science

Theory of Plate Movements

The theory of plate tectonics and continental drift was proposed at the beginning of the last century by a German scientist, Alfred Wegener. This is the first theory to provide a comprehensive view of the processes that provide the earth's major surface features including the continents and ocean basins and explanations of the basic causes and distribution of earthquakes, volcanoes, and mountain belts. Alfred Wegener became the "father of continental drift" by amassing considerable supporting evidence that the continents moved over time. Prior to the 1960's, most geologists held the view that the ocean basins and continents had fixed geographic positions and were of great antiquity. This profound reverse in scientific thought was described as a scientific revolution. Based on the plate tectonics model, the entire lithosphere of the Earth is broken into numerous segments called plates. According to the Pangea theory, each plate is slowly and continuously moving. As a result of the motion of the plates, three types of plate boundaries were formed, namely: divergent, convergent, and transform plate boundaries. The processes involved in the three types of boundaries are seafloor spreading, ocean continent subduction, earthquake activity, and volcanic activity. On the other hand, the possible causes of plate movements are the continental drift theory, seafloor spreading, plate tectonics, convection current.

volcanoes

volcanoes are generally described as mountains that emit volcanic products like lava rocks ashes and gases from the interior of the earth through its vent

Volcanic Belt

Most volcanoes in the world are located along divergent plate boundaries. One of the boundaries is the Mid-Atlantic Ridge, part of the Mid-Atlantic Belt located on the floor of the Atlantic Ocean. • A large number of volcanoes found in the Pacific Ocean in a belt called the Pacific Ring of Fire, which is part of the Circum-Pacific Belt • Also found in convergent plate boundaries such as Mid-Continental Belt.

Rayleigh Waves

Rayleigh Waves move in an elliptical motion, producing both vertical and horizontal motions. This moves the ground up and down and sides to side in the same direction that the wave is moving. It is named after Lord Rayleigh (John William Strutt).

seismology

The study of earthquakes and the waves they created SEISMOS= TO SHAKE

What geologic feature is formed when the edge of the plate is crumpled by the pressure exerted by the adjacent plate?

mountain ranges

inactive volcano

no recorded eruption. the physical form has been intensively weathered and eroded, bearing deep along gullies.

TRANSFORM FAULT/ TRANSFORM BOUNDARY (conservative)

s a fault along a plate boundary where the motion is predominantly horizontal, two plates are sliding past each other, this forms a transform plate boundary. Natural or human-made structures that cross a transform boundary are offset - split into pieces and carried in opposite directions. Rocks that line the boundary are pulverized as the plates grind along, creating linear fault valley or undersea canyon. Transform plate boundaries can occur underwater or on land. Along these boundaries, the crust is neither destroyed nor created, major earthquakes occur in this boundary.

seismologist

scientist who study earthquakes

What happens when a continental plate collides with an oceanic plate?

the oceanic plates sink into the mantle

earthquakes

the shaking and trembling of the earths crust caused by a sudden releases of energy. it occurs when rocks along a certain fault line suddenly move.

dormant volcano

these are NOT CURRENTLY ERUPTING BUT HAVE ERUPTED WITHIN RECORDABLE HISTORY AND ARE EXPECTED TO ERUPT AGAIN IN THE FUTURE

active volcano

these are volcanoes that are CURRENTLTY ERUPTING OR ARE EXPECTED TO ERUPT IN THE NEAR FUTURE.

extinct volcano

these volcanoes are CONSIDERED AS DEAD AND ARE NOT EXPECTED TO ERUPT IN THE FUTURE

In which type of plate boundary is San Andreas located?

transform

CONVERGENT PLATE BOUNDARY (destructive)

with two tectonic plates collide towards each other, one plate eventually slides beneath the other, this process is called subduction. Converging oceanic plates will cause the formation of trenches, and these trenches will become sources of earthquakes. The leading edge of the subducted plate will eventually reach the mantle causing it to melt and turn into magma. • The molten material will rise to the surface creating a volcanic island arc parallel to the trench. Volcanic island arc is a chain of volcanoes position in an arc shape.

