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The Science of the Ocean

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Earth is a water planet (possibly one of a few in the galaxy) ... spinning causes gravitational attraction, eventually forming sun and planets ... – PowerPoint PPT presentation

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Title: The Science of the Ocean


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 Earths 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 Earths 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 Earths radius
  • Accounts for only slightly more than 0.02 of the
    Earths mass (0.13 of Earths volume)

6
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7
The World Ocean
  • On A Human Scale
  • the ocean covers 361,000,000 km2 (139 million
    square miles) of the Earths 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 3.796 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, (1.51)
  • the Southern Hemisphere is 80.9 ocean, 19.1
    land (41)

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14
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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
  • 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

17
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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 planets 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 900 AM on October 26, 4004 BC
  • 1800s - 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 4.5 - 4.6 bya

21
Sources of H2O
  • 1. Outgassing
  • water vapor released from the earths 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 earths irregular surface
  • mantle must have lost some of its mass as water
    to produce the oceans
  • 2. Comets
  • mostly small ice comets colliding with the earth
    to produce water

By 4 bya, that earths surface had cooled enough
for water to exist primarily as a liquid
22
Earths 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 ----gt 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?
  • Earths 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 Earths
    atmosphere
  • cyanobacteria formed stromatolites (2.8bya)
  • produced oxygen as a byproduct of photosynthesis
  • 6H2O 6CO2 sunlight -----gt 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 Earths
    atmosphere
  • cyanobacteria formed stromatolites (2.8bya)
  • produced oxygen as a byproduct of photosynthesis
  • 6H2O 6CO2 sunlight -----gt C6H12O6 6O2

29
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