The Earth

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The Earth Powered By Docstoc
					Introduction
to Planet
Earth
                  Earth
• Distance around the Earth is about
  40,075 km at the equator.
• Avg. distance from sun 149,600,000 km
• Divided into two hemispheres-Northern
  and Southern.
• Three main features are the
  – Land – Lithosphere
  – Water – Hydrosphere
  – Air -- Atmosphere
            The Atmosphere
• Theorized - 4 billion years ago
  atmosphere contained two deadly
  gases, methane and ammonia.
• Through chemical reactions triggered by
  sunlight over many years the deadly
  gases and water vapor caused nitrogen,
  hydrogen, and carbon dioxide to form.
• A layer of Ozone gas formed from
  oxygen
   – Prior to this layer forming, only
     microscopic organisms lived below
     the surface of the oceans.
          After the Ozone Layer

• Blue green bacteria surfaced from the
  water and used the energy from the
  sunlight to combine carbon dioxide
  and water to produce food which is a
  byproduct of Oxygen. Oxygen
  remained near surface.
• More green plants began to grow,
  again increasing the Oxygen content.
• Teachers' Domain: Life Before Oxygen
        Present Atmosphere
• A mixture of gases
  – Nitrogen 78% (most abundant)
  – Oxygen 21%
  – Carbon Dioxide
  – Water Vapor
  – Argon                       Less than 1%
  – Other trace gases
First: Nitrogen



                                    Nitrogen cycle



                        6. Movement of
                        nitrogen in air back to
                        ground

                                                       5.
                      3. Animal
                      eats plants
                                                  4.




1. Nitrogen fixing         2. Plants use
Bacteria convert to        nitrates
nitrates
1. Oxygen: used directly from atmosphere by
   most plants and animals.
2. Carbon Dioxide Cycle: removed from
   atmosphere by plants and returned by
   respiration of plants and animals. The decay of
   plants and animals returns carbon dioxide to
   the air.
     But the burning of fossil fuels (oil,coal) adds
      carbon dioxide to air---concern of dangerous
      levels. -----Traps more of the sun’s heat in
      atmosphere which increases the
      temperature of Earth…. Greenhouse
      effect.
Water Vapor—
Causes weather conditions— clouds,
 fog, dew, rain, snow fall
    Absorbs heat energy given by sun.

Solid Particles—dust, smoke, dirt.
              The Water Cycle
             Teachers' Domain: Global Water Distribution




The WATER CYCLE refers to the continuous movement of water
between the Earth’s surface and atmosphere.
Sedimentary-Earth’s Natural Water
             Filter
• Surface water often contains
  contaminants.
• Spring water is filtered through
  sediment, sand, and gravel where
  solids are suspended in
  water and trapped in the
  sediments. In the end, water
  that bubbles out or pumped from
  aquifers several hundred feet
  below the surface is on average
  more than 99.9 % free of
  contaminants.
Exosphere Above a height of about 500km is the
exosphere, a layer where the atmosphere merges into
space. Satellites are stationed in this area, 500km to
1000km from Earth.

Thermosphere The thermosphere is the fourth layer in
the atmosphere, between 80km and 110km above the
Earth. Space shuttles fly in this area and it is also where
the aurora lights are found. Auroras are wispy curtains of
light caused when the sun strikes gases in the atmosphere
above the Poles. The temperature is high in this layer.

Mesosphere Beyond the stratosphere the air is very thin
and cold. This area is known as the mesosphere, and is
found between 50km and 80km above the Earth’s surface.
The upper area of this region is the coldest part of the
atmosphere. This layer helps protect Earth from meteroids.
Stratosphere The stratosphere is the second layer of air
above the Earth’s surface and extends to a height of 50km.
It is here that we find the ozone layer. The ozone layer
absorbs much of the sun’s harmful radiation that would
otherwise be dangerous to plant and animal life. The jet
stream winds blow in this area.

Troposphere The troposphere is the layer closest to the
 Earth, approximately 11km high. Weather occurs only in
 the troposphere because it is this layer that contains most
 of the water vapor.
  Layers
   of the
Atmosphere



     OZONE
1. Solar Radiation 100%                  30% lost to space by reflection &
                                         scattering


                          5%backscattered to
                          space by atmosphere


                                             20% reflected from clouds




                                     20% of radiation absorbed
                                     by atmosphere & clouds


50% of direct & diffused radiation                       5% reflected from
Absorbed by land & sea                                   land-sea surface
                                                                                 30% lost to
                                                                                 space by
                                                                                 reflection &
                                                                                 scattering



50% of direct and diffused
Radiation absorbed by
Land and sea.



