Chapter 3 - Geology 209 - University of Calgary

• Natural radioactivity.

What contributed to the extremely high temperature at Earth's interior?

• Geoid-shaped.
• Density of 5.5g/cm^3
• Mass of 5.973 x 10^24kg.
• Earth's radius is not constant - varies at the equator and poles.

What are the characteristics of Earth?

(There are four main points)

• Study layers and bodies of rocks on the Earth's surface (outcrops, wells, mining galleries).
• Study rocks intersected by the wells drilled for other purposes.
• Seismic wave investigation.

What are some methods used to study the Earth's interior?

(There are three main methods)

• An explosive charge is detonated at Earth's surface, inland, or sea-floor, causing seismic waves.
• Waves controlled by chemical composition and environmental characteristics of the rock and subsurface fluids through which they travel.
• Signal received is filtered and interpreted.

Seismic Wave Investigation

(There are three main points)

• Natural phenomena that happen at the Earth's subsurface causing large amounts of mechanical energy to be discharged.
• Caused by strata re-arrangement.
• Seismic waves often travel throughout the entire planet.

Earthquakes

(Three main points)

The place where an earthquake happens.

Hypocenter

The point of the Earth's surface situated above the hypocenter.

Epicenter

• Body waves.
• Surface waves.

What are the two kinds of wave functions?

• Travel inside the Earth's interior.

Body Waves

• Travel inside the shallowest parts of the Earth.

Surface Waves

• Primary (p-waves).
• Secondary (s-waves).

What are the two kinds of body waves?

• The fastest waves.

Primary Waves

• Fast (6-14km/s).
• Compress and release rocks in the direction of the propagation.
• Perpendicular to the travel direction of s-waves.
• Travel through solid and liquid media.

What are some characteristics of primary waves?

(There are four main points)

• Travel at 3.6km/s.
• Movement in the direction of the wave propagation in the vertical s-waves and perpendicular to it in the case of horizontal s-waves.

What are the characteristics of secondary waves?

(There are two main points)

• Measure earthquake amplitude (max. s-wave height) and magnitude (amount of released energy).

Seismograms

• Inner core.
• Outer core.
• Mesosphere.
• Asthenosphere.
• Lithosphere.

What are the five layers of Earth?

A iron-dominated and nickel sub dominated part of the Earth situated at the center.

The Core

• Average density is 11g/cm^3.
• Extremely hot.

What are the characteristics of Earth's core?

(There are two main points)

A silicate dominated part of the Earth.

The Mantle

• Minerals with SiO4 in their composition.

Silicates

• Forms 80% of Earth's volume.
• Average density is 3.3g/cm^3.

What are the characteristics of the Earth's mantle.

• Boundary between mantle and core.

Guttenberg Discontinuity

The thinnest layer of the Earth which is silicate dominated.

The Crust

• Oceanic crust.
• Continental crust.

What are the two kinds of crust in the Earth's composition?

• Average thickness of 7-8km.
• Consists of silicates of iron and magnesium.
• Average density of 3g/cm^3.
• ~180 million years old.

What are the characteristics of oceanic crust?

(There are four main points)

• Average thickness of 35-40km.
• Dominated by light metals (Na, K, Al), however, silicates, O2, sulfur, etc. occur in small amounts.
• Average density of 2.7g/cm^3.
• Oldest crust is 4 billion years old.

What are the characteristics of continental crust?

(There are four main points)

• Boundary between crust and mantle.

Mohorovicic Discontinuity

The outermost layer of the Earth consisting of the crust and uppermost part of the mantle.

Lithosphere

• Thickness ranges from 100-250km.
• Solid state.

What are the characteristics of the lithosphere?

(There are two main points)

• North American Plate.
• Eurasian Plate.
• African Plate.
• South American Plate.
• Australian-Indian Plate.
• Antarctic Plate.
• Pacific Plate.

What are the seven major lithospheric plates on Earth?

• Pacific Plate.

Which plate consists of solely oceanic crust?

The lower layer of the crust and upper part of the mantle situated under the lithosphere.

Asthenosphere

• Lower boundary at a depth of ~660km.
• Upper part is plastic, supporting the lithospheric plate dynamics.

What are the characteristics of the asthenosphere?

(There are two main points)

The lower mantle.

Mesosphere

• Occurs at depths ranging from 660-2900km.
• Considered solid, but has rocks capable of slow flow.

What are the characteristics of the mesosphere?

(There are two main points)

A layer of the Earth situated below the Gutenberg discontinuity.

Outer Core

• Depths of 2900-5170km.
• Liquid state due to high temperatures and iron-nickel alloy.
• Permanent heat transfer from outer core to mesosphere at GD.

What are the characteristics of the outer core?

(There are four main points)

A layer of the Earth situated below its boundary with the outer core down to the center of the Earth.

Inner Core

• Iron-nickel alloy is solid.
• Rotation is independent from the rest of the Earth.
• Distinct trend of inner core solidification from fluid outer core.

What are the characteristics of the inner core?

(There are three main points)

• 35% Iron.
• 30% Oxygen.
• 15% Silicon.
• 13% Magnesium.
•

The Elemental Composition of the Core (5)

• 46% Oxygen.
• 28% Silicon.
• 8% Aluminum.
• 6% Iron.
• 4% Magnesium.
•

The Elemental Composition of the Crust (6)

• Iron and Nickel melting point.
• Became highly mobile and sunk towards the protoplanets center, making up the core's composition.

What is the important event that contributed to the Protoearth structure evolution?

A process where the heavier elements concentrated in the core and the lighter ones in the mantle.

Gravitational Differentiation Process

• Early atmosphere of the Earth favored the formation of new minerals, causing the two to separate.

How did the crust and mantle separate?

• S-waves.

What seismic waves do not travel through liquid media?

b) Continental Crust.

What kind of crust is thicker?

a) Oceanic Crust
b) Continental Crust
c) Transitional Crust
d) Asthenosphere
e) Lithosphere

• The crust.

What is the Earth's outermost layer?

• The outer core.

What layer in Earth's internal structure is liquid?

• Depth.

The vertical distance between the hypocenter and the epicenter of an earthquake is referred to as...

• Layered.

Earth's internal structure is best described as...

• Asthenosphere.

What component of the Earth is plastic?

• The core.

What component of the Earth is situated below the Guttenberg discontinuity?

• Inner core.

This component of the Earth is liquid but behaves as a solid:

e) All of the Above

Which of the following components of Earth's interior is/are silicate-dominated?

a) Mantle
b) Mesosphere
c) Asthenosphere
d) Lithosphere
e) AOTA

• Outer core.

S-waves do not pass through this component of the Earth: