STRUCTURE OF THE EARTH

1. ATMOSPHERE- it is composed of several layers of gases that surround

the earth

2. BIOSPHERE- it is composed of all living things on the planet.

3. LITHOSPHERE- it is composed of the earth’s crust and mantle

Lithos(stone or rocky) sphaira ( sphere)

4. Hydrosphere- it is composed of water in all its forms, solid, liquid and

gaseous

4 MAIN LAYERS OF THE EARTH

CRUST

The outer layer of the earth which is about 4-25 miles thick consisting of sand

and rock.

Lays above the mantle and is the earth’s hard outer shell, the surface on which

we are living.

The crust extend downward from the surface to an average depthof 35km

where the mantle begins.

The crust is rich in element such as silicon, aluminium, calcium, sodium and

potassium.

2 KINDS OF CRUST

a. CONTINENTAL CRUST- forms the continents. It is the dry land. This is

the above type of crust and made up of sial or silicon- aluminium roc. It is

10-50 km thick and older than oceanic crust.

b. OCEANIC CRUST- it is the wet land. 8 – 10 km thick and consists of dark, dense igneous rocks, such as basalt

and gabbro. It is composed of somatic or silicon- magnesium rock. It contains more mafic minerals and is

thinner and denser than the continental crust.

THE MOHOROVICIC DISCONTINUITY

MOHO is the portion in which it separates the crust and the mantle.

ANDRIJA MOHOROVIC is a geologist who concluded that the zone of difference in density between the rocks of crust and mantle is due to the change in velocity

of the seismic waves as they passed from the crust to the mantle.

MANTLE

The thickest layer that reaches about half of the distance to the center of the

earth which lies below the crust.

It is the largest layer in the earth, making up 82% of the volume.

It is made up of rock that is very hot, but solid.

The upper most part of the mantle and the crust together form a rigid layer

called the lithosphere.

. Asthenosphere- a region of partially melted rock

CORE

-It is the inner part of the earth

-This part of the earth is about 1,800 miles (2,900 km) below the earth’s surface.

-it consists of two parts: Liquid Outer Core and Solid Inner Core

- the core is makes up 16 percent of the volume of the earth and about 31 percent of the mass.

Inner Core

-probably mostly metallic iron alloyed with a small amount of nickel, as its density is somewhat greater than that of pure metallic iron.

- It is the center of earth, is solid and about 780 miles (1250 km) thick is a dense ball of solid metal.

- The inner is in solid form due to its high temperature and immense pressure.

Outer Core

- Is a mass of molten iron and probably contains small amounts of lighter elements, such as sulphur and

oxygen, because its density is slightly less than that of pure metallic iron.

- the presence of the lighter elements depresses the freezing point and is probably responsible for the outer core’s liquid state.

Earth as a living planet

The earth has enormous distinct features such as the water-filled depression called oceans and seas. Outstanding scenic views of mountains,

waterfalls, and plains will definitely be a good place to live by.

Plate Tectonics

Tectonics comes from the Greek word, tektonikos, which means builder

It is a theory developed in the late 1960s to explain how the outer layers of the Earth move and deform.

It helps to explain continental drift, the spreading of the sea floor, volcanic eruptions and how mountains are formed.

It has proven to be so useful that it can predict geologic events and explain almost all aspects of what we see on the earth.

THEORY OF ISOSTACY

ISOSTACY- phenomenon wherein

continental and oceanic crusts have the ability to rise and sink

- crusts floats on top of the mantle like ice cubes in water

-happens when Earth’s crust gains weight due to mountain formation or glaciations

PLATE BOUNDARIES

PLATE BOUNDARY- region where plates meet- the plates move apart, collide or

slide past to each other

THREE TYPES OF PLATE BOUNDARIES

1) Divergent Boundaries- plates move apart, moving away from each other, leaving a gap between.- occur along ocean ridges (Mid-Atlantic Ridge and East Pacific Rise

2) Convergent Boundaries- plates move together- occur when two plates bump into each other

A) Oceanic-continental convergence - RESEARCH

B) Oceanic-Oceanic Convergence - RESEARCH

C) Continental- Continental Convergence- RESEARCH

SUBDUCTION - descent of the old crust back down into the mantle sinks into asthenosphere where it is remelted

3) Transform Boundaries- plates slide past each other- plates slide horizontally past one another along a fault

DIASTROPHISM

- Comes from the Greek word meaning, “twisting”

- Movements of the parts of the earth’s crust as a process of deformation that produces continents and ocean basins in the earth’s crust

- Series of processes by which major features of earth’s crust are formed and changed vecause of relative changes of position and deformation of rocks

- Movement may be strong and sudden that we feel the shaking of earth’s surface, we call this EARTHQUAKE

TWO MAJOR TYPES OF SLOW STRUCTURAL DEFORMATIONS1. FOLDING- occurs when a part of

crust crumples, bends upward and downward

TWO MAJOR PARTS OF A FOLD Arch or Anticline Trough or Syncline

2. Faulting- occurs when crust is fractured due to unequal forces acting in opposite directions

- Vertical forces produce Uplift - Horizontal forces produce

Compression or Tension

FAULT MAY BE CLASSIFIED Normal Fault Reverse Fault Strike-slip Fault

EVIDENCES OF DIASTROPHISM

1.) Plain- a broad flat area; the difference in elevation between the highest and lowest points of plains

2.) Mountains- highland with a relatively small summit are which are elevated from the base to the summit which is more than 600 meters

3.) Cordillera- major or principal mountain range of a continent

4.) Hill- highland less massive than mountain summit and is more than 150 meters but less than 600 meters

5.) Plateau- highland but it’s top is broad and flat like a plain

6.) Cliff- steep high side of plateau or rock

7.) Volcano- a hill or mountain formed around a weak area of the Earth’s crust through which molten rocks from beneath reaches the surface

8.) Valley- relatively long and flat area between 2 highlands

9.) Swamp- wet land saturated with water but may have varied vegetation

10.) Peninsula – piece of land surrounded by water

11.) Isthmus- narrow strip of land that connects peninsula with mainland

12.) Delta- deposit of sand and soil at the mouth of a river

Earth as a living planet

The earth has enormous distinct features such as the water-filled depression called oceans and seas. Outstanding scenic views of mountains, waterfalls, and plains will definitely be a good place to live by.

