Transcript The Origin of the Earth

The Origin of the Earth
Explanations About the Earth’s
Origins
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Throughout history there has been numerous
ideas, theories, legends, and explanations
about the origins of the Earth
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As time and technology advances we are
becoming more knowledgeable about our
Earth and its origins.
Meteorites: Key to Earth’s Age
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A not very obvious, but very important source
of information about the Earth is meteoritesespecially Chondrite meteorites
Chondrite Meteorites: Key to
Earth’s Age
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Most meteorites that are recovered on Earth are chondrites:
~86% of witnessed falls are chondrites
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Formed when various types of dust and small grains that were
present in the early solar system accreted to form primitive
asteroids.
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Chondrites are the enigmatic chondrules, millimeter-sized
objects that originated as freely floating, molten or partially
molten droplets in space
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Chondrites also contain refractory inclusions which are among
the oldest objects to form in the solar system
Chondrite Meteorites: Key to
Earth’s Age
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Analyses of these granules reveal they contain
water and other volatile elements that have
turned into gases at relatively low temps.
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This tells us that meteorites have not melted since
their formation
Measuring meteorites for radioactive decay
indicates that they formed up to 4.6 billion years
ago- the date of the Earth’s beginning
The Formation of the Earth
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These new data reveal that the early histories
of the inner planets in the solar system are
complex and involve processes no longer
observed. Evidence of these processes has
been preserved in Mars, while it has been
erased in Earth. So Mars is probably the best
opportunity to understand how Earth formed.
Earth Gains Mass and Loses
Atmosphere
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Earth is formed through accretion of dust and
gases
After solar wind swept away the remaining
interplanetary dust and gases, accretion
continued as meteorites and other matter
collided with the earth adding to its mass
Earth Gains Mass and Loses
Atmosphere
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As the Earth grew in size its gravitational
attraction increased
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This pulled in even more meteorites
It is thought that the Earth approached its current
size with in a few million years of the collapse of
the nebula (big bang)
Differentiation: Forming an Iron
Core
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Figure 2.10 in your text book shows the series of
events that led to the major changes in the Earth after
ignition of solar furnaces
The melting interior is a result from the accumulated
heat of gravitational energy
Once the interior melted the heavier elements of iron
and nickel were attracted inward to form our dense
core.
The lighter compounds such as magnesium and
silicon moved outward to create a crust
Differentiation: Forming an Iron
Core
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Differentiation of this type, which lead to the
layers within the Earth’s interior, could only
occur in a liquid or semi-liquid.
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Differentiation Examples (driving forces)
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Oil and water
Candle in the wind
Mercury and water
Mentos and Cola
What is the Center of the Earth?
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One of the most distinctive features of the earth's
interior is how it seems to be layered by density, with
the heaviest stuff in the center, and the lightest
material at the surface.
In fact, the earth probably looks a lot like a hard
boiled egg if you could cut it open.
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The yellow stuff in the center (the yolk) relates to what we
call the core.
The egg's shell is like the earth's crust - a thin veneer of
rigid, low density material at the surface.
The white stuff in between is like the earth's mantle - the
largest layer which, in the case of the earth, is of medium
density
Second Atmosphere
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A second major event in the Earth’s history
was the formation of a new atmosphere
replacing the early one, which had been
removed by solar wind that accompanied the
ignition of the sun’s furnace.
The gases made up this new atmosphere cam
from the melting of the rocks in the Earth’s
Mantle and Crust.
Second Atmosphere
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The volcanic eruptions released volatile elements and
compounds including: methane, water vapor,
ammonia, sulphur dioxide, hydrogen, and carbon
dioxide.
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By this time the Earth’s crust cooled enough to become
solid and temperatures were between freezing and boiling
water
The water vapors in the early atmosphere converted to
liquid and fell like rain- the water collected to create the
unique features of our oceans
The Arrival of Life
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After the various process stated previously
Earth was in a condition to sustain life
The earliest signs of life on Earth are in rocks
3.5-3.8 billion years ago
The Arrival of Life
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Early life forms had to adapt to life with no
oxygen (or little if any was present)
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Oceans provided the most favorable conditions to
live
According the evolutionary theory, species
appeared that used the process of photosynthesis to
create food from sunlight, carbon dioxide and
other minerals.
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These species are responsible for creating the third
major change of the earth: an atmosphere with
significant amount of oxygen
Critical Thinking
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Scientists from NASA's Johnson Space Center (JSC)
and the Lunar and Planetary Institute and the
University of California, Davis (UCD) has found that
terrestrial planets such as the Earth and Mars may
have remained molten in their early histories for tens
of millions of years. The findings indicate that the
two planets cooled slower than scientists thought and
a mechanism to keep the planet interiors warm is
required.
Critical Thinking
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What ideas/tools/technologies could we
implement to ensure that the interior of our
planet stays warm?
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What effects does a cooling planet have on
Earth (land formations, water, etc) and its
inhabitants?
Homework/Further Explorations
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Complete Questions 14a, 14b, 15a, 15b, and
16 on page 33 in your textbook.
Please use complete sentences when answering
the questions
Questions are due for tomorrow, and will be
discussed at that time