The Composition and Layers of the Physical Earth
Planet Earth The Composition and Layers of thePhysical Earth Chapter Objectives The Earth as a system How large is the Earth?
What is Earths shape? Evidences..? The spheres of the Earth and their compositions. Atmosphere Hydrosphere Geosphere Earth as a System Earth is a dynamic body with many separate buthighly interacting parts or spheres. Earth as a system Nearly endless array of subsystems. e.g. hydrologic cycle, carbon cycle Sources of Energy Sun Drives external processes Weather and climate, Ocean circulation, & Erosional processes Earths Interior nuclear, chemical, & thermal energy drives internalprocesses Volcanoes, Earthquakes, & Mountain building Humans are part of the Earth system Earths Size Earths Circumference distance around the earth was firstmeasured by Eratosthenes 2000 years ago. Measured the distance between Egyptian cities of Alexandria andSyrene. Measured the suns angle at noon at each location. Difference in angle is a fraction of a circle. Multiple distance by fraction to get circumference. Obtained 46,250 km very close to the real 40,000 kmcircumference Eratosthenes Method Earths Numbers Equatorial Polar Diameter Circumference 12,174 km The Earths Shape The shape of the Earth is usually thought of as a
Spheroid Oblate Sphere The Earths Shape The shape of the Earth is usually thought of as a From observations & measurements by earth scientistswe know that the Earth is slightly flattened at the poles,and slightly budging at the equator. Thus, the shape iscalled a(n) Earth looks spherical from space
Earths Shape Because the Earth spinning on its axis It bulges at the equator It flattens at the poles Earth looks spherical from space Evidence of Nearly Spherical Shape
As we now know that the Earth is NOT flat (as it was oncebelieved). Columbus, Magellan The position of the sun and the stars depends on the position onEarth, thus the earth has to be curved. On of the best known stars in the North Star The angle of Polaris in the sky increases as one travels towards the NorthPole, where it is directly overhead (90) POLARIS 42 At North Pole At ALCS Evidence Cont. Ship masts appear 1st on the horizon.
Earths shadow is curvedwhen seen during a lunareclipse. *Astronauts havephotographed Earthfrom space* Star Trails (Time Lapse Photography)
Evidence for Earths Rotation on its axis Spheres of the Earth Geosphere: Consists of all the rock and fluid innerlayers of the Earth Spheres of the Earth Geosphere: Consists of all the rock and fluid innerlayers of the Earth Hydrosphere: Consists of all the water on Earthssurface; oceans, rivers, lakes, streams, etc. Covers~71% of surface. Spheres of the Earth Geosphere: Consists of all the rock and fluid innerlayers of the Earth Hydrosphere: Consists of all the water on Earthssurface; oceans, rivers, lakes, streams, etc. Covers~71% of surface. Atmosphere: Consists of the shell of gases thatsurrounds the earth Average Chemical Compositions
ESRT Front Cover Percent Composition of the Atmosphere
Our atmosphere is mostlyNitrogen (78%), followedby Oxygen (21%). CO2makes up less than 1%. Properties of the Atmosphere
ESRT Page 14 Ozone Depletion The ozone absorbs harmful UV rays from the Sun.
Depletion caused by CFCs (ChloroFluoroCarbons)found in aerosols, Styrofoam, and refrigerants. Problem from ozone depletion is increased skin cancerin humans. Atmospheric Phenomena
Aurora Borealis in Ionosphere Hydrosphere All the water on the Earth covers ~71% of the surface
Freshwater (2%) Rivers,Lakes, Streams, &Marshland Marine (97%) SaltwaterOceans Ice (1%) Continental andMountain/Alpine Glaciers Structure of Earths Geosphere
Page 28 in Text . Compositional Zones Crust The thin outer most zone
Continental & Oceanic crust make up 1% of the Earths Mass. The Lower boundary is the MOHO or Mohorovicic Discontinuity MOHO Compositional Zones Crust The thin outer most zone
Continental & Oceanic crust make up 1% of the Earths Mass. The Lower boundary is the MOHO or Mohorovicic Discontinuity Mantle Below the crust Denser than crust 66% of Earths mass Silly-putty like Compositional Zones Crust The thin outer most zone
Continental & Oceanic crust make up 1% of the Earths Mass. The Lower boundary is the MOHO or Mohorovicic Discontinuity Mantle Below the crust Denser than crust 66% of Earths mass Silly-putty like Core Composed mainly of Iron and Nickel. Outer core is a dense liquid Inner core is a dense solid 33% of Earths mass Structural Zone Three compositional zones are divided into five structural zones: Lithosphere Crust and cool brittle upper mantle. 15 300 km thick Asthenosphere Less ridged layer with more ability to flow due toenormous amount of heat and pressure (plasticity). 200 250 kmthick Stiffer Mantle Layer od solid mantle rock Outer Core Dense liquid, mostly iron Inner Core Dense solid of iron and nickel ESRT Pg 10 What happens to the density fromthe crust towards the inner core? What happens to pressure as yougo towards the core? What happens to temperature asyou go towards the core? Which layers are liquids (abovemelting point)? What is the depth of theboundary between the Mantle &Outer Core? How do we know? From Seismic Waves
Scientists studying earthquakes have found that seismicwaves travel through the Earths interior at differentspeeds and directions. The differing speeds are due to thedifferent densities of the existing zones or layers. Think about trying to run through air vs trying to runthrough water These Seismic Waves are called P (primary) and S(secondary) waves. Seismic Waves The Seismic Waves change speed and direction as they pass throughlayers of different densities. Notice the S-waves do not travel through the liquid outer core zations/es1009/es1009page01.cfm