Earth as a System

Chapter 2, Section 1 - Earth: A Unique Planet                                                                                                                              

Earth is Unique...
  • Only planet in our solar system with liquid water on the surface.
  • Only planet in our solar system with large amounts of oxygen (O2) gas.
  • Only planet known to support life.
Earth Basics
  • 3rd planet from Sun.  (Approximately 93 million miles away.)
  • Formed 4.6 billion years ago.
  • Made of mostly rock.
  • Approximately 71% of the surface is covered by the global ocean.
  • Oblate spheroid - slightly flattened sphere.
    • Bulges at equator, compressed at poles.
    • Equatorial circumference: 40,074 km.
    • Polar circumference: 40,007 km.
  • Average diameter: 12.756 km.
  • Relatively smooth surface - only 20 km difference between highest and lowest points.

Earth's Interior
Only the outer few kilometers can be directly observed.  The rest are studied using earthquake waves (like sonar, or a sonogram).

Compositional Zones - Divisions based on composition (chemistry).
  • Crust - The thin, solid outermost layer of the Earth, above the mantle.
    • 1% of Earth's mass.
    • Two types...
      • Oceanic crust - Made of basalt and lies beneath the ocean.  5-10 km thick.
      • Continental crust - Made of granite and makes up continents.  15-80 km thick.
    • Moho (Mohorovicic discontinuity) - The lower boundary of the crust.
  • Mantle - The layer of rock between Earth's crust and core.
    • Almost 2/3 of Earth's mass.
    • 2,900 km thick.
    • Made of rock; denser than the crust.
  • Core - The central part of the Earth, below the mantle.
    • About 1/3 of Earth's mass.
    • Sphere with a radius of about 3,500 km.
    • Composed of mainly iron and nickel.
Structural Zones - Divisions based on physical structure.
  • Lithosphere - The solid, outer layer of the Earth that consists of the crust and the rigid upper part of the mantle.
  • Asthenosphere - The solid, plastic layer of the mantle below the lithosphere; made of mantle rock that flows very slowly, which allows tectonic plates to move on top of it.
  • Mesosphere - ("Middle Sphere")  The strong, lower part of the mantle between the asthenosphere and the outer core.
  • Outer Core - A dense liquid layer, starting at a depth of about 2,900 km.
  • Inner Core - A dense, rigid solid, starting at a depth of about 5,150 km.

Earth as a Magnet

Earth has a North and South geomagnetic pole.  The magnetic field extends between them.  The area of space around the Earth that it covers is called the magnetosphere.

Some scientists think that it is caused by currents in the outer core.
  • Sun has a magnetosphere, but has very little iron.
  • Moon has a magnetosphere, but doesn't have a liquid core.

Earth's Gravity

Gravity - The force of attraction between all matter in the universe.
  • Newton's Law of Gravitation
    • The force of attraction between two objects depends on their masses and the distance between them.
      • Greater mass = stronger gravity.
      • Greater distance = weaker gravity.
Mass vs. Weight
  • Mass - A measure of the amount of matter in an object.
    • Measured in grams (g) or kilograms (kg).
    • Does not change as location changes.
  • Weight - A measure of the strength of the pull of gravity on an object.
    • Measured in Newtons (N).
    • Changes with distance from the center of the Earth.

Chapter 2, Section 2 - Energy in the Earth System                                                                                                                       

Earth-System Science

System - An organized group of related objects or components that interact to create a whole.
  • Systems vary in size.  Smaller systems can be part of larger systems.
  • Systems have boundaries.  (These can be arbitrary, depending on the system being studied.)
  • Systems can have matter and energy flowing through them.
Matter - Anything that has mass and takes up space.  (Protons, atoms, cells, rocks, trees, planets, etc.)

Energy - The ability to do work.  (Heat, light, vibrations, electromagnetic waves, etc.)

Closed System - A system in which energy, but not matter, is exchanged with the surroundings.
Open System - A system in which energy and matter are both exchanged with the surroundings.

Earth System is almost a closed system.
  • Sunlight enters, heat is given off.
  • A small amount of rock/dust hits Earth from space, and a few hydrogen atoms escape into space.

