OS101--Marine Environment --
Winter 2007
BEGINNINGS OF THE UNIVERSE, EARTH, AND LIFE
Sverdrup Chapter 2
I.
The Universe and Solar System
A. Dimensions
- The universe has about 1020 stars
- The Milky Way is one of many galaxies in the universe
a. Composed of about 100 billion stars
b. Approximately 100,000 light years across
- The Earth is one of 8 planets in the solar system
- We’re in one of the arms of the Milky Way
Distances are so large when we look at space, that we have to use units that are almost
incomprehensible to humans.
Astronomical Unit: The distance from Earth to Sol, our sun
Light Year: The distance light travels in one year in a vacuum
- Light travels at 2.99792 x 108 m/s
One AU is about 1.45 x 10-5 light years, or about 7.5 light minutes…so, it takes 7.5
minutes for sunlight to reach Earth. Now think about how far everything else is!
-
We know that the universe is still expanding, because other
galaxies appear to be moving away from us
Therefore, we’re still riding the wave from the Big Bang, and
things are getting further apart.
B. The Solar System
- The sun formed about 5 billion years ago
- Proto-earth formed about 4.8 billion years ago
a. It was 1000x bigger, and 500x heavier than today
b. An object about the size of Mars hit Earth, and left
behind the solid metal core…the lighter rock formed the
moon
- The inner planets heated up enough to strip away their
atmospheres—these were trapped by the outer planets, Jupiter,
Saturn, Uranus, Neptune
II.
Earth’s Composition
A. - Earth was close enough to the sun to stay hot, but far enough away
to keep its atmosphere
- This heat allowed the separation of elements by mass:
a. Core—solid metal center (Fe, Ni)
b. Mantle—liquid magma (Fe, Si, Mg)
OS101--Marine Environment --
Winter 2005
c. Crust—thin outer layer, aluminosilicates
B. Crustal Rocks divided into three categories:
- Igneous Rock
a. Basalts, form the oceanic basins (cooled very fast)
b. Granites, lighter, forms the continents (cooled slowly)
- Sedimentary Rock
a. Clastics: weathered inorganic sediments, classified by
size of the particles:
i. Conglomerates (boulder-gravel sized)
ii. Sandstones (.062-2.0 mm)
iii. Siltstones (.004-.062 mm)
iv. Shales (<.004 mm)
b. Carbonates: formed from marine organisms
- Metamorphic Rock
a. Formed from igneous and sedimentary rock
b. Need high heat and pressure—forms under mountains
III.
Relative vs. Absolute Dating
• In the 19th century, scientists realized rock layers indicated age—the deeper the
older the rock was.
• If you know there are characteristic fossils in a certain type of rock, you can
date the layer—but it only tells you that it’s younger or older than other layers
• Marie and Pierre Curie discovered radioactivity…allows very exact dating of
rocks based on the presence of radio-isotopes
• We use different radio-isotopes for different methods. Some are very longlived (e.g. U238) while others are quite short (e.g. N13). We can use this to our
advantage. For example, if you wanted
IV.
Geological History
• About 4.5 billion years ago, the earth’s crust formed
• Very little atmosphere, but lots of volcanic out-gassing was occurring—the
atmosphere was mildly reducing, and had no oxygen
• Until about 3.9 billion years ago, the earth was bombarded by meteorites
• About 4 billion years ago, condensation of water vapor formed the oceans
A. Volcanoes could provide enough water over 4 billion years 100 times
over, and there’s still plenty assuming 99% recycling of the water
B. Louis Frank has hypothesized that much of the water actually comes
from “ice balls” that are constantly hitting the earth
• The presence of an atmosphere warms the earth from about –21°C to +14°C
Salts
• The salts in the ocean must have come from crustal rocks
• Mass balance suggests that the less-volatile elements (Na, Ca, K, Si, Mg, Fe)
came from weathering of the rocks
OS101--Marine Environment --
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V.
Winter 2005
Concentrations of reactive elements (Cl, S, CO2, N) must come from
volcanoes, because there’s more than could come from weathering alone
Origins of Life
• Life began about 3.85 billion yrs ago.
• The first organisms were probably "heterotrophic."
• Heterotrophs are organisms that depend on an external food supply,
• For example, they breakdown organic molecules to obtain energy
• Modern analogs are the Archea: methanogens. break down sugars to form
methane
• Autotrophic Organisms
• can produce their own food, produce complex organic molecules from
simple inorganic raw material; however this requires an energy source
• chemosynthesizers (=chemoautotrophic) (using chemical energy)
• photosynthesizers (=photoautotrophic) (using light energy harvested by
chlorophyll)
• 3.5 billion year old fossils are simple algae (blue-green algae or cyanobacteria)
• cyanobacteria evolved to exploit the changing environment (aerobic
respiration)
• Modern photosynthesis evolved through the exploitation of various
mechanisms taken from other organisms…this was described as the
Endosymbiosis Hypothesis by Lynn Margulis in 1974
- Endosymbiosis means the primitive cell incorporated some
aspect of the engulfed (eaten) cell, and over evolutionary
periods, incorporated it into its own reproductive cycle
- Examples include mitochondria, Photosystem I, Photosystem II
(which were incorporated from various types of bacterial cells)