GEO 101 Lecture 5: Lecture #5
21 Feb 2018
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The Rock Cycle- processes and paths as earths materials changes
(diagram)
What was early Earth like?
• The Earth is just a big ball of molten rock, called magma
(magma ocean)
• No water: surface temperature higher than boiling point
• Atmosphere- poisonous gases
Cooling Earth Down-
• Crust- oceanic and continental
• Mantle- plastic, not molten
• Core
o Outer-liquid
o Inner-solid
Heavy materials sink down, the lighter materials float
Igneous Rocks- rocks that have formed by crystallization of this
molten (liquid) material called magma
• Partial melting of rocks at depth- magma
• Magma at the surface is called lava
• Lava=extrusive rocks or volcanic rocks- on surface
• Magma=intrusive rocks or plutonic rocks- below surface
o What is magma made of?
▪ Liquid portion (melt)- solution of mobile ions,
mostly Si and O
▪ Solids (if present)- silicate minerals, mineral
crystals and rock bits
▪ Volatiles- dissolved gases in the melt (makes
volcanoes so explosive)
o Factors affecting magma transformation
▪ Heat
Temperature increases in the upper crust
Geothermal gradient- rapid change of
temperature with depth
Rocks are near melting point, but pressure
keeps them solid (can decrease
temperature and decrease pressure and it
will liquefy)
▪ Pressure
Increase in pressure makes it more difficult
for rocks to liquefy
Melting due to decrease in pressure
(decompression)
▪ Volatiles
find more resources at oneclass.com
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Document Summary
The rock cycle- processes and paths as earths materials changes (diagram) What was early earth like: the earth is just a big ball of molten rock, called magma (magma ocean, no water: surface temperature higher than boiling point, atmosphere- poisonous gases. Cooling earth down: crust- oceanic and continental, mantle- plastic, not molten, core, outer-liquid, inner-solid. Heavy materials sink down, the lighter materials float. Solids (if present)- silicate minerals, mineral crystals and rock bits: volatiles- dissolved gases in the melt (makes volcanoes so explosive, factors affecting magma transformation, heat. Geothermal gradient- rapid change of temperature with depth. Rocks are near melting point, but pressure keeps them solid (can decrease temperature and decrease pressure and it will liquefy: pressure. Increase in pressure makes it more difficult for rocks to liquefy. Melting due to decrease in pressure (decompression: volatiles. Causes rocks to melt at a lower temperature. Adding volatiles or water vapor allows materials to melt easier.
