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Inside the Earth. Review of Density… Density is an expression of the relative heaviness of a substance mass per unit volume grams per cubic centimeter (g/cm 3 ) The density of pure water is 1g/cm 3 . Granite rock is about 2.7 times denser at 2.7g/cm 3 . . Formation of the Earth.
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Review of Density… • Density is an expression of the relative heaviness of a substance • mass per unit volume • grams per cubic centimeter (g/cm3) • The density of pure water is 1g/cm3. • Granite rock is about 2.7 times denser at 2.7g/cm3.
Formation of the Earth • The most dense material (Iron and Nickel) settled to thecore (center) • Less dense matter (Silicates) formed the vast interior of the Earth (mantle). • The least dense material (Granite and Basalt) formed the Earth’s solid stony crust. • Volcanic eruptions continued through the crust.
Formation of the Earth Continued… • With each eruption, gases, water vapor, ash andlava (molten material) were brought to the surface. • The water vapor and gases formed the atmosphere. • As the Earth cooled the water vapor turned to water and the rains started. • The oceans formed from runoff. This also supplied the ocean with the mineral content it has today.
IGNEOUS ROCKS • Formed from molten material including volcanic lava, ash, or bombs as well as magma below Earth’s surface
TYPES OF IGNEOUS ROCKS BASALT GRANITE
Composition (What it is made of) • Crust • Mantle • Core
How are the earth’s layers similar to an egg? Earth’s Layers
Outer layer 5-25 miles thick Broken into pieces - plates 2 types of crust Oceanic moredense – 2.9g/cm3 made of basalt Continental least dense – 2.8g/cm3 made of granite The Crust
Middle layer Very thick Largest layer Upper Mantle – “Floats on plastic” 3.3 g/cm3 Plastic Mantle – 3.5 g/cm3 Lower Mantle – The Mantle
The Core • Made mostly of iron • 1/3 of the earth’s mass • Very hot • The most dense • Divided into 2: • The outer core • made up of liquid iron and nickel • density of 11.8g/cm3 • The inner core • made up of solidiron and nickel • density of 16.0g/cm3
Physical Structure of the Earth(The Layers) • Crust (less than 1% of the total volume of the Earth) Oceanic Crust - Basalt Continental Crust - Granite • Mantle (83% of the total volume of the Earth) • Lithosphere • rigid upper layer • Plate in the “plate tectonic theory” • Asthenosphere • solid rock that flows slowly (like hot asphalt) • “plastic” layer • Mesosphere most dense of the mantle - rigid thickest layer of the mantle - silicate • Core (16% of the total volume of the Earth) • Outer Core • liquid • Inner Core • solid, very dense
Subduction Zone Ocean trench Ocean Solid mantle= Lithosphere Continental Crust Oceanic crust Continental Crust Solid Mantle Solid Mantle Plastic mantle = Asthenosphere Plastic Mantle Label the following: -Continental Crust -Ocean -Oceanic Crust -Solid Mantle -Plastic Mantle -Original Subduction Zone -New Subduction Zone
Density Layering • The overall density of the Earth is 5.5g/cm3 • The crust changes continually to balance the amount of lighter and denser material. • Erosion and glacial melting decreases the density of the crust. • Volcanic eruption will increase the density.
Seismic waves • Evidence of distinct layers in the Earth with different densities comes from the observations of seismic waves (the vibrations generated by earthquakes and explosions) • As seismic waves move through the Earth, wave patterns may change indicating the waves were: • Reflected: bounced back due to extreme density • Refracted: directional change • Measuring the changes in the velocity of these waves as they travel through the Earth provides information on the number of layers and the thickness and composition of the layers.