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Plate Tectonics, Earthquakes and Volcanoes: 

Plate Tectonics, Earthquakes and Volcanoes







Plate Movement: 

Plate Movement

Earth’s layers: 

Earth’s layers Lithosphere (Crust)-several miles thick at the ocean floor, up to 22 miles thick below continents, “moving plates” Asthenosphere (Mantle)-layer below consisting of solid earth

Types of plate movement: 

Types of plate movement

4 types of movement: 

4 types of movement Diverging -Spreading Transform -Transgressional Converging -Subduction -Over-riding

Types of Plate Movement: 

Types of Plate Movement Convergent – two plates converge or come together 3 types – Ocean Plate VS. Continental Plate Ocean Plate VS. Ocean Plate Continental Plate VS. Continental Plate Ocean plates are most dense. They will SUBDUCT under the less dense Continental Plates. Two Continental Plates converge, neither SUBDUCT, and plates OVERRIDE

3 Types of Converging Plates: 

3 Types of Converging Plates Peru-Chile Trench Japan Trench Himalaya Tibetan Plateau


Subduction This refers to the process in which one plate goes underneath (or subducts) the other. It occurs when two oceanic of when one oceanic and one continental plates converge. (When two continental plates meet, they buckle and form mountain ranges. See When the plate subducts, an oceanic trench is created. Aleutian Island Trench

Subduction animation: 

Subduction animation


Over-Riding Since these are usually separated by an oceanic crust, the oceanic crust slides under one of the continental plates. From there, the two continental plates collide, but, because they're both light, neither one sinks into the mantle. The two continue to push on another until tension is too much and they both begin to rise. This is when mountain ranges, such as the Alps and Himalayas in Europe and the Urals in Asia form. As a matter of fact, because these plates constantly push and strain on one another, these mountains are getting higher and higher each day.


Converging animation

Mountain Formation: 

Mountain Formation

Effects of movement: 

Effects of movement


Spreading These are two plates that move apart. When the plates pull apart, something has to rise to fill in the hole. Magma from the mantle rises upward from the crust to fill the gap. Then, it hardens, pulls away from the hole, and makes way for more magma to ooze out. This occurs in the creation of ocean ridges (sea floor spreading). These are just like mountains, only on the ocean floor. In fact, this process has created a 46,600 mile-long Mid-Ocean Ridge System. It is through these spreading centers that the sea floor replenishes itself; new magma rises, forms a "plug", and, eventually, the youngest part of the sea floor is born.


Mid Atlantic Ridge


Mid Atlantic Ridge


Mid Atlantic Ridge

Transgressional : 

Transgressional These are two plates that move sideways. You can find these boundaries along fault lines; where earthquakes occur. Because the plates suddenly, violently pull apart in the opposite direction, the ground is left unsettled and an earthquake results.


Ring of Fire

Hot spots/weaknesses: 

Hot spots/weaknesses

Island Formation: 

Island Formation

Earthquake Damage: 

Earthquake Damage



Alaskan Earthquake: 

Alaskan Earthquake

Alaskan Earthquake: 

Alaskan Earthquake

Loma Prieta Quake 1989: 

Loma Prieta Quake 1989

Loma Prieta Effects: 

Loma Prieta Effects

Folds and Faults: 

Folds and Faults

P waves and S waves: 

P waves and S waves P (Primary) waves: Also called compressional or longitudinal waves, P waves are the fastest seismic waves produced by an earthquake. They oscillate the ground back and forth along the direction of wave travel, in much the same way as sound waves, which are also compressional, move the air back and forth as the waves travel from the sound source to a sound receiver. S (Secondary or shear) waves: S waves oscillate the ground perpendicular to the direction of wave travel. They travel about 1.7 times slower than P waves. Because liquids will not sustain shear stresses, S waves will not travel through liquids like water, molten rock, or the Earth's outer core.


Our most vulnerable land falls into two general categories:    1. areas covered by the huge amount of fill poured into San Francisco Bay since 1845 to transform 77 square miles (200 square km) of tidal and submerged areas into land; and    2. areas along existing and filled stream channels and flood plains, particularly those areas with deposits less than 10,000 years old. Effects of Liquifaction 1. areas covered by the huge amount of fill poured into San Francisco Bay since 1845 to transform 77 square miles (200 square km) of tidal and submerged areas into land; and 2. areas along existing and filled stream channels and flood plains, particularly those areas with deposits less than 10,000 years old.


People do not feel any Earth movement. A few people might notice movement. Many people indoors feel movement. Hanging objects swing back and forth. Most people indoors feel movement. Hanging objects swing. Dishes, windows, and doors rattle. The earthquake feels like a heavy truck hitting the walls. Parked cars rock. Almost everyone feels movement. Sleeping people are awakened. Doors swing open or close. Dishes are broken. Pictures on the wall move. Small objects move or are turned over. Everyone feels movement. People have trouble walking. Objects fall from shelves. Damage is slight in poorly built buildings. People have difficulty standing. Drivers feel their cars shaking. Some furniture breaks. Loose bricks fall from buildings. Drivers have trouble steering. Houses that are not bolted down might shift on their foundations. Tall structures such as towers and chimneys might twist and fall. Well-built buildings suffer slight damage. Well-built buildings suffer considerable damage. Houses that are not bolted down move off their foundations. Some underground pipes are broken. The ground cracks. Reservoirs suffer serious damage. Most buildings and their foundations are destroyed. Some bridges are destroyed. Large landslides occur. Most buildings collapse. Some bridges are destroyed. Large cracks appear in the ground. Underground pipelines are destroyed. Almost everything is destroyed. Objects are thrown into the air. The ground moves in waves or ripples. Large amounts of rock may move. Mercalli Intensity Scale


Mercalli effects of Loma Prieta 1989


As a general rule, an increase of one magnitude unit corresponds to ten times greater ground motion, an increase of two magnitude units corresponds to 100 times greater ground motion, and so on in a logarithmic series. Richter Scale Richter Earthquake Magnitudes Effects Less than 3.5 Generally not felt, but recorded. 3.5-5.4 Often felt, but rarely causes damage. Under 6.0 At most slight damage to well-designed buildings. Can cause major damage to poorly constructed buildings over small regions. 6.1-6.9 Can be destructive in areas up to about 100 kilometers across where people live. 7.0-7.9 Major earthquake. Can cause serious damage over larger areas. 8 or greater Great earthquake. Can cause serious damage in areas several hundred kilometers across.

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