Module 1- Lesson 1: Volcanoes, Earthquakes, and Mountain Ranges
• Our country is part of the Pacific Ring of Fire. Thus, we often experience earthquakes,
and we are home to many majestic but terrible volcanoes.
• Our Earth has four layers consisting of different materials, namely, crust, mantle, inner,
and outer core.
• Lithosphere which is composed of the crust and the upper mantle.
• Lithosphere is said to be in constant but very slow motion. These motions are not the
same everywhere. This movement of the lithosphere is called tectonics.
• According to the Plate Tectonics Theory, the entire lithosphere of the Earth is broken into
numerous segments called plates.
• The arrows show the direction of the plate movement, and the other lines are the fault
lines.
• As they interact along their margins, important geologic processes take place, such as
the formation of major mountain ranges, active volcanoes, and earthquake epicenters.
It means to say that, where there are earthquakes, crusts can either meet or move apart
and form mountains and volcanoes.
• Plate movements may result in earthquakes. Earthquakes may happen anytime, either
on land or under water. Earthquakes on land can be caused either by tectonic plates
movement or volcanic eruptions. Earthquakes under the sea can cause tsunami.
• Our country, the Philippines, is situated in a place where Plate Tectonics is very
evident- the Ring of Fire. It is a long chain of volcanoes and other tectonically active
structures that surround the Pacific Ocean. The Ring of Fire is one of the most geologically
active areas on Earth and a site for frequent earthquakes and powerful volcanic eruptions.
• Philippines is known to be resilient or flexible, we have high hopes that our resilience
could also always mean preparedness.
• Risks can cause harmful effects to our environment, our country as a whole, and our
communities in particular. These may even result to the death of people who are not
prepared for these natural disasters.
Module 2- Lesson 2: Plate Boundaries
• Plate boundaries are the lines at the edges of the different pieces of the lithosphere.
Lithospheric plates are moving due to the convection current in the Earth’s interior.
Lithosphere is made up of crust and upper part of the mantle. There are two types of
crusts: the continental crust which is thicker but less dense, and the oceanic crust,
which is thinner and denser.
• According to the Plate Tectonic Theory, the Earth’s lithosphere consists of crust and
upper mantle that move slowly and constantly over time. This movement causes the
formation of plate boundaries namely: divergent, convergent, and transform fault
boundaries.
• Divergent Boundary is formed when two tectonic plates move apart from each other
creating tension. Molten rocks called magma rise from the Earth’s mantle to the surface.
The Earth’s surface is cool enough to solidify the magma that rose up, thus, creating
new oceanic crust or seafloor. Divergent boundary
is also known as
constructive
boundary. Mid-ocean ridge is formed by the divergence between oceanic plates while
continental rift valley is formed between continental plates. Rift valley can also be found at
the bottom of the ocean where seafloor spreading occurs. Both the formation of mid-ocean
ridge and rift valley had occurrence of earthquake. Examples are boundaries between South
American plate and African plate, Pacific Plate and Nazca Plate, and North American Plate
and Eurasian Plate.
• Convergent boundary is formed when two plates move toward each other. This
boundary has three types: Oceanic- Continental plate boundary, Two Oceanic plate
boundary, and Two Continental plate boundary. In Oceanic-Continental plate boundary
and two oceanic plate boundaries, the oceanic plate bends downward into the mantle
through the process called subduction. The leading edge of the subducted plate
melts in the mantle and magma rises forming continental volcanic arc in oceaniccontinental plate boundary, which is parallel to the trench that is formed due to
subduction while in two oceanic plate boundary, island volcanic arc is formed parallel to
the trench. Earthquake occurs at this boundary. Since oceanic plate is destroyed at the
convergent boundary, this boundary is also called destructive boundary. Examples are
boundaries between Eurasian plate and the Philippine plate, Nazca Plate and South
American Plate, and Pacific Plate and Australian Plate. With two continental plates
converging, tension zone is formed. Both plates collide and buckle up causing mountain
ranges such as the Himalayas Mountain ranges. There is no subduction, no trench
and no volcanoes formed in this type of convergent boundary.
• Transform fault boundary is formed when two plates are sliding past each other. It is
also called Strike-slip fault. Rocks that line the boundary split into pieces as the plates
slip at each other. A crack is then formed creating an undersea canyon or linear fault
valley. San Andreas Fault is an example to this.
Module 3- Lesson 1: Processes and Landforms Along With Convergence of Plates
• The continental crust curves upward on top the oceanic crust due to its lesser
density. The oceanic crust, due to its greater density, stays below.
• When an oceanic crust converges with a continental crust, a crack in between the
crusts underwater, called trench, is formed. Since the oceanic crust has greater mass
due to the presence of water on it, so, its density also is greater. This causes it to dive
down or subduct under the overriding plate, the continental plate.
