The Earth as a planet Chapter 6
Earth as a Planet • - 4.6 billion years old • Compared to other planets in the solar system • Concepts of Living, Active and “dead” planets • The Earth as a Living Planet, Our moon as a dead planet • Shape and size – contributes to a living planet
A DEAD PLANET • CRATERS – POCKED MARKED • NO ATMOSPHERE OR VERY LITTLE • NO PLASTICITY OF MANTLE - INACTIVE • NO OR VERY WEAK ELECTROMAGNETIC FIELD • SLOW ROTATION OR DAY • CORE MAY BE SOLID BUT NO LIQUID CORE • NO SIEMIC ACTIVITY OR VERY LITTLE • SMALL
Active Planet • Constant Seimic activity constant • Mantel has plasticity and is still hot • Electromagnetic field may be strong • Some atmosphere – could be toxic • Rotation could be slow or fast • Iron core – possible liquid core • Could have water
Sulfuric acid spews from volcanic activity giving the atmosphere a yellow tinge. Imence acid lighting storms erupt throughout the surface of the planet.
A Living Planet • Organic growth and Lie • High Seismic activity • Protective Ozone layer and Magnetic Field • Water • Oxygen • Size and spin – distance from star • Soft mantle, iron core, liquid core.
Our earth in all it’s majesty has supported life for at least 3 billion years
Alien planets may look different then ours. But if there is some form Of life it makes it a living planet.
Jupiter's Moon Ganymede man have some form of life under the ice wher There is a good chance of water.
The concept of Density • Density is the relationship of mass to volume. • Why do we need to know density? e.g., gas giants are big but have low density. Density of other material for example. The Earth 5.5, Water 1.0, Iron 7.8, air .0012, silicate rocks 3.0. • Density, differentiationand gravity – how they combine to make a planet
Differentiation Toward Surface Fragile crust Dense Materials Magma Heavy metals, Iron Less Dense Materials When a Planet first forms Density is Constant Dense materials displace less dense materials To Core
Differentiation The process of differentiation Pressurized dense core Magma Magma Heavy metals, Iron Mostly Silicates
Composition of the earth: • The crust 12 to 50 miles thick – mostly silicates and organic material, minerals, some heavy metals. • Oxygen • Silicates • Iron • Copper • Lead, gold, silver, and uranium
Earth’s mean radius 6350 km • Earth’s mass 6 x 1024 km • 5.51 grams/cubic centimeter
Composition of the earth • : • The crust 12 to 50 miles thick – mostly silicates and organic material, minerals, some heavy metals. • The mantle, a semi hard layers of silicates, and magma just below the crust • The liquid and iron core , a semi rotating mass of magma swishing around a core of iron and heavy elements e.g., lead,
The earth’s surface • Fault lines – Pacific Rim – plates constantly moving creating shear, compression and tensional stress. • Volcanoes and earthquakes at or near the fault line – both caused by movement • Magma and lava – lava is outside on the surface, magma is in the earth, but is basically the same in composition.
The Process of Rifting • :In the crust there are pockets of magma. • Convection: is where hot magma rises to the surface cools and settle back. This creates a cycle. • This cause a separation of the crust above the convection flows. The crust thins out too. • If above land – ground surface lava flow possible. At the sea bed, flat separation, crust is very thin, possible breech of magma.
Rifting -Separation over time, Crust will also thin out Example 5b Convection and Rifting
Subduction • The process of a plate moving under another plate • Creates mountains – plate/fault lines always nearby.
S and P waves • When seismic activity occurs- earthquke etc, the energy creates waves • P wave long waves – will go through liquid and matter • P waves can detect seismic activity, and travel though the earth to the adjacent side. • S- Waves, shorter waves but cannot travel through liquid. Do the most damage. • S- Waves have detected the earth’s liquid core.
P waves in air are simply sound waves • P waves in air are simply sound waves and the speed of sound is around 340 m/s for ordinary temperatures. • Water can support P waves but not S waves, and the speed of these P waves (speed of sound) in water is about 1450 m/s. • P waves : Speed 5000 m/s. The P waves from an earthquake arrive first, but because of their small amplitudes don't do as much damage as the S waves and surface waves which follow.
S waves are transverse waves • S waves are transverse waves which involve movement of the ground perpendicular to the velocity of propagation. • They travel only through solids, and the absence of detected S waves at large distances from earthquakes was the first indication that the Earth has a liquid core. • S waves travel typically 60% of the speed of P waves. • They are typically more damaging than the P waves because they are several times higher in amplitude.
P –wave: Similar to a Sound wave (longintudal) S-wave: A transverse wave- cannot Travel through liquids
Electromagnetic field • Created by the planet’s rotation and the liquid core • Friction of the liquid magma and the iron core created a static charge • Relationship between magnetism and electricity • How magnet lines of force work and polarity • The earth’s Van Allen belts, location, and how they work to prevent harmful radiation from the sun reaching the earth’s surface. • Cosmic rays in space.
An iconic photograph marking the start of the space age shows three men thrusting a satellite above their heads. William Pickering, James Van Allen and Wernher von Braun lofted a scale model of the Explorer 1 satellite at the US National Academy of Sciences barely two hours after the real thing went into orbit on the night of 31 January 1958. EXPLORER 1 REVEALS VAN ALLEN BELT IN 1958
Atmospheres: • Earth and some planets have an atmosphere. • Is usually a gas of some sort • Earth’s atmosphere is composed of: • 79% Nitrogen, • 20% Oxygen, . • 03% Carbon Dioxide • less than 1% other. • The oxygen probably was produced by organic life such as plant life and other gases out gassed from the crust or comets. The original atmosphere was lost into space. Probably methane and hydrogen.
Layers of the atmosphere • Troposphere up to 18 km • Stratosphere 18km to 50 km • Mesosphere 50 km to 90 km • Ionosphere 90 to 300 km (aurora’s)
High Energy Radiation Absorption • Absorption is mainly caused by three different atmospheric gases. • Water Vapor H2O • carbon dioxide • ozone.
Ozone Layer • Ozone Layer – protects us from ultraviolet radiation. Oxygen we need to live is O2 and Ozone is O3 – Explain the difference, when highly energetic particle hits an atom of O2, it splits apart. When these free atoms collide with an O2 atom it makes an O3 atom.
Breathable oxygen molecule = O2 Free oxygen is = O Ozone is O3
Question? • Why is the sky blue and sunsets red? • The Tyndall Effect show that light waves scatter differently per there wave length. • Thicker atmosphere scatters blue light more than red or yellow thus red sunsets. • The sky is blue because there are fewer particles to scatter then at the horizon.