Transcript Planet Earth

Topic
Earth as a System
1A
Planet Earth
The Composition and Layers of
the Physical Earth.
Earth Science Review Book - Chapter 1
Holt Text – Chapter 2
Chapter Objectives:
The Earth as a system.
How large is the Earth?
What is the Earth’s shape? Evidences…
The spheres of the Earth and their
compositions.
Atmosphere
Hydrosphere
Geosphere
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Earth as a System
Earth is a dynamic body with many separate
but highly interacting parts or spheres
Earth as a system
Consists of a nearly endless array of subsystems
(e.g. hydrologic cycle, carbon cycle)
Sources of energy
• Sun - drives external processes
– Weather and climate, Ocean circulation &
Erosional processes
• Earth's interior – nuclear, chemical & thermal
energy drives internal processes
– Volcanoes, Earthquakes & Mountain building
Humans are part of the Earth system
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Earth’s Size
Earth’s circumference - distance around the
earth was first measured by Eratosthenes
2000 years ago.
Measured distance between Egyptian cities of
Alexandria and Syrene.
Measured sun’s angle at noon at each location.
Difference in angle is a fraction of a circle.
Multiply distance by fraction to get
circumference.
Obtained 46,250 km, very close to the real
40,000 km circumference!
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Eratosthenes Method
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Earth’s Numbers
Polar
Diameter
12,714km
Polar
Circumference
40,007km
Equatorial
12,756km
Equatorial
40,074km
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The Earth’s Shape
The shape of the Earth is usually
Sphere
thought of as a _______________.
From observations & measurements
by earth scientists we know that the Earth is
slightly flattened at the poles and slightly
bulging at the equator. Thus the shape is
Oblate
Spheroid
called a(n) _____________
_____________
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Earth’s Shape – Due to the Earth is
spinning on its axis so it slightly bulges at the
equator and flattens at the poles.
Earth Looks Spherical from Space
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Evidence of Nearly Spherical Shape
1. As we now know that the Earth is not
flat as was once believed. Columbus
2. Another evidence is Star paths
through the sky.
One of the best known stars is the North
Star (POLARIS)
We can observe many stars traveling in a
circular or curved pattern over time
around Polaris.
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Star Trails (Time Lapse Photography)
Photograph by Josh Walawender: http://www.ifa.hawaii.edu/~joshw/Astrophotos/2006_06_30/KeckLGS_Trails.html
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Other Evidences…
3. Ship masts appear 1st on horizon.
4. The angle of the North Star changes
when you move north or south. This
could only happen on a spherical
surface.
5. Earth’s shadow is curved when seen
during a lunar eclipse.
6. Astronauts have photographed the
earth from space.
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Spheres of the Earth
Geosphere: Consists of all the rock and
fluid inner layers of the Earth.
Hydrosphere: Consists of all the water
on Earth’s surface; oceans, rivers,
lakes streams etc. Covers ~71% of
surface.
Atmosphere: Consists of the shell of
gases that surrounds the Earth.
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Spheres of Earth
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Average Chemical Compositions
ESRT - Front Cover
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Percent Composition of the
Atmosphere
Our atmosphere
is mostly
nitrogen (78%)
followed by
Oxygen (21%);
CO2 makes up
less than 1%
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Atmosphere Layers
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Properties of the Atmosphere
ESRT - Page 14
Thermosphere
Mesosphere
Stratosphere
OZONE
Troposphere
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OZONE DEPLETION
The ozone absorbs harmful UV rays
from the Sun.
Depletion caused by CFC’s
(ChloroFluoroCarbons) found in
aerosols, Styrofoam and refrigerants.
Problem from ozone depletion is
increased skin cancer in humans and
animals.
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Ozone Depletion
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Atmospheric Phenomena
Aurora Borealis in Ionosphere over Canada
Sun Rays
Light
IONS
Ionosphere
Photograph of Northern Lights from Space - NASA
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Northern Lights
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Hydrosphere
All the water on the Earth
= ~71% of Surface.
Freshwater [2%] –
Rivers, Lakes, streams, &
marshland.
Marine [97%] – Saltwater
Oceans
Ice [1%] – Continental
and Mountain glaciers
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The Structure of Earth’s Geosphere
Page 28 in Text
Moho
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Compositional Zones
Crust- The thin solid outer most zoneContinental & Oceanic crust 1% of
Earth’s mass. Lower boundary is the
MOHO.
Mantle- Below the crust; denser than
crust and 66% of Earth’s Mass.
Core- Composed mainly of Iron and
Nickel. Outer core is a dense liquid,
Inner Core is dense solid. 33% of
Mass.
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Structural Zones
The three compositional zones are
divided into five structural zones.
Lithosphere- Crust and cool brittle upper
mantle. 15-300 km thick
Asthenosphere- Less rigid layer with the
ability to flow due to enormous heat and
pressure. (plasticity) 200-250 km thick
Stiffer Mantle- Layer of solid mantle rock.
Outer Core- dense liquid mostly iron
Inner Core - dense solid of iron and nickel
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Density
Increases
ESRT – Page 10
1. What happens to density
from the crust towards the
inner core?
2. What happens to pressure
as you go towards the core?
3. What happens to
temperature as you go
towards the core?
Pressure
Increases
Temperature
Increases
4. Which layers are Liquids
(Above the melting point?)
5. What is the depth of the
boundary between the
Mantle & Outer Core?
Depth
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How do We know?
From Seismic Waves.
Scientists studying earthquakes have found
that seismic waves travel through the
Earth’s interior at different speeds and
directions. The differing speeds are due to
different densities of the existing zones or
layers.
These Seismic waves are called P and S
waves.
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Seismic Waves
The Seismic Waves
change speed and
direction as they
pass through layers
of different
densities.
Notice the S-waves
do not travel
through the liquid
outer core.
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