• Subduction is the process by which a plate dives under a less dense plate. At the
mantle, the leading edge of the subducting plate melts or becomes fluid. It turns
into a hot molten material which we call magma.
• Due to the heat in the mantle, the magma builds up a pressure that enables it to
push the ground above it. The column of rising magma is called a mantle plume.
• When there is volcanic activity such as an eruption, the ground moves and so an
earthquake is felt. Because subduction continues, a group of volcanoes, called
volcanic arc, is formed at the surface of the continental crust along the boundary
where the two crusts converged.
• The movement of the ground may cause disturbance in the ocean. The water may
flip or kick upwards to a few meters high. This is what we call tsunamis, a Japanese
term for harbor wave. This event is very dangerous when it moves inland destroying
lives and properties.
• The convergence of two oceanic crusts results to some similar events compared to the first
type of convergence. Tsunamis may be formed. Earthquakes may happen. There is also
subduction, because one plate is denser than the other. The front part of the subducting
plate becomes magma upon reaching the mantle. Then it builds up pressure due to heat,
pushes the crust above it forming a volcano. This is a continuous process. Since the
plates are moving, the volcano will move with the plate. It becomes extinct when it is
no longer above the magma deposit in the mantle. A new volcano will then be formed.
This series of volcanoes is called volcanic island arc since it is surrounded by water.
• This explains why the Philippines is mostly loaded with volcanoes. The different
islands were believed to have originated from convergence of two oceanic crusts.
• Converging continental crusts or plates result to a collision zone which could cause shallow
earthquakes. At that place, a crack called fault is formed. This type of convergence will cause
no subduction, since the two plates have the same densities. There would be no volcanoes
formed, no tsunamis. The convergence will result to a group of high landforms which we call
mountain ranges.
Module 3- Lesson 2: Processes and Landforms Along Divergent of Plates
• Divergent plate boundaries mostly happen under the oceans. As plates pull away from each
other, a vertical space which may extend deep down into the lowest layer of the crust is
created. It is a rift valley. The force of separation creates a tension zone. A shallow earthquake
may happen with this plate movement.
• As the plates move away, the gap between them increases. While this happens, materials from
the mantle may rise filling up the space. These materials pile up near the tension zone forming
mountain-like structures called oceanic ridges. But new materials from the mantle may push
the old ones. The filled-up space between the plates becomes a new seafloor. This process is
known as seafloor spreading.
Module 3- Lesson 3: Processes and Landforms Along Transform Fault Boundary
• This third type of plate boundary is mostly found in oceans, but there are few that traverse
through continental crust. This is characterized by plates moving horizontally against each
other producing a crack called fault on the ground. The force the plates exert can break the
rocks and other materials under the ground. The shaking usually ends abruptly. This is why it
brings about strong earthquakes. The fault could swallow humans, cars, and buildings. Murky
odorous water from under the ground may spring up from the fault. Most faults do not
totally close when the shaking ceases since the adjoining edges have already moved farther
from each other.
Module5- Lesson 1: Evidence of Plate Movements: Continental Drift Theory
• In 1912, Alfred Lothar Wegener (pronounced as vey-guh-nuh r), a German meteorologist, proposed a
theory that about 200 million years ago, the continents were once one large landmass.
• This Pangaea started to break into two smaller supercontinent called Laurasia and Gondwanaland
during the Jurassic Period. These smaller supercontinents broke into the continents and these
continents separated and drifted apart since then.
• Wegener is remembered as the originator of the Continental Drift Theory by hypothesizing in 1912
that the continents are slowly drifting around the Earth and was once a large landmass called
Pangaea, a Greek word which means “All Earth.” Wegener’s curiosity about the idea on drifting
continents started when he noticed the edges of South America and Africa in a World Map can be
fitted like a jigsaw puzzle.
• Alfred Wegener collected diverse pieces of evidence to support his theory, including geological “fit”
and fossil evidence. It is important to know that the following specific fossil evidence was not
brought up by Wegener to support his theory.
• Wegener did not collect the fossils but he called attention to the idea of using these scientific
documents stating there were fossils of species present in separate continents in order to support
his claim.
• Geological “fit” evidence is the matching of large-scale geological features on different continents.
It has been noted that the coastlines of South America and West Africa seem to match up,
however more particularly the rock terrains of separate continents conform as well. Examples
include the Appalachian Mountains of eastern North America linked with the Scottish Highlands, the
familiar rock strata of the Karroo system of South Africa matched correctly with the Santa Catarina
system in Brazil, and the Brazil and Ghana mountain ranges agreeing over the Atlantic Ocean.
• Glaciers carve rocks and leave marks as they move. In this evidence, scientists can determine the
direction of movement of each continent.
• Existence of coal deposits in Antarctica suggested that it was once located near the region of earth
where climate is enough to support complex life forms such as plants and tall trees.
