Understanding the Pieces

Tectonic – refers to the word meaning “to build”

Volcanic eruption – a geologic process that occurs when magma is released from a volcano.

Earthquake – it is the shaking or vibration of the ground.

Mountain – these are large crustal landforms that rise above Earth’s crust.

Plate tectonics – it is a theory that has been developed to explain the observed evidence for a large scale
of motions of Earth’s lithosphere.

TECTONIC PLATES

- “tectonic” is a term derived from the Latin word tectonicus or the Greek word tektonikos,
which means “to build”
- used by scientists to describe the movement of the lithosphere
- massive, irregular slabs of solid rock that envelope the surface of Earth lithospheric plates

Plate Tectonic Theory

- the idea that the Earth’s crust are broken into sections called tectonic plates or lithospheric
plates that move around on the mantle
- explains the different processes that cause the formation of different geologic features and
phenomena

The fact that Africa and South America fit themselves like pieces of a jigsaw puzzle became an evidence
that these two landmasses were once part of a big whole chunk of landmass.
Alfred Wegener (1880 – 1930)

- a German meteorologist and geophysicist

- hypothesized and suggested that the landmasses of Earth were once merged into a
supercontinent known as PANGAEA.

The lithosphere is the outermost layer of Earth composed of the upper part of the mantle and the crust.
It extends to about 80 km deep.

The crust is made of various types of rocks and sediment floating on top of the malleable upper mantle
that extends from the surface to about 50 km. deep.

Earth’s crust has two types:

The continental crust is thicker and less dense, which makes it “float” over a denser and relatively
thinner oceanic crust.

The plate tectonics theory suggests that the lithosphere is divided into fragments known as plates.
These plates are divided into large and small plates.

The seven major plates are the:

North American,
South American,
Eurasian,
Pacific,
Indo-Australian,
African, and
Antarctic Plates

The intermediate plates include the:

Philippine,
Caribbean,
Cocos,
Nazca,
Scotia,
Juan de Fuca, and
Arabian Plates
Each of these plates moves in a slow and constant motion. The Pacific Plate, for instance, moves at a
rate of approximately 8 cm (3 inches) per year, whereas the North American plate moving at
approximately 3 cm (1 inch) per year.

The plate tectonic theory explains how Earth’s features were built.

Earthquake Distribution

- Majority of the earthquake centers or areas are located along plate margins. The strengths
of earthquakes can range from shallow to destructive.
- Earthquakes release different types of seismic waves. The primary and secondary waves
travel within the interior of the Earth, and are responsible for the detection of an
earthquake

Triangulation Method - used to determine the epicenter of an earthquake

 The difference in arrival time between the primary waves and the secondary waves, which
comes from a seismograph wave in seismic recording stations is recorded.

 Using the S-P graph, it will tell us the distance of the earthquake’s focus to the station.

 If three recorded measurements were done at different stations, triangulation method will be
used to find its epicenter.

Volcano Distribution

- The distribution of volcanoes is mostly found along plate margins, which can be either
destructive or constructive boundary. Volcanoes are also found in areas where there is
subduction plates.

What do you mean by the term “subduction?”

- the action or process in plate tectonics of the edge of one crustal plate descending below
the edge of another

Some volcanoes are formed from the subduction, resulting from the collision of two plates.

Over time, the magma builds a series of volcanoes known as a volcano arc.

Most of these volcano arcs are found around the region of Pacific Ring of Fire.
 Mountain Ranges

- Aside from the occurrences of earthquakes and active volcanic activities along plate
margins, one surface feature that is also present are chains of mountains.
- Mountains have been formed due to the movement of plates, either apart or toward each
other.
- Some are formed underwater or on the seabed.

Charles Wyville Thomson (1830 – 1882)

- a Scottish marine zoologist who led the Challenger expedition in 1872

- He discovered the Mid Atlantic Ocean Ridge together with the rest of the members of
expedition.
- Mid Atlantic Ocean Ridge is formed by plates that are pulling apart.

Harry H. Hess (1906 – 1969)

- an American geologist
- proponent of seafloor spreading
- captain in charge of the expedition and research about the ocean floor
- He discovered that the ocean floor is not flat or smooth; instead, it is rough and full of land
features.
- He realizes that the ocean floor is drifting apart causing these ocean floor features.

