Earth Materials and Resources

Ms. Ma. Irene G. Gonzales, LPT

Did you know that?

• Materials that have the greatest density have the

greatest gravitational force of attraction, and as a

result they have tended to concentrate close

together at and near the center of Earth.

• Earth’s interior is primarily composed of solids, the

densest of the three states of matter.

Did you know that?

• Liquids are not as dense as solids; thus, most of

Earth’s liquid water lies at the planet’s surface

thousands of kilometers above the densest solids

located deep inside Earth.

• Gases, with an even lower density than liquids,

have the weakest gravitational attractive force and

are held relatively loose around Earth as the

atmospheric envelope.

Did you know that?

• Planet Earth has a radius of about

6400 kilometers.

• Through direct means, by mining

and drilling, we have been able to

penetrate and examine only an

extremely small part of that

distance.

Did you know that?

• Mining and drilling activities have helped establish

the notion of the geothermal gradient – that

temperature increases with increasing depth inside

Earth.

SEISMIC WAVES

• The most important evidence that

scientists have used to gain indirect

knowledge of Earth’s interior is the

behavior of various shock waves,

known as seismic waves.

• Seismograph – instrument that

records seismic waves from an

earthquake even when the

earthquake is centered thousands of

kilometers away from the

seismograph’s location.

TWO MAJOR TYPES OF SEISMIC WAVES

• P (Primary) waves – travel faster and are first to

arrive at a recording seismograph

• S (Secondary) waves – travel more slowly than P

waves

NOTE: Both types of waves speed up in denser

material and slow down when passing through

material that is less dense.

TWO MAJOR TYPES OF SEISMIC WAVES

• P (Primary) waves – pass through all types of

matter, including liquids and gases

• S (Secondary) waves – can only move through

solids

CORE

• Innermost section of Earth

• Radius of about 3,360

kilometers

• 1/3 of Earth’s mass

• Under enormous pressure

• Composed primarily of IRON

and NICKEL

INNER CORE

• Radius of about 960

kilometers

• Speed of P waves traveling

through the inner core shows

that it is a solid with a very

high material density of

about 13 grams per cubic

centimeter

OUTER CORE

• Forms 2400 kilometer thick

band around the inner core

• Blocks the passage of S

waves, therefore, Earth

scientists conclude that the

outer core is MOLTEN, that

is, it consists of liquid

(melted) rock matter

TAKE NOTE

• Temperatures at the top of

the outer core are estimated

to be 4800 degrees Celcius,

increasing to 6900 degrees

Celcius at the very center of

the Earth.

TAKE NOTE

• Melting temperature of rock

matter increases with

pressure and pressure

increases with depth

beneath Earth’s surface

MANTLE

• Representing nearly 2/3 of

Earth’s mass

• Largest of Earth’s interior zones

• Thickness of approximately 2885

kilometers

• Earthquake waves that pass

through the mantle indicate that

it is composed of solid rock

matter

• Less dense than that of the core

MANTLE

• Consists of silicate rocks (high in

silicon and oxygen) and also

significant amounts of iron and

magnesium

MANTLE

• The interface between the

mantle and the overlying crust is

marked by a significant change

of density, called a Mohorovicic

discontinuity, which is indicated

by an abrupt decrease in the

velocity of seismic waves as

they travel up through this

internal boundary.

CRUST

• Earth’s solid exterior, outermost

layer of the solid Earth

• Composed of a great variety of

rock types that respond in

diverse ways and at varying

rates to surface processes

• Only portion of the lithosphere of

which Earth scientists have

direct knowledge, yet it

represents only about 1% of

Earth’s planetary mass

CRUST

• Comprises the ocean floor and

the continents

• Extremely think in comparison to

the size of the planet

• Cold compared with the mantle

and behaves in a more rigid and

brittle manner

KIND OF EARTH’S CRUST

1. OCEANIC CRUST (basaltic) –

has a density of 3.0 grams per

cubic centimeter and is only a

few kilometers thick

- Composed of basalt, a heavy,

dark – colored, iron – rich rock

that is also high in Silicon (Si)

and magnesium (Mg)

- Forms the vast, deep ocean

floors and lava flows on all of

the continents

KIND OF EARTH’S CRUST

2. CONTINENTAL CRUST

(granitic) – comprises the major

landmasses on Earth that are

exposed to the atmosphere

- Has an average density of 2.7

grams per cubic centimeter

which is lesser than that of

oceanic crust

- Considerably thicker than

oceanic crust with an average

thickness of 32 to 40 kilometers

KIND OF EARTH’S CRUST

2. CONTINENTAL CRUST

(granitic) – contains more light –

colored rocks than oceanic

crust does and can be regarded

as granitic in composition

LITHOSPHERE

• Structural sense: refer to the

brittle outer shell of Earth,

including the crust and the

rigid, uppermost mantle layer

• Responds to applied stress like

that of an elastic solid

• Elastic solids are rigid and

brittle

– At the threshold value, it fails by

fracturing.

ASTHENOSPHERE

• Greek word asthenias, meaning

without strength

• Layer of the upper mantle that

responds to stress by

deforming and flowing rather

than by fracturing

• Has the characteristics of a

plastic solid