GEOLOGYShaping of the Earth

By: OMAR M. JACALNE

Diastrophism

The movement of the solid parts of the earth.

These movements can be:Subsidence: sinking of the crust or

the solid part towards the mantle.Uplift: rising of the crust or the

solid part.

Tectonic Plate Rigid sections of the lithosphere that

moves as a unit.› Convergent Boundary – a boundary which

two plates move towards each other.› Divergent Boundary – a boundary which

two plates move apart.› Transform Plate Boundary – a boundary

when two plates slide past each other.

Lithosphere The solid portion of the earth’s crust. Crust – the outer portion of the Earth.

› Continental crust – the thick part of the Earth’s crust not located under the ocean (less dense)

› Oceanic Crust – the thinner part of the Earth’s crust located beneath the ocean.

Theories of the Earth’s Surface

Continental Drift Theory Proposed by ALFRED WEGENER in 1912. The theory explains that the continents we

know today was once a one big super continent knows as Pangea and surrounded by a huge body of ocean called the Pnathalassa.

This theory has given way to a lot of breakthroughs in geology and scientific history such as the formulation of other theories and the process of mountain formation.

CONTINENTAL DRIFT THEORY

CONTINENTAL DRIFT THEORY

CONTINENTAL DRIFT THEORY

Evidences of the Continental Drift Theory

The fit of the continents. The similarity of fossils in different

continents. The similarity of rock type and age along

the matching coastlines. The continuity of geologic features from

continent to continent. The presence of coal seams in Antarctica. The presence of Tillites in different

continents.

Seafloor Spreading Theory

Seafloor Spreading Theory

Proposed by HARRY HESS of Princeton University.

The theory accounts about the movement of the continents by the formation of the new oceanic crust which pushes away continental crust.

The theory is a great support to the preceding one which is the Continental Drift theory.

Plate Tectonics Theory

Plate Tectonics Theory The theory of plate tectonics provides a useful

way to explain the causes of earthquakes, volcanoes, oceanic mountain ranges, and other geological features and events.

The theory explains that the outer shell of the earth is made up of thin, rigid plates that move relative to each other. The theory of plate tectonics was formulated during the early 1960s, and it revolutionized the field of geology. Scientists have successfully used it to explain many geological events, such as earthquakes and volcanic eruptions as well as mountain building and the formation of the oceans and continents.

Types of Plate Boundary Divergent Plate Boundary: Formed when

two plates are moving away from each other.

Convergent Plate Boundary: Formed when two plates are moving towards each other.

Transform Plate Boundary: A plate boundary where two neighboring plates are neither spreading apart nor colliding with each other. Instead, the plates are sliding past each other.

Faults Crack in the 

crust of the earth along which there has been movement of the rocks on either side of the crack.

Types of Fault: Normal Fault: A

normal fault forms as a result of tension. The rock layers in the Earth's crust are pulled apart, and gravity causes one section to move downward in relation to the other.

Types of Fault: Dip – Slip

Fault/Reverse Fault: A reverse fault forms as a result of compression. The rock layers in the Earth's crust are squeezed together, and the force pushes one section upward in relation to the other.

Types of Fault: Strike – Slip

Fault: A strike-slip fault forms when the rock layers on opposite sides of a fault slide past each other horizontally. This type of fault is sometimes called a tear, wrench, or transcurrent fault.

FOLDING A bend in a rock layer

caused by forces within the crust of the earth. The forces that cause folds range from slight differences in pressure in the earth’s crust, to large collisions of the crust’s tectonic plates.

SEISMOLOGY-study of earthquakes

An earthquake is a sudden shaking or vibration in the earth’s crust. The crust is divided into sections, called plates, which continually move in relation to each other and are bordered by faults. When plates suddenly move past each other, the built-up strain is released along the fault, and the rock fractures.

An earthquake also can be triggered by molten rock moving up into the chamber of a volcano before eruption.

Seismic wave is the energy wave generated by an earthquake or an artificial motion.

Types of Seismic Waves Body Waves: Seismic waves that travel through the

earth’s interior. P – Waves (Primary/Push – pull): They travel through

the earth by pushing rocks in the direction they are traveling. They are almost twice as fast as the S – waves and can travel through all states of matter.