Continental drift theory One of its major tenets was that a

supercontinent called Pangaea then split into two major continent groups;

1. Laurasia, the northern supercontinent, containing

North America and Eurasia, except India.

2. Gondwanaland, the southern supercontinent, composed of all the present day southern hemisphere continents and India.

Continental drift in the existence of Gondwanaland it began breaking apart into smaller continents about 200 million years ago.

The smaller continental fragments then “drifted” to their present positions.

Based on Alfred Wegener booked “The Origins of Continents and Oceans” set forth some of the following evidences:

1. The super continental Pangaea2. The remarkable similarity

between the coastlines of South America and Africa.

3. Identical fossils widely separated landmasses.

Earth’s crust

It is consist of a number of moving pieces of plates that are always colliding or pulling apart.

Lithosphere-Consist of large and small plates-Separates plates that ride on the more fluid asthenosphere and moves slowly in relationship to

Lithosphere-Scientist believe that this is broken into a series of plates, or segments.-According to the theory of plate tectonics, these plates move around on Earth’s surface over long periods of time.

Plate Tectonics

Tectonics It is a term that refers to the

deformation of the earth’s crust.

Plane Refers to the subdivision of the

earth’s crust and lithosphere into a number of tectonically coherent blocks.

Plate Tectonics (Refers to the information and migration of lithospheric plates.

It is the theory developed in the late 1960s to explain how the outer layers of the Earth move and deform.

It helps to explain continental drift, the spreading of the sea floor, volcanic eruptions and how mountains are formed.

Since the development of the theory, geologist have had to re-examine almost every aspect of Geology.

It has proven to be useful that it can predict geologic events and explain almost all aspects of what we see on the earth.

The theory of plate tectonics, a far more encompassing theory than continental drift, holds that Earth’s rigid outer shell called the lithosphere is consist of seven large and numerous smaller segments called plates that are in motion relative to each other. Most of Earth’s seismic activity, volcanism, and mountain building occur along the dynamic margins of these plates.

According to the plate tectonic theory, the surface of the earth is broken into about twenty large sections called plates. The plates contain the crust and deeper rock of the lithosphere.

Faults

The distinctive break in the rock along which movement of earth’s crust occurs.

Can be visible on the surface of the crust or can be underground.

Forces can be applied to a solid mass such as rock.

The three main forces in the Earth’s faults:

1. Tension or the pulling apart Stretches an object from

opposite directions2. Compression or the squeezing

It occurs when the forces push an object from opposite direction.

3. Shear or sliding past results when faults slide each

other.

There are three main classifications according to direction of the movement in the Earth’s faults:

1. Normal fault One block that can move down

and the other can move up, or vice versa.

Usually caused by tensional forces; as rocks are pulled apart (tension), gravity pulls the hanging block downward, causing it to slide off the other sub-adjacent block.

2. Reverse or Thrust fault One block move over the other

block. Usually caused by compressional

forces which pushes the hanging

block upward opposing Earth’s gravity.

It also occurs where forces tend to push sections of the crust together.

3. Strike slip faulting Caused by the lateral movements

of blocks of rocks; rocks move (slip) past one another along the direction of strike.

Asthenosphere

The liquefied part of the mantle or the zone of partial melting.

The layer which facilities the movement of the lithosphere.

The source of the basaltic magma that makes up much of the oceanic crust and rises through volcanic vents on the ocean floor.

SEA FLOOR SPREADING

Sea Floor Spreading

Is the process of plate divergence and injection of magma.

Is a process that occurs at mid-ocean ridges, where the new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge.

It helps explain continental drift in the theory of PLATE TECTONICS.

Shrinking is the opposite location of the other part of the Sea Floor Spreading.

Basaltic Magma

Rises up the fractures and cools on the ocean floor to form new sea floor. Older rocks will be found farther away from the spreading zone while younger rocks will be found nearer to the spreading zone.

Example:

The Atlantic Ocean has undergone seafloor spreading over the last 165 million years ago at an average rate of 6 cm/year, therefore, its opposite part .

Pacific ocean would be shrinking due to the atlantic ocean’s spreading.

This was discovered by HARRY HESS, a geologist in 1960’s.

GEOLOGIC TIME SCALE

Geologic Time Scale - divides Earth history into units of varying magnitude. - commonly presented in CHART FORM with the oldest time and event

The Earth is about 4.6 billion years old scientists have indirect evidence of what took place in the past in the record of the earth’s rocks.

2 TYPES OF DATES used by geologists to interpret Earth history a. Relatives dates

-which put events in their Proper Sequence of Formation

b. Numerical dates - which pinpoint the time in years when an event took place

EONS - principal subdivisions of the geologic time scale

1) HADEAN (beneath the Earth)2) ARCHEAN (ancient)3) PROTEROZOIC (early life)4) PHANEROZOIC (visible life)

ERAS - small duration of time - defined by fossil collection which makes it the most useful in Phanerozoic eon partition

PERIODS - much smaller time scale which further subdivided the Phanerozoic eon

* PRE-CAMBRIAN- time span which all animals were

soft-bodied or microscopic

-have division called EPOCHS. ( time when humans and its ancestors come into sight