Transcript Energy in the Earth System - HCIPS

• Floating through space…what makes a
planet “alive”….why do some of the things
in space look “dead”?
• Sun (stars) shines on many of these “dead”
things.
Why is the Earth “alive”?
• Where does the energy of our planet come
from?
Why is the Earth’s inner core so
hot?
• Show this video as attention getter:
http://www.teachersdomain.org/resource/ess
05.sci.ess.earthsys.hologlobe/ (not great)
Energy in the Earth System
Internal Sources (1%)
And
External Source (99%)
Heat
Internal Sources
The Earth's major source of internal
energy is radioactive decay, and
gravitational contraction of the
Earth's interior.
• Earth
– has internal and external sources of energy that
create heat.
– The sun is the major external source of energy.
– 2 sources of internal energy are the decay of
radioactive isotopes and the gravitational
energy from the earth's original formation.
• The outward transfer of earth's internal heat drives
convection circulation in the mantle that propels
the plates comprising earth's surface across the
face of the globe.
• Heating of earth's surface and atmosphere by the
sun drives convection within the atmosphere and
• oceans, producing winds and ocean currents.
• Global climate is determined by energy transfer
from the sun at and near the earth's surface. This
energy transfer is influenced by dynamic
processes such as cloud cover and the earth's
rotation, and static conditions such as the position
of mountain ranges and oceans.
•
Internal Energy - is generated within or because of the Earth. It only amounts to about 0.013% of the
total energy reaching the Earth's surface, but is responsible for deformational events that build mountains
and cause earthquakes, for melting in the Earth to create magmas that result in volcanism. Two source of
internal energy are:
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Radioactive Decay
Some elements like Uranium, Thorium, and Potassium have unstable isotopes that we say are
radioactive.
When a radioactive isotope decays to a more stable isotope, subatomic particles like protons, neutrons,
and electrons are expelled from the radioactive parent atom and are slowed and absorbed by surrounding
matter.
The energy of motion (kinetic energy) of these particles is converted to heat by the collision of these
particles with the surrounding matter.
Although radioactive isotopes like 235U (Uranium), 232U, 232Th (Thorium), and 40K (potassium) are
not very abundant in the Earth, They are sufficiently plentiful that large amounts of heat are generated in
the Earth.
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Conversion of Gravitational Energy
Gravity is the force of attraction between two bodies.
The force of gravity acts between the Sun, Earth, and Moon to create tidal forces, which cause the Earth
to bulge in the direction of the Moon. This bulging is kinetic energy, which is converted to heat in the
Earth.
• Gravity has other energy effects near the surface of the Earth. All objects at the Earth's surface are
continually being pulled toward the center of the Earth by the force of gravity.
• When an object moves closer to the center of the Earth by falling, slipping, sliding, or sinking, kinetic
energy is released.
Some of the heat flowing out of the Earth is heat that has been produced by gravitational compaction
of the Earth which has caused matter to move closer to Earth's center.
Internal Sources of Energy
• The earth's interior would have cooled off
by now if there weren't some source of
energy which happens to be radioactive
decay of elements such as uranium.
Internal Sources of Energy
• Gravitational contraction also contributes to the
interior source of energy.
• The accretionary process led to an increasingly
greater gravitational attraction, forcing the Earth
to contract into a smaller volume so this increased
compaction caused the conversion of gravitational
energy into heat energy which heats the earths
interior.
• Internal Sources of Energy
• •
When Earth formed about 4.6 billion years ago, its
interior was heated by radioactive decay and gravitational
contraction.
• •
The decay of radioactive atoms still generates
enough heat to keep Earth’s interior hot. Earth’ interior
also retains much of the energy from the planet’s
formation.
• •
By the process of convection, the heat in Earth’s
interior is transferred through the layers of Earth and is
released at Earth’s surface.
• 1. Model the fission of unstable elements
• 2. Describe how gravitational energy from
the earth's origin supplies a source of energy
• 3. Model convection currents in a solid and
demonstrate how crustal plate movement
occurs
• There are three main sources of heat in the
deep earth: (1) heat from when the planet
formed and accreted, which has not yet
been lost; (2) frictional heating, caused by
denser core material sinking to the center of
the planet; and (3) heat from the decay of
radioactive elements.
• It takes a rather long time for heat to move out of
the earth. This occurs through both "convective"
transport of heat within the earth's liquid outer
core and solid mantle and slower "conductive"
transport of heat through nonconvecting boundary
layers, such as the earth's plates at the surface. As
a result, much of the planet's primordial heat, from
when the earth first accreted and developed its
core, has been retained.
•
The amount of heat that can arise through simple accretionary processes,
bringing small bodies together to form the proto-earth, is large: on the order of
10,000 kelvins (about 18,000 degrees Farhenheit). The crucial issue is how
much of that energy was deposited into the growing earth and how much was
reradiated into space. Indeed, the currently accepted idea for how the moon
was formed involves the impact or accretion of a Mars-size object with or by
the proto-earth. When two objects of this size collide, large amounts of heat
are generated, of which quite a lot is retained. This single episode could have
largely melted the outermost several thousand kilometers of the planet.
• Additionally, descent of the dense iron-rich
material that makes up the core of the planet to the
center would produce heating on the order of
2,000 kelvins (about 3,000 degrees F). The
magnitude of the third main source of heat-radioactive heating--is uncertain. The precise
abundances of radioactive elements (primarily
potassium, uranium and thorium) are is poorly
known in the deep earth.
