What Is a Volcano & How Does One Form? 4/27/17

What is a volcano & how does one form? 4/27/17

• volcano= a weak spot in the crust, usually a mountain, created through plate tectonics @ subduction zones that explodes lava to the surface
• a lot of them in Hawaii b/c Hawaii is made of volcanoes
• magma=molten rock INSIDE the volcano
• lava= molten rock OUTSIDE the volcano
• Ancient Greeks thought Hephaestus, God of fire & forge, lived in volcanoes; eruption meant he was working at the forge...Roman God Vulcan, which gives the word volcano
• Ancient Polynesians/Hawaiians believed in Pele, Goddess of Fire
• All volcanoes have the same key structure
• Most explosive landform on Earth
• Can go extinct…never erupt again!
• Formed the first atmosphere by releasing CO2
• Main vent lets magma escape
• Subsequent eruptions build up the volcano
• Pressure build up causes the eruption
• Beautiful but dangerous & deadly!
• Nature’s fireworks show!
• PT causes volcanoes by creating weakness in the crust where magma can escape…divergent & subduction zones
• NOT @ transform or C VS C boundary b/c an opening in the crust is NOT formed @ these boundaries
• Subduction zone volcanoes are the strongest/biggest boomers!
• Found 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

What do volcanoes look like on the inside? 5/3/17 (structure)

• No matter the outside, ALL volcanoes have the SAME internal structure

1)crater= bowl shaped area @ the top of the volcano surrounding the vent

2)central vent= opening allowing magma to escape in the crater @ the top

3)pipe= long tube connecting the magma chamber to the vent… “straw”

4)magma chamber= pocket/pool of magma under the volcano

5)side vent= opening on the side that allows magma to escape

6)lava flow= area covered in lava which spewed from the vent

Why does a volcano erupt & what happens during an eruption? 5/9/17

• dissolved gases in the magma expand (bubbles) as it rises in the pipe
• less rock pressure allows gases to expand as magma rises
• dissolved gases push magma farther up the pipe
• eruptions differ depending on amt of silica in the magma (SiO2):

1)quiet eruption=low silica magma is thin & runny so flows easily & gently…BLUB-BLUB!low viscosity…viscous=thickness

*pahoehoe lava is HOT!!!, runny & fast moving

*aa lava is hot!, slow moving, thicker

*lava flows/oozing, lava rivers, lava burps

*Hawaiian Islands

2)explosive eruption= high silica magma which is viscous/thick & chunky! so plugs up the vent like a cork causing ++++++++ pressure…BOOMERS!

*pyroclastic flow= “cloud” of explosive eruption made of ash, cinders, bombs, poisonous gases & is HOT!

What did I learn from the video: Eyewitness Volcano 5/12/17

What are the different forms of volcanic mountain? 5/15/17

(glue chart)

• 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

book page 232-235, 228

• caldera= collapsed volcanic mtn formed when the magma chambers empties after a huge eruption (Crater Lake)…huge hole/crater shape
• volcanic soil=rich in nutrients b/c of the ash, ++++fertile & holds water well
• dike=magma forced across rock layers & hardened…vertical or diagonal (II)
• sill=a horizontal dike but btwn rock layers (II)
• volcanic neck= magma hardened in the pipe, softer surrounding rock wears away, looks like a “big tooth mountain” (Ship Rock) (II)
• batholith=massive rock formed by hardened magma (Sierra Nevada Mtns) (II)
• geysers= spout of HOT! water and steam erupting out of the ground (Old Faithful)
• hot spring=
• geothermal activity=
• igneous intrusion (II)=volcanic rock forced in among other types of rock