Download the layers of the earth - NATSCI-A7

What
is
the
use
of
locating
seismic
discontinuities?
• Locating these disturbances enable scientists to
map the inner regions of the Earth. This science,
known as tomography originates from the
knowledge gained from discontinuities.
• Tomographists have found that this planet is
divided into six regions: the inner core, the
outer core, the lower mantle, the upper
mantle, the transition region, and the
crust (oceanic and continental).
0- 40 Crust
40- 400 Upper mantle
400- 650 Transition region
650-2700 Lower mantle
2700-2890 D'' layer
2890-5150 Outer core
5150-6378 Inner core
• We know that the crust plunges
down to adepth that varies
between 5 to 70 km, making it
the thinnest layer. It is mainly
composed of rocks, which are
subdivided into two groups –
sial and sima.
• The continental crust is mainly
composed of silica and alumina,
hence called sial. On the other
hand, oceanic crust, which is
mainly composed of silica and
magnesium, is called sima.
• is the smallest part of Earth, only 0.099% of its
mass and reaching a small depth of 0-6 miles (010 kilometers). In the beginning of time, it was
possible that this area did not exist for through
frequent volcanic activity does only the crust
form.
• Evidence of this is marked by the oceanic ridge
system, which is a 25,000 mile (40,000-kilometer)
array of many volcanoes which creates layer after
layer of new crust at the rate of 17 km3 per year.
• The ocean floor is covered in basalt originating
from volcanic activity and as a matter of fact,
Iceland and Hawaii are two island systems that
emerged from the accumulated basalt.
• The second smallest area of the Earth is the
Continental crust, making up only 0.374% of the
Earth's mass and extending a short depth of 0 31 miles (0-50 kilometers).
• Looking at the percent by composition, the
continental crust makes up only 0.554% of the
mantle-crust mass.
• The layer is composed primarily of crystalline
rocks made of low-density buoyant minerals
dominated mostly by quartz (SiO2) and feldspars
(metal-poor silicates).
• This is the outer part of the Earth composed
essentially of crystalline rocks.
• The continental crust and the oceanic crust are
also referred to as the lithosphere because of the
cool and rocky conditions that exist in its chemical
composition.
• We know that the mantle reaches
down to a depth of about 2,890 km.
While the crust is the thinnest layer,
the mantle is the thickest.
• The upper mantle is represented by
the asthenosphere, a highly viscous
layer that supports the lithosphere.
Like
the
lithosphere,
the
asthenosphere plays a significant role
in plate tectonics.
• Despite
the
extremely
high
temperatures in the mantle (up to
4,000 degrees Celsius), even higher
than the melting points of the rocks
that constitute it, the very high
pressures there prevent melting from
taking place.
 its
chemical
composition
includes
silicon,
magnesium, and oxygen.
 also contains some iron, calcium, and aluminum.
 is comprised of 72.9% of the antle-crust mass,
making the Earth abundant in the chemical
elements of silicon, magnesium and oxygen, the
layer's primary components.
Through excavations in volcanoes, scientists have found that this part of
the crust composes of 15.3% of the total mantle-crust mass and is made
of crystalline forms of Olivine (Mg,Fe)2SiO4 and pyroxene (Mg,Fe)SiO3.
• The upper mantle makes up 10.3% of the Earth's mass, extending a
depth of 6-250 miles (10-400 kilometers).
• A relatively large portion when compared to the other interior layers.
• This layer is not completely made of solid minerals for scientists
speculate that the asthenosphere could be partly liquid molten.
• The next layer, the Transition region
comprises 7.5% of Earth's mass with a
depth
of
250-406
miles
(400-650
kilometers).
• This layer is also known as the mesosphere
and is 11.1% of the mantle-crust. It is made
of mainly basaltic magmas with amounts of
calcium, aluminum and garnet (an
aluminum-bearing silicate mineral.
• The layer becomes dense when the garnet
mineral cools but is buoyant and light when
subject to heat due to the low melting
points.
At the center of the Earth is
the inner core, a solid
sphere believed to be
made up of an iron-nickel
alloy. That the solid inner
core is distinct from the
liquid outer core was
suggested
by
Inge
Lehmann, a seismologist
who based his theories
on earthquake-generated
seismic waves.
• The inner core is a solid section of the
Earth and is unattached to the mantle,
being suspended by the molten outer
core.
• This solidified state is the result of a very
intense pressure-freezing process that
occurs
in
temperature
increases.
most
liquids
decreases
or
when
pressure
• is mainly composed of melted iron and nickel.
• They are melted because the pressures at these
depths are not sufficient to prevent the much
higher temperatures, which range between 4,400
degrees Celsius to 6,100 degrees Celsius, from
melting the rocks there.
• Convection in the outer core, which move the
liquefied metals about, is believed to be the
source of the magnetic field that encapsulates
the Earth and protects it from cosmic radiation.
• The outer core of Earth is a scorching hot, electrically
conductive liquid in which convection takes place.
• The outer core is in the range of 200 to 300
kilometers (125 to 188 miles) thick and represents
about 4% of the mantle-crust mass.
• This layer is sometimes identified as part of the lower
mantle due to its geographical nature.
• However, studies on seismic discontinuities suggest
that this "D" layer might differ chemically rom the
lower mantle lying above it.
1. http://library.thinkquest.org/28327/html/u
niverse/solar_system/planets/earth/interio
r/layers_of_earth.html
2. http://www.universetoday.com/61856/the
-earths-layers/
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