Transcript Geol155.origins

Origins
Stars and Seas
Earth is a Water Planet
• Ocean covers 71% of Earth’s surface
• Life on Earth almost certainly evolved in the ocean
• 3rd rock from the Sun
– Earth’s position allows H2O to exist in its 3 states
– Too far – H2O frozen
– Too close – H2O evaporates
The Science of the Ocean
• Over 97% of the water on
Earth is found in ocean
• Less than 3% is found in
glaciers, lakes, rivers, and
ground water
The Origin of Earth
• Big Bang = 15 billion years ago (bya)
– Releases clouds and dust
• Solar System formed about 5 bya
– Vast cloud collapses under its own gravity
– Central mass hot enough for thermonuclear fusion (HHe)
– Formation of our Sun
• Earth formed about 4.6 bya
Origin of the Earth
• Meteors and Asteroids bombarded
the Earth
– Gravity caused clouds to attract
more particles
– Impacted material accumulated at
Earth’s surface – trapping heat
• Gravitational compression
– Increased weight of material
compressed interior – further
heating Earth’s interior
• Density Stratified planet
– Heavier, dense iron and nickel
sank to core; while lighter
silicates formed outer crust
Origin of the Ocean
• Oceans are byproducts of
heating and differentiation
• Earth warmed and partially
melted
– Hydrogen and Oxygen
released by volcanic venting
– Vapor condensed with other gases
to form clouds
– Hot Earth boiled rains into vapor
– As Earth cooled, H2O condensed
to form rain
– Rain formed our oceans
Origin of the Atmosphere
4 steps
1. Primordial gases
– Later lost from Sun’s radiation
2. Volcanic venting, bombardment of icy comets
– Exhalation from Earth’s surface
3. Volcanic activity
– Addition of CO2, H2O and other gases
4. Plant/bacterial life addition of oxygen
– Addition of Oxygen
Today’s Ocean
• Traditionally divided into 4 large basins
– Pacific, Atlantic, Indian, and Arctic Ocean
• Marginal seas connect the 4 large basins
– Mediterranean, Gulf of Mexico, Red Sea
• Oceans are interconnected