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Week 23: Lava & Viscosity

• Compare & contrast  magma vs. lava and volcanism vs. volcanoes

  • magma=underground, volcanism=activity of magma coming from the ground, creation/movement

• describe the parts of a volcano and what is causing it to form

  • batholith - lava lake

  • conduit - from batholith to vent

  • vent - where lava comes out

  • cone - exterior shape

• Name and describe two lava textures and explain what could cause one vs. the other to form.  Be able to identify what type from an image or sample.

  • Pahoehoe and A’a, viscosity levels

• identify lava formations from an image and explain what they are or how they form

• Define viscosity and use the term in its variations like viscous/non-viscous, high, and low viscosity to properly refer to magma that is resistant to flow and that is not resistant to flow.

• Know how viscosity is affected by temperature (inverse relationship) and silica (proportional relationship)

Week 24: Volcanic Eruptions, Science & Hazards

• List the 3 categories of things erupted from volcanoes, the main types of gasses and the different types of pyroclastics.  

  • Lava

  • Gas

    • water vapor, carbon dioxide, sulfur dioxide

    • methane, chlorine, ammonia, etc.

  • Pyroclastic

    • Ash - smallest

    • Lapilli - 2nd smallest

    • Lava Blocks - bigger than 64mm

    • Lava Bombs -football shaped

• List and describe the 6 volcanic hazards and give examples from our class lecture

  • Lava

    • 1000-2000* C

    • slow: 0.25mph average

    • Mt. Nyiragoago 1977 lava lake destruction

  • Poison Gas

    • less deadly, is diluted in air, but can be deadly by proximity

    • Lake Nyos 1986, Cameroon, lake bubble burst on village

    • gass=more explosive eruptions

  • Pyroclastics

    • most deadly, with direct and indirect effects

    • starvation and effect on climate is most impactful

    • Mt. Tambora 1815, Indonesia, island of Sumbawa: top 4000 ft of mt off, global ash impact by jetstream, black sky for a week, no summer in new england: THEY BLAMED BEN FREAKING' FRANKLIN. Ben. FRANKLIN.

  • Pyroclastic Flow

    • avalanche of pyroclastics and gas, 100-430 mph, at temps higher than 500* C

    • mostly at explosive eruptions, through the collapse of magma collumn

    • least escapable hazard

    • Mt. Pele 1902 Martinique, St. Pierre: horizontal blast and flow kills 30,000 leaving jail dude the only one alive (cement jail one window)

  • Lahar

    • mudflow slurry of pyroclastics and water along river valleys, triggered by melting glaciers/snow

    • viscosity of wet concrete. slow. leaves behind a rock.

    • 1985 Nevada del ruiz, Columbia

    • eruption melted the snow and glaciers around there

  • Tsunami and Earthquakes

    • earthquakes from rising magma or from eruptions

    • tsunamis from displacement of water by eruption/landslide (warning sign: retreat)

    • Krakatoa 1883, Indonesia: loudest sound ever heard, 2000 miles away, 46 m tall tsunami, the complete collapse of a volcano.

• Categorize eruptions as explosive or effusive and explain what affects this eruption style.

  • Explosive: gas trapped releases with magma

  • Effusive: ongoing, less gas

Week 25: Volcanic Structures

• Describe how volcanoes form.

  • magma erupts out of a vent and material builds a cone

    • melted rock is less dense than solid rock

    • blocked path builds up pressure

    • more pressure=more explosivity

• Describe the 3 types of volcanoes including their shape, what they are made of, what type of eruption they tend to have, the type of magma/lava, examples in the world. 

  • 	Cinder Cone	Composite Cone	Shield Cone
    Characteristics	Steep, big crater, small	Mide steepness, layers of lava/pyroclastics	Gently Sloped, big, all lava
    Eruption Style	Explosive Low VEI Singular short eruptions Pyroclastics	Explosive High VEI Multiple eruptions Pyroclastics and Lava	Effusive lots of lava continuous
    Magma	Gassy	intermediate to felsic, high viscosity, gassy	Mafic, primitive, low viscosity, hot magma
    Where	all locations	Subduction Boundaries	Oceanic Hotspots Divergent Boundaries
    Examples	Sunset Crater, New Mexico Paricutin 1943 in a farmer’s field over Decarde	Mt. St. Helens Mt. Rainier Krakatoa Mt. Pele Nevada Del Ruiz	Iceland Mauna Loa (biggest) Olympus Mons (mars)

• Explain how the shape of cones is related to the eruptive materials and eruption style (and give examples) and why it is important to understand these connections.

  • The shape of volcanic cones is determined by the type of eruptive materials and eruption style. For example, stratovolcanoes have steep slopes due to explosive eruptions with viscous lava. Shield volcanoes have gentle slopes from effusive eruptions with runny lava. Understanding these connections is crucial for predicting volcanic behavior and hazards.

  • Stratovolcanoes, like Mount St. Helens, have steep slopes due to explosive eruptions with viscous lava, creating tall, conical shapes. Shield volcanoes, such as Mauna Loa, have gentle slopes from effusive eruptions with runny lava, resulting in broad, low-profile structures. These differences in eruptive materials and eruption styles influence the overall shape and size of volcanic cones.

• Explain how a caldera forms and why Yellowstone has one

  • volcanic cone and chamber collapses with absence of magma, creating caldera
    

Week 26: Igneous Rocks

• List the 3 common ways that magma is formed and give examples of where that might occur

  • Decompression melting (divergence zones)

  • adding water (subduction zones)

  • heating crust from below (hot spots)

• Describe how magma can evolve including the principles of Bowen’s reaction series and how this affects the magma and igneous rock formation location (just honors)

  

  • as minerals cool/crystalize they do so based on melting points which differ, so composition changes over time as more and more minerals are removed

  • they get more rich in silica as they evolve

• Classify igneous rocks based on their textures as intrusive or extrusive as well as specific textures like vesicular or coarse-grained or by color as felsic, intermediate, or mafic if given a rock or a picture of a rock.  Honors students will also need to be able to identify igneous rocks by name from a picture or hand sample.

  • Intrusive: underground

  • Extrusive: above-ground

  • Vesicular: holey (gas)

  • Coarse-grained = intrusive

  • Fine-grained = extrusive

  • Lighter in color = felsic = more silica

  • Blackish = mafic = less silica

  • 

• Identify and describe different types of igneous intrusions (just honors)

  • Sill: intrusive igneous rock when magma intrudes parallel to the rock in cracks

  • Dike: intrusive igneous rock when magma intrudes NOT parallel in cracks

  • Batholith: solidified magma chamber

  • volcanic neck: hardened magma in central conduit

  • Lacolith: mass of igneous intrusive rock lens-shaped uplift of layers (black hills)