Download Classifying Volcanoes

Volcano Basics
1. Why do Volcanoes Form?
a. Plate tectonics; colliding plates produce excess magma which rises to the surface, after
coming to the surface it cools and hardens forming the sides of the volcano
2. Parts of a volcano (draw diagram into notebooks)
a. Magma Chamber- area where magma pools and builds up pressure before being
released as an eruption
b. Magma- liquid rock that is beneath the surface of the Earth
c. Lava- liquid rock that is above the surface of the Earth
d. Central Pipe- main tube that magma flows through from the magma chamber
e. Vent- opening in the volcano where gas and magma are released
f. Volcanic Debris- also called ejecta, or tephra, this is material that is ejected from the
vent of the volcano (dust, ash, rocks, or bombs)
g. Layers- alternating layers of lava and debris, these create the volcano
h. Dike- old lava that has hardened and crosses layers of debris
i. Lava tube- channels of hardened lava that form in old lava flows and allow the lava to
move far away from the vent
3. Classifying Volcanoes
a. How often they erupt
• Active- erupts constantly, or erupting right now
• Intermittent- erupts on a regular basis
• Dormant- hasn’t erupted in a while but could in the near future (Sleeping)
• Extinct- hasn’t erupted in recorded history
b. The way they erupt
• Oozing- highly fluid lava (called effusive, low viscosity, low gas pressure)
• Violent- very sticky lava (high viscosity, high gas pressure)
• Violent then oozing- sticky lava forms a plug, after the initial eruption the
remaining magma slowly oozes out (starts out with high, changes as pressure drops)
c. Volcanoes Cone Structure
• Cinder-Cone: Tall with steep sides (violent eruptions)
• Shield-Cone: Gentle sloping sides (oozing eruptions)
• Composite-Cone: Steep at the top gentle at the bottom (Stratovolcano) (violent then
oozing eruptions)
4. Types of Ejecta- scientists call this tephra
• Ash or Dust- sandy, fine, small particles, gray colored (looks like smoke)
• Cinders- pea sized granules of cooled magma
• Rocks- baseball sized pieces of cooled magma
• Bombs- bowling ball sized and larger, up to 100 metric tons
5. What happens before an eruption?
a. Indicators of volcanic eruptions
i. Clouds of smoke and ash seep out from cracks in the mountain
ii. Changes in the tilt of the side of the mountain
iii. Bulging in the sides of the mountain
iv. Increase in sulfur dioxide gas levels
v. Earthquakes signal movement in the magma chamber
vi. Lightning storms happen just before the eruption
b. Bulging, and tilting is caused by magma entering the mountain
6. What is the impact of an eruption?
a. Destroy homes, and harm people- lava burns and destroys everything in its path, ash
falls from sky builds up in thick layers
b. Decrease in ozone layer- causes increases in skin cancer
c. Pollution Effects
i. Global climate change- ash, dust, and gas particles reflect solar radiation this leads
to Global Cooling (average temperatures drop 1-2°)
ii. Global Climate Change continues- ash, dust, and gas particles increase the amount
of green house gases that raise the temperature of the Earth which is Global
Warming
iii. Sulfur Gas- released from the volcano combines with ozone gas to make sulfuric
acid droplets which fall as acid rain
iv. Vivid Sunsets- pinks, purples, blues, oranges, reds, yellows; happen because of
pollution in the air
7. What is a hot spot?
a. An area where magma keeps pushing up and erupts through the Earth’s crust and forms
volcanoes even when the plate over that area keeps moving. This forms chains of
volcanoes.
i. Emperor Sea Mount Chain