• Fossils are preserved remains or traces of organisms (plants and animals) from the remote past.
Four fossil examples include: the Mesosaurus, Cynognathus, Lystrosaurus, and Glossopteris
•
The Mesosaurus is known to have been a type of reptile, similar to the modern crocodile, which
propelled itself through water with its long hind legs and limber tail. It lived during the early Permian
period (286 to 258 million years ago) and its remains are found solely in South Africa and Eastern
South America. It was a coastal animal.
•
The now extinct Cynognathus, was a mammal- like reptile. Roaming the terrains during the
Triassic period (250 to 240 million years ago), the Cynognathus was as large as a modern wolf. Its
fossils are found only in South Africa and South America. As a land dominant species, the
Cynognathus would not have been capable of migrating across the Atlantic. The Lystrosaurus,
which translates to “shovel reptile,” is thought to have been a herbivore with a stout built like a
pig. Lystrosaurus fossils are only found in Antarctica, India, and South Africa. Similar to the land
dwelling Cynognathus, the Lystrosaurus would have not had the swimming capability to traverse
any ocean.
•
Possibly the most important fossil evidence found is the plant, Glossopteris. The Glossopteris fossil
is found in Australia, Antarctica, India, South Africa, and South America—all the southern
continents. Glossopteris
• seed is known to be large and bulky and possibly could not have drifted or flown across the oceans to a separate
continent. Therefore, the continents must have been joined at least one point in time in order to maintain the
Glossopteris’ wide range across the southern continent.
Module5- Lesson 2: Evidence of Plate Movements: Seafloor Spreading Theory
• The idea of continental drift circulated in scientific circles until World War II, when sounding
gear called SONAR produced new evidence of what the seafloor looked like. The gear, developed
in the 1930s, bounced sound waves off the seafloor to determine its depth and features.
• It happened that the command of one attack transport ship, the USS Cape Johnson, was given to
Harry Hammond Hess, a geologist from Princeton University. Hess, then in his late thirties,
wanted to continue his scientific investigations even while at war. So he left his ship’s sounding
gear on all of the time, not just when approaching port or navigating a difficult landing.
• Harry Hess observed that the rate of formation of a new seafloor at the mid-ocean ridge is not
always as fast as the destruction of the old seafloor at the subduction zone.
• If subduction zone is faster than the seafloor spreading, the ocean shrinks. He published his
theory in History of Ocean Basins (1962), and it came to be called “seafloor spreading.”
• In the early 1960s, dating of ocean-core samples showed that the ocean floor was younger at the
Mid-Atlantic Ridge but progressively older in either direction, confirming the reality of seafloor
spreading.
Module5- Lesson 3: Evidence of Plate Movements: Magnetic Reversal
•
Further evidence came along by 1963, as geophysicists realized that Earth’s magnetic field
had reversed polarity many times, with each reversal lasting less than 200,000 years. There
had been an average of 4 to 5 reversals
• A magnetic compass can tell direction. The needle of a magnetic compass usually points to the
North Pole of the Earth which is actually the South Magnetic Pole at present. The crystalized
irons in rocks found in the seafloor acts as magnetic compass that can tell the earth’s magnetic
field direction.
• Seafloor spreading was strengthened with the discovery of the magnetic rocks near the ridge
following a pattern aside from the fact that the rocks near the ridge are younger than those
farther from ridge.
• Magnetic reversal also called “magnetic flip” of the earth happens when the North Pole is
transformed into South Pole and South Pole becomes North Pole.
Module 4- Lesson 1: Mantle Convection
• Plate tectonic Theory developed in 1960s, stating that the Earth’s lithosphere is broken up
into a several pieces called plates that move slowly.
•
A convection current is a heat transfer process that involves the movement of energy
from one place to another. The convection currents tend to move a fluid, gas particles, or
molten rock. These are due to the differences in the densities and the temperature of a
specific gas or a fluid. Due to this temperature difference, the hot fluid tends to rise as it
expands, whereas cold fluid tends to sink because it contracts.
•
Convection current also happens in the mantle. Mantle convection is a process by which
a thermal convection occurs in the inner layer of the earth.
•
Lithospheric plates are flowing in an area called asthenosphere.
•
Asthenosphere is a soft, less rigid upper part of the mantle where the lithospheric plates
float and move with around. Plates move slowly and constantly when the hot less dense
material rises.
•
In the process of slab pull, the presence of a heavier subducting plate pulls down the
trailing slab into the subduction zone.
•
In a ridge push or gravitational sliding process, the old oceanic crust becomes heavier
than the new oceanic crust and sinks because of the weight of the raised ridge which pushes
down the older oceanic crust towards the trench at the subduction zone.
•
According to scientists, the motion is driven by a convection current mechanism within
the earth.
•