Earth's Four Spheres
  1. Atmosphere
    • A mixture of gases that surrounds a planet or moon.
    • Earth's atm. is composed of:
      • 78% nitrogen
      • 21 % oxygen
      • 1% argon, carbon dioxide, water vapor, helium, etc.
  2. Hydrosphere
    • The portion of the Earth that is water (except gaseous water vapor).
    • 71% of Earth's surface is covered in water.
    • 97% of Earth's water is salt water and found in the oceans.
    • 3% of Earth's water is fresh water and found in lakes, ponds, rivers, streams, glaciers, polar ice caps, groundwater.
  3. Geosphere
    • The mostly solid, rocky part of the Earth.
    • Extends from the center of the core to the surface of the crust.
    • Rock is cycled between the interior and exterior by volcanoes and plate tectonics.
  4. Biosphere
    • The part of the Earth where life exists.
    • Includes all of the living organisms on Earth, and any organic matter that has not decomposed.
      • Once organic matter decomposes, it becomes part of the other spheres.

Earth's Energy Budget
  • First Law of Thermodynamics
    • Energy is transferred between systems, but it cannot be created or destroyed.
  • Second Law of Thermodynamics
    • When energy is transferred, matter becomes less organized.  Over time, energy is spread out more and more evenly.
    • Energy transferred as heat always moves from an object at a higher temperature to an object at a lower temperature.
Matter and energy are constantly moving between the spheres by means of...
  • chemical reactions
  • radioactive decay
  • radiation of energy (ie - light & heat)
  • growth and decay of organisms
Internal sources of Earth's energy...
  • radioactive decay
  • gravitational contraction
  • Convection
    • The movement of materials due to differences in temperature.  (Warm fluids rise, cool fluids sink.)
    • Transfers heat from the core to the outer layers.
    • Drives plate tectonics, which shape Earth's surface.
External sources of Earth's energy...
  • Solar radiation
    • warms atmosphere and surface
    • drives winds and ocean currents
    • provide energy for plants (which then feed animals)
  • Gravitational energy
    • generates tides, which cause currents and mixing of ocean water.

Cycles in the Earth System

Reservoir - A place where matter or energy is stored.
Cycle - A group of processes in which matter and energy repeatedly move through a series of reservoirs.

Nitrogen Cycle
  • Nitrogen is used to make proteins and DNA, but most living things can't use it directly from the air.
  • Cycle...
    • N2 gas is converted to N-compounds by bacteria in soil and the roots of certain plants.
    • N-compounds in soil are taken in by plants, which are eaten by animals.
    • When organisms excrete or die, N-compounds are converted back into N2 gas and released into the atmosphere.
Carbon Cycle
  • Carbon is used to build organic molecules and in fuels for life processes.
  • Cycle...
    • Short-Term Cycle

      • Plants absorb CO2 from the air, and convert it into carbohydrates.

      • Animals eat plants, getting the carbohydrates.
      • Organisms release CO2 during respiration, in their organic wastes, and when they die and decay.
    • Long-Term Cycle
      • Remains of living things can be buried and formed into carbonate rock (ie - limestone).
Phosphorus Cycle
  • Phosphorus is used in DNA and to help build cells.
  • Cycle...
    • Rocks break down, releasing P into soil and water.  (Can also be excreted by some organisms.)
    • Plants absorb P through their roots; animals get it from eating plants.
    • When organisms die, their P is released back into the environment.
Water Cycle
  • All living things contain water.
  • Cycle...
    • Evaporation - Water changes from liquid to gas.
    • Condensation - Water changes from gas to liquid.
    • Precipitation - Water falls to the ground (rain, snow, sleet, hail).
    • Runoff - Water moving along the Earth's surface.
    • Groundwater - Water below the surface of the ground.
    • Transpiration - Evaporation of water cause by plants.

Human Influence...
  • Burning of fossil fuels.  (Carbon cycle)
  • Monoculture farming.  (Nitrogen & Phosphorus cycles)
  • Fertilizer use.  (Nitrogen & Phosphorus cycles)
  • Pollution.  (Water cycle)

Chapter 2, Section 3 - Ecology                                                                                                                                                   

Ecology - The study of the relationships between living (biotic) things and their nonliving (abiotic) environment.

Ecosystem - A community of organisms and their abiotic environment.
  • Can be a rotting log.
  • Can be an ocean.
  • Can be the biosphere.
Producers - Organisms that use the Sun's energy to make their own food.  (Plants, algae)
Consumers - Organisms that get their energy by eating other organisms.  (Animals, fungi)
    Decomposers - Consumers that get energy by breaking down dead organisms.

Carrying Capacity - The largest population that an environment can support at any given time.  (Limited by resources.)

Food Web - A diagram that shows the feeding relationships among organisms in an ecosystem.
    A food chain shows only one set of relationships.

Human activity can have drastic impacts on the environment.


Chapter Assignment
  Pg. 50-51 #2-4, 10-24.
    *Note: For #2-4, your sentences should demonstrate that you understand what the term means.