Earth's Interior

Earth’s InteriorWhat’s inside our Earth?

Lithosphere (based on Physical properties)

“Moho”(Mohorovicic

discontinuity):

The boundary between mantle and crust.

Aesthenosphere (based on physical properties.

•Part of the upper mantle.

•The rigid lithosphere is thought to "float" or move about on the slowly flowing asthenosphere.

•Partly melted rock.

•Plasticity: describes the ability for a solid to flow (tar-like, malleable, ductile).

•Density – 3.5g/cm3

NOTICE THAT…

Depth

Density

Temperature

Pressure

THEY ALL INCREASE AS YOU GO DEEPER INTO THE EARTH.

Layers of the Earth1. Crust

Top layer, hard, brittle, thin.Density – 2.7g/cm3

Temperature – 0° -1000° C (1832 ° F) 2 types of crust:a) Continental - thick (30 - 70 km) (19 – 43 mi)- granitic- high in Al, Mg, K, and Si. b) Oceanic - thin (5 - 10 km) (3 – 6 mi)- basaltic rock- high in Fe, Mg, & Ca.

•Continental Crust is LESS DENSE than Oceanic Crust.

2. Mantle

80 % of the Earth’s volumeLava likePlasticityMantle convection (responsible for plate movement).

A) Depth – 30 km – 2900 km (20 – 1800 mi)B) Density – 3.3g/cm3 – 5.8 g/cm3

C) Composition – Fe, Mg, Ca, Al (heavier)D) Temps - 870° - 2200° C (1598 – 3992° F)

3. Outer Core

A) Depth – 2900 – 5100 km (1800 – 3170 mi.)B) Density – 9.5 – 11.5g/cm3

C) Composition – LIQUID Fe (Iron) and Ni (Nickle).D) Temps - 2200° - 5000° C (3992 - 9032° F)

“Magnetic Dynamo Effect - As the Earth rotates, the liquid outer core spins, creating the Earth's magnetic field.

4. Inner Core

A) Depth – 5100 km – 6378 km (3169 – 3963 mi)

B) Density – 11.6 - 12g/cm3

C) Composition – SOLID Fe and Ni

D) Temps – 5000° to 6700° C (12,092 ° F).

How do we know about the Earth’s Interior?By Seismic Waves…

Seismic waves are the waves of energy caused by volcanoes, earthquakes, or explosives.

Body Waves…

Body waves travel through Earth.

Two types of body waves are:

1)primary waves (P waves).

2)secondary waves (S waves).

What Are Primary Waves?The P wave is also known as a compressional wave or a “push/pull” wave.

Fastest

P waves move through liquid and solid material at rates of (4-7km/sec).

What Are Secondary Waves?The S wave or secondary wave can also be called a shake wave.

Slower than P waves.

These waves move ONLY through SOLID material at a rate of (2-5km/sec).

Path of seismic waves in a planet with layers having differing denseties (seismic velocities).

Path of seismic waves in a planet with layers having differing denseties (seismic velocities).

P-waves

S - wave

Surface Waves (2 types)

Travel on the surface

1) L – waves: move side to side in a horizontal plane.

Surface Waves cont..2) Rayleigh waves: Like rolling ocean waves, they move both vertically and horizontally in a vertical plane

Most destructive.

Our view comes from study of earthquake (seismic) waves.

The Earth’s interior

consists of concentric

layers.Crust

Mantle

Core

Our view comes from study of earthquake (seismic) waves.

The Earth’s interior

consists of concentric

layers.Crust

Mantle

Core

Probing Earth’s Interior

Travel times of P and S waves vary depending on the properties of the materials they pass through.

Waves travel faster in harder substances.

Probing Earth’s Interior

Path of seismic waves in a planet with uniform seismic velocity (density).

Path of seismic waves in a planet with uniform seismic velocity (density).

Path of seismic waves in a planet with a steady depth increase in density (seismic velocity).

Path of seismic waves in a planet with a steady depth increase in density (seismic velocity).

Fig. 2.12ab

W. W. Norton