Igneous+Rocks+and+Volcanic+Activity


 * 11/30 Concept Map

12/1 Concept Map

Concept Map 12/2

**


 * Igneous Rocks **
 * Andesite **
 * Basalt **
 * Diorite **
 * Gabbro **
 * Granite **
 * Obsidian **
 * Pegmatite **
 * Peridotite **
 * Pumice **
 * Rhyolite **
 * Scoria **
 * Tuff **



134-140 Notes
 * Volcanic Structures and Eruptive Styles **
 * Some volcanoes are only 30 meters (100 feet) high and formed during a single eruptive phase that may have lasted only a few days.
 * Volcanic landforms come in a wide variety of shapes and sizes, and each structure has a unique eruptive history.
 * Volcanologists have been able to classify volcanic landforms and determine their eruptive patterns.
 * Anatomy of a Volcano **
 * Volcanic activity frequently begins when a fissure (crack) develops in the crust as magma moves forcefully toward the surface.
 * Successive eruptions of lava, pyroclastic material, or frequently a combination of both often separated by long periods of inactivity eventually build the structure we call a volcano.
 * Located at the summit of most volcanoes is somewhat funnel-shaped depression is called a crater.
 * Some volcanoes have very large circular depressions called calderas
 * Many of these vents however emit only gases and are appropriately called fumaroles
 * Shield Volcanoes **
 * Shield volcanoes are produced by accumulation of fluid basaltic lavas and exhibit the shape of a broad, slightly domed structure that resembles a warrior’s shield.
 * Mauna Loa is one of five overlapping shield volcanoes that together comprise the Big Island of Hawaii.
 * Olympus Mons is a huge shield volcano on Mars
 * Mature shields have steeper flanks while their summits are comparatively flat
 * Another feature to a mature avtive shield volcano is a large steep-walled caldera that occupies its summit.
 * Calderas form when the roof above the magma chamber collapses.
 * In their final stage of growt the activity on mature shields is more sporadic and pyroclastic ejections are more prevalent.
 * Cinder Cones **
 * Cinder cones aka Scoria Cones are built from ejected lava fragments that take on the appearance of cinders or clinkers as they begin to harden while in flight.
 * These pyroclastic fragments range in size from fine ash to bombs that may exceed a meter in diameter.
 * Cinder cones are composed mostly of loose pyroclastic material they sometimes extrude lava
 * Cinder cones are the most abundant
 * Most cinder cones are produced by a single short lived eruptive event.
 * Cinder cones are found by the thousands all around the globe.
 * Composite Cones **
 * Earth’s most picturesque yet potentially dangerous volcanoes are composite cones or stratovolcanoes
 * Most are located in a relatively narrow zone that rims the Pacific Ocean appropriately called the Ring of Fire.
 * The classic composite cone is a large nearly symmetrical structure composed of both lava and pyroclastic deposits.
 * Just as shield volcanoes owe their shape to fluid basaltic lavas composite cones reflect the nature of the erupted material