VolcanoesChapter 6

What are volcanoes?•They are openings in the Earth that erupt gases, ash, and lava

Kilauea – most active volcano in the world

Effects of eruptions:- volcanic ash (global temp.)

-Lava flows-Fires-Lahars (mudslides)-Acid rain

Formation•Magma is forced upward towards the Earth’s surface (WHY?)

•Flows out through openings called VENTS

Where do they occur?

• Divergent Plate boundaries

Iceland

Convergent plate boundaries

Andes Mountains – South America

Hot Spots • The Hawaiian Islands

Types of Eruptions•Based on

- amount of water vapor or other gases trapped in magma

- Silica content of magma

Quiet EruptionsBasaltic magma

Iceland Kilauea

Explosive Eruptions

Granitic & Andesitic MagmaMt. St. Helens Soufriere Hills

Mt. Pinatubo

Forms of Volcanoes

Shield Volcano – quiet eruptions of basaltic magma layering to form broad volcanoes with sloping sides

Cinder Cone – Explosive eruptions of tephra which form steep sided, loosely packed volcanoes

Composite Volcano

– A combo of quiet and violent eruptions usually steep