE
GLASSY TEXTURE
OBSIDIAN
Forms when gas-poor felsic
lava cools very quickly.
PUMICE
Forms when gas-rich felsic lava
cools very quickly.
IGNEOUS PROCESSES AND IGNEOUS ROCKS
IGNEOUS ROCK CLASSIFICATION
COMPOSITION
PHANERITIC
APHANITIC
GLASSY
Dunite
Ultramafic
(Very Dark) Peridotite
Mafic (Dark) Gabbro
Intermediate
(Gray)
Diorite
Felsic
(Light)
Granite
Basalt
Scoria
Andesite
Rhyolite
Felsite
Obsidian
Pumice
IGNEOUS PROCESSES AND IGNEOUS ROCKS
CREATION OF MAGMA
Rocks are generally composed of several minerals.
Consequently, rocks don’t just simply melt.
Different minerals melt at different temperatures.
Rocks undergo PARTIAL MELTING.
Some of the rock stays solid.
Generally those minerals with high melting point
are last to melt.
Those with lower melting points become liquid first.
HEAT, PRESSURE and WATER CONTENT all affect the
melting of rocks.
IGNEOUS PROCESSES AND IGNEOUS ROCKS
CREATION OF MAGMA
HEAT
Comes from:
Radioactive Decay
Heat produced from Earth’s formation still
rising to be released.
Frictional heat from plate movement.
Temperature rises with depth in the Earth
THERMAL GRADIENT.
Increased temperature causes minerals to melt.
IGNEOUS PROCESSES AND IGNEOUS ROCKS
CREATION OF MAGMA
PRESSURE
High pressure on rocks acts to make the bonds stronger.
Pressure increases -- melting point increases.
If pressure is released quickly, melting will occur.
IGNEOUS PROCESSES AND IGNEOUS ROCKS
CREATION OF MAGMA
WATER CONTENT
Water, even in small amounts lowers melting point.
Due to polarity of water molecules.
Decreased pressure and water content greatly lowers
melting point.
Increases bond breaking ability of water.
In subduction zones, wet oceanic crust is pushed down
with increasing pressure causing increased
melting.