Volcanic Activity Flashcards
What are the two factors that control volcanic eruptions?
Viscosity & Gas Content
What is Viscosity?
A magma’s silica (Si) content determines viscosity
Viscosity controls how easily magma can erupt
Low Silica=
Runny Rivers
High Silica=
Sticky Mounds
What is Gas Content?
Magma gas can be low or high, depending on source
High gas content gives magma its ‘explosive power’
Lava flow Eruptions are characterized by there?
low viscosity and low gas content,
runny magma remains fluid and flows downhill ,
usually gentle, fairly safe, can be enormous
WHAT IS Pahoehoe?
Hot flow with a ropy texture
As lava cools, it breaks up into:
jagged aa texture
Underwater, flow make round blobs=
Pillow Lava texture
Pyroclastic Eruptions are characterized by there?
Medium to High Viscosity & Gas Content
Sticky Magma explodes into small solid bits as it erupts
always violent, often destructive, can erupt up or sideways
The 2 types of Pyroclastic Eruptions are?
Ash Clouds and Nuee Ardentes
Ash Clouds are characterized by?
Very fine dust with some larger chunks
Cold ash- turns into TUFF
Hot ash- makes WELDED TUFF
What is Nuee Ardentes?
glowing cloud of hot ash and gas. Hugs the ground like an avalanche
Olivine Crystals settle _________________
to the bottom, making ultramafic magma
Mantle magma rises __________________
through the cracks between plates.
