warm up!!! thursday 1/31/08 describe a magma chamber!
TRANSCRIPT
WARM UP!!!WARM UP!!!
Thursday 1/31/08
Describe a
magma
chamber!
Types of Volcanic Eruptions
Why do volcanoes erupt?
• Magma rises to the surface because it is LESS DENSE than the surrounding rock.
• Gases and magma build up inside the volcano and eventually erupts.
Parts of a Volcano…This diagram is located on pg. 185 in your textbook.
It would be a good idea to use the book to find out the information about each part!
Characteristics of Magma• Temperature:
– Hotter = Less Viscous (thinner)– Cooler = More Viscous (thicker)
• Silica Content:– Low Silica = Less Viscous (thinner)– High Silica = More Viscous (thicker)
The thicker the magma, the more explosive the eruption!
Types of Eruptions
1.Quiet
2.Violent
Quiet Eruptions
• Runny lava oozes from volcano vents
• Ex. Iceland and Hawaii
• Produce two types of lava:– Pahoehoe: FAST and HOT– Aa: SLOW and COOL
Violent Eruptions
• Thick and sticky magma plugs vents like a cork. Pressure builds up and eventually explodes.
• Pieces of lava/rock create a pyroclastic flow of ash, cinders, and bombs.
1. Ash = small pieces2. Cinders = medium pieces3. Bombs = large pieces
Mount St. Helens BEFORE the eruption…(1980)
Mount St. Helens DURING the VIOLENT eruption…
Pyroclastic Flow
Mount St. Helens AFTER the eruption…
Stages of Volcanoes
• Active: Can erupt at any moment
• Dormant: May awaken and become active. There is magma still underneath it.
• Extinct: Unlikely to erupt again. No longer has magma underneath it.