Earth s internal processes
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Earth’s internal processes กระบวนการเปลี่ยนแปลง ภายในโลก PowerPoint PPT Presentation


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Earth’s internal processes กระบวนการเปลี่ยนแปลง ภายในโลก.

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Earth’s internal processes กระบวนการเปลี่ยนแปลง ภายในโลก

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Earths internal processes


(Plate)

Convection current theory


Continental Drift Theory

..1915 Alfred Wegener

The origin of Continental and Oceans

  • 250 (Pangea)




Sea Floor Spreading Theory

..1960sAmerican geologist Harry H. Hess

  • Theory of lithospheric evolution that holds that the ocean floors are spreading outward from vast underwater ridges

  • - Discovery mid-ocean ridge

  • samples of the deep ocean floor show that basaltic oceanic crust and overlying sediment become progressively younger as the mid-ocean ridge is approached, and the sediment cover is thinner near the ridge

  • rock making up the ocean floor is considerably younger than the continents


(Plate Tectonic Theory)

13

3



Plate Tectonics

  • Divergent boundaries

  • Convergent boundaries

    • Oceanic-continental convergence

    • Oceanic-oceanic convergence

    • Continental-continental convergence

  • Transform boundaries


LITHOSPHERE AND ASTHENOSPHERE

  • The lithosphere

  • the upper rigid mantle :

  • the overlying oceanic or continental crust :

  • The asthenosphere is capable of flow.


DIVERGENCE

  • Heat flow causes the lithosphere to break apart (divergence) and form a rift valley. These rift valleys form the boundaries between plates and new rock is formed as the magma cools. This is referred to as sea-floor spreading.

  • Older rock is pushed aside where new rock is forming. As distance from mid-ocean ridges increases, age of rock also increases. Most divergent boundaries have mid-ocean ridges with deep rift valleys along their entire length.

OLDER ROCK

OLDER ROCK

HEAT FLOW


DIVERGENCE WITH TRANSFORM FAULTS

  • Rift valleys are broken into segments by transform faults. Movements along these fractures are a source of earthquakes that occur along the ridge.

  • transform faults


mid-ocean ridges


TRANSFORM BOUNDARY

  • At the boundaries of some areas, the lithospheric plates are sliding past each other. Frequent earthquakes occur along these transform boundaries as huge masses of rock move.


TRANSFORM BOUNDARY

San Andreas Fault


TRANSFORM BOUNDARY

  • The San Andreas Fault, located in western California

  • San Andreas Fault

  • the source of frequent earthquakes.

  • the Pacific Plate and the North American Plates are sliding past each other.

  • average rate about 5 cm per year. 5

  • Some areas have not moved for centuries. Pressure has been building and is thought to be the most likely places for future earthquakes.


CONVERGENCE:ocean-continental plate boundary

  • Continental crust is made of granite, which is less dense than ocean crust, which is made of basalt.

  • The more dense ocean crust subducts (goes under) continental crust, forming a deep trenchon the ocean floor.

  • trench

  • High temperatures and pressures in the asthenosphere cause the subducting plate to melt.


CONVERGENCE:ocean-continental plate boundary

  • Magma then rises to the surface and escapes in volcanic eruptions, forming major mountain ranges on the continent.

  • Eruptions can be very violent and earthquakes at subduction boundaries occur much deeper in the lithosphere than at other plate boundaries.


CONVERGENCE:ocean-continental plate boundary


CONVERGENCE:oceanic-oceanic plate boundary

  • Where two ocean plates converge, the older, more denseocean crustal plate subducts under the younger, less dense.

  • the older crust is farther from the mid-ocean ridge where it was originally formed as new seafloor.

  • Island arcs are formed near ocean trenches as subducting plates are melted and rise to the surface as volcanic eruptions.

  • Island arcs

  • Island arcs are found along the Aleutian Trench and Tonga Trench in the Pacific Ocean


CONVERGENCE:oceanic-oceanic plate boundary


CONVERGENCE:continental-continental plate boundary

  • If converging plates are both carrying continents, the continents may be welded into a single larger continent. This converging boundary is known as a collision boundary. The collision causes the lithosphere to be pushed up into a mountain range.


CONVERGENCE:continental-continental plate boundary


CONVERGENCE: India colliding with Asia

  • The Himalayan Mountains are an example of a collision boundary that is still forming today.

  • India is pushing northward into China at a rate of about 5 cm each year.

  • 5

  • India is now welded to the Eurasian continent with the worlds highest mountains and frequent earthquakes.


CONVERGENCE

  • This map shows the Australian-Indian plate colliding with the Eurasian plate. Find India and the Himalayan Mountains.

HIMALAYAN

MOUNTAINS

INDIA


Physical world maplocations of mountain ranges

  • Mountain ranges are formed at active plate boundaries where tectonic plates are converging.

Cascades

Himalayas

Andes


WORLD MAP TECTONIC PLATE BOUNDARIES


Earthquakes

(Richter)

M = log A- log Ao

M

A

Ao

0.001 .


Deeper focus earthquakes occur in subduction zones along convergent plate boundaries. Shallow focus earthquakes occur along mid-ocean ridges and transform boundaries.


EARTHQUAKE FOCI DEPTH [Japan trench region]

  • Japan is an island arc created from the subduction of the Pacific Plate. Earthquakes in western Japan are deeper than earthquakes in eastern Japan.


Many earthquakes and volcanic eruptions surround the Pacific Ocean. This is known as the Ring of Fire.


Tsunami

A

B

D

C


Tsunami


Volcanism

()

active volcanoes

domant

extinct


Volcanic activity occurring at subduction boundaries usually results in more violent eruptions.

Figure #1 Mount St. Helens

Figure #2 Mt. Uluigalau Volcano, Fiji


TECTONIC HOT SPOTS

  • Not all volcanism occurs at plate boundaries. Hot spots are usually located in the middle of lithospheric plates. The hot spot seems to remain in the same location while the plate moves over it. This results in a chain of extinct volcanic islands like the Hawaiin Islands.

Direction of Plate Movement

North

KAUAI

OAHU

MOLOKAI

Active Volcano is over the Hot Spot

MAUI

HAWAII


stratovolcanoesComposite volcano

Fujiyama

Principal Types of Volcanoes

  • steep-sided

  • symmetrical cones


Cinder cone


Shield volcano


Caldera


Caldera


PLATE TECTONICS AND THE ROCK CYCLE

New rocks are continually being created due to tectonic forces.

  • Igneous rocks form from the solidification of magma and volcanic lava.

  • Metamorphic rocks are changed by the heat and pressure caused by converging of tectonic plates.

  • Sedimentary rocks are created when other rocks are weathered and eroded, deposited as sediments, and then compacted and cemented.Find the location of each of these processes in the diagram below.


IgneousRocks

Volcanic rocks(also called extrusive igneous rocks)

(Lava)

(Basalt) (Andesite) (Rhyolite)

Plutonic rocks(also called intrusive igneous rocks)

(>1 ) (Granite) (Diorite) (Gabbro)


Volcanic Rocks


Sedimentary rocks

- (Clastic Sedimentary Rock) (Sandstone) (Shale) (Conglomerate)

  • (Nonclastic Sedimentary Rock) (Limestone) (Chert)

  • (Rock Salte) (Coal)



Metamorphic Rock

- (Regional metamorphism) (Foliation) (Gneiss) (Schist) (Slate)

- (Contact metamorphism) (Nonfoliation) (Marble) (Quartzite)


(Slate)

(Gneiss)

(Quartzite)

(Marble




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