Mountain Belt

• Location of mountain ranges located along plate boundaries where the collision of plat occurs. Volcanoes and earthquakes are concentrated in the Circum-Pacific Belt while mountain ranges surround most of the Pacific basin. • A continuous chain of mountains can also found in the Mid-Continental Belt. • The Mid-Atlantic Ridge is a vast chain of underwater mountains on the floor of the Atlantic Ocean making the longest mountain range in the world. • Most of the highest mountain ranges in the world found in Asia. The highest mountain peaks are in Himalayas.

Two types of Transform Plate Boundaries

1. Continental - continental 2. Oceanic - oceanic

Three types of Convergent Plate Boundaries

1. Continental - continental convergence 2. Oceanic - oceanic convergence 3. Oceanic - continental convergence

Earthquake Belt

A similar distribution of volcanoes that commonly occurs along the plate boundaries, the Circum-Pacific Belt also known as Ring of Fire, which has the highest incidence of earthquakes. About 70% of the world's earthquakes occur in this region. • The belt stretching from Mid-Continental Belt is where about 20% of the Earth's earthquake has occurred. The rest of the earthquakes occur in divergent boundaries such as the Mid-Atlantic Ridge as well as transform plate boundaries.

How to locate the earthquake epicenter?

In order to locate the epicenter of an earthquake, you need to determine the time interval between the arrival of the P and S waves (the S-P interval) on the seismo-grams from at least three different stations. Locating the epicenters will determine which fault lines are active. Generally, the less active fault line stores a great amount of potential energy that could cause a major earthquake once released. Hence, areas near fault lines that remain inactive for a long period of time are prone to experience a major earthquake. The distance between the beginning of the first P wave and the first S wave tells you how many seconds the waves are apart. This number will be used to tell you how far your seismograph is from the epicenter of the earthquake. In order to locate the epicenter, the distance between the first P wave and the first S wave is measured.

how would surroundings be affected by an earthquake?

as an earthquake occurs energy moves out in all direction from the focus . the energy that is released carried by a vibration is called seismic waves

Why are new crusts built along the ocean floor?

as the floor moves away from each other the heat from.the mantle the crust less dense which become rock and new crust along

Why are the mountain building and volcanic activities associated with earthquakes?

building mountains and volcanic activities associated with earthquake because plate tectonics are moving

What are the landforms that can be created by magma?

by various process magma can landforms such as domes,plateus and volcanoes

PHIVOLCS

classified the volcanoes in the Philippines according to its eruptive history

Deep trenches are found

convergent

In which plate boundaries the strike-slip fault commonly found?

convergent

major earthquake occur

convergent

plates subduct

convergent

volcanoes are formed

convergent

Which plate boundary results in the widening of the ocean floor?

divergent

Two types of Divergent Plate Boundaries

1. Continental - continental divergence 2. Oceanic - oceanic divergence

EVIDENCE SUPPORTING PLATE MOVEMENTS

1. Continental Fit shows that there seems to be a close fit like that of a jigsaw puzzle between the coastlines of continents on opposite sides of the Atlantic Ocean. The eartern shorelines of South America and the western shorelines of Africa seem to fit together. 2. Similarities in rock layers and mountain ranges are found in continents across the ocean. Rocks with the same type, age and mountain ranges are discovered in both South America and Africa. The courses of several mountain ranges seem to end at the coastline of one continent and apparently continue to another continent across the ocean. 3. Fossils of extinct plants and animals are found on the rocks that are the same age and these rocks are widely distributed in continents. Fossilized leaves of an extinct plant Glossopteris were found in 250 million years old rocks. These fossils were in the continents of Southern Africa, Australia, India, and Antarctica, which are now separated from each other by wide oceans. The large seeds of this plant could not possibly travel a long journey by the wind or survive a rough ride through ocean waves. Mesosaurus, cynognatus and Lystosaurus are freshwater reptiles. Fossils of these animals were discovered in different continents, such as in South America and Africa. It is impossible for these reptiles to swim over the vast oceans and move from one continent to another. Fossils were also found in Antarctica. 4. Glacial Evidence, such as scrubs and scratches which are created as glaciers slide along the surface are found in different continents indicating these glaciers once covered a large continent. 5. Coral reefs and coal-forming swamps found in the tropical regions are now in places that are very cold. Indicate that the Northerns Hemisphere has a tropical climate when the Southern Hemisphere was covered with glaciers. 6. Stripes and magnetic material on the seafloor provide a strong evidence of tectonic movements. They show that the Earth's magnetic field has shifted.

