Chapter 2 Earth as a System

Section 1 Earth: a Unique Planet

Prove to me that the Earth is Round!

Proof

• We do not see the bottom of a boat when it sails away

• We can see pictures from space

Lunar Eclipses

Eratosthenes -Greek astronomer from ~ 2000 years ago determined the

circumference of the round earth. He used two wells, the angle of the sun's shadow and the distance between the two wells to determine the circumference.

Eratosthenes was within 15% of the correct answer. He made two mistakes1. The wells were not dug straight down2. Seine and Alexandria are not directly north and south of each other.

Earth Basics

• The earth is 3rd rock from the sun. She was formed over 4.6 billion years ago. Approximately 71% is covered in water, hence the nickname "The Blue Planet".

• It is not a true sphere. We are called an OBLATE SPHEROID or

better yet, SPHEROIDAL. We have two different measurements for the circumferences.

• Earth's Circumference:Equatorial 40,074 kmsPolar 40,007 kms.

• Earth's Diameter:Equator 12,756 kms (7,972.5 miles)Poles 12,714 kms (7,946.25 miles)

. 3% difference

Earth's InteriorThe Layers of the Earth: Science Reference Tables :OSA:NYSED

Crust - Lithosphere• 1% of Earth's mass• The thickness and depth varies

under oceans 5 to 10 km under continents 15 to 80 km

• All drilling and mining is done in this layer - we have never gone deeper than the crust.

• Made up of lighter rocks and minerals.

• Temperature increases with depth until it reaches approx 1000o C

• Below 70 meters the temperature starts to increase 1o C for every 40 meters of depth. The rate slows down after several kilometers so that the center of the earth is approximately 6000 – 7000o C.

Asthenosphere- This is the thin slush like layer between the crust and mantle

Moho (Mohorovici discontinuity)

Mantle -• Approximately 2/3 mass of the Earth's mass• Approximately 2900 km thick• The temp is between 1500 – 3200 o C • The temp increases with depth• It is a solid with liquid properties• It is made up of heavy metals:• Iron (Fe)• Magnesium (Mg)• Silicon (Si)

Outer Core -• The depth is approximately 3000 – 5000 km• The temp is between 5000 – 6000o C• The temp increases with depth• It is made up of liquid like metals:

Iron (Fe)Nickel (Ni)

Inner Core -• The depth is approx 5000 – 6000 km• The temp is approx 6500o C p• It is made up of solid:

Iron (Fe)Nickel (Ni)

Why does the temperature increase in the crust?

• Compression

• Radioactive decay – Uranium and Potassium gives off heat energy with the crust.

• There may be still some heat left over from the earth’s formation.

• Friction from movement of and in the crust.

Earth as a magnet:

• The magnetic field in the Earth is like having a bar magnetic inside a ball. The positive end is the north (we use a compass to prove this) and the negative end is the South Pole.

• True North which is where North and South Pole are, magnetic north is about 11o different. This becomes evident when you look on maps; you will see two arrows to point to either magnetic north or true north.

• Our magnetic field helps protect us against the harmful solar winds produced by the sun.

Earth's Gravity:

• Weight is the measure of the strength of the pull of gravity on an object. Measured in Newton. Can change depending on where you are.

• Mass is how much stuff is in side of an object. It depends on volume. Does not change depending where you are.

• Where do we weigh more? At the North Pole or the EquatorWhy?

The North Pole – because you are closer to the middle of the earth and gravity has more pull on you. Gravity is the force that holds us together and holds us on the earth. As the earth spins, the gravity pulls us closer to the center of the earth, which is the center of gravity. The difference is about 0.3% less!

Section 2 Energy in the Earth System

• Systems:• A group of objects that interact with

each other to create something whole. The system may seem to work alone, however, most systems are linked to one another. Uses Matter and Energy

• Matter - anything that has mass and takes up space.

• Energy - the ability to do work. Can be heat, light, vibrations, even electromagnetic waves.

There are two types of systems (ok maybe a third that I made up).Open – an Island

An open system is a state of a system, in which a system continuously interacts with its environment. A free transfer of energy or matter.

Closed – a biodomeA closed system is a system in the state of being isolated from the environment. It is often used to refer to a theoretical scenario where perfect closure is an assumption, however in practice no system can be completely closed; there are only varying degrees of closure. A limited exchange of energy and matter.

Quasi - Earth.The exchange or transfer of energy or matter is limited.

Earth's Four SpheresUsing these systems we can learn a great deal. There

are 4 main systems (spheres) that we study.

• Atmosphere- the air surrounding the earth• Hydrosphere- all waters: ocean, rivers, lakes and groundwater• Geosphere – hard surfaces including volcanoes and such• Biosphere – all living things great and small

• http://www.classzone.com/books/earth_science/terc/content/visualizations/es0102/es0102page01.cfm?chapter_no=visualization

Our interactions between all of the “spheres” make us very DYNAMIC. Some of the interactions are small and minor, some are quick and massive while others cover such a large scale that they take so long we don’t notice.

Dynamic – what is it??????

It means ever changing and interacting. Sometimes interactions occur on a one time basis, and some occur on a regular basis. We call these “cycles” or “cyclic”. The ones that make us dynamic are water, carbon, nitrogen and phosphorus and energy.

Even though we are Dynamic, we are also balanced –

matter can neither be created nor destroyed so we maintain a balance called DYNAMIC EQUALIBRIUM. This simply means that for every action, there is an equal reaction. For every mountain that erodes, one is created by volcano. For every rain drop that falls, more is evaporated. And so on.

