CHAPTER 10

Section 1 Objectives  Describe the movement and formation of magma.  Define volcanism  List the three locations where volcanism occurs.

Magma  Liquid Rock  Formed when mantle material flows to areas of lower pressure quicker than it cools.  It is less dense than solid rock – this is why it rises.  Most forms at plate boundaries.

Lava  When MAGMA breaks through and erupts on the earth’s surface it is called LAVA.

VENT  Opening that allows molten rock to flow on the surface of the earth.

Volcano  The material on the earth’s surface that builds up around the vent.

Major Volcanic Zones  Red dots represent active sites where major volcanoes or earthquakes have occurred in the twentieth century. Taken together, the sites outline vast "plates" that drift around on the surface of our planet. The arrows show the general directions of the plate motions.

Three Locations Volcanism Occurs:  1. Subduction Zones  2. Mid-Ocean Ridges  3. Hot Spots Volcanism Subduction Zones Mid-Ocean Ridges Hot Spots

Subduction Zone  Island Arcs Pacific Ring of Fire ○ Aleutian Islands ○ Group of Islands that make up Japan

Mid-Ocean Ridges  Seafloor Spreading  Iceland – Part of the MOR above sea- level

Hot Spots  Not along plate boundaries.  Formed where magma works its way through the interior of a plate. Hawaiian Islands Yellowstone

Section 2 Objectives  Summarize the relationships between lava types and the force of volcanic eruptions.  Describe the major types of pyroclastic material.  Identify the three main types of volcanic cones.  Summarize the events that may signal a volcanic eruption.

2 types of lava  Mafic Most of oceanic crust Dark color ○ Rich in Magnesium and Iron

2 types of lava  Felsic Most of continental crust Lighter color ○ Contains more silica, less Magnesium and iron

pahoehoe  Formed when mafic lava cools quickly on the outside and continues to flow and wrinkles.

aa  Surface breaks to form jagged chunks.

Pillow Lava  When lava flows out of fissures in the ocean floor, it cools rapidly and forms rounded shapes.

Pyroclastic Material  Felsic Lava Explodes! Throwing fragments of rock into the air. Blocks Bombs Lapilli Ash Dust

Three main types of Volcanoes  Shield Broad base Gently sloping sides ○ Example: Hawaiian Islands Belknap Shield Volcano, Oregon

Cinder Cone  Very steep slopes Composed of fragments ejected from the volcano. Can also be a composite volcano or stratovolcanoes ○ Mount Shasta, California (pictured) ○ Mount Fuji, Japan ○ Mount St. Helens

Craters  Funnel shaped pit at the top of the volcanic vent

Calderas  When the magma chamber empties and collapses, a caldera is formed. Example: Krakatau

Prediction of Volcanic Eruptions  Volcanoes are one of natures deadliest forces. Pompeii

Prediction Continued  Seismographs  Temperature Changes  Earthquakes  Bulging at Surface  History of the Volcano Recording has not been long enough to establish a pattern

Section 3 Objectives  Summarize the Evidence for extraterrestrial volcanism.  Explain the differences between volcanism on earth and Io

The Moon  Covered in Basaltic Lava Flows  Evidence of past volcanism  Meteorite impacts were filled with lava Continued bombardment could have created enough heat to produce lava.

Mars  Volcanic Features on the Surface  Largest is shield volcano Olympus Mons

Io  Moon of Jupiter.  In 1979 Voyager 1 and 2 showed nine volcanoes erupting.  About the size of our moon.  Possibly most active volcanism in the solar system.  Lava is possibly sulfur and sulfur dioxide.  Plumes reach hundreds of km high.