Earthquakes, volcanic activities, and mountain building mostly happen or can be observed along the
plate boundaries in Earth’s lithosphere.
Plate Boundaries
- the border between two tectonic plates.

3 Types of Plate Boundary

 Divergent boundaries - rifting

 Convergent boundaries - buckling
 Transform boundaries - shear

Divergent Boundary

 when two plates move away from one another

 constructive boundary

 characterized by tensional stresses that normally produce long rift zones, normal faults, and
basaltic volcanism.

 Boundary between two plates that are moving apart or rifting

 RIFTING causes SEAFLOOR SPREADING

 Makes new crust

 If the boundary is found between two continental plates you are left with a rift valley. ... If two
oceanic plates begin moving away from each other it creates a mid-oceanic ridge.

 Features of Divergent Boundary:

 Mid-ocean ridges - is an underwater volcanic chain. This feature is where spreading takes place

 Rift valley – linear shaped lowland, creating rift

Convergent Boundary

- when two plates move towards each other

- destructive boundary

- Destroys crust and forms new mountains

 - Boundaries between two plates that are colliding

Types of Convergent Boundary

 Oceanic-oceanic convergence
- During subduction, the subducting plate descends into the mantle.
- Due to extreme temperature, the plate is heated and magma is generated.
 Oceanic-continental convergence
- It occurs when an oceanic plate pushes into and moves underneath a continental plate.
- The continental plate that overrides the oceanic plate lifts up to create volcanoes and
mountain ranges.
 Continental-continental convergence
- The result of convergence is the formation of tall mountain ranges.

Transform Boundary

- when two plates slide horizontally past one another

- conservative boundary
Earthquake
- a sudden and violent shaking of the ground

Anatomy of an Earthquake

Fault is a crack across which the rocks have been offset first. In an earthquake, stored energy is suddenly
released through a movement along a fault

Epicenter – the point on the Earth’s surface directly above the focus.

Hypocenter (focus) - the point within the Earth along a geological faults where the earthquake
originates
Types of Seismic Waves
Seismic waves

- Emanating from the focus can travel as body waves or surface waves.
- Can travel as body waves or surface waves

Types of Seismic Waves

 Body Waves - travel in all directions from the focus

through the body of the Earth waves that travel below the
surface of the Earth
 Surface Waves - travel along the surface of the Earth from the
epicenter.

Body Waves - travel below the surface of

the Earth

• P waves (Primary Wave)

- compressional waves
- Travel through the interior of Earth and
through solid and fluid materials.
- Fastest wave, first to arrive in any
seismic station
- P-wave is longitudinal, they travel in the
same direction as the particles they
vibrate

• S waves (or secondary waves)

- are shear waves

- Travel through solid materials only within the interior of Earth
- move material perpendicular to wave movement
Surface Waves - travel along the earth’s surface

 Love Wave
- Lateral movement of the surface
 Rayleigh Wave
- Rolling movement of the surface (similar to an ocean wave)

Predicting an earthquake is not easy as predicting the occurrence of a typhoon. An earthquake does not
have impending signs or warnings before it occurs.

Seismograph - the instrument that detects and measures seismic waves

Seismometer

- the internal part of a seismograph

- works as a pendulum that swings back and forth, which is attached to a barrel that rotates
and makes prints of the ground shaking

Magnitude

- is the quantitative measure of the amount of energy by an earthquake

- it is measured using a seismograph

The Richter Scale is the most common scale for the magnitude of an earthquake. It is sometimes
called the local magnitude (ML). In this scale, A 5.3-magnitude is 10 times stronger than a 4.3-
magnitude earthquake.
Intensity

It refers to the amount of damage caused by an earthquake. It varies in different areas or places
depending on the distance from the epicenter of an earthquake.

The first scale used in identifying earthquake intensity was the Rossi Forel Intensity Scale, which
becomes the basis for the development of the now widely used scale known as the Modified Mercalli
Intensity Scale.

The Philippine Volcanology and Seismology (PHIVOLCS) developed an intensity scale used in the
country to determine the extent of the effect of such earthquakes. It ranges from scarcely perceptible
up to extremely devastating. This is most appropriate to our country because we lie along Pacific Ring
of Fire, where active plate movement is evident.

