I. Parts of a volcano rim crater vent pipe Parasitic cone

II. Locations of volcanoes A. Along subduction zones (convergent boundaries) B. Along mid-ocean ridges (divergent boundaries)

C. Hot spots (not along plate boundaries) The magma chamber is well below the lithosphere and does not move. The lithospheric plate moves which creates a chain of volcanic islands.

V. Volcanic cones (three basic shapes) A.Shield cones- have broad bases and gently sloping sides (15 º)because they are made of mafic lava. These cones are typically large and have quiet lava eruptions. Example: Hawaii

V. Volcanic cones (three basic shapes) A.Shield cones- Geometric Structure Silica Low Gases Low Eruptive Style Quiet Where in the World? Hawaii Igneous Rx created Basalt – Pahoehoe, aa

B.Cinder cones- have steep slopes (up to 40 º) and are not more than 100 meters high because they are made of felsic lava. These cones create explosive eruptions. Example: SP crater in Arizona

V. Volcanic cones (three basic shapes) Cinder Cones Geometric Structure Silica High Gases High Eruptive Style Explosive Where in the World? Arizona Igneous Rx created Pumice/Scoria

C.Composite cones (stratovolcanoes)- these cones are created by alternating quiet and explosive eruptions Examples: Mt. Fuji- JapanMt. Hood- U.S. Mt. Rainier- U.S.Mt. Shasta- U.S. Mt. St. Helens- U.S.

V. Volcanic cones (three basic shapes) Composite Cone Geometric Structure Silica Very High Gases Very High Eruptive Style Very Explosive Where in the World? Mt. St. Helen’s Igneous Rx created Pumice/Scoria

D. Fissure: fracture or crack in rock along which there is a distinct separation from which lava erupts. Example: Hawaii

V. Volcanic cones (three basic shapes) Fissure Eruption Geometric Structure Silica Low Gases Low Eruptive Style Quiet – Medium Where in the World? Hawaii - Iceland Igneous Rx created Basalt

ERUPTION UPDATES htmlhttp://hvo.wr.usgs.gov/kilauea/update/maps. html maumau_newgasvent.htmhttp:// maumau_newgasvent.htm

III.There are three types of lava: (mafic, felsic, intermediate) A.Mafic- dark in color and contains high amounts of iron and magnesium. 1.Has a low viscocity- (flows easily) 2.Volcanoes with mafic lava are not explosive.

a. Types of mafic lava: -pahoehoe- has a wrinkled surface. Formed when lava is still hot. -aa- has a jagged appearance. Formed when lava cools down some.

B.Felsic- lavas with a lot of silica. Are light in color and less dense than mafic lava. 1. Are viscous lavas (thick) 2.Often contain high amounts of dissolved gases. 3.Volcanoes with felsic lavas are explosive.

B.Intermediate lava- composition is between felsic and mafic lava.

IV.Types of pyroclastics (tephra)- material that explodes out of a volcano. Volcanic ash- between 0.25 and 2mm in diameter Lava Flow – Magma that erupts onto Earths Surface. Lahar - Pyroclastic mudflow/landslide.

Pyroclastic Flow - flows are fast-moving currents of hot gas and rock Volcanic bombs- aerodynamic tephra Volcanic blocks- can be as large as a house

Volcanic Gases The principal components of volcanic gases are water vapor (H 2 O), carbon dioxide (CO 2 ), sulfurwater vaporcarbon dioxidesulfur –either as sulfur dioxide (SO 2 ) (high-temperature volcanic gases) or hydrogen sulfide (H 2 S) (low- temperature volcanic gases), nitrogen, argon, helium, neon, methane, carbon monoxide and hydrogen.

VI.Caldera- a large basin-shaped depression caused from a volcano that collapses. Examples: Krakatoa- Indonesia Crater Lake- Oregon

VII. Volcanic rock A.Extrusive igneous rock- Molten rock that cools above ground. The rock cools fairly quickly and the crystals are not large enough to be visible.

B.Intrusive igneous rock- molten rock that cools below ground. This takes a long time and large crystals form.

Pikes Peak is made of intrusive igneous rocks (granite). It was molten rock deep within the Earth and it cooled off slowly over time. Pikes Peak is a batholith