Earth - The Earth The purpose of today's lecture is to...

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Unformatted text preview: The Earth The purpose of today's lecture is to today' identify some of the major components of the Earth, and to describe briefly how they function. The descriptions use a systems approach. Description of the natural components will permit recognition of the impacts of human intervention. The Earth The Earth's age is ~4.5 billion years. Earth' The oldest rocks are ~4 billion years old. Major components of the Earth's interior Earth' are: Inner & Outer Core (~31% of volume together) Mantle (~68% of volume) Crust (<0.5% of volume) Earth's Structure Earth' Earth has Crust 0.5% Mantle 68.1% Core 31.4% (inner/outer) The continents only cover about 29% of the earth's surface and the oceans cover ~71%. The Earth Prior to the 1960s geologists lacked a coherent organizing framework for the entire world. During the 1960s the systems model called `plate tectonics' developed and tectonics' became widely accepted. Today plate tectonics is the dominant framework and few scientists doubt it. The Earth The crust is thin, ~10 km thick under the oceans and ~35 km thick under the continents. The crust is divided into rigid sections that extend below the crust proper called `plates'. plates' The crust is stable within plates, but plates move with respect to each other. Plate Tectonics Plates and plate boundaries do not coincide with continental margins. There are ~12 big plates and many small ones. There are three different kinds of plate margin: Spreading Centers Subduction Zones Shear Zones 1 Spreading Centers Mainly oceanic. Huge ridge systems on the scale of the Rocky Mountains with cracks in the middle. Location of volcanic activity. Location of shallow earthquakes. New rock is added to the surface, rocks are young, sediments are thin, and the crust moves away as rock is added. Subduction Zones The edge of one plate dives under the edge of another plate and goes back into the interior of the Earth where it eventually melts. Deep earthquakes, volcanic material offset from contact zone. Location of deep ocean trenches (~ 37 000 feet deep). Shear Zones Two plates are simply rubbing past one another. No new material added and one plate does not dive under the other. The San Andreas Fault Zone is a good example. Southern California is headed north along the edge of the North American plate while the rest of us are headed west. Tectonic Plates The largest is Pacific plate, which is located mostly beneath the ocean All of the other large plates include both continental and oceanic crust The Atmosphere Meteorology is the short-term study of the shortatmosphere. Climatology is the long-term study of the longatmosphere. Time scale, not subject matter, is the difference between the two. The Earth's Energy Balance Earth' We intercept the appropriate amount of solar energy given our size and distance from the sun. This energy is received evenly at the outer edge of the atmosphere. Water/land, latitude, albedo, seasonality and other factors influence energy distribution within the atmosphere. 2 Global Radiation Input/Output Atmospheric Energy Redistribution The uneven receipt of energy must be equalized so the Earth redistributes solar energy by shipping heat (hot air and water) from heat surplus areas to heat deficit (cold) areas, and by sending heat deficit air and water (cold) to heat surplus (hot) areas. We call the byproducts of these processes weather and/or climate. A `Climate' Defined Climate' The World Meteorological Office defines 30 years as the minimum record for a `climate'. climate' A single year cannot represent climatic change. A `Climate' Defined Climate' Out 10 New Years 10 Old Years Old 30-Year Record In New 30-Year Record The Hydrosphere Oceans cover ~71% of the earth's earth' surface. The water seems to have accumulated steadily through geologic time. It comes from volcanic activity. The chemistry (saltiness) of seawater is what we would expect given the solubility of material in most rocks. Ocean Currents Surface ocean currents are the product of prevailing winds (e.g., we live in the zone of the prevailing (westerlies). There are large spiral surface currents called gyre(s) in the major oceans. 3 Global Ocean Surface Currents Deep Ocean Currents Deep ocean currents are controlled by thermohaline conditions, that is by water temperature plus water saltiness. Hot water is less dense than cold water, freshwater is less dense than salty water. The densest water in the oceans is cold and salty. Ocean Energy Redistribution The oceans are responsible for ~20% of the energy redistribution that occurs across the earth. This is critical and plays an important role in climatic change. Hydrologic cycle and the water storage of the globe Hydrologic Cycle 4 The Origins of Life This topic is too complex and too tangential for me to discuss in this class. 5 ...
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This note was uploaded on 04/07/2008 for the course GEOG 210 taught by Professor Thorn during the Spring '08 term at University of Illinois at Urbana–Champaign.

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