• In sum, there was no shortage of heat in the early
earth, and the planet's inability to cool off quickly
results in the continued high temperatures of the
Earth's interior. In effect, not only do the earth's
plates act as a blanket on the interior, but not even
convective heat transport in the solid mantle
provides a particularly efficient mechanism for
heat loss. The planet does lose some heat through
the processes that drive plate tectonics, especially
at mid-ocean ridges. For comparison, smaller
bodies such as Mars and the Moon show little
evidence for recent tectonic activity or volcanism.
• The Earth’s internal energy comes from two sources. The
first is the warming caused by the formation of the planet.
Scientific evidence indicates Earth and the other planets
were formed by accretion (collisions and sticking) of
planetesimals. The kinetic energy of these impacts raised
the planet’s temperature as it formed, so much so, that
early Earth consisted of melted rock and metal. Since that
time, Earth has been slowly cooling as this primordial
internal energy is radiated back to space. The second
source of internal energy is from decay of radioactive
elements present in Earth materials. For example, the
decay of Uranium-238 in the Earth’s crust, mantle, and
core release energy that ultimately warms surrounding
material.
• The Earth’s internal energy drives plate
tectonics, which can results in amazing
effects such as tearing apart continents and
creating new mountain ranges. But plate
tectonics work slowly (i.e., on a geologic
time scale), with average movement of only
a few centimeters per year.
External Sources of Energy
• Solar energy from the sun is also an external
source of energy for the earth.
• Energy from the Sun drives drastic changes to
Earth’s atmosphere—called weather—causing the
precipitation and wind that erodes these mountain
ranges. Additionally, the atmosphere retains
enough of the Sun’s energy to raise the Earth’s
surface temperature by more than 30 degrees
Celsius (60 degrees Fahrenheit). This is called the
greenhouse effect and is a common occurrence on
planet’s with relatively thick atmospheres.
• External Energy Sources
• •
Earth’s most important external energy
source is the sun.
• •
Solar radiation warms Earth’s atmosphere
and surface. This heating causes the movement of
air masses, which generates winds and ocean
currents. Many chemical reactions on Earth also
require solar energy.
• •
Another important external source of energy
is gravitational energy from the moon and sun.
This energy helps generate tides that cause
currents and drive the mixing of ocean water
• 1. Demonstrate through the use of chemical
formulas the release of energy through the
fusion of elements on the Sun
• 2. Model rotation and revolution of the
Earth/Sun system and the effects of these
movements on Earth's seasons
• 3. Demonstrate the effect of solar energy on
Earth's weather patterns and ocean currents
• 4. Demonstrate how the curvature of Earth, the tilt
• of Earth on its axis, and the relative position of
• Earth and Sun impact the amount of solar energy
• absorbed by Earth's surface and the relationship
• to Earth's seasons
• 5. Predict weather conditions and air mass
movements through the use of weather maps
• Solar Energy - reaches the Earth in the form of radiant
energy, and makes up 99.987% of the energy received by
the Earth.
• About 40% is immediately reflected back into space by the
atmosphere and oceans.
• Some is converted to heat and is absorbed by the
atmosphere, hydrosphere, and lithosphere, but even this
eventually escapes into space.
• Some is absorbed by plants during photosynthesis and is
stored in plants, used by other organisms, or is stored in
fossil fuels like coal and petroleum.
• Solar Energy drives the water cycle, causing evaporation
of the oceans and circulation of the atmosphere, which
allows rain to fall on the land and run downhill. Thus solar
energy is responsible for such natural disasters as severe
weather, and floods.
Vocabulary (5 terms)
• 1. Internal energy- The total kinetic and potential
energy associated with the motions and relative
positions of the molecules of an object, excluding
the kinetic or potential energy of the object as a
whole. An increase in internal energy results in a
rise in temperature or a change in phase.
2. External energy3.Radioactive decay-An instance of such
disintegration
4.Gravity- The natural force of attraction between
any two massive bodies, which is directly
proportional to the product of their masses and
inversely proportional to the square of the distance
between them.
• https://mrdawson.wikispaces.com/ESS1.1
• Energy resources: forms of energy used on
earth…good video and questions at
http://www.teachersdomain.org/resource/ph
y03.sci.ess.earthsys.energysource/
• Types of energys:
http://earthsci.org/mineral/mineral.html
Radioactivity
• When Becquerel (1896) accidentally placed
a uranium sample on a photographic plate,
he found the plate to be partially exposed.
This startling discovery led to the discovery
of radioactivity.
• Materials that are radioactive contain atoms whose nuclei split apart,
giving off energy and charged particles. As the nuclei break apart, the
resulting radiation is absorbed by matter to produce heat. In many
cases the radiation is in the form of extremely short-wavelength
gamma radiation, and also there are often particles, alpha (helium
nuclei) or beta (electrons), that can have considerable energies. These
radiations and particles interact with other particles, transferring
energy that ultimately becomes heat in the material that has absorbed
the radiation. This is the form of heat that warms the interior of the
earth. This radioactive decay produces energy, and a more stable
element is formed.
• Although Earth’s average heat from radioactivity and the original
gravitational sources is extremely small on the average compared with
energy from the sun, there are "hot spots" around Earth. (Gravitational
heat is energy released when masses aggregate, converting their
original potential energy due to their separation into heat energy.) The
original gravitational heat, along with the production of heat by
radioactivity in the earth, is still very substantial, so much so that at
depths of 30--50 km, the temperature is more than 500 oC. It is
especially interesting that heat flow decreases with the age of ocean
floors or continental areas. This decrease is connected to fundamental
properties of radioactivityChalf-life and mean lifetime, which allow us
to date these areas.