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/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 the core (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 and lava (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

Earth’s Layers How are the earth’s layers similar to an egg?

The Crust Outer layer 5-25 miles thick Broken into pieces - plates 2 types of crust Oceanic more dense – 2.9g/cm3 made of basalt Continental least dense – 2.8g/cm3 made of granite

Oceanic and Continental Crust

The Mantle Middle layer Very thick Largest layer Upper Mantle – “Floats on plastic” 3.3 g/cm3 Plastic Mantle – 3.5 g/cm3 Lower 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 solid iron and nickel density of 16.0g/cm3

Physical Structure of the Earth Crust (less than 1% of the total volume of the Earth) Continental Crust 2.7 g/cm3 granite Oceanic Crust 2.9 g/cm3 basalt Mantle (83% of the total volume of the Earth) Lithosphere (lower crust and upper mantle) Plate in the “plate tectonic theory” Floats on upper mantle like water 3.1 g/cm3 Asthenosphere solid rock that flows slowly (like hot asphalt) “Plastic” layer 3.3 g/cm3 Mesosphere 4.5 g/cm3 Core (16% of the total volume of the Earth) Outer Core liquid iron and nickel density of 11.8g/cm3 Inner Core Solid iron and nickel density of 16.0g/cm3

-Original Subduction Zone Ocean trench Ocean Solid mantle= Lithosphere Continental Crust Oceanic crust Continental Crust Solid Mantle Solid Mantle Plastic Mantle Plastic mantle = Asthenosphere 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.