13.2 Volcanic Eruptions

Volcanic EruptionsSection 13.2

Volcanic Eruptions· volcano - vent (opening) in Earth's surface through magma and gases are expelled· viscosity - measure of a material's resistance to flow

thicker material, greater viscosityaffected by temperature, silica content, and dissolved

gases· quiet or explosive· factors that determine the violence of eruption

composition of magmatemperature of magmadissolved gases in magma

Types of MagmaMAFIC

· low in silica· thin· dark in color· rapid movement· dissolved gases escape easily· smooth-flowing eruptions· creates broad-based volcanoes

FELSIC· high in silica· thick· light in color· slow movement· dissolved gases do not easily escape· explosive eruptions· creates steep-sided volcanoes

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1 All of the following influence how violent a volcanic explosion will be EXCEPT

A

B

C

D

dissolved gases in magma

temperature of magma

composition of magma

depth of magma chamber

2 MATA: Describe felsic lava.

A high in silica

B explosive eruptions

C smooth flowing

D light color

E dissolved gases escape easily

F thick

Materials Associated with Volcanic Eruptions

· lava flowspahoehoe lava - looks like ropeaa lava - jagged chunksblocky lava - large chunks

· gaseswater vapor, carbon dioxide, sulfur, hydrogen, chlorine

· pyroclastics - "fire fragments"ash, dust, lapilli, bombs, blocks (increasing in size)

13.2 Volcanic Eruptions

Types of Volcanoes· shield

broad base w/gentle sloping sidesquiet eruptions of mafic lavaex. Hawaiian Islands

· cinder conesteep sloping sidesexplosive eruptions w/large pyroclastics

· composite (stratovolcano)form large volcanic mountainsalternate btwn quiet and explosive eruptionsmost violent eruptionsmost active found in Pacific Ring of Fire

3 Ash, lapilli, and bombs are all examples of

A pyroclastics

B lava flows

C volcanoes

D lava viscosity

4 MATA: Which volcano(es) could erupt with felsic lava?

A shield only

B shield and composite

C composite only

D composite and cinder cone

E cinder cone only

F cinder cone, composite, and shield

CAlderas· like a crater· magma chamber below a volcano empties and the cone crumbles inward· may fill with water and form lakes

Predicting Volcanic Activity· NO reliable way· methods of prediction

1. change in earthquake activity around volcano2. bulging - areas of magma pushing against volcano3. volcano's past behavior

5 A change in a volcano's behavior is a reliable indicator that the volcano is about to erupt.

True

False