What are volcanoes? 4/26/17
- volcano=a weak spot in the crust,formed by plate tectonics,that erupts out magma/lava…Mt w/ hole in it filled with liquid rock
- magma=liquid rock INSIDE the volcano
- lava=liquid rock OUTSIDE the volcano
- Ancient Greeks thought volcanoes were the home of Hephaestus, God of Fire & Forge…Roman God Vulcan which gives the word “volcano”
- Ancient Polynesians/Hawaiians believed in Pele, goddess of the volcano
- Form on divergent & convergent PT boundaries
- Most explosive land form on Earth
- Volcanoes keep building up by erupting
- Can be extinct, never erupting again & be just a cone shaped mtn.
- Magma chamber is a “hot bubbling furnace”
- Created the atmosphere by releasing CO2
- Create while destroying
- Beautiful, yet deadly & dangerous…Nature’s fireworks show!
- Crater is created in the first eruption when the top is blown off the mtn.
- PT divergent & subduction zones create a weakness/crack in the crust where magma can escape
- Located on all continents except Australia
- Ring of Fire=lg volcanic belt outlining the Pacific Ocean; most volcanoes are here
- Island arc= arc of volcanoes formed along a deep ocean trench @ OvsO boundary: Japan
- Volcanic arc= arc of volcanoes formed along a CvsO boundary: Andes Mts in South America & Cascade Range of North America (Oregon & Washington)
- Hot spot volcanoes=volcano found in the middle of a plate rather than on a boundary: Hawaii & Yellowstone National Park (Wyoming/Montana)
What does a volcano look like on the inside? 5/3/17 (structure)
- ALL volcanoes have the SAME internal structure
1)crater= bowl shaped/indent area surrounding the vent @ the top of the volcano…where an eruption “starts”
2)pipe= long tube in the ground that connects the magma chamber to the surface/vent… “the straw”
3)vent= opening where magma comes out & turns into lava
4)magma chamber= pocket/pool of magma from the mantle @ the bottom of the volcano
5)side vent= vent on the side of the volcano
6)lava flow= flow of lava going down the volcanic mtn
Why do volcanoes erupt and what happens during an eruption? 5/9/17
- force of expanding gases pushes the magma from the chamber, through the pipe, out the vent
- gases are dissolved in magma
- gases expand b/c pressure from the earth decreases as magma rises
- Silica (SiO2) content of magma creates two types of eruption:
1)quiet eruptions= low silica magma; thin, runny, quiet oozing
*pahoehoe lava= HOT!! very runny & thin consistency/ low viscosity
*aa lava= hot! more viscous than pahoehoe
*lava flows, lava rivers, lava drips into the ocean, lava burps
*Hawaiian volcanoes
* “Blub-Blub”
2)explosive eruptions= high silica magma; thick, sticky, clogs vent like a cork!
* pyroclastic flow= mix of poisonous gases, ash, cinders & bombs hurtling down the volcano side HOTTTT!!!!!
* forms obsidian (volcanic glass) & pumice
*BOOMER!!!!
What are the different forms of volcanic mountain? 5/16/17
(glued in stuff)
- three stages of volcanic activity:
-active=is erupting right now
-dormant= “sleeping”-may erupt in the future
-extinct= will never erupt again…DEAD!
What other landforms are created by volcanic activity? 5/18/17
- caldera= a large crater formed by a large eruption when the magma chamber empties & collapses
- volcanic soil= broken down ash adds potassium & phosphorous to the soil making it ++++fertile
- dike=magma that hardened across layers of rock vertically or diagonally-II
- sill= magma that hardened between layers of rock horizontally-II
- volcanic neck=magma hardened in the pipe (Ship rock)-II
- batholith=LARGE dike/sill formation (Sierra Nevada Mtns)-II
- geysers=hot column of water and steam shooting in to the air (Old Faithful)
- hot spring=natural pools of earth heated water
- geothermal activity= “Earth heated”…hot springs & geysers & other stuff that happens in volcanic areas
- igneous intrusion (II)= when magma hardens underground “intruding” on the other rock layers
What did I learn from the video: Eyewitness Volcano 5/12/17