FAMOUS MOUNTAIN RANGES IN THE WORLD

1. Himalayas 2. Andes 3. Alps 4. Rockie 5. Appalachian 6. Ural 7. Great Dividing Range

Findings that support Seafloor Spreading Theory

1. Rocks are younger at the mid-ocean ridge. 2. Rocks far from the mid-ocean ridge are older. 3. Sediments are thinner at the ridge. 4. Rocks at the ocean floor are younger than those at the continents.

What causes an earthquake?

An earthquake is caused by a sudden slip on a fault. The tectonic plates are always slowly moving, but they get stuck at their edges due to friction. Figure 2.2 shows an earthquake that took place in the Philippines. The area where an earthquake occurs is called a fault, or where the surface slipped. In addition, the location below the earth's surface where the earthquake starts is called the hypocenter or focus, and the location directly above it on the surface of the earth is called the epicenter.The magnitude of an earthquake is based on the measurement of the maximum motion recorded by a seismograph. The most commonly used are the Local Magnitude (ML) or known as the Richter magnitude, the surface wave magnitude (Ms), body-wave magnitude (Mb), and moment magnitude (Mw).

convection current (ARTHUR HOLMES)

As a substance like water is heated, the less dense particles rise while denser particles sink. Once the hot less dense particles cool down, they sink, and the other less dense particles rise. This continuous process is called convection current. This is exactly what happens in the Earth's mantle. The hot, less dense rising material spreads out as it reaches the upper mantle causing upward and sideward forces. These forces lift and split the lithosphere at divergent plate boundaries. The hot magma flows out of the mantle and cools down to form the new ocean crust. The downward movement of the convection current occurs along a convergent boundary where the sinking force pulls the tectonic plate downward.The convection currents rotate very slowly, as they move and drag the plates along. Because of convection current, the tectonic plates can move slowly along the tectonic boundaries, pushing each other, sliding past each other, and drifting away from each other. This process is further illustrated below. As an oceanic crust moves away from a divergent boundary, it becomes denser than the newer oceanic crust. As the older seafloor sinks, the weight of the uplifted ridge pushes the oceanic crust toward the trench at the subduction zone. This process is called ridge push. Slab pull is the other possible process involved in the tectonic plate movement. The weight of the subducting plate pulls the trailing slab into the subduction zone just like a tablecloth slipping off the table and pulling items with it.Now that you understand what happens inside the Earth and its effects on the Earth's surface, you should be able to realize that the tectonic activities at the surface just like volcanic eruptions and earthquakes are inevitable. You should view the Earth as a dynamic planet and still the most fascinating planet for it offers you a home that no other planet can. Since you can't prevent these tectonic activities from happening, the following performance task will enable you to contribute meaningfully to minimizing the damage that these phenomena can bring.

continental drift

As you have previously learned, Alfred Wegener was a German meteorologist. In 1912, his theory proposed that about 200 million years ago, the continents were once large masses. He called this land mass as "Pangea", a Greek word which means "All Earth." Afred Wegener's theory explained how Pangea evolved up to the present continents today. He further claimed that Pangea started to break into smaller supercontinents called Laurasia and Gondwanaland during the Jurassic Period. These smaller supercontinents broke into the other continents and these continents separated and drifted apart gradually.

Divergent plate boundaries are in the continental and oceanic lithosphere. Effects that are found at a divergent boundary between oceanic plates include a submarine mountain range such as the Mid-Atlantic Ridge, volcanic activity in the form of fissure eruptions, shallow earthquake activity, and widening ocean basin. When continental plates converge, the breaking of the crust into several segments leads to the formation of down faulted valleys called rift valleys. As the valleys continue to spread it will develop into a linear sea.