Figure 10a: Sunlight warms the earth's surface only during the day, whereas the surface constantly
emits infrared radiation upward.

Without water vapor, CO2, and other greenhouse gases, the earth's surface would constantly emit
infrared radiation (IR); incoming energy from the sun would be equal to outgoing IR energy from the
earth's surface. Without the greenhouse effect, the earth's average surface temperature
would be -18°C (0°F) . Earth’s avg. temp is 15 deg C with the Greenhouse effect.
 Nitrogen




             Greenhouse Gases:
    Oxygen
                Water Vapor, Carbon
             Dioxide, Methane, Nitrous
Argon        Oxide, Ozone
    Greenhouse effect is not a bad
               thing!
It keeps the earth warm enough for us to
 live here. Without the greenhouse effect,
 the earth would be a cold planet and would
 not be able to support life. Gases like
 carbon dioxide and methane let the sun's
 radiation into our atmosphere, but don't let
 the heat that is radiated back from the
 earth's surface out of the atmosphere into
 space. This is similar to how an actual
 greenhouse keeps the plants inside warm,
 giving the effect its name.
          The Greenhouse Effect




Teachers' Domain: Global Warming:
The Physics of the Greenhouse Effect
  So far the Earth seems to be the
      only planet to support life
• It is the only planet with liquid water and its
   perfect distance from the sun. Its atmosphere
   has the right mixture of gases and protection
   layer
  from meteor impacts
  and dangerous rays.
  Life forms have
  adapted to land,
  water, and air.
• Teachers' Domain: Ingredients for Life: Water
• Discussion groups :

  ―What significance or functions does each layer of the
    Earth’s atmosphere have on living organisms?‖
                                                                         1300 km
                        Earth’s Interior


                                                                          2900 km




                                                                          2250 km


                                                                         1300 km


Mantle made mostly of the elements silicon, oxygen, iron, and magnesium.
Composition of mantle found by studying rocks of volcanoes and ocean floor.
              Earth’s Interior
• Major layers
  – Crust – thinnest, solid
     • Moho – Boundary between Crust & Mantle
  – Mantle – most massive
  – Inner Core – liquid (Ni & Fe)
  – Outer Core – solid high pressure (Ni & Fe)
• Sub layers
  – Lithosphere- crust + upper mantle
  – Asthenosphere – soft flowing mantle
When a solid has the ability to flow
 it has the property of plasticity.
• The rock in the mantle can flow like a thick
  liquid. The high temperature and pressure
  in the mantle allow the solid rock to flow
  slowly, thus changing shape.
 How did scientists learn about the
         Earth’s interior?
• By studying seismic waves produced by
  earthquakes.
• Seismic Waves
   Earth’s Crust: Continental and
              Oceanic
• The outermost layer
  – Very thin compared to other layers
  – Most cannot be seen due to soil, rock, and
    water
  – Made up of 3 types of solid rocks
    • Igneous rocks
    • Sedimentary rocks
    • Metamorphic rocks
                   Igneous Rocks
• Form when hot liquid rock from deep
  within the Earth cools and hardens as it
  reaches the surface

