Bell Ringers Learning Target: I can describe a volcano's structures and emissions. Bell Ringer: Copy the chart from the white board onto a piece of lined paper. Fill in the first two sections: “What do I know?” and “What do I want to learn?”
Extra Terms Caldera dike Viscosity basalt Pillow lava pyroclastic flow Lahar fumarole Volcanic ash bombs Hydrothermal circuit
Volcanoes • Mountains built up by molten rock that has risen to the earth’s surface through a vent. • Volcanologist • a volcano geologist
Bell Ringers Learning Target: I can describe a volcanoes structures and emissions. Bell Ringer: Complete Worksheet 7C: Volcanic Structure.
Pahoehoe lava flow • Fast flowing lava • Has a shiny surface and an appearance similar to twisted rope when hardened
‘A’a lava flow • Slow flowing lava that has a rough broken surface with sharp edges when hardened
Pillow lava flow • Forms under water
Gaseous Emissions • Magma contains many dissolved gasses • As the magma rises, the pressure is reduced • As the pressure is reduced, the gasses separate and escape
Glowing avalanche – mixture of hot solid particles suspended in water vapor and other gases • At night it glows a dull red • So heavy that it flows quickly down a volcano’s slope instead of rising into the air • Also called a pyroclastic flow • Can move at up to 93 mph and contain gases from 100-800*C • Suffocates or incinerates everything in its path
Bell Ringers Learning Target: I can describe a volcanoes structures and emissions. Bell Ringer: Why were there no deaths from the Eyjanfjallajokull volcano eruption in 2010?
Superheated water vapor • Lahar – a mud-flow of volcanic ash mixed with water
At Nevado del Ruiz in Colombia over 23,000 people died when a lahar, started by a relatively minor eruption of the volcano, swept down the river valleys on the side of the edifice and destroyed Armero and Chinchina. The footage of rescue efforts after the lahar were devastating and heartbreaking. Sadly, this disaster was mostly preventable as the citizens of these towns could have had at least an hour's warning to walk to higher ground, but the Colombian government did not have an effective plan in place. I clearly remember driving through the area hit by the lahar a few years after it occurred. The whole area paved by the mud, rock hard by the time I saw it a few years later. However, if any good came from this event, it was that it opened many people's eyes around the world to the dangers posed by volcanoes and the relatively simple solutions to preventing tragedies like this.
Fumaroles – a vent in the ground where steam and gases from volcanic activity escape • Carbon dioxide escaping from fumaroles can be dangerous
Solid Emissions • Solidified lava; also called pyroclastic materials • Ash – tiny, angular, glassy fragments • Tephra – an accumulation of loose ash • Cinders – pieces of solidified magma a little larger than ash • Bombs – masses of lava that solidify while flying through the air
Where are Volcanoes Found? • Most active volcanoes are located in two volcano belts
Bell Ringers Learning Target: I can describe several ways that volcanoes are classified. Bell Ringer: Complete a mind map of volcanic emissions. Start with a circle labeled “volcanic emissions”.
Bell Ringers Learning Target: I can describe several ways that volcanoes are classified. Bell Ringer: Study the image below. What would you infer is the difference between a dike and a sill?
Classifying Volcanoes • There are three major ways to classify volcanoes. • Structure • Activity • Explosivity
Structure • Shield Volcano • Cinder Cone Volcano • Composite Volcano
Shield Volcano • Emits mostly lava in quiet eruptions • Dome shaped with relatively flat slopes • Broadest type of volcano
Examples of Shield Volcanoes • Hawaiian Islands • Mauna Loa – the world’s largest active volcano • Mauna Kea - greatest actual height of any mountain on earth • Surtsey – formed a new island in 1963 • Now supports plant life and animals • Olympus Mons on Mars • Largest volcano in the solar system
1: Water vapor cloud 2: Cupressoid ash 3: Crater 4: Water 5: Layers of lava and ash 6: Stratum 7: Magma conduit 8: Magma chamber 9: Dike
Olympus Mons, Mars Maxwell Montes, Venus Mt. Everest, Earth
Cinder Cone Volcano • Emits mostly cinders, ashes, and bombs • Relatively steep slopes • Results from a single, short eruptive period • Typically small • Paricutin in Mexico
Composite Cone Volcano • Emits lava and solid debris in alternately quiet and explosive eruptions • Size is between shield and cinder cone • Typical “volcano shape” • Most volcanoes are composite volcanoes. • Fuji in Japan • Mt. Rainer and Mt. St. Helens in Washington • Mt. Vesuvius in Italy