Plate Tectonics

Views of the Earth http://www.matter.org.uk/schools/Content/Seismology/earth_core.html

View of Earth’s Interior http://pubs.usgs.gov/publications/graphics/FigS1-1.gif

A. The Earth in Cross Section I. There are 4 major zones that make up the Earth: A. : Outer, thinnest layer of the Earth. There are two types: 1. : -Thickness: -Composition: -Density: 2. : Crust Oceanic Up to 5-8 km thick. Mostly basalt Approx. 3.0 g/cc Continental Up to 30-40 km thick. Mostly granite Approx. 2.7 g/cc

A. Crust Continent Ocean basalt granite 5 to 8 km thick 30 to 40 composed of composed of basalt granite that is that is 5 to 8 km thick 30 to 40 km thick

B. : Found below the crust. Has two parts: 1. : Upper, “plastic” mantle. -partially melted material; 250 km; “weak sphere” 2. : Rest of mantle; actual temperature is below the melting point. NOTE: The boundary between the crust and mantle is called the , or MOHO. C. : Only liquid layer of the earth; Composed mainly of iron. 2,200 km D. : Solid, innermost layer of Earth; Composed mainly of iron and nickel. 1,228 km Mantle Asthenosphere Stiffer Mantle Mohorovicic Discontinuity Outer Core Inner Core

Stiffer Mantle Asthenosphere is is Partially melted Not melted B. Mantle Stiffer Mantle Asthenosphere is is Partially melted Not melted

A. Inner Core A. Outer Core Only liquid layer Solid center of Earth composed of composed of Iron and Nickel Iron

B. Crustal Movement I. Dynamic Crust -The crust and outermost part of the Mantle is called the : “rock sphere”; 15-300 km thick, outermost and rigid A. The first theory of crustal movement was introduced in 1915 by Alfred Wegener, and was called --Evidence for this theory include: 1. 2. Correlation of rock layers/fossils: lithosphere The Theory of Continental Drift Edges of continents fit together like puzzle pieces Rock layers and fossils Found on opposite sides of ocean basins match up.

Puzzle Pieces that Fit http://pubs.usgs.gov/publications/graphics/apres.gif

FOSSILS http://pubs.usgs.gov/publications/graphics/Fig4.gif

3. Mountain chains: 4. Climate evidence: 5. Crustal age: Some mountain chains seem to be continuous from continent to continent. Ancient climates were different from today. Ex: glacial deposits in tropical regions; coal deposits in Antarctica. Rocks of the ocean basins are much younger than continental rocks.

Climate http://volcano.und.nodak.edu/vwdocs/vwlessons/plate_pics/F1.6b.gif

Continental drift mountain chains climate evidence crustal age crustal puzzle fit of continents correlation of rock layers mountain chains climate evidence crustal age crustal age

Sea-floor spreading B. Sea Floor Spreading: Theory that states that ocean floors are forming and spreading out from the ridges. 1. Convection cell: Driving force for Spreading theory. Hot, molten material from the mantle pushes upward, cools and solidifies at the surface to form new ocean rock.

1. Evidence a. Igneous Ocean Rocks: b. Magnetic Reversal: Evidence shows that igneous rock formed at the ocean ridges is younger than rock found further from the ridges As molten ocean rock cools, the magnetic minerals in the rock align themselves with the Earth’s magnetic field. If the magnetic field is opposite what it is today, the minerals will point to the south magnetic pole. The ocean rocks show that during past history, Earth’s magnetic field has reversed a number of times.

Sea Floor Spreading Igneous Ocean Convection rocks Cells Magnetic evidence driven by Igneous Ocean rocks Convection Cells Magnetic Reversal

PLATES C. Plate Tectonics: States that Earth’s lithosphere is made up of a number of solid pieces, or plates, that move in relation to each other. Pacific Plate is the largest plate Text http://www.extremescience.com/graphics/platetecmap.gif

I. Plate Boundaries A. Convergent: --3 Types: 1. : Two continental plates coming together. Ex: Two plates coming together. Continental-Continental India-Asia boundary (Himalayas)

Continental-Continental Convergence http://pubs.usgs.gov/publications/graphics/Fig21contcont.gif http://pubs.usgs.gov/publications/graphics/Fig24left.gif

I. Plate Boundaries A. Convergent 2. : Oceanic and Continental plates coming together. --Typically will form an along a , where the ocean plate pushes under the continental plate. Ex: Continental-Oceanic ocean trench subduction zone West Coast of South America

Oceanic-continental convergence http://pubs.usgs.gov/publications/graphics/Fig21oceancont.gif South American Plate and Nazca Plate colliding http://pubs.usgs.gov/publications/text/Nazca.html

I. Plate Boundaries A. Convergent 3. : Two ocean plates coming together. --Typically will form an as one plate pushes under the other. Ex: B. Divergent: -- Usually form: Ex : Oceanic-Oceanic island arc Marianas Trench Two plates moving opposite each other. ocean ridges mid-Atlantic Ridge

Oceanic-Oceanic Convergence http://pubs.usgs.gov/publications/graphics/Fig21oceanocean.gif