Effects of Earthquakes

Many earthquakes have been recorded in the country as seen on the DOST-PHIVOLCS website with the
time, the date, and the origin of the earthquake. It ranges from light to destructive shakes that damage
infrastructures, and leaves hundreds of deaths. Aftershocks are also eminent especially if a strong
earthquake hits.

The most destructive recorded earthquake that hit the country happened at the Moro Gulf in 1976, with
a magnitude of 8.0 and is tectonic in origin. The earthquake occurred near the Cotabato Trench, which is
known as a region of subduction in the southern Philippines. This earthquake has even reached the
Visayas region due to its intense shaking. It also caused a tsunami that was 4.5m high.

Another strong earthquake that hit the country was the Luzon island earthquake in 1990 with a
magnitude of 7.8. The earthquake was due to the strike-slip movement along the Philippine Fault that
resulted in ground rupture from Aurora to Nueva Ecija. Its epicenter was known to be in Rizal, Nueva
Ecija and it was felt over regions of Cordillera, Central Luzon, and even in Metro Manila. Fatalities were
recorded, and most of them were from Central Luzon and Cordillera region.

Another effect of earthquakes is ground rupture. In 2013, the island of Bohol was struck by a 7.2
magnitude earthquake that resulted in the splitting and dropping of the ground especially along fault
lines.

Aside from the Philippines, Indonesia and Japan are countries that have the greatest number of
earthquakes. This is because they are also located in the Pacific Ring of Fire.
SAFETY MEASURES BEFORE EARTHQUAKE

Advance preparation is important to know what to do if an earthquake strikes. Preparing emergency kits
are encouraged.

An emergency kit should include important things that can be easily used and consumed once an
earthquake happens. ; water, first-aid kits – flashlights, personal hygiene and sanitation kits, batteries,
nonperishable foods, copies of personal documents, extra shirts

SAFETY MEASURES DURING EARTHQUAKE

During an earthquake, it is important to remember the “Drop, Cover, and Hold” rule. When the ground
is shaking, one must not panic. Proceed with the drop, cover and hold position until the shaking
subsides. Once the shaking stops, do not immediately stand and run; wait for a few minutes before
leaving in an orderly manner. Proceed to an open area that is free from any falling material or debris.

SAFETY MEASURES AFTER EARTHQUAKE

After an earthquake, do not return immediately inside the house or building. Stay for a while outside
and check yourself for possible injuries so that immediate care can be given. Possible aftershocks may
also be felt, so stay a few minutes where you are before going to the evacuation area.

The Pacific Tsunami Warning System (PTWS)

- is a system used to detect earthquakes that may cause tsunamis. It was established in 1949
with several international members including the Philippines.
- They are responsible for disseminating tsunami warnings after meeting the known criteria in
the generation of tsunamis.
- The information that they receive from different international agencies becomes their basis
of the bulletin.

Plate movement is the major cause of earthquakes.

Earthquakes happen everyday at various intensities
and magnitudes.
VOLCANISM

- the process wherein magma escapes from Earth’s interior to form cool and hard rocks

A volcano is a landform with an opening at its tip. This opening, called the crater, allows molten magma
to flow outside the surface.

The lava pertains to magma that has finally reached the surface.

When it flows outside the surface of Earth, it is called EXTRUSIVE VOLCANISM. As time goes by, lava
cools and hardens, and then it becomes a rock. This type of rock is known as igneous rock.

INTRUSIVE VOLCANISM happens when magma do not move out from the opening of a volcano. Instead
magma flows along a chamber inside the crust and, from there, it hardens to become a rock.

In a volcanic eruption, the flow of magma or lava is affected by temperature and composition. However,
the amount of dissolved gas also affects its flow rate at the least. The magma’s ability to flow is called
viscosity.

The greater the viscosity, the greater its resistance to flow. For magma to flow faster, the temperature
must be high, making it less viscous

Another influence of volcanic behavior is the composition of chemicals present in the magma. Magma
contains silica (SiO2), which affects its viscosity. The greater the silica content, the more viscous the
magma.

