The Earth is: The third planet in our Solar System; A
terrestrial planet; Composed of a rocky planet with a gaseous
atmosphere
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The study of the Earth is called Earth Science. Earth Science
contains many disciplines including: a. atmospheric sciences b.
geology (both physical & historical) c. hydrology d.
oceanography e. meteorology & climatology f. astronomy
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The Earth was formed at the same time as the other planets in
our Solar System. The theory as to the formation of our planet is
called the Nebular Hypothesis. This hypothesis says that our solar
system evolved from an enormous rotating cloud called the solar
nebula.
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The nebula was composed mostly of hydrogen and helium. About 5
billion years ago, the nebula began to contract. It assumed a flat,
disk shape with the protosun (pre-Sun) at the center.
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Next, the inner planets (terrestrial) begin to form from
metallic and rocky clumps. Then, the larger outer (Jovian) planets
began forming from fragments with a high percentage of ices.
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A C D E B
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But. how was the Earth (specifically formed!?!?!?!?!
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As Earth formed, the decay of radioactive elements and heat
from high-velocity impacts caused the temperature of the Earth to
increase. Denser materials coalesced or became concentrated toward
the interior or core. Lighter rocky components floated
outward..toward the Earths surface.
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Next, gaseous material escaped from Earths interior (through
volcanoes) to produce the primitive atmosphere. The primitive
atmosphere was made of methane, ammonia and carbon dioxide. There
was NO free oxygen (O 2 ) because it is too reactive.
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The Earth is composed of many different spheres. The different
spheres describe different parts of our Earth.
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The Earths Spheres!!!!
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The hydrosphere contains: All the water on the planet including
the liquid water (oceans, lakes, rivers), the groundwater, the
glaciers and ice caps, and the water found in the atmosphere.
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The glaciers and the ice-caps are also called the
cryosphere.
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The oceans are the largest part of the hydrosphere! They make
up 71% of the Earths surface. 97% of the hydrosphere is found in
the oceans. The oceans are marine or salt water.
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The atmosphere is the thin gaseous layer that surrounds our
planet. It is comprised of 78% Nitrogen (N 2 ), 21% oxygen (O 2 ),
0-4% H 2 O v, 1% argon (Ar), and.038% carbon dioxide (CO 2 )
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The gases are held close to the Earths surface by gravity! The
atmosphere is divided into layers: troposphere, stratosphere,
mesosphere, thermosphere and then the exosphere.
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The geosphere is part of the Earths major spheres. The
geosphere is made of the Earths interior, rocks/minerals, and
landforms such as mountains.
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The geosphere is made of four parts: Crust (two types: oceanic
and continental) Mantle Outer Core Inner Core
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The biosphere is the area on Earth where life can possibly be
found. It covers the upper geosphere, the hydrosphere, and the
lower atmosphere.
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Lets explore the Solid Earths layers in more detail!
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The inner core is the innermost layer of the Earth. The inner
core is made of iron (80%) and nickel. It is extremely hot about 5
000 C.
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Even though the inner core is SO hot, it is a solid. Why is it
a solid?
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The inner core extends from 6,360 km (the center of the earth)
to 5,150 km (the bottom boundary of the outer core).
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The inner core is the densest part of the Earth. The density is
15 g/cm 3
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The existence of an inner core that is distinct from the liquid
outer core was discovered in 1936 by seismologist Inge Lehmann
using observations of earthquake-generated seismic waves that
partly reflect from its boundary and can be detected by sensitive
seismographs on the Earth's surface. outer coreInge Lehmannseismic
wavesseismographs
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Outer Core!
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The outer core is the next layer of the Earth. The outer core
mainly consists of iron and nickel and about 10% sulphur and
oxygen.
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The temperature in the outer core is about 4 500C. Because of
this high temperature, the outer core is molten or liquid.
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The density of the outer core is 11g/cm.
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The outer core extends from 5,150 km (the boundary with the
inner core) to 2, 890 km (the boundary with the mantle) below the
earth's surface.
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The liquid outer core spins (because of convection & the
Earths rotation). The inner core does not spin because it is a
solid. So the outer core spins around the inner core.
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This spinning causes the earth's magnetic field. Magnetism has
been used by sailors to navigate the seas for thousands of years.
Magnetism also influences electro- particles outside the atmosphere
of the earth (>37,000 miles into space).
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The Mantle!
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The mantle is the largest part of the earths structure. It
makes up 80% of the mass and 70% of the volume of the Earth!
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The mantle extends from 2, 890 km to ~65 km. The density of the
mantle ranges from 5 g/cm 3 (lower mantle) to 4 g/cm 3 (upper
mantle)
The temperature of the mantle ranges from 3000 C near the outer
core to about 750 C near the crust boundary. Pressure keeps the
lower mantle solid.
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The mantle is mostly solid (because of high pressure) but
contains a liquid portion called the asthenosphere. The liquid
portion (asthenosphere) is found in the upper mantle. This material
moves by convection and is what causes plate tectonic movement and
earthquakes!
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The region above the asthenosphere (upper mantle) and the
entire crust are collectively called the lithosphere. This layer is
solid and floats on the asthenosphere.
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The Crust!
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There are two types of crust: oceanic and continental.
Continental crust is what makes up the continents, is thicker and
less dense (2.7 g/cm 3 ). Oceanic crust is what makes up the ocean
depressions, is thinner, and more dense (3.0 g/cm 3 ).
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The crust is very thin: only 1% of the volume of the entire
earth! It extends from the surface to around 65km deep.
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The crust is made of igneous, sedimentary and metamorphic rock.
Most of these rocks are made of silicates. OxidePercent SiO 2 60.6
Al 2 O 3 15.9 CaO6.4 MgO4.7 Na 2 O3.1 Fe as FeO6.7 K2OK2O1.8 TiO 2
0.7 P2O5P2O5 0.1
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The crust is not one solid piece of rock. It is broken up into
pieces called plates. The plates are made of the crust plus the
upper mantle (lithosphere). These plates float on the asthenosphere
and move.
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The temperature of the crust increases with depth, reaching
values typically in the range from about 10C (50F) to 300C at the
boundary with the underlying mantle.
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The deepest hole ever dug is the Kola Superdeep Borehole, dug
by the former USSR. The hole, SG-3, reached 12,261 metres (40,230
ft) in 1989, and remains the deepest hole ever drilled.