Divergent plate boundaries are in the continental and oceanic lithosphere. Effects that are found at a divergent boundary between oceanic plates include a submarine mountain range such as the Mid-Atlantic Ridge, volcanic activity in the form of fissure eruptions, shallow earthquake activity, and widening ocean basin. When continental plates converge, the breaking of the crust into several segments leads to the formation of down faulted valleys called rift valleys. As the valleys continue to spread it will develop into a linear sea.

Earth's crust is generally divided into two, the older, thicker, and less dense continental crust generally made of different granite rocks refer to as "Sial" (silicate and aluminum) and the younger, denser oceanic crust generally made up of different kinds of basaltic rocks refer to as "Sima" (silicate and magnesium). The transition zone between these two types of crust is sometimes called Conrad discontinuity. The dynamic geology of Earth's crust is informed by plate tectonics.

Earth's crust is generally divided into two, the older, thicker, and less dense continental crust generally made of different granite rocks refer to as "Sial" (silicate and aluminum) and the younger, denser oceanic crust generally made up of different kinds of basaltic rocks refer to as "Sima" (silicate and magnesium). The transition zone between these two types of crust is sometimes called Conrad discontinuity. The dynamic geology of Earth's crust is informed by plate tectonics.

MOUNTAIN FORMATIONS

Have you ever wondered how a mountain is formed? A mountain is formed due to various geological processes like the movement and opposition of tectonic plates while a volcano is formed around a vent that allows magma to reach the surface of the earth. It all has to do with plate tectonic activities. Also, mountain belts form along tectonic active coastlines and above subduction zones. Much of the sedimentary rocks are marine in origin. In addition, a mountain is a landform that stretches above the surface of the Earth that can be steep like a peak or probably not so steep. Volcanoes can be similar to mountains, but volcanoes have a certain pressure inside a magma chamber that creates an orifice through which lava and hot gases erupt into the atmosphere. Most of the world's major mountain belts are located along tectonic plate boundaries. Movements of tectonic plates create volcanoes along the plate boundaries which erupt and form mountains. A mountain ranges or a hill range is a series of mountains or hills arranged in a line and is connected by high ground. It is formed by a variety of geological processes, but most of the significant changes on the Earth are the results of plate tectonic activities. Mountain Belt is a long chain of mountain ranges. The subrange is a small chain of mountains. The longest mountain range in the Philippines and also known as the backbone of the northern island of Luzon is called the Sierra Madre.

seafloor spreading

In the early 1960's, scientist Harry Hess, together with Robert Dietz, suggested an explanation to the continental drift. This is the Seafloor Spreading Theory. According to this theory, hot, less dense material from below the earth's crust rises towards the surface at the mid-ocean ridge. This material flows sideways carrying the seafloor away from the ridge and creates a crack in the crust. The magma flows out of the crack, cools down and becomes the new seafloor. Overtime, the new oceanic crust pushed the old oceanic crust far from the ridge. The process of seafloor spreading allowed the creation of new bodies of water. For example, the Red Sea was created as the African plate and the Arabian plate moved away from each other. Seafloor spreading is also pulling the continents of Australia, South America, and Antarctica away from each other in the East Pacific Rise. The East Pacific Rise is one of the most active sites of seafloor spreading, with more than 14 centimeters every year

PLATE BOUNDARIES

Is a fracture that separates one plate from other plates. Adjacent plates can move relative to one another in three different ways. They can move towards each other and converge or collide, they can split or pull apart, or they can slide horizontally against each other in opposite direction. When plates move, the results are seen along the plate boundaries. A change in one plate boundary may cause other plate boundaries to change.

