1. The Science of the Ocean
The Earth System
Earth is a water planet (possibly one of a few in the galaxy)
Ocean covers 71% of the Earth’s surface, and influences the crust and atmosphere
Life on Earth almost certainly evolved in the ocean

2. The Science of the Ocean
The Earth System
Over 97% of the water on or near Earth’s surface is contained in the ocean
Less than 3% is held in land ice, groundwater and all the freshwater lakes and rivers

3. Global Water Distribution

4. Global Water Distribution

5. The World Ocean On A Planetary Scale
Average depth of the ocean is a tiny percentage of the Earth’s radius
Accounts for only slightly more than 0.02% of the Earth’s mass (0.13% of Earth’s volume)

7. The World Ocean On A Human Scale
the ocean covers 361,000,000 km2 (139 million square miles) of the Earth’s surface
the average depth of the ocean is 3,796 meters (12,451 feet)
the average temperature is 3.9oC (39oF)

8. The World Ocean On A Human Scale
the Mariana Trench, the deepest spot in the ocean, is 11,022 meters (6.85 miles), 2,192 meters (1.36 miles) deeper than Mt. Everest is high (5. 5 miles)
the tallest mountain on Earth is the island of Hawaii, an active volcano with a base 5998 meters (3.7 miles) deep and rising 4,204 meters ( 2.6 miles) above sea level, a total height of 6.3 miles

9. The World Ocean On A Human Scale
average land elevation is 840 meters (2,772 feet)
average ocean depth is meters (12,451 feet), 4.5x greater than elevation

10. The World Ocean

11. The World Ocean

12. The World Ocean On A Human Scale
the Northern Hemisphere is 60.7% ocean, 39.3% land, (1.5:1)
the Southern Hemisphere is 80.9% ocean, 19.1% land (4:1)

15. Origin of the Earth Big Bang - 15 billion years ago (bya)
expansion of the universe from a single point
Solar System formed ~ 5 bya
collapse of rotating interstellar dust and gas
spinning causes gravitational attraction, eventually forming sun and planets from accretion of materials

16. Origin of the Earth Inner Planets Outer Planets
heavier elements with high melting and boiling temps.
Earth Composition - iron (Fe), nickel (Ni), magnesium (Mg), silicates (SiO4) water (H2O)
Outer Planets
Jupiter, Saturn, Uranus, Neptune mainly composed of hydrogen (H), methane (CH4) ammonia (NH4) ices

18. Earth and Oceans - 4.5 bya Late in the accretion phase
decay of radioactive elements generates heat
as molten earth cooled, gravity pulled most of the Fe into form the planet’s core
lighter elements, (Si, Mg, Al and O2 formed less dense compounds and moved to the surface

19. How Old is the Earth? Archbishop Usher of Ireland
Earth created at 9:00 AM on October 26, 4004 BC
1800’s - physicists and geologists realize the earth must be very old
Lord Kelvin estimated the age of the earth as only a few million years old, based on how fast it cooled down
reliable age data became available with the development of radiometric dating, using the decay rate of radioactive isotopes to date rocks

20. Earth is an active planet and its original surface rocks no longer exist
oldest rocks have been dated to 3.8 bya
moon rocks have been dated to 4.2 bya
meteorites that have struck the earth have been dated bya

21. Sources of H2O
1. Outgassing
water vapor released from the earth’s mantle by vulcanism
as earth cooled, clouds formed and most of the water vapor released from the mantle condensed and fell as rain, accumulating in depressions on the earth’s irregular surface
mantle must have lost some of it’s mass as water to produce the oceans
2. Comets
mostly small ice comets colliding with the earth to produce water
By 4 bya, that earth’s surface had cooled enough for water to exist primarily as a liquid

22. Earth’s Atmosphere 4.5 - 3.5 bya
primary atmospheric gases were methane, ammonia, carbon dioxide and water vapor
carbon dioxide reacts with water to form carbonic acid (CO2 + H2O ----> H2CO3)
dissolves rocks, releasing chemical nutrients essential to the evolution of life.

23. Origin of Life - 3.5 bya Definition of Life complex organization
exchanges energy and material with external environment
self-replicating
evolves

24. Water is an ideal medium for the physical-chemical reactions that are necessary for life.
retains heat (high heat content)
moderates temperature
ideal solvent - dissolves many chemicals
transports nutrients

25. Evolution of Life Is life unique to Earth?
Earth’s original atmosphere contained a mixture of water vapor, ammonia, methane and hydrogen
Possible energy sources were electrical discharge, ultraviolet light, geothermal and hydrothermal heat (volcanoes)

26. How Did Life Evolve? Surface pools - biosynthesis
evaporation of water in shallow pools may have concentrated organic building blocks
energy supplied by sunlight
Deep ocean
energy supplied by hydrothermal vents
Extraterrestrial?
life on Earth seeded from somewhere else in the universe

27. How Did Life Evolve? Oldest known fossil organisms
anaerobic bacteria (3.5 bya)
live in oxygen free environment
Evolution of photosynthesis changed Earth’s atmosphere
cyanobacteria formed stromatolites (2.8bya)
produced oxygen as a byproduct of photosynthesis
6H2O + 6CO2 + sunlight -----> C6H12O6 +6O2

28. How Did Life Evolve? Oldest known fossil organisms
anaerobic bacteria (3.5 bya)
live in oxygen free environment
Evolution of photosynthesis changed Earth’s atmosphere
cyanobacteria formed stromatolites (2.8bya)
produced oxygen as a byproduct of photosynthesis
6H2O + 6CO2 + sunlight -----> C6H12O6 +6O2