  Large crystals
Igneous rock from Maine
         Sedimentary Rocks
• Form when sediments – small pieces of
  rocks, sand, and other materials are
  pressed and cemented together by the
  weight of others over long periods of time.
Sedimentary rock from Utah
         Metamorphic Rock
• Sometimes sedimentary and igneous
  rocks are subjected to pressures so
  intense or heat so high that they are
  completely changed.
Metamorphic rock from Maine
  Thickness of the crust varies
• Oceanic crust ~ 3 mi thick
  – silicon, oxygen, iron, and magnesium
    (constantly recycled).
• Continental crust is about 25 mi thic
  – made mostly of silicon, oxygen, aluminum,
    calcium, sodium, and potassium. More silica
    rich than oceanic crust.
Earth’s Lithosphere is made up of the
 crust and upper part of the Mantle
            Continental Drift
• Alfred Wegener
  – Continental Drift
     • Puzzle pieces South America & Africa
     • Geology (rock)
     • Paleontology (fossils)
             Plate Tectonics
• What is a ―Tectonic (Lithospheric) Plate‖ ?
   – massive, irregularly shaped slab of solid rock
   – composed of both continental and oceanic
     lithosphere.
• Lithospheric plates sliding along Asthenosphere
   – Plate Boundaries (4.1)
   – Formation of Ocean Floor (4.2)
   – Rifting (4.6)
 The Earth’s Changing Surface
• Forces within the
  Earth itself push and
  pull on the rocks of the
  Earth’s crust changing
  its shape and volume.
  They also move up,
  down, and sideways
  causing them to break,
  tilt, and fold. This is
  called deformation.
   Three Types of   Stress
1. Compression
2. Tension
3. Shearing
Types of Stress
Fracture joints
Stress sometimes causes rocks to
         break or crack
• 1. Fault—Movements along a fault
    can be up, down, or sideways.
  – Earthquakes often form along faults in
    the Earth’s crust.
       Fault




Foot
               Hanging
Wall
               Wall
Foot Wall




                          Hanging
                          Wall


            Compression
            Lateral Fault




Foot Wall                   Hanging
                            Wall
http://www.earthguide.ucsd.edu/earthguide/diagrams/faults/index.html
Normal
Fault              L side lower,
                   hanging wall

• Big Bend,
Boquillas Canyon
between Texas
                                   Footwall
and Mexico.
Thrust (Reverse) Fault Example
                     Hanging wall
                     sliding over
                     foot wall
Example Lateral Fault
(Las Vegas, Nevada)
Fault-block mountains are formed
by the raising of huge blocks of the
   earth's surface relative to the
        neighboring blocks.
Mountains sometimes form when many
 layers of the Earth's crust are moved
   vertically upward at fault lines by
 pressures caused by plates colliding.
            Fault Block Mountain




Form along a fault line -- the rocks on one side of the fault are forced
upward, while the rocks along the other side sink.
Fault Block Mountains




      Juniper Canyon
       Rift Valley
When a block of rock between
two normal faults slide down.
Rift Valley in Kenya
          2. Folding
• Sometimes when stress is applied
  to rocks of the crust, the rocks
  bend but do not break.
 * Can fold either upward—anticline
    or downward—syncline
 * Some large enough to form
    mountains
Folded Mountains are believed to have been formed when the edges of two
adjacent rock layers were pushed together causing the layers to buckle like a
wrinkled rug. Scientists have learned that under great pressure and steady force,
rocks can actually bend rather than break.
 Anticline and Syncline


            Syncline

Anticline
Factors that determine whether
  rocks will FAULT or FOLD
1. Temperature
2. Pressure
3. Rock type
  – Brittle (sandstone) likely to break
  – Ductile (rock salt) likely to fold
4. Stress
  – Gradual—will usually fold
  – Sudden—will usually break
                    Plateaus
• A large area of flat land that is raised high
  above sea level.
• Consist of horizontal rock layers.
• Layers remain flat.
• May be formed by a slow flat topped fold,
  vertical faulting (crust pushing upward), or by
  a series of molten rock flows.
             Molten Rock
• Flowing on the surface of Earth: Lava
• Deep within the Earth: Magma
• Lava piles up and forms a plateau
                   Domes
• Sometimes magma pushes upwards but does
  not reach the Earth’s surface causing the rock
  layers above to fold upward.
• The uplifted area caused by rising magma forms
  a dome.
• Domed Mountains appear to be formed when molten rock is
  forced upward beneath an overlying rock layer, pushing the
  rock above into a blister-like dome - molten rock does not reach
  the surface. Domed mountains are often found in the same
  areas as volcanic mountains since they also result from
  volcanic activity.
As you recall beneath the
     As you recall….
Earth’s crust is the mantle, made of
rock that flows slowly.




The rocky crust floats on top of the mantle, exerting a downward force.
The mantle also exerts an upward force on the crust.
A balance exists between the two forces called ISOSTASY.
•Isostasy
If the Mississippi River dumps tons of mud and sand particles into the
Gulf of Mexico, will the Gulf become shallow and eventually disappear?

				
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