Ch. 18 Notes Day 1 10/13/16

Objectives SWBAT explain the relationship between the strength and type of a volcanic explosion and the type of rock and debris it produces SWBAT explain the importance of Silica content in volcanic products an how it controls the strength of the explosion.

Ring of Fire The Ring of Fire is a continuous, 25,000 mile long series of 452 oceanic trenches, volcanic arcs, and volcanic belts associated with numerous plate boundaries in the Pacific Ocean Region

Volcanic eruptions produce three major rock types based on the type of eruption. Basalt Andesite Rhyolite

Basalt Low silica content (50%) Rock Type: Mafic Low viscosity Low gas content Temperature: 1100 C Associated with non-explosive eruptions. Produces large basalt floes Material Source: Oceanic crust at divergent boundaries

Shield Volcano Quiet, non-explosive eruption (lava comes out slowly) of usually basaltic lava. Made of layers of solidified basaltic lava Gentle slopes

Andesite Medium silica content (60%) RockType: Mafic/Felsic (Intermediate) Medium Viscosity Medium Gas Content Temperature: 1000 C Associated with semi- explosive to explosive eruptions. Material Source: Oceanic & Continental crust at convergent oceanic-continental boundaries.

Composite or stratovolcanoes Repeated cycle of non-explosive and explosive eruptions Built from alternating layers of tephra and lava Typically produce andesite and rhyolite Tall and majestic

Rhyolite High silica content (70%) Rock Type: Felsic High viscosity High gas content Temperature: 800 C Associated with highly explosive eruptions. Material source: Continental crust from continental-continental convergent boundaries

Cinder Cone Volcano Explosive Eruptions Steep Slopes built from tephra (ash and rocks) Smallest of all volcanoes Usually form at edges of larger volcanoes Usually made from basalt and rhyolite

Ch. 18 Notes Day 2

Objectives SWBAT explain the anatomy of a volcano SWBAT the difference materials that are ejected from a volcano during an eruption and their effect on the surrounding environment

Caldera Volcano Most Explosive Eruptions Volcano literally blows itself up and creates a large crater Typically produce rhyolite

Anatomy of a Volcano

Tephra – mixture of ash, rocks, lava, and pyroclasts (lava that hardens in mid air) thrown from a volcano as it erupts. ASH – Very fine-grained fragments (< 2 mm) BLOCKS – Very large pyroclasts launched from a volcano LAPILLI – Pea- to walnut-size pyroclasts (2 to 64 mm). They often look like cinders BOMBS – Fragments (> 64 mm)

Gasses Given off During Eruptions The most abundant gas is water vapor (H2O), followed by carbon dioxide (CO2) (green house gas, contributes to global warming) sulfur dioxide (SO2) (very poisonous) Secondary gases are also include: hydrogen sulfide (H2S), hydrogen (H) carbon monoxide (CO) hydrogen chloride (HCl) hydrogen fluoride (HF) helium (He)

Magma vs. Lava Magma is molten rock trapped BELOW the earth’s surface Lava is molten rock AT or ABOVE the earth’s surface

Pyroclastic Flows Mixture of ash, gases, and tephra that “avalanche” from a volcano Hot (> 700 °C) Can be faster than 100 mph

Hot Spot Unusually hot regions of Earth’s mantle where high- temperature plumes of magma rise to the surface. Can be linked to the path of convergent plate boundaries