S – Waves (Secondary/Shear): They travel through the earth by displacing rocks at right angles to their direction of travel. They cannot pass through fluids.

Surface Waves: Seismic waves that travel in the surface or subsurface layers of the crust.

Rayleigh Waves: It shakes the ground up and down. Love Waves: It shakes the ground side by side.

Volcano A volcano is an opening in the crust of a

planet from which lava flows. A volcanic mountain forms when magma from the planet’s mantle forces its way through the crust in the form of lava or ash and then forms a cone on the planet’s surface. On the earth, volcanoes form near hot spots within the earth’s crust or in regions over subduction zones at the boundaries of tectonic plates.

Parts of VolcanoCrater: A crater is the bowl-shaped depression at the top of a volcano through which lava and/or ash and hot gases are ejected when the volcano erupts. A meteorite crater is the depression formed in the ground by the impact of a meteorite.Vent: The passage way of the magma through the crater and out of the surface as lava.

Parts of VolcanoMagma Chamber: Magma is molten rock material that exists within the Earth in its lower mantle and crust. Magma that flows onto the Earth’s surface through volcanoes and rifts in its crust is called lava and forms extrusive igneous rocks. Caldera: A caldera is the collapsed crater of a volcano. It forms when an eruption empties the magma chamber that lies under the crater and the top of the volcano collapses under its own weight.

Parts of VolcanoLava Flow: A lava flow is a deposit of rock material that flows out of the vent of a volcano. Lava is molten rock, or magma, that originates within the mantle of a planet. Typically, the magma contains many gases and is ejected forcefully. This type of material settles to become an ash flow.

Types of Volcanoes1. Fissure Volcano: A fissure volcano, also called a fissure vent, is a long crack in the Earth’s surface through which magma pours out. The flows from fissure volcanoes produce thick sheets of basalt that can extend for thousands of square kilometers. The Columbia Plateau in the northwest United States and the Deccan Plateau in India are examples of

Types of Volcanoes2. Shield Volcano: A shield volcano is formed from recurring flows of fluid, basaltic lava rather than from a single explosive eruption. Because basaltic lava is thin and runny, these flows gradually build up gently sloping, shieldlike mounds with wide bases. Volcanic shields may be either small or large, and the largest shield volcanoes are many times larger than the largest composite volcanoes.

Types of Volcanoes3. Dome Volcano: A dome volcano, sometimes called a plug dome, is made up of viscous, acidic, extruded lava that fills a summit crater. Hard spikes of solidified lava can block the vents, eventually resulting in powerful, explosive eruptions. Dome volcanoes tend to have steep, somewhat convex sides. Examples of dome volcanoes include Lassen Peak, in the Sierra Nevada, and Mount Pelée, on Martinique

Types of VolcanoesCinder Cone: A cinder cone is a volcano that is formed primarily of basaltic cinder and loose volcanic ash deposited by a pyroclastic, or explosive, eruption. Because cinder cones are formed from loose material instead of lava, they are subject to erosion and are usually much smaller than composite volcanoes.

Types of VolcanoesComposite Volcano: A composite volcano, also called a stratovolcano, is formed from a combination of nonexplosive lava flows and pyroclastic, or explosive, eruptions. The successive layers of lava and ash solidify and accumulate additional mass over time. Composite volcanoes are often symmetrical and conical in shape, with slopes that are higher and steeper than those of shield volcanoes. Examples of composite volcanoes include Mount Fuji, in Japan, and Etna, in Sicily.

Types of VolcanoesCaldera: A caldera is a round or oval-shaped low-lying area that forms when the ground collapses because of explosive eruptions. An explosive eruption can explode the top off of the mountain or eject all of the magma that is inside the volcano. Either of these actions may cause the volcano to collapse. Calderas can be bigger than the largest shield volcanoes in diameter. Such volcanic features, if geologically young, are often outlined by an irregular, steep-walled boundary (a caldera rim), which reflects the original ringlike zone, or fault, along which the ground collapse occurred. Some calderas have hills and mountains rising within them, called resurgent dome, that reflect volcanic activity after the initial collapse.