Earth's Energy Budget• Energy exists in many forms, such as heat, light, chemical energy, and

electrical energy. Energy is the ability to bring about change or to do work. Thermodynamics is the study of energy.

• Two types of Energy• Internal Source:• Geothermal - from inside the earth• Compression• Radioactive decay – Uranium and Potassium gives off heat energy with the

crust.• There may be still some heat left over from the earth’s formation.• Friction from movement of and in the crust.

• External Source:• This is really not like a cycle at all but a budget or a balance sheet.

The amount of energy coming into a system should always equal the amount of energy going out. That is why it is also called the Earth’s Energy Budget.

External Source:This is really not like a cycle at all but a budget or a balance

sheet. The amount of energy coming into a system should always equal the amount of energy going out. That is why it is also called the Earth’s Energy Budget.

Some of the energy is directly used like the solar, tidal and geothermal. And some is stored for later usage like fossil fuels, water, ice, live plants and some sedimentary rocks.

Unlike the other cycles – a little energy is lost and never retrieved. This is called the physics of the Law of Thermodynamics.

Law I• Energy can never be created nor destroyed, only changed from one form to

another.Law II

When energy changes, it is converted from a more organized, more concentrated form to a less organized, less concentrated one (some energy is always lost making it so).

Potential energy, as the name implies, is energy that has not yet been used, thus the term potential. Kinetic energy is energy in use (or motion). A tank of gasoline has a certain potential energy that is converted into kinetic energy by the engine. When the potential is used up, you're outta gas!

Humans and insects and other live creatures also have an effect the interactions of the cycles and systems that occur on Earth. It causes the ripple effect. When someone does something in one area, it triggers a chain reaction elsewhere. Like the butterfly that flaps its wings in Africa that produces a Hurricane on Long Island.

The Cycles In the Earth:

Nitrogen Cycle

Nitrogen is a gas. Our atmosphere is approximately 78% nitrogen. We cannot use this for life. In order to use it, it must go though some changes, called fixing. It means it changes it from the air version to the compounds we can use though a chemical process.Air to soil through nitrogen fixingSoil to plant and animal (plants use it to grow - animal eats plants)Back to air though decayRepeat

Carbon CycleCarbon is never destroyed – just rearranged from one form to another. Sometimes it is a quick change like a decomposing apple and then it sometimes takes a very long time like a plant decaying, being buried and squished then later burned as coal.

• Even though we feel that carbon can be dangerous (carbon monoxide, etc), it is essential for life. It is the building block for all organic materials and organism. We are carbon based life forms, just ask any alien.

• Carbon enters the atmosphere as a by-product (bad breath, fluctuant, composts, volcanoes, etc.)

• Carbon is removed from the atmosphere by:– Plants for photosynthesis– Phytoplankton uses it for photosynthesis and when they die

they release it into the water that releases it.• Carbon is diffused out of the oceans (diffuse means to

move from high concentrations to low and since the air is lower than the water it is released into the air)

Phosphorus cycle

• Phosphorus moves through every sphere except the atmosphere because it is rarely a gas.

• It gets to the soil from rocks breaking down and being dissolved in water, or when an animal dies.

• Plants absorb it and it becomes part of them• Animals eat the plant, and both die, returning it to the ground.

Water CycleWater Cycle• 97% of water is in oceans - salt water97% of water is in oceans - salt water• 2 ½ % of water is frozen - glaciers2 ½ % of water is frozen - glaciers• ½ % of water is fresh drinking ½ % of water is fresh drinking • streams - very littlestreams - very little• rivers – very littlerivers – very little• lakes – a little morelakes – a little more• swamps – a little moreswamps – a little more• UNDERGROUNDUNDERGROUND- majority of drinking water- majority of drinking water

• Water Cycle TermsWater Cycle Terms• EvaporationEvaporation - water vapor going into the atmosphere - water vapor going into the atmosphere• - usually by the sun, directly or indirectly- usually by the sun, directly or indirectly• CondensationCondensation - water gas (H2Og) changing to Water Liquid (H2Ol) - water gas (H2Og) changing to Water Liquid (H2Ol)• - must have condensation nuclei (dust) to form clouds- must have condensation nuclei (dust) to form clouds• Precipitation Precipitation - gravity pulling water from the clouds- moisture source - gravity pulling water from the clouds- moisture source

for local water budget. for local water budget.• Transpiration Transpiration - process by which green plants lose water through their- process by which green plants lose water through their• leavesleaves• evapotranspiration evapotranspiration - evaporation & transpiration combined - evaporation & transpiration combined • the way most water enters the airthe way most water enters the air

Section 3 - Ecology• Ecosystem• A community of organism and the abiotic (non living) environment

they inhabit.• Balancing the forces in an Ecosystem• Small changes in any part of the environment can affect the ecosystem,

however, the system usually has the ability to maintain and restore itself.• When the change is a large one, like a fire or a flood, the ecosystem can

be disrupted for some time. Eventually it will go back to its normal state.• Energy Transfers in an Ecosystem• The sun is the ultimate source of energy. The energy is cycled through

the various cycles and it all works together.• Humans as stewards of the Environment• All Earth's systems are interconnected. A change in one system can effect

another system.• By helping preserve the environment and not treating Mother Earth poorly

we become stewards of the planet. We become responsible for Mother Earth and her wellbeing. In other words, don't hurt Mother Nature.

•