Continental- Continental Plate Boundaries Plate Tectonics Convergent meet at Convergent moving plates come together Examples Continental- Oceanic Oceanic- Oceanic Continental- Continental Continental- Continental Continental- Continental

Plate Boundaries Divergent Move apart

Divergent Plates Text http://pubs.usgs.gov/publications/graphics/lava_fountains.gif http://pubs.usgs.gov/publications/graphics/Fig16.gif

I. Plate Boundaries C. Transform Fault: -Forms where Ex: Two plates sliding horizontally past each other. two plates move past each other without subduction occurring. San Andreas Fault, California

Plate Boundaries Transform Move Horizontally Past Each Other

Transform Boundaries http://pubs.usgs.gov/publications/graphics/Fig25.gif http://pubs.usgs.gov/publications/graphics/San_Andreas.gif

C. Evidence of Crustal Activity I. Crustal Activity A. Deformed Rock Strata --Originally, sedimentary rocks form However, observations made of Earth’s surface indicate that This includes: 1. Tilting: flat, horizontal layers. original rock formations have been changed through past Earth movements. Rock layers are found at an angle to their original formation.

1. Folding: 2. Faulting: Rock layers get warped, or bent as a result of compression. Pressure on rock layers causes them to break. The boundary between the broken layers is called a fault.

2. a. Types of faults There are three types of forces that cause faulting

1. Normal The force of tension causes normal faulting. Normal faulting is when the hanging wall moves downward. This type of faulting is common at divergent plate boundaries. Examples of this type of faulting are the Sierra Nevada mountains and the eastern border of California.

2. Reverse The force of compression causes reverse faulting. Reverse faulting is when the hanging wall moves up. This type of faulting is common at convergent plate boundaries. An example of this faulting is the Rocky Mountains.

3. Strike Slip The force of shearing causes strike-slip faulting. Movement along this type of fault is not up and down, but sideways. This type of faulting is common at transform plate boundaries. Examples of this type of faulting is the San Andreas fault.

B. Displaced fossils: Shallow water fossils have been found at high elevations, and deep water fossils have been found in shallow water areas. This means the crust has been moved.

crustal activity deformed rock displaced strata fossils tilting shallow fossils at high elevation deep fossils in shallow water areas tilting folding faulting faulting

Results of Crustal Activity I. Results of Crustal Activity A. Earthquakes: Sudden movement of rocks along a fault which releases a large amount of energy. This energy is the earthquake. --focus: The point in the earth where the earthquake occurs. --epicenter: The point on the surface directly above the focus

--Types of earthquake waves: 1. : Also called compressional waves; the motion of the ground is parallel to the direction of wave motion. These waves can pass through Primary (P) waves solid or liquid material.

2. : Also called compressional waves; the motion of the ground is perpendicular to the direction of wave motion. These waves can pass through Shear (S) waves solid material only. 3. : Waves that ripple the surface of the Earth, causing most of the damage of an earthquake. Long (L) waves

--When traveling through the same material, travel faster than -Since these waves travel at different speeds in different density materials, we can use earthquake waves to tell us about the interior of Earth. When an earthquake occurs, both P waves and S waves are released. In many places on Earth, both waves are received; however, in other places, only P waves are received. Since S waves cannot pass through a liquid, the conclusion is that P waves S waves. some part of Earth’s interior is liquid.

results of crustal activity Earthquakes types of waves P waves S waves L waves

-If an earthquake occurs under the ocean, the energy is also released through the ocean water. When it reaches the coastline of a continent or island, it may form a large, fast moving wave called a . They may move at speeds of and may be !!!! tsunami 200 mph 150 ft. high

A. Earthquake Strength -The strength of an earthquake can be determined in one of two ways: 1. : Used to describe the amount of energy released by an earthquake. It ranges from to , and each increase on the scale indicates a release of times more energy!!! --To record earthquake waves, seismologists use a , which can be used to record the arrival time of the waves and the intensity of the waves. Richter Scale 9 32 seismograph

1. : Used to describe the earthquake in terms of the amount of damage done. It ranges from to . --Why is the Richter scale better to compare earthquakes that occur in different places on Earth? Modified Mercalli Scale I XII It compares the amount of energy released, which is constant for the same intensity earthquake.

Earthquakes measured using Richter Scale Mercalli Scale

A. Volcanoes: --How do they form? 1. Molten rock from within the earth, called , along with gases, begins to rise up through cracks and weak spots in the crust. 2. When this molten material, along with gases from inside earth, break through the surface, it may flow out on the surface, and then it is called . --Where do they form? 1. 2. 3. : Weak points in the crust, located over unusually high heat flow in the mantle. Although the crust may move, -Ex: magma lava In mountain ranges formed along continental-oceanic boundaries. Along ocean ridge systems Hot spots the hot spot remains in the same place in the mantle Hawaiian Island chain

Volcanoes Shield lava lava and ash Composite ash and cinder Cinder erupts lava lava and ash Composite erupts ash and cinder Cinder erupts