Because the magma’s dissolved, gases also affects the viscosity, the less dissolved gases in the magma,
the greater its viscosity. The dissolved gases are mainly carbon dioxide and water. The escape of gases in
the magma gives the volcano their explosive characteristic

Just like earthquakes, volcanoes are found along either converging or diverging tectonic plates.

An example of a chain of volcanoes found in diverging plates is the Mid-Atlantic Ocean Ridge. Volcanoes
found in the Pacific Ring of Fire have converging tectonic plates.

Volcanoes that arise from the excretion of magma to the mantle are known as hotspots. When a column
of magma rises from the underwater seabed, it gives rise to the piled hardened rocks forming the
volcanoes.

Due to plate movement, the once active volcano moves away to the mantle plume and gives rise to
another pathway of magma to the surface. The once active volcano then dies out, and new active
volcano emerges. As the mantle keeps moving, chains of volcano are born

During a volcanic eruption, a volcano emits large volume of gases, pyroclastic materials and lava. It also
creates mild earthquakes along the area.
The lava flows from the opening of the volcano, with most of them estimated to be basaltic in
composition. There are two types of lava flow:

1. aa (pronounced as “ah-ah”) is rough and jagged

2. pahoehoe (pronounced as “pahhoy-hoy”) exhibits smooth surface characteristics

A cloud of thick gas is also being released, accompanied with ashes in a volcanic eruption, considered to
have adverse effects on living things.

Despite its hazardous effect to organisms, a volcanic eruption can also be advantageous. The materials
that came from a volcanic eruption make the soil more fertile.

PREPARING FOR VOLCANIC ERUPTION

As you evacuate, do not panic. Proceed to the designated evacuation area set up by the local
government. This area is situated outside the volcanic danger zone identified by the PHIVOLCS.

Once you are in the evacuation area, stay inside the temporary shelter. Doing so will prevent you from
inhaling the ashes brought about by the eruption.

Do not return to your house after the eruption. Wait for the instructions given by the authority. This is
to ensure your safety before going back to your houses.

Volcanic eruptions, though destructive, can also bring about positive impact on the environment.

Orogeny - process of mountain building

MOUNTAIN - refers to a large surface feature that rises above its relative

MOUNTAIN RANGE - a series of mountain chains. characterized by a group of mountains that are close
to one another

Stages Of Mountain Ranges Formation

1. accumulation of sediments
2. an orogenic period of rock deformation and crustal uplift
3. a period of crustal uplift caused by isostatic rebound and block faulting
Like earthquake occurrences and volcanic formation and activities, mountain building is linked to plate
movement, where collision takes place between plates.

Island arc-type mountain building, whose major features are deep ocean trenches and volcanic arcs.

An island arc occurs when two oceanic plates converge , and as the leading plate subducts from the
other, the plate piles up, forming volcanic island arcs that consist of igneous and metamorphic rocks.

Another type of mountain building is the Andean-type mountain building. This type of mountain building
occurs along continental plate boundaries.

For continental crush collision, the crustal plates move toward each other and create a bulge between
them, forming a compressional mountain.

The most visible effect of orogenesis is the faulting and folding of the lithospheric plate; metamorphism
and igneous activity are also present.

Folding and faulting happens when high pressure tends to cause the lithosphere to bend and break the
surface of Earth. Folding happens when a force compresses the crust, causing the crust to bend from its
sides. Ex: Himalayas in Asia and the Alps in Europe

MONTHLY TEST ANS

Geologic activities in plate boundaries can be determined by the type of plate boundary.

Lithosphere is divided into fragments of plates.

Most of the volcano arcs are found in the Pacific Ring of Fire.

The plate tectonic theory explains the different processes that cause the formation of geologic features
and phenomena.

Seafloor Spreading -- The process for new oceanic lithosphere forming at mid ocean ridges.
Tectonic Plates -- One of the very large sections of hard, solid rock making up Earth's outer layer.

Epicenter -- Using the difference in the travel time of P waves and S waves taken from three
earthquake recording stations, the earthquake’s ________ can be determined.

Asthenosphere -- Over what surface do lithospheric plates move?

Sinking process -- Which phrase would best describe the process of subduction?
Continental crust is older than oceanic crust.

