Dr. Jeff AmatoGeological Sciences

RocksIgneous Rocks

Themes for today:

(1) Heat and the Earth(2) Melting processes(3) Differentiation(4) Igneous rock classification(5) Plate tectonics and igneous rocks

How do we know the Earth is hot?

Why is the Earth hot inside?

(1) Early collisions create heat.

Planetesimals Protostar

Planetesimal

~1 km

(2) Radioactive decay creates heat

Geothermal Gradient

Rate of T increase with depth

Why is the Earth hot on theSURFACE?

90%

10%

What controls heat loss?

Radiation

Conduction

Convection

Themes for today:

(1) Heat and the Earth(2) Melting processes(3) Differentiation(4) Igneous rock classification(5) Plate tectonics and igneous rocks

How to form magma:

1)Raise the temperature

2)Lower the pressure

3)Add water

Phase Diagram for Water

Melting dry rocks

Melting wet rocks

How to form magma:

1)Raise the temperature: CRUSTAL MELTING

2)Lower the pressure: DECOMPRESSION MELTING

3)Add water: HYDRATION MELTING

Themes for today:

(1) Heat and the Earth(2) Melting processes(3) Differentiation(4) Igneous rock classification(5) Plate tectonics and igneous rocks

Igneous Rock Classification

UltramaficMafic

IntermediateFelsic

From Ultramafic to Felsic….

Fe, Mg, Ca decreasesDensity decreasesSiO2 increasesK, Na increases