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Earth’s Structure. Part I. Earth’s Structure. From space the Earth looks small and fragile. . What are some of the things that you notice about our planet when you see this image? . The Earth is composed of several integrated parts (spheres) that interact with one another:. Atmosphere
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Earth’sStructure Part I
Earth’s Structure From space the Earth looks small and fragile. What are some of the things that you notice about our planet when you see this image? The Earth is composed of several integrated parts (spheres) that interact with one another: • Atmosphere • Hydrosphere • Lithosphere (solid Earth) • Biosphere
Earth’s Structure Atmosphere:the clouds high in the atmosphere represent the very thin blanket of gases that covers our planet. The planets organisms not only use these gases for life processes, this air protects us from harmful radiation from the sun. Hydrosphere:the global ocean is the most prominent feature of our (blue) planet. The oceans cover ~71% of our planet and represent 97% of all the water on our planet. The oceans and lakes of the planet Earth are teeming with a great diversity of life.
Earth’s Structure Solid Earth:represents the majority of the Earth system. Most of the Earth lies at inaccessible depths. However, the solid Earth exerts a strong influence on all other parts (ex. magnetic field) of the planet. Biosphere:includes all life on Earth - concentrated at the surface. Plants and animals don't only respond the their environment but also exercise a very strong control over the other parts of the planet. Life has become amazingly successful on land over the past 400 million years.
The Earth System Atmosphere This figure shows the four spheres of the Earth. Each sphere has an intimate relationship with the other spheres as interactions between the spheresoccur constantly. What are some of the interactions between these spheres? Biosphere Hydrosphere Solid Earth
ORIGIN OF THE EARTH Gravitational compression Meteors and Asteroids bombarded the Earth Density stratified planet
EARTH’S INTERIOR CORE d • Dense • Inner Core is solid • Outer Core is liquid MANTLE • Less dense than core • Mostly solid • Upper mantle is partially molten CRUST • Outermost layer • Very thin and rigid
EARTH’S INTERIOR • Lithosphere is rigid layer of crust and mantle overlying partially-molten asthenosphere. Ocean Crust (granite & basalt rocks) } • Mantle extends to a depth of ~ 2,900 km and plastic in the upper section. This section is called the asthenosphere and has elasticity like silly putty. Composed of silicate minerals. Lithospere • Continental crust composed of quartz and feldspar minerals. Density is ~ 2.8g/cm3 } Upper Mantle (asthenosphere) • Oceanic crust composed of basalt; basalt rich in iron/magnesium minerals. Density is ~ 3.0 g/cm3 Mantle (silicate minerals) Lower Mantle Outer Core • Core composed of solid inner core and liquid outer core composed of iron and nickel. Core (iron, nickel and sulfur) Inner Core 6,371 km (3,960 mi
EARTH’S INTERIOR Sea Level Oceanic Crust 0 20 • Crust is approximately 20 - 80 km thick • Solid, rigid rock • Tends to be thicker beneath continents and thinner beneath oceans • Oceanic crust is denser than continental crust. 40 km 60 Crust Asthenosphere 80 0 km • Mantle is approximately 2,900 km thick • Semi-fluid • Upper section is the asthenosphere 1000 2000 3000 • Outer core is approximately 2,250 km thick • Liquid iron (Fe) and nickel (Ni) 4000 • Inner core is approximately 1,220 km thick • Solid Fe and Ni 5000 6000
Conditions at the core-mantle boundary Pan of water Convection Cell • The liquid core moves and flows transferring heat to the mantle. • The hotter mantle material is less dense and circulates upward. • The cooler mantle material is more dense and circulates downward. • Convection currents circulate the mantle material. Gas Stove • An increase in temperature is applied to the bottom of the pan. • Water heats up, becomes less dense and circulates upward. • Water cools at the surface becomes more dense and circulates downward. • This circulation is called CONVECTION
Evidence of Internal Structure Granite Basalt • Density • calculate density of Earth • speculate on probable compositions • Meteorites • Use composition and age to determine composition and age of Earth • Seismic waves • Travel times and direction give indication of internal structure of Earth
Types of Seismic Waves • P waves • Primary waves • Travel fastest (~ 6 km/sec) • Push and pull movement • Travel thru solids and liquids • S waves • Secondary waves • Move side-to-side • Slower (~ 4 km/sec) • Travel thru solids only
Seismic Waves Earthquake Epicenter Seismic station records both P and S waves 1050 Seismic station records no P and S waves 1400 1400 Seismic station records P waves only S-wave shadow zone
Seismic Waves Shadow zone (no P-waves detected) Center of seismic disturbance Solid Inner Core Crust Crust (A) Mantle Outer Core Shadow zone (no S-waves detected) Inner Core Center of seismic disturbance (B) Crust Center of seismic disturbance (C) Crust Scientists use waves from earthquakes to determine the Earth’s interior. Earthquakes generate P-waves and S-waves within the earth. Shadows occur on the opposite side of the earth from the earthquake epicenter because the outer core reflects S-waves, and bends P-waves. S-waves are reflected because they cannot travel through liquids, and they cast a larger shadow than the bent P-waves.
