EPSCIE120 Lecture Notes - Lecture 2: Subduction, Plate Tectonics, Heavy Metals
29 Jun 2018
School
Department
Course
Professor
Four Key Events in the Development and Evolution of Earth
1. The Great Bombardment - occurred up to 700 m.y after the formation of Earth. Was bombarded
with asteroids, meteorites and large rocks from space. By the end of the great bombardment, the
internal structure of Earth was set.
2. Differentiation - Earth’s temp was thousand of degrees. Earth separated into layers of different
density. Heavy metals like iron sank to the centre and lighter ones like carbon floated to the top.
3. First Life - Cyanobacteria - single-celled anaerobes. 3.6 b.y.a. Transformed Earth’s atmosphere
by removing CO2 and converting it by photosynthesis into free oxygen.
4. The Aerobic Atmosphere - The oceans were oxygenated first and more photosynthetic life
emerged to help Cyanobacteria.. The transition to Aerobic was complete by 2.2 b.y.a. Initiates
first ice age.
Early Earth - 80% C02. the gases reacted causing violent lightning storms.
Modern Atmosphere - 21% Oxygen, 78% Nitrogen and 1% Other (C02, H, He, Ne, Ar and 03)
Structure of the Earth
Inner Core (solid) - Mostly iron and nickel metal. Temp up to 7000 degrees. Extreme pressures.
Outer core (liquid) - Molten iron and nickel. Temp between 4000 and 6000 degrees. Less pressure.
Mantle (molten) - Oxygen, Si, Mg, Fe and other ions. Temp between 500 and 2000 degrees. Contains the
asthenosphere.
Crust (solid) - the surface of our earth made up of the materials we use everyday.
Layers of the Atmosphere
-Exosphere
-Ionosphere
-Mesosphere
-Stratosphere
-Troposphere
-Earth
Rock Cycle
Three main types of rocks:
1. Sedimentary rocks
2. Igneous rocks
3. Metamorphic rocks - means ‘changed’. Buried deep underground. Re-emerge on the surface as
something new.
Theory of Continental Drift
-Alfred Wegener noticed this pattern in 1912.
-Suggested that the continent are moving away from each other.
-Believed that 250 mya all of the continents were joined as one called Pangea and that over time
they moved to form the model of the Earth we have today.
Plate Tectonics
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Four key events in the development and evolution of earth: the great bombardment - occurred up to 700 m. y after the formation of earth. Was bombarded with asteroids, meteorites and large rocks from space. By the end of the great bombardment, the internal structure of earth was set: differentiation - earth"s temp was thousand of degrees. Heavy metals like iron sank to the centre and lighter ones like carbon floated to the top: first life - cyanobacteria - single-celled anaerobes. Transformed earth"s atmosphere by removing co2 and converting it by photosynthesis into free oxygen: the aerobic atmosphere - the oceans were oxygenated first and more photosynthetic life emerged to help cyanobacteria The transition to aerobic was complete by 2. 2 b. y. a. Early earth - 80% c02. the gases reacted causing violent lightning storms. Modern atmosphere - 21% oxygen, 78% nitrogen and 1% other (c02, h, he, ne, ar and 03) Inner core (solid) - mostly iron and nickel metal.
