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ASTA01H3 (100)
Lecture 1

ASTA01H3 Lecture Notes - Lecture 1: Lithosphere, Subduction, Natural Resources Defense Council


Department
Astronomy
Course Code
ASTA01H3
Professor
Parandis Tajbakhsh
Lecture
1

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Plate Tectonics
The convection of mantle also gives rise to plate tectonics.
The lithosphere is broken into a number of plates which float on top of the mantle due to
the convection of the mantle.
Plate tectonics is the theory which describes the Earth’s surface geology as a result of the
slow motion of the plates.
Tectonics refers to any “building” on the surface of a planet which reshapes the surface
through stretching, compression, or other forces influencing the lithosphere.
The motion of the crustal plates brings about volcanism, earthquakes and mountain
building.
Two types of crustal plates: Continental Plates and Oceanic Plates.
Continental plates are old and have a thickness of 20-70 kms while oceanic
plates are young and have thickness of 5-10 kms.
On!Earth,!the!crust!floats!on!the!semi-liquid!mantle.
The!continental!crust!is!less!dense!than!the!oceanic!crust.
Oceanic plates are constantly recycled into the mantle by diving under continental
plates and melting into the mantle.
The recycling of the rocks into the mantle plays an important role in regulating the
climate of the Earth.
Climate Regulation
One of the major gases released during outgassing of the atmosphere is CO2.
But CO2 only comprises 0.041% of the atmospheric gases! So where is the outgassed
CO2?
It turns out that most of the CO2 on Earth is locked in carbonate rocks such as the lime
stone.
Measurements show that the amount of locked up CO2 is 170,000 times more than the
amount of CO2 in the atmosphere.
The mechanism that regulates the amount of CO2 in our atmosphere is called inorganic
carbon dioxide cycle or CO2 cycle.
CO2 Cycle
Atmospheric CO2 dissolves in water, producing a mild acid known as Carbonic Acid
(H2CO3)
The mildly acidic rain fall, erodes rocks and takes the minerals to the bottom of the ocean.
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