• 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/ess05.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:  

• 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. 

• 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 energy-3.Radioactive decay-An instance of such disintegration4.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.5. Solar energy-The energy transmitted from the Sun.

• https://mrdawson.wikispaces.com/ESS1.1

• Energy resources: forms of energy used on earth…good video and questions at http://www.teachersdomain.org/resource/phy03.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.