Volcanoes

Parts of a volcano Magma chamber Neck

◦ Vent/crater Cone/ash/lava

flow Tephra/SO2/gases

Cinder Cone

Steep sided cone Explosive

eruptions Lava type: tephra

◦ felsic◦ Traps gases, thick

Example: Paracutin Mexico

Plate bound – c/c

Shield volcano Rounded sides

◦ Dome Quiet eruptions Lava type: flows and

fountains◦ Mafic – no granite, little

gases, flows readily Example: Hawaii Plate bound: o/o

Strato volcano/ composite Cone not as steep as a

cinder cone Layers of tephra and

lava flow felsic and mafic Explosive and quiet

eruptions Example: Mt. St.

Helens, Mt Ranier Plate bound: o/c

Types of lava Pahoehoe:

◦ Quiet◦ Lava flow◦ Finger-like projections◦ Fast flowing like a river

pahoehoe

Aa - A type of lava having a rough, jagged surface.

It is relatively slow moving , thick

in the form of massive blocks

The blocks size between the size of a football and the size of a house.

Aa flow

Pillow lava – lava formed under water

tephra

Pele’s hair◦ Spun glass◦ Made by fountains◦ https://

www.youtube.com/watch?v=OEMyYNziXrc

◦ https://www.youtube.com/watch?v=Q8NXO6YxBmU

Pele’s tears Volcanic glass

Tephra

Pyroclastic flow

A pyroclastic flow  a fast-moving

current of hot gas and rock (collectively known as tephra),

speeds moving away from a volcano of up to 450 mph.

Pyroclastic flow

Pompey

http://epod.usra.edu/archive/images/pyroclasitcflow.jpg

Hot spot

Hot spot Hawaii

Felsic Mafic

Temp Low High

SiO2 content High > 70% Low <50%

Volatile content High 10% water Low <2%

viscosity High (very thick) Low (very fluid)

Magma Properties

Type volcano Type lava Type boundary Type of Eruption

Dome/shield Hawaii

Mafic o/oHot spot quiet

Cinder cone Vesuvius/Etna

Felsic c/c explosive

Composite/Strato Mt. St. Helen’s

Mafic and Felsic o/c quiet/explosive

Relationship between volcanic type magma and plate boundary