Layers of Earth & Seismic Waves

Crust

• Thinnest and most outermost layer of the Earth

• 35km from surface

Mohorovicic Discontinuity or Moho

• Interface between the crust and mantle

Continental Crust

• Thick (35-40km)

• Buoyant

• Mostly Old

• Made up of Granite

Oceanic Crust

• Thin (7-10km)

• Dense

• Young

• Basalt

Mantle

• Found Beneath the Crust

• 2900km from the Earth’s Surface

• Solid but it can flow (Plasticity)

• Thickest Layer of Earth

• The hot material (magma) in the mantle rises to the top of the mantle, cools, then sinks, reheats, and rises again. These convection currents cause changes in the Earth’s surface

Beno Gutenberg

• German Seisomologist

• Observed that P Waves diminish and eventually die about 105 degrees , then about 140 degrees away the P waves reappear

Gutenberg Discontinuity

• Marks the boundary between the mantle and outer core

Core

• Beneath the Mantle

• Innermost Layer of the Earth

• Composed of Nickel and Iron Alloy

• 16% of Earth’s Volume

• Molten (liquid) metal that is about 4,700°C (8,500°F)

• 1,800 miles beneath the crust and is about 1,400 miles thick

Outer Core

• Liquid Layer

• Zone that generates Earth’s Magnetic Field

• Convection flow of Metallic Iron

• 3000 celsius

• 2270km

Inner Core

• Solid Layer

• Materials are stronger than the outer core

• 5000 celsius

Earth’s Magnetic Field

it is created by the rotation of the outer fluid, core around the solid inner core This creates an electrical current.

Inge Lehmann

• Discovered the Solid Inner Core inside the molten Outer Core

Seismic Waves

• Waves of energy caused by the sudden breaking of rocks within the earth or an explosion

Seismograph

Energy that travel through the earth and is recorded on

P Waves (Primary Waves/Compression Waves)

• Fastest kind of seismic wave

• Can move through solid rock and fluids.

• Pushes and Pulls the rock it moves.

S Waves (Secondary Waves/Transverse Waves)

• we feel after an earthquake

• Slower than P Waves

• Can only move through solid rocks

• Moves rock up and down, or side to side

Love Waves

• Fastest Surface Wave

• Moves the ground from Side-to-Side

Augustus Edward Hough Love 

British Mathematician who worked out the mathematical model for love wave in 1911

Rayleigh Waves

• Rolls Along the Ground

• Moves the ground up and down and side to side in the same direction the wave is moving

Lord Rayleigh

named after him and Mathematically predicted the existence of Rayleigh Waves in 1885