Convergent fault -- Two rocks move towards each other.

 Increases with distance from a mid-ocean ridge -- the thickness of the lithosphere, the age of oceanic
lithosphere, the depth to the sea floor

Why don’t earthquakes, volcanic eruptions, and mountain ranges occur randomly on Earth? -- Because
their occurrence is a result of geological processes that originated from the movement of lithospheric
plates.

The occurrences of earthquakes and volcanoes around the world gave support to Wegener’s
ideas. Where do most earthquakes and volcanoes occur? -- at the boundaries between lithospheric plates

How do rock particles move during the passage of a P wave through the rock? -- back and forth parallel to
the direction of wave travel

When one plate slides underneath another, it _____ and the magma _____. -- melts, rises
Why does oceanic crust sink beneath the continental crust at the subduction zone? -- the oceanic crust
has a greater density

It’s because the plates are continuously moving. – concept of volcanic eruption
The farther the area from the source, the weaker the impact of the earthquake will be on that area.

How mountain ranges were formed --because of continental-continental convergence

Island Arc volcanoes occur in the ocean when the crust is subducted at A convergent boundary, melting
part which rises back up forming volcanoes.

Which source should you check to find out if an active fault traverses -- The Hazard Maps of the Philippine
Institute of Volcanology and Seismology (PHIVOLCS)

Q1 PLATE TECTONICS

Continental crust is thicker and less dense compared to oceanic crust.

Wegener hypothesized that the landmasses of Earth were once merged into supercontinent.

Plate margins are the edges where two plates meet.

The plate tectonic theory explains the different processes that cause the formation of geologic
features and phenomena.

In the Pacific Ring of Fire, the Philippines is situated.

Most earthquakes and volcanoes lie along the boundaries of plates.

Q2 PLATE BOUNDARIES
At which plate boundary would you see a subduction zone? –
convergent

Which plate boundary result in a midocean ridge? – divergent

When two plates move apart, it is called Divergent.

San Andreas fault is an example of Transform Boundary.

Mid-Atlantic Ridge is an example of Divergent Boundary.

Mountain ranges is formed when two plates collide with each other.

Subduction zones are the regions where a portion of the tectonic

plates are diving beneath other plates into earth's interior.

At which plate boundary would you expect to find folded mountains? –

convergent

Q3 EARTHQUAKE

It is a type of fault in which the hanging wall moves up relative to the footwall as a result of compression. --
Reverse fault
Type of fault that causes the rock to move horizontally -- strike-slip fault
It describes the degree or extent of damage an earthquake has caused. – Intensity

These waves cause rock particles to move upward, up, backward, and down in a path that contains the direction of
the wave travel. -- Rayleigh waves
A natural phenomenon that is characterized by a sudden, violent shifting of massive plates underneath Earth’s
surface. – Earthquake

Surface waves consist of the L and R waves

Which of the following sequences is the correct list based on the different arrivals of waves from first to last? -- P
waves - S waves - Surface waves
It is the point within the Earth along a geological faults where the earthquake originates. – Hypocenter

This happens when the ocean floor abruptly deforms and vertically displaces the overlaying water. – Tsunami

Refers to the forces and events that lead to a large structural deformation of Earth’s lithosphere. – Orogeny

The lowest point of fold – SYNCLINE

Sharp-peaked anticline fold – TIGHT FOLD
Peak of folded rock layer – ANTICLINE
Fracture between two blocks of rock – FAULT
Type of mountain building that occurs along continental plate boundaries – ANDEAN TYPE
Series of mountain – MOUNTAIN RANGES
Series of volcano – VOLCANIC ARC
Type of mountain building that has ocean trench and volcanic arc – ISLAND ARC TYPE
Lava flow that exhibits rough surface – AA

Q4 EARTH'S INTERIOR AND EVIDENCES OF PLATE MOVEMENT

This is Alfred Wegener's idea that continents have moved and are still moving slowly across the Earth's surface. --
Continental Drift Theory
These are the mechanical layers of Earth. -- lithosphere, asthenosphere, mesosphere, outer core, inner core
layer of the Earth from densest to least dense. -- inner core, outer core, asthenosphere, lithosphere

The mantle takes up the 67 percent of the total mass of Earth.