Rheology of magma

Question 1

What is the definition of rheology?

Answer 1

The study of how materials flow

Question 2

What is viscosity a measure of?

Answer 2

The resistance of a fluid which is being deformed by either sheer stress or extensional stress

Question 3

What is the relationship between magma viscosity and explosiveness?

Answer 3

Explosiveness is a function of magma viscosity
More viscous=more explosive

Question 4

What is the definition of viscosity?

Answer 4

A fluids internal resistance to flow

Question 5

How is viscosity linked to silica content?

Answer 5

More linkages through o ataoms
More tetrahedra linked = more viscous
Increased silica = more linkages

Question 6

What is the effect of h2o on viscosity?

Answer 6

Water breaks down the silica polymers
Oxygen breaks chain and adds a terminus
Hydrogen atoms each bond to a terminal, balancing the charge
Increasing water = decreasing relative viscosity

Question 7

What is the effect of bubbles on viscosity?

Answer 7

Bubbles can increase or decrease magma viscosity
High viscosity- caused by flow around the bubbles
Low viscosity- reduced volume fraction of fluid due to bubbles
In less viscous magma- bubbles can escape easily

Question 8

What is the effect of crystal on viscosity?

Answer 8

Adding particles = increased viscosity
No slip on crystals like with bubbles
More crystals = more viscous
Differences in aa and pahoehoe lava viscosity due to crystal content

Question 9

What is the effect of pressure on viscosity?

Answer 9

Increased pressure = lower viscosity

Question 10

What is the effect of temperature on viscosity?

Answer 10

Decreased temperature = increased viscosity
(partly due to crystallization)