Diapositive 1

1
How a lava flow cools down?
2
Focus
Crystallization

• Crystallization occurs when the temperature
  exceed the overcooling.

• Crystallization is exothermic.

• Crystallization requires the element to diffuse.

• Crystallization involves a change of matrix
  composition and thus a change of heat capacity.

3
Problem
4
Problem
Hypothesis

• 1D T T(x)

• no advection the lava is established

• Heat capacity constant

• no problem of chemical diffusion

5
Problem
Question
Knowing the dimensions of the reservoir
1) How long does it take to cool down the lava
flow?
2) How big would we expect the crystals to be?
6
Resolution
1st step no insulator (crust)
i) no crystallization

• No heat generation

It is the same problem as Lord Kelvin
7
Resolution
1st step no insulator (crust)
ii) crystallization

• we have heat generation from the nucleation

8
Resolution
1st step no insulator (crust)
iii) Crystallization crystal growth

• we have heat generation

We will have to consider 2 sources of heat
generation nucleation and growth
9
Resolution
2nd step it exists an insulator (crust)
It means decreasing the thermal diffusivity
coefficient in the 1st step

• we can answer i) ii) and iii) very fast

I expect bigger crystals than in the first step
10
Resolution
3rd step lets consider chemical diffusion
It means adding a temperature limit condition to
heat generation

• we can answer the questions just solving i) and
  iii) by intervals

I expect smaller crystals and than faster cooling
down
11
Resolution
4th step the temperature is not homogeneous
It means the insulator becomes thicker.
It occurs when the matrix reaches its glass
temperature transition
We will have to consider a decreasing heat flux
with time
12
Interest
This resolution will help me to evaluate if the
microlites form while external process or inside
the conduct of the volcano, and thus if they
contribute to change in the eruptive style.