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The Earths’ Interior

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Earth Facts

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Happy the man whose lot it is to knowthe secrets of the earth. He hastens not

to work his fellows' hurt by unjust deeds,but with rapt admiration contemplateimmortal Nature's ageless harmony,

and how and when her order came to be.Such spirits have no place for thoughts of

shame.- Euripides (484-406 B.C.)

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Inside the Earth

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Crust

• The exterior portion of the earth

• Lies above the Moho discontinuity

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Crust• 3 types of solid rock – igneous,

sedimentary, & metamorphic• Oxygen & silicon• Oceanic crust 8 km thick: basalt• Continental crust 32km thick:

granite & basalt

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Elements in the Crust• Oxygen 46.6% • Silicon 27.72% • Aluminum 8.13% • Iron 5.00% • Calcium 3.63% • Sodium 2.83% • Potassium 2.59% • Magnesium 2.09% • Titanium 0.40%

• Hydrogen 0.14%

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Mantle• Layer between

the crust and the core

• Silicon, oxygen, iron & magnesium

• 870°-2200°c• 2900 km thick

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Lithosphere

• Thin outer shell of the earth

• Consisting of the crust and the rigid upper mantle

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Lithosphere

• Rigid layer• Broken up

into 7 major lithospheric plates

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Asthenosphere

• Zone of the mantle beneath the lithosphere

• Consists of slowly flowing solid rock

• Plasticity: when solid rock flows

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Moho

• The Mohorovicic discontinuity• Croatian scientist found

increased speed of seismic waves

• Boundary between the mantle and the earth’s crust

• Reveals increase in density

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Seismic Waves

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Shadow Zones

• Location on the earth’s surface where no seismic waves or only P waves can be detected.

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Core• Central portion of earth• Below the mantle• Depth of about 2,900 kilometers

(1,800 miles)• Consisting of iron and nickel• Liquid outer core and a solid

inner core

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Magnetosphere

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Magnetosphere

• Region of space that is affected by the Earth’s magnetic field

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The Dynamic EarthPlate Tectonics

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Theory of Continental Drift

• 1900’s Alfred Wegener proposed that the earth used to be one giant landmass that split to form today’s continents

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Continental Drift

• Pangaea –“all lands” –a single

landmass–origin of all

the continents

• Panthalassa –“all seas” –giant ocean

that must have surrounded Pangaea.

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Wegener's Evidence for Continental Drift

• The shape of continents suggests they once fit together –Noticed first in 1858 as soon

as good maps were being made

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Wegener's Evidence for Continental Drift

• Fossils – The glossopterus flora and fauna are now found in widely separated continents in the southern Hemisphere.

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Fossil Evidence• Fossils

support Wegener’s theory

• Glossopteris• Mesosaurus• Lystrosaurus• Cynognathus

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Wegener's Evidence for Continental Drift

• Paleoclimate evidence• Distribution of Paleozoic

–Coral reefs–Coal beds–Deserts

• 250-300 million years ago

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Wegener's Evidence for Continental Drift

• Rock types and mountain ranges can be traced across now widely separated continents.

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Rock Evidence

• Glacial deposits

• Folded mountains

• Coal deposits

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Wegener's Evidence for Continental Drift

• Evidence of ancient glaciers in all of the southern continents

• Do you think all of this satisfied the critics?

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Where is the Force?

• What makes the plates move?

• The answer is on the ocean floor

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Mid-ocean Ridge

• System of undersea mountain ranges

• Wind around the earth• 65,000 km• Ocean rocks much younger

than continental rocks

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Mid-Atlantic Ridge

• Undersea mountain range • Steep, narrow valley down

the center 

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Seafloor Spreading

• Movement of the ocean floor away from either side of a mid-ocean ridge

• Caused by convection currents

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Seafloor Spreading

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Convection Cells

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Uneven heating causes movement in fluids

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Paleomagnetism of the Ocean Floor

• Magnetic fossil record of the alternating magnetic field of the ocean floor.

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Plate Tectonics

• Theory that the lithosphere is made up of plates that float on the asthenosphere

• Plates possibly moved by convection currents

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Types of Crust

• Oceanic crust–Material that makes up the

ocean floor• Continental crust

–Material that makes up landmasses

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Divergent Boundary

• Formed by two lithospheric plates that are moving apart

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Rift Valley

• Steep, narrow valley • Formed as lithospheric

plates separate

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Convergent Boundary

• Border formed by the collision of two lithospheric plates

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Continental vs. Continental

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Oceanic vs Continental

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Subduction Zone

• Region where one lithospheric plate moves under another.

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Ocean Trench

• Formed when one oceanic crust is subducted under another oceanic crust

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Oceanic vs Oceanic

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Island arc

• Chain of volcanic islands• Formed by subduction at

ocean trenches

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Transform Fault Boundary

• Formed by two lithospheric plates that slide past each other

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Theory of Suspect Terrains

• – theory that continents are a patchwork of pieces of land that have individual geologic histories

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The earth was made so various,that the mind of solitary man,

studious of changeand pleased with novelty,

might be indulged.

- Cowper, English poet

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Crust

• Asthenosphere

–Lithosphere

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Continental Drift

• Hypothesis stating that the continents once formed a single landmass

• Broke up and drifted to their present location

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The Earths’ Interior