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Earth science (also known as '''geoscience''', '''the geosciences''' or '''the Earth Sciences'''), is an all-embracing term for the sciences related to the planet Earth . It is arguably a special case in Planetary Science , being the only known Life -bearing planet. There are both Reductionist and Holistic approaches to Earth science. The major historic Discipline s use Physics , Geology , Geography , Meteorology , Mathematics , Chemistry and Biology to build a quantitative understanding of the principal areas or '' Spheres '' of the Earth system. EARTH'S SPHERES Earth science generally recognizes 4 spheres, the lithosphere, the hydrosphere, the atmosphere, and the biosphere. These correspond to rocks, water, air, and life. Some practitioners include the cryosphere (ice) as a distinct portion of the hydrosphere and the pedosphere (soil) as an active, intermixed sphere as part of Earth's spheres. volcano into the ocean on the Island Of Hawaii ]]
EARTH'S ENERGY In , the rate of energy transformations inside the Earth is about 37 x 1012 J/s (37 terawatts). The heat escaping from inside the Earth is only about 0.02% of the amount of energy Earth receives from Sun in the form of sunlight, and radiates back into space in the form of Infrared Blackbody Radiation (~1.74 x 1017 J/s = 174 petawatts). From the study of Neutrino s radiated from the Earth (see KamLAND ), scientists have recently estimated that about 24 terawatts (65%) of this rate of Energy Transformation is due to Radioactive Decay (principally of Potassium 40, Thorium 232 and Uranium 238), and the remaining 13 terawatts is from the continuous gravitational ''sorting'' of the Core and Mantle of the earth, energies left over from the Formation Of The Earth , about 4.57 billion years ago (this sorting represents continuing Gravitational Collapse of the Earth into the maximally compact object which is consistent with its composition-- a process which releases gravitational potential energy), and finally - from Tidal Flexing of Earth's interior and crust. The magnitude of all of these energy sources decline over time, and based on half-life alone, it has been estimated that the current Radioactive Energy of the planet represents less than 1% of that which was available at the time the planet was formed. As a result, geological forces of Continental Accretion , Subduction and Sea Floor Spreading , account for 90% of the Earth's energy. The remaining 10% of geological tectonic energy comes through Hotspots produced by Mantle Plumes , resulting in Shield Volcanoes like Hawaii , Geyser activity like Yellowstone or Flood Basalt s like Iceland . Tectonic process are driven by heat from the Earth's interior. The process is a simple heat engine which works via the upward buoyancy-induced motion of hot, low density Magma after expansion by heat. The processes Metamorphically Alter crustal rocks, and (more importantly from the energy view) during Orogenies , lift them up into mountain ranges. The potential energy represented by the mountain range's weight and height thus represents heat from the core of the Earth which has been partly transformed into gravitational potential energy. This potential energy may be suddenly released in landslides or Tsunami s. Similarly, the energy release which drives an earthquake represents stresses in rocks that are mechanical potential energy which has been similarly stored from tectonic processes. An earthquake thus ultimately represents kinetic energy which is being released from elastic potential energy in rocks, which in turn has been stored from heat energy released by radioactive decay and gravitational collapse in the Earth's interior. The energy which is responsible for the geological processes of erosion and deposition is a result of the interaction of solar energy and gravity. An estimated 23% of the total insolation is used to drive the Water Cycle . When Water Vapour condenses to fall as Rain , it dissolves small amounts of Carbon Dioxide , making a weak Acid . This acid acting upon the metallic Silicate Mineral s that form most rocks produces Chemical Weathering , removing the metals, and leading to the production of rocks and sand, carried by wind and water downslope through gravity to be deposited at the edge of continents in the sea. Physical Weathering of rocks is produced by the expansion of ice crystals, left by water in the joint planes of rocks. A Geologic Cycle is continued when these eroded Sediment s are buried and later uplifted into mountains. Similarly meteorological phenomena like Wind , Rain , Hail , Snow , Lightning , Tornado es and Hurricanes , are all a result of energy transformations brought about by solar energy on the planet Earth. It has been estimated that the average total ''solar incoming radiation'' (or Insolation ) is about 1350 watts per square meter incident to the summit of the atmosphere, at the equator at midday, a figure known as the Solar Constant . Although this amount varies a little each year, as a result of Solar Flares , Prominences and the Sunspot Cycle . Some 34% of this is immediately reflected by the planetary Albedo , as a result of clouds, snowfields, and even reflected light from water, rock or vegetation. As more energy is received in the tropics than is re-radiated, while more energy is radiated at the poles than is received, climatic homeostasis is only maintained by a transfer of energy from the tropics to the poles. is the release of stored energy from below the surface of Earth originating in radioactive decay and gravitational sorting in the Earth's core and mantle of energies left over from its formation]] This transfer of energy is what drives the winds and the Ocean Current s. Like biological processes, all meteorological processes involve transformation of energy from a concentrated form such as sunlight into a less concentrated form, such as far infrared radiation (i.e., heat radiation) at the much smaller characteristic temperatures that occur on Earth, and thus is diffused into many photons. However, energy may be temporarily locally stored during this process, and the sudden release of such stored sources is responsible for the dramatic processes mentioned above. For example, the kinetic energy of a snow-avalanche or hurricane is due to the sudden release of energy previously captured from solar radiations. METHODOLOGY Like all other scientists, Earth scientists apply the Scientific Method : formulate hypotheses after observation of and gathering data about natural phenomena and then test those hypotheses. In Earth science, data usually plays a major role in testing and formulating hypotheses. PARTIAL LIST OF THE MAJOR EARTH SCIENCE TOPICS Atmosphere Biosphere Hydrosphere
Lithosphere or geosphere
Pedosphere
Systems Others NOTES AND REFERENCES SEE ALSO |
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