Mantle convection animation radiant energy
from decay in Earth’s core
hypothesis: CONVECTION CURRENTS IN THE MANTLE DRIVELITHOSPERE PLATE MOVEMENT
Infer: Unequal heating of the mantle material causes rock to flow in convention currents
IGNEOUS ROCKS ARE FORMED FROM MAGMA IN THE LITHOSPHERE
extruding magma = lava
granite
basaltMagma contains minerals that form crystals during cooling
• slow to cool• visible crystals
Cools within the lithosphere
INTRUSIVE IGNEOUS
gabbro
• Quick to cool • microcrystal formation glassy, even
EXTRUSIVE IGNEOUS
Cool outside the lithosphere (air/water)
obsidian
lava
magma
magma
ONE MAGMA POOL, TWO IGNEOUS PROCESSES
andesite
diorite
• One magma pool can create both intrusive and extrusive rocks
• differ in crystal size, but not chemistry
ONE MAGMA POOL, CHEMICALLY DIFFERENT ROCKS
• Melt/crystallization temp varies from mineral to mineral
• As rocks are formed, partial melting can occur, and magma chemistry changes
• Next rocks to form reflect new chemistry
melt and crystallize at a higher temp
melt/crystallize at a lower temp
ONE MAGMA POOL, CHEMICALLY DIFFERENT ROCKS
1400 F
800 F
Plate material heated to 1000F, then cooled, would produce what rock types?
MAJOR MAGMA TYPES
• granitic – highest SiO2, >70%
Magma is defined by it’s silicate – SiO2 - concentration
• basaltic – lowest SiO2, <50%
• andesitic – medium SiO2 partial melting of basalt and granitic
basalt
andesiterhyolite
