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Earth's Interior & Convection in Mantle

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Lilia Negron

on 24 January 2013

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Transcript of Earth's Interior & Convection in Mantle

photo credit Nasa / Goddard Space Flight Center / Reto Stöckli Ls. 3.1 Earth's Interior Earth Structure & Material How do Geoligist learn
about Earht's Interior? Geologist- scientific study of the origin, history & struc. of the Earth.
Have found methods to study interor of Earth.
Use two main types of evidence:
1. Direct Evidence > rock samples
2. Indirect Evidence > seismic waves Feat. of Earth's Crust, Mantel & Core 1. Crust- layer of rock that forms Earth's outer skin.
Layer of solid rock that includes both dry land & ocean floor.
Main elements are oxygen & silicon
Crust is thick under high mnts. & thin beneath ocean floor. Mantle- made of rock that's very hot but solid.
Contains more magnesium & iron than rock above it.
Divided into 3 layers based on physical charac.
3,000 km. thick. 3. Core- made mostly of metals iron & nickel.
Consists of 2 parts: outer & inner core.
Below mantle. 1. Radiation- transfer of energy
carried in rays.
Sun transfers light & heat through air. 2 types of Seismic Waves:
1. P Wave- longitudinal earthquake wave.
Travels through interior of Earth.
First to be recorded by seismograph. 1. Direct Evidence:
Rocks give geologist clues about Earth's struc. & conditions inside Earth.
Rocks that are blasted from volcanoes also give evidence. 2. Indirect Evidence:
Seismic waves, prod. by earthquakes, show geologist how they travel through Earth.
Speed & path > clues about struc. of Earth.
Path reveals areas where the form or make up changes. 2. S Wave-transeverse earth-
quake wave.
Travels through interior of Earth
Second to be recorded in seismograph. Pressure- result of force pressing on an area.
Deeper inside the Earth > greater mass of rock is pressing down from above.
Weight of rock above > pressure inside Earth increases with depth.
Deeper down inside the Earth > greater the pressure. Temp. inside Earth increases as pressure increases.
Mass of rock that presses down from above affects temp. inside Earth.
High temp. inside Earth are result of great pressure squeezing rock & release of energy from radioactive substances. Earth is made up of 3 layers.
3 main layers of Earth are the crust, mantle, & core.
Layers vary greatly in size, composition, temp, & pressure. b. Continental Crust- crust that forms of the continent.
Composition varies, but overall is like granite- light in color and coarse grains. a. Oceanic Crust- lies beneath the ocean.
Composed of ocean sediment & basalt- dark, fine grained rock. 1. Lithosphere- upper most part of mantle.
Brittle rock.
Strong, hard & rigid rock. 2. Asthenosphere-less rigid, hotter & increasing pressure.
Below lithosphere.
Can bend like metal spoon but still solid. 3. Mesosphere- hot & more rigid
Stiffness due to high pressure.
Has layer, transition zone, lies beneath asthenosphere.
Includes lower mantle. 3 Layers of Mantle a. Outer Core- layer of molten metal surrounding inner core.
dense, liquid

b. Inner Core- dense ball of solid metal.
Extreme pressure squeezes atoms of iron & nickel so much that they cannot spread out & become liquid. Magnetic Field:
Created by massive circulation of hot liquid beneath the mantle.
Earth's magnetic field > planets act like giant bar magnet.
Affects whole planet. Ls.9.2
Convection & the Mantle How is Heat Transferred?
Heat constantly transferred inside Earth & all around Earth's surface.
Heat always moves from warm > cold.
Obj. heated > particles move faster > have more energy.
Transfer-movement of energy from warm to cooler obj.
3 types of heat transfer: radiation, convection & conduction. Convection Currents 2. Convection-heat transferred by movement of fluid.
Current created as warm air rises from ground.
Warm air heats cooler air above. 3. Conduction-Heat transferred bw. materials that are touching. Constant flow of heat (less dense) rising up while cool (more dense) lowers.
Flow that transfers heat in fluid- convection current.
Heating & cooling of fluid, change in fluid density & force of gravity combine to set convection currents in motion.
W/ out heat > convection current will stop. Convection Current in Earth Inside Earth, mantle & core give off lg. amounts of heat that is transferred by convection currents.
Heat from core & mantle cause convection currents in mantle.

Convection currents are also in outer core.
Cause Earth's magnetic field.
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