TEMPERATURE  The deeper you go, the hotter it gets. & Celsius 4,000° C 4,000 km 2,000 km & kilometers 5,000° C 6,000 km F F mi.

EARTH’S INTERIOR STRUCTURE  Heat flows outward from the interior  Crust insulates us from interior heat.  Mantle is semi-molten.  Outer core is liquid.  Inner core is solid.

3 Major Layers Crust Mantle Core 5 Major Layers Lithosphere Athenosphere Lower Mantle Outer Core Inner Core (Mesosphere)

COMPOSITIONAL LAYERSPHYSICAL LAYERS (lower mantle)

EARTH’S INTERIOR STRUCTURE

Thin outer layer – Continental Crust Lighter (less dense), granitic rock – Oceanic Crust Dense, Basaltic rock Crust thickness varies: up to 70 km in some mountain regions up to 70 km in some mountain regions Less than 5 km in ocean regions Less than 5 km in ocean regions

The layer below the crust – About 2890 km thick Region of slowly moving convection cells

Composition – Peridotite a mostly solid basaltic type rock There are 3 regions - based on temperature & plasticity No one has ever drilled to the mantle. It is also very hot

Center of Earth – Composed of iron-nickel material Under extreme pressure 13x more dense than water CORE

LITHOSPHERE (Sphere of Rock) Includes Crust & Upper Mantle Crust & uppermost mantle ~ 100 km thick – Continental Crust Lighter (less dense), granite rock – Oceanic Crust Dense, Basalt rock – Upper mantle

Lithosphere (solid sphere) – Solid brittle rock layer – Includes crust & uppermost mantle Extends to a depth of about km

ASTHENOSPHERE (Weak Sphere) – Upper mantle directly below lithosphere – Extends to a depth of about km Hot, plastic rock – Exhibits partial melting – Rock easily deforms (key contribution to Plate Tectonic Theory) Hard rock that acts like warm tar or honey

Temperature: 900°C to over 4,000 °C (1,652°F - 7,230 °F) – Generate mantle plumes heated by core Heat transferred upward  Rest of the mantle  Much stronger and hotter than the Asthenosphere  2550 km thick  Mesosphere

2 Distinct Regions Outer Core Inner Core

Outer Core Liquid layer below Mantle Iron & Nickel composition Temperature  F (  C) – Under less pressure than inner core – Allows this region to melt About 2260 km thick generates Earth’s Magnetic Field

Inner Core Solid Layer beneath the Outer Core Iron & Nickel composition Temperature-9,032 – 10,832  F (5,000-6,000  C) – extreme high pressure – Keeps region solid even though it is the hottest region High density – ≈ 1220 km radius

Flow of liquid metallic iron in outer core generates magnetic field called the “Magnetosphere” N S North magnetic pole South magnetic pole

Studies of the path of P & S waves helped to identify the boundaries of Earth’s layers – Determined that the outer core is liquid

- Seismic waves change direction – As pressure increases w/depth elastic properties of rocks change Slows P-waves by bending them Produces a Shadow Zone because S-waves are not transmitted

Mohorovicic Discontinuity (Moho) – A boundary that separates the crust from the mantle – Andrija Mohorovicic – 1909, Yugoslavian Seismologist Noticed increase in seismic wave speeds below 50 km of depth

Moho –Velocity of seismic waves increases abruptly below 50 km of depth –Separates crust from underlying mantle Mohorovicic Discontinuity

Shadow Zone –Absence of P waves from about 105 degrees to 140 degrees around the globe from an earthquake –Can be explained if Earth contains a core composed of materials unlike the overlying mantle

Composition of Earth’s layers is determined by: – Studying seismic data – Rock samples from the crust and mantle – Meteorites Assumed to be made up of original Earth forming material – High-pressure experiments on Earth materials Squeezing and heating material under conditions similar to Earth’s deep interior

Crust –Early seismic data and drilling technology continental crust - mostly light, granitic rocks Ocean crust – dark, dense, basaltic rocks Mantle - Composition is less certain o Some lava that reaches surface comes from the asthenosphere Core - Thought to be mainly dense iron and nickel o similar to metallic meteorites o surrounding mantle believed to be composed of rocks similar to stony meteorites