4 main types of seismic waves

P-WAVES AND S WAVES ( BODY WAVES) RAYLEIGH AND LOVE WAVE (SURFACE WAVES)

Magnetic Reversal

Seafloor spreading was strengthened with the discovery that the magnetic rocks near the ridge follow a pattern aside from the fact that rocks near the ridge are remarkably younger than those father from the ridge. A magnetic compass tells us directions on Earth. It also proves that the Earth has a magnetic field. The needle of a magnetic compass usually points to the North Pole of the Earth which is the South Magnetic Pole at present. The Earth's magnetic field is generated in the very hot molten outer core and has already existed since the birth of our planet. The Earth's magnetic field is a dipole, one that has a North Pole and a South Pole. Magnetic reversal is also called magnetic 'flip' of the Earth. It happens when the North Pole is transformed into a South Pole and the South Pole becomes the North Pole. This is due to the change in the direction of flow in the outer core. Magnetic reversals happened many times in the past. The occurrence of magnetic reversals can be explained through the magnetic patterns in magnetic rocks, especially those found in the ocean floor. When lava solidifies, iron bearing minerals crystallize. As these crystallize, the minerals behave like tiny compasses and align with the Earth's magnetic field. So, when magnetic reversal occurs, there is also a change in the polarity of the rocks. This allowed scientists to visualize the magnetic stripes in the ocean floor similar.

Location of an Epicenter

The epicenter is usually the location where the waves from an earthquake are highly intense. As a result, it is also the area where the most damage can possibly occur. However, it is not always the case. If an earthquake is particularly large, it may run across a large section of a plate boundary. In this case, the epicenter might only be one of the many hotspot areas and the damage could be greater elsewhere.

types of volcano

active dormant extinct

plates move apart

divergent

rift valley develops

divergent

the ocean floor widens

divergent

during an earthquake a sudden release of stored energy in the earth in the earth crust creates seismic waves. sometimes they cause tsunamis and fire which may lead to loss of live and damage to property

during an earthquake a sudden release of stored energy in the earth in the earth crust creates seismic waves. sometimes they cause tsunamis and fire which may lead to loss of live and damage to property

What occurs when two plates move past against each other?

earthquake

active volcanoes

erupted within historic times (within the last 600 years). accounts of these eruption were documented by man. erupted within the last 10,000 years based on the analyses of material from young volcanic deposits

love waves

is named after Augustus Edward Hough Love. It has a horizontal motion that is transverse to the direction the wave is traveling and is the fastest surface wave and moves the ground from side to side.

DIVERGENT PLATE BOUNDARY (constructive)

is the region where crustal plates are moving away from each other and in opposite directions. This either happens at mid-ocean ridges (the so-called seafloor spreading) or at rifted continental margins. • Along these boundaries, earthquakes are common and magma (molten rock) rises from the Earth's mantle to the surface, solidifying to create a new oceanic crust.

Earth's crust

is the thin outermost shell of a terrestrial planet. It is essentially floating on hot, semi-fluid rock called magma on the upper layer of Nthe mantle called asthenosphere which causes the crust to crack and move. When two pieces of crust, called plates, interact, or move apart with each other they create earthquakes, volcanoes, mountain ranges, deep trenches, island chains, create rift valleys and oceans.

INTENSITY

measures how strong an earthquake feels to the observer/ visible damage. Mercalli Scale: I-XII

potentially active volcano

morphologically young-looking but with no historical records or analytics of eruption

Which action of the plate boundaries results in the formation of the rift valley? slipping against each other

separation

In which type of plate are new ocean crusts formed?

spreading plates

Where are trenches formed?

subduction zones

MAGNITUDE

the amount of energy released from the interior of the earth. Richter Scale: 1-8

the distance between the beginning of the first p wave and the first s wave tell you how far your seismograph is from the epicenter of the earthquake

the distance between the beginning of the first p wave and the first s wave tell you how far your seismograph is from the epicenter of the earthquak

MAJOR BELTS

three major belts in the world, which are frequented by volcanic activities and earthquakes of varying intensities are the Circum - Pacific Belt, Mid - Atlantic Belt, and the Mid - Continental Belt.

plates rub against each other

transform

P WAVES OR PRIMARY WAVES

travel faster than other seismic waves. it is considered as the first signal from the earthquake to be felt. this maybe transmitted through liquid gases and solids

S WAVES OR SECONDARY WAVES

type of elastic waves and are one of the 2 mains of elastic body waves. it is also called shear waves

What surface features result when the mantle in the area melts?

volcano

How can a rift valley give rise to a new ocean?

when two plates move away from.each other there will be a low land area that can give rise to the ocean