Transcript Day1-AM2-Earths Interior (Goswami)

Earth’s Interior
ARGHYA GOSWAMI (RAJ), POSTDOC
[email protected]
Is Earth a Sphere?
• The Earth is only approximately spherical, so no
single value serves as its natural radius.
• Distances from points on the surface to the
center range from 6,353 km to 6,384 km (3,947–
3,968 miles).
• The average distance from Earth's center to its
surface, about 6,371 kilometers (3,959 miles).
Earth’s internal structure
(Based on Physical Propeties)
• Atmosphere
• A layer of gases, retained by Earth's gravity
• Has a mass of about 5.15×1018 kg, three
quarters of which is within about 11 km
(6.8 miles).
• The Kármán line, at 100 km (62 miles), or
1.57% of Earth's radius, is often used as the
border between the atmosphere and outer
space.
• Hydrosphere
• Discontinuous layer of water at or near the
Earth’s surface
• Includes all liquid and frozen surface
waters, groundwater held in soil and rock,
and atmospheric water vapor.
• It holds about 1.4 billion cubic kilometers
(326 million cubic miles) of water (mass is
about 1.4 × 1018 tonnes, which is about
0.023% of the Earth's total mass)
• Geosphere
• The geosphere is considered the portion of
the Earth system that includes the Earth's
interior, rocks and minerals, landforms
Earth Science (12th Edition)
Tarbuck, Lutgens, Tasa
What is Earth’s Interior Like?
Earth scientists study the bending/refraction and
reflection of seismic waves (P and S waves) to
understand Earth's interior.
Earth Science (12th Edition)
Tarbuck, Lutgens, Tasa
The Changing Earth (6th Edition)
by Monroe & Wicander
Views of Earth’s
layered structure
Earth Science (12th Edition)
Tarbuck, Lutgens, Tasa
Earth’s internal structure
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Inner Core
• Sphere with a radius of 1,216 km (754 miles)
• Behaves like a solid.
• Temperature of surface of the Sun (5700 K
or 5430C), pressure is 330 to 360
gigapascals (3,300,000 to 3,600,000 atm)
• Composed of an iron–nickel alloy, average
density of nearly 12.8 ~ 13.1 g/cm3
Outer Core
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Earth Science (12th Edition)
Tarbuck, Lutgens, Tasa
Below mantle, liquid layer
A sphere having a radius of 3,486 km (2,161
miles), 2,270 km (1,410 miles) thick
Composed of an iron–nickel alloy, average density
of nearly 11 g/cm3
Convective flow of metallic iron within generates
Earth’s magnetic field
Temperature ranges from 4,300 K (4,030C;
7,280°F) in the outer regions to 6,000 K
(5,730°C; 10,340°F)
Earth’s internal structure
• Mantle
• Below crust to a depth of 2,900 kilometers
(1,800 miles)
• Composition of the uppermost mantle is
the igneous rock peridotite (changes at
greater depths)
• Temperatures range between 500 ~
900°C (932 to 1,652 °F) at the upper
boundary with the crust; to over 4,000 °C
(7,230 °F) at the boundary with the core.
• Crust
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•
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Thin, rocky outer layer
Varies in thickness
Roughly 7 km (5 miles) in oceanic regions
Continental crust averages 35–40 km (25
miles)
• Exceeds 70 km (40 miles) in some
mountainous regions
Earth Science (12th Edition)
Tarbuck, Lutgens, Tasa
Earth’s internal structure
• Continental crust
• crust composed of felsic granitic rocks ,
rich in silica and aluminum (also called
SiAl)
• Upper crust is more granitic
• Lower crust is more akin to basalt
• Average density is about 2.7 g/cm3
• Up to 4 billion years old
• Oceanic Crust
• Composed of mafic rocks (basaltic
composition) rich in silica and
magnesium (also called SiMa)
• Density about 3.0 g/cm3
• Younger (180 million years or less) than
the continental crust
Earth Science (12th Edition)
Tarbuck, Lutgens, Tasa
Earth’s internal structure
(Based on Physical Propeties)
• Lithosphere
• Crust and uppermost mantle
(about 100 km thick)
• Cool, rigid, solid (Plate)
• Asthenosphere
• Beneath the lithosphere
• Upper mantle
• To a depth of about 660
kilometers
• Soft, weak layer that is easily
deformed
• Mesosphere (or lower mantle)
• 660–2,900 km
• More rigid layer
• Rocks are very hot and capable
Earth Science (12th Edition) of gradual flow
Tarbuck, Lutgens, Tasa
Earth’s internal
structure
o Boundaries between
the layers are called
discontinuities.
 Mohorovičić
discontinuity (Moho)
 between crust and
mantle
 Gutenberg
discontinuity
 between mantle and
core
Earth Through Time (9th Edition)
Harold Levin