Plate Tectonics

Topics: Plate tectonics, Subduction, Convergent boundary Pages: 23 (5406 words) Published: June 15, 2013
Plate Tectonics
Designed to meet South Carolina Department of Education 2005 Science Academic Standards

Table of Contents
 Plate Tectonics: The Beginning (slides 3 and 4)  Layers of the Earth (slides 5 and 6) Standard 8-3.1  What are Tectonic Plates- movement? (slides 7 and 8) Standard 8-3.6 Tectonic Plate boundaries (slides 9-21) 1. Convergent boundary Ocean-continent (slide 10) Continent-continent (slide 11) Oceanic-oceanic (slide 12) Volcanism (slide 13) 2. Divergent boundary Sea-floor spreading (slide 14) The Mid-Atlantic Ridge (slide 15) Sea-floor Exploration and Age Dating (slides 16-19) 3. Transform Boundary (San Andreas Fault, J. Tuzo Wilson) (slide 21)  Faults (slides 22-24) and Folds (slide 25)  Plate movement over Geologic Time (slides 26-29)  Creation and change of Landforms (slides 30-33) Standard 8-3.7 Volcanic eruptions (Mt. St. Helens) (slide 32) Mountain building events (Appalachian vs. Himalayas) (slide 33)  Tectonics and the Ocean Floor (slide 34) Standard 5-3.2 Continental margins (slide 35) Passive (slide 36) Active (slide 37)  South Carolina Standards (slides 39-40)

2

Plate Tectonics: The Beginning
Background
 At the beginning of the 20th Century, scientists realized that that they could not explain many of the Earth‘s structures and processes with a single theory. Many scientific hypotheses were developed to try and support the conflicting observations. One hypotheses was continental drift, which was proposed by Alfred Wegener in a series of papers from 1910 to 1928.  The principal thought of continental drift theory is that the continents are situated on slabs of rock, or plates, and they have drifted across the surface of the Earth over time; however, originally, they were all joined together as a huge super-continent at one time.

 In the 1960‘s, the theory of continental drift was combined with the theory of sea-floor spreading to create the theory of plate tectonics.

Alfred Lothar Wegener (1880-1930)

(Photograph courtesy of the Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany.)

Table of Contents

3

Plate Tectonics: The Beginning
 The idea for Wegener's theory was sparked by his observation of the nearly perfect “fit” of the South American and African continents.

Additional evidence supporting the continental drift theory:

The “fit” of two continents.

1. Fossils of the same plant (Glossopteris) found in Australia, India, Antarctica and South America. 2. Fossils of same reptile (Mesosaurus) found in Africa and South America. This animal could not have swum across the existing Atlantic Ocean!

3. Glacial deposits found in current warm climates and warm climate plant fossils found in what is now the Arctic. 4. Nearly identical rock formations found on the east coast of U.S. and the west coast of Europe 4 and eastern South America and western Africa. Table of Contents

Standard 8-3.1

What are Tectonic Plates?
The Earth is made up of three main layers:
1. The Core is at the center of the Earth. It is divided into an inner and outer core. 2. The Mantle is the layer surrounding the core. The upper mantle is partially molten and called the asthenosphere. 3. The Crust, or lithosphere, is the rigid outer-most layer. Thick continental crust underlies continents, and thin, very dense oceanic crust underlies oceans. Table of Contents

The layers of the earth.
Modified after Plummer/McGeary, 7th ed., pg. 14

5

Inner Core Thickness Physical Properties 1,216 km Solid Iron; extremely dense (17 g/cm3)

Outer Core 2,270 km Molten Iron, very dense (12 g/cm3) 30%

Mantle 2,900 km Made mostly of silicates of magnesium and iron; moderately dense. Behaves like melted plastic in upper-most section (5.5 g/cm3) 65%

Crust Continental 35-90 km Oceanic 7-8 km Made of silicate rocks and oxides; slightly dense; rigid. (2.67-3.3 g/cm3) 5%

Percentage of Earths’ Mass

Standard 8-3.1

What are Tectonic Plates?...
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