Mt. Kilimanjaro

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Mt. Kilimanjaro Alexandra Offer
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Mt. Etna Molly Hodson
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So Where do we begin our study of
The Earth ?
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The Creation of the Solar System
Begin with the Big Bang approximately 12
billion years ago. Space expanded rapidly and
then began to contract. As temperatures cooled,
Hydrogen and Helium gases formed. Denser pockets
of gas condensed further due to gravity.
Accumulations became galaxies. Began to rotate to
form disc-shaped clouds. Center collapsed to form
the Sun. As heat increased in the Sun, particles
were blown away as solar wind. Particles
collided and accreted becoming planetesimals.
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So how did we get to here?
As larger and larger particles collided, larger
planetesimals were formed. Some of these
continued to collide and the largest became the
planets, while the smaller ones may have become
moons.
Intense solar radiation heated the closest
planets causing the lighter elements to be
vaporized and blown out into space. This
concentrated the heavier elements like iron and
nickel on the inner planets and the lighter
elements on the outer planets.
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The Earths Earliest History
Beginning of the Earth was extremely
violent. Grew by planetesimal impact. Became very
hot, heated to the melting point of
iron. Innermost rocks began to become compressed,
so more heat. Radiogenic heat was added due to
radioactive fission. Earth underwent
differentiation into layers.
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Early Differentiation of the Earth
What was the Earths early composition? Need to
consider meteorites that have struck the earth to
get an idea of composition. Most are iron and
nickel. Some contain chondrules. Small rocky
bodies within the meteorites that may represent
matter condensing from the original solar
nebula. Earths composition should be similar
to these meteorites. However - Meteorites are 35
iron, while Earths surface rocks only 6 .
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Early Differentiation of the Earth
Where did the iron go? As Earth was still
accreting, temperature rose above melting point
of iron. Iron liquified. Because of higher
density, iron sank into the proto-Earths center
due to gravity. Lighter elements rose to the
surface. Originally, Earth was homogeneous. Due
to heat and melting, Earth materials separated
forming concentric zones of differing
density. Thus, Differentiation.
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Differentiation and the Earths Interior
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Earths Interior
Three Principal Layers Each has different
Composition and density (mass/volume). CRU
ST - Outermost layer Density low
Composition is silicon and oxygen-based minerals
and rocks. Crust is extremely
thin. Consistency is rocky.
Composed of two general types. Continental
crust Oceanic crust
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Earths Interior
MANTLE - Middle thin layer Density
medium Composition is silicon and
oxygen-based but also includes iron
and magnesium. Consistency is plastic.
Contains two parts, Upper and Lower Mantle. CORE
- Inner layer Density high
Composition is primarily iron and nickel.
Contains two parts Inner core is solid. Outer
core is liquid.
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Subdivisions of the Earths Interior
Within these three principal layers are
subdivisions.
Crust consists of OCEANIC CRUST
(brown) CONTINENTAL CRUST (green). Oceanic
crust is thin (8-10 km), dense, and found
below ocean basins (blue). Continental crust is
thicker (20-70 km), has low density and forms the
bulk of continents. The crust rides on the very
upper most portion of the mantle.
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The outermost sublayer is the most active
geologically. Large scale geological processes
occur, including earthquakes, volcanoes, mountain
building and the creation of ocean
basins. Contains parts of the upper mantle and
all of the crust. Called the LITHOSPHERE (rock
layer).
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Lithosphere is a strong layer, but
brittle. Represents the outer approximately 100
km of the Earth. Thicker where continents exist,
thinner under oceans. Below the lithosphere
resides the ASTHENOSPHERE (weak layer).
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Asthenosphere is part of the upper
mantle. Asthenosphere is heat softened and acts
like a plastic. It is weak, slow flowing, yet
solid rock. (Things that make you go,
hmmm.) Generally 100 to 350 km beneath Earths
surface.
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Overlying the lithosphere is the
ATMOSPHERE. Composed of gases released during
volcanic eruptions and from plant respiration.
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Outgassing from volcanoes also helped produce the
water in the Earths ocean basins. Led to the
initial development of the HYDROSPHERE. Together,
the Lithosphere, Atmosphere and
Hydrosphere support the BIOSPHERE.
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Atmosphere of the Earth is a thin and fragile
layer.
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Thermal Energy of the Earth
Heat led to the initial differentiation of the
Earth. Produced core, mantle and crust. Thermal
energy is still being moved from place to place
in the Earth. Goes from warm to cool areas.
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Methods of Thermal Energy Transfer
1. CONDUCTION Small particles (atoms) get
excited by external heat. Vibrate
rapidly. Collide with other particles and sets
them in motion. Not an efficient way to move
heat in the Earth. Rock is a very POOR conductor
of heat.
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Methods of Thermal Energy Transfer
2. CONVECTION Material moves from one place to
another, taking heat with it. When Earth got hot
enough that parts melted or softened enough to
flow, convection occurred. Heat was transferred
by rising fluids. Much better method of
transferring thermal energy. Rising hot material
caused first volcanic eruptions.
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Methods of Thermal Energy Transfer
3. RADIATION Heated objects radiate energy as
well.
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Methods of Thermal Energy Transfer
Convection is the most important mechanism for
geologic processes.
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Rock Types and the Rock Cycle
ROCK - a naturally occurring aggregate of
minerals formed within the Earth.
Basaltic Dike Acadia Natl Park, Maine
Delicate Arch, Arches Natl Park, UT
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Rock Types and the Rock Cycle
A MINERAL is a naturally occurring, inorganic
solid, consisting of either a single element or
compound, with a definite chemical composition
(or varies within fixed limits), and a
systematic internal arrangement of atoms.
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Pyrite FeS2
Diamond C
Beryl Be3Al2(Si6O18)
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Rock Types and the Rock Cycle
Three types of rocks. These are present in the
crust and at the Earths surface. Each have
fundamentally different origin. IGNEOUS SEDIMENT
ARY METAMORPHIC
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Igneous Rocks
- Cooled and solidified from MOLTEN material. -
Formed either at or beneath the Earths
surface. - MELTING of pre-existing rocks required.
Granite
Basaltic Lava
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Sedimentary Rocks
- Pre-existing rocks are weathered and broken
down into fragments that accumulate and are
then compacted or cemented together. - Also
forms from chemical precipitates or organisms.
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Metamorphic Rocks
- Form when pre-existing Earth materials are
subjected to heat, pressure and/or chemical
reactions and change the mineralogy,
chemical composition and/or structure of the
material.
Gneiss
Slate
Coal
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Any rock type can become any other rock type
given time and processes acting on them. These
changes are reflected in the ROCK CYCLE.