Getting an A in Science

• Taking ownership or control of the information learned in class and taking responsibility for your work– This means:

• Practicing (reviewing, restating, preparing)

• Applying (creating, thinking, using)

• Planning (studying, completing projects and homework, being prepared-pencils, books)

Continental Drift

How many continents are there?

7- North America, South America, Africa,

Europe, Asia, Australia, Antarctica

Have the continents always looks like this?

Were the continents always located in the same position?

http://www.youtube.com/watch?v=WaUk94AdXPA&feature=related

Puzzle Activity

• Cut the continents apart.

• Try to assemble the puzzle.

• What clues did you use to help you put it back together correctly?

A continental puzzle

Discovering Earth’s Past

• Using your textbook (pages 98-104) complete the worksheet on continental drift and seafloor spreading.

• Worksheet is due tomorrow

Continental Drift• Who?

– Alfred Wegener (German meteorologist)

• When?– 1912

• He noticed the puzzle-like fit of the continents http://maps.google.com

• He proposed that the continents were joined together in the past, in a large land mass called Pangaea.

• Over time, the continents drifted (moved) apart– Wegener named his theory “Continental Drift”.

Describe it

He supported his theory with four pieces of evidence.

• Matching fossils of animals on once connected land areas.

1. Animal Fossil Clues

2. Plant Fossil Clues

Fossils of the plant Glossopteris are found in rocks in South Africa, India, Australia, South America,

and Antarctica

3. Climate Clues

• Glacial evidence in Africa, South America, Australia

• Fossils found in Antarctic soil indicate that the now frigid continent was once lush with trees and ferns, and home to

dinosaurs, amphibians, and later, marsupials.

4. Rock Clues - similarities and ages

Mountains in South America and Antarctica are believed to have formed as part of the same

mountain chain.

Wegener’s theory made sense, but no one wanted to accept it until they knew HOW the

continents moved.

Years later someone came up with an explanation of HOW the

continents moved

Seafloor Spreading

• Who?– Harry Hess (A Princeton

University scientist)

• When?– 1960’s

Using new technology, they looked at the ocean floor

• Hess and other scientists mapped the ocean floor using sonar

• They detected underwater mountain ranges

• Further examination of the ocean floor with a submarine showed underwater volcanoes.

• A variety of life living near the warm vents of the volcanoes was found

• Sampling the rocks near the volcanoes revealed that there was a pattern to their formation.

Describe Seafloor Spreading

• Magma in the mantle rises and pushes the plates apart, forming new oceanic crust.

http://www.absorblearning.com/media/item.action?quick=12n

http://education.sdsc.edu/optiputer/flash/seafloorspread.htm

Seafloor Spreading causes Continental Drift

Now we could explain HOW the continents moved:

He supported his theory with two pieces of evidence.

1. Rock agesYoungest rocks are found at the mid-ocean ridges

and they become increasingly older farther from the edges.

2. Magnetic Clues

• Magnetic iron particles record the time of the rock formation.

• When the magnetic north pole switched places, iron in the rocks recorded this informationhttp://www.youtube.com/watch?v=BCzCmldiaWQ

http://www.absorblearning.com/media/attachment.action?quick=12w&att=2789

A map of the ocean floor provides even more evidence http://maps.google.com/

Iceland shows seafloor spreading above the water, which makes it

easier to study

Plate Tectonic Theory

• Theory of Plate Tectonics -Earth’s crust is broken into plates which float and move.

Earth’s crust made of many plates is similar to the shapes on a outside of

a soccer ball.

There are about 13 plates covering Earth’s surface

Two Types of Plates• Continental Plates – lighter, thicker, made of

granite

• Oceanic Plates – heavier, thinner, made of basalt

Plate Boundaries (edges)

When the plates move, their boundaries, or edges, can scrape each

other or collide.

Convergent Boundary

• Plates move toward each other

Convergent Boundary

• When two continental plates move into each other, the plates combine and form mountains. (India into Asia)

http://www.classzone.com/books/earth_science/terc/content/visualizations/es1105/es1105page01.cfm?chapter_no=visualization

http://www.absorblearning.com/media/attachment.action?quick=12t&att=2783

Convergent Boundary• When an oceanic plate runs into a continental

plate, the heavier oceanic plate subducts (sinks) into the mantle and melts back into magma.

• Volcanic mountains and deep sea trenches are created along this edge.

http://www.absorblearning.com/media/attachment.

action?quick=12s&att=2781

Oceanic plate into continental

• Example: Pacific plate (oceanic) subducts (sinks) under Japan (continental). http://maps.google.com/

Divergent Boundary

• Plates move apart

When both diverging plates are oceanic, it is called seafloor spreading

(Mid-Atlantic Ridge)

When both diverging plates are continental it is called rift valley

formation (Africa)

http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::640::480::/sites/dl/free/0072402466/30425/19_21.swf::Fig.%2019.21%20-%20Evolution%20of%20a%20Divergent%20Plate

%20Boundary

Transform Boundary

• Plates slide past each other

San Andreas Fault

San Andreas Fault, CA

• Each time the plates slide past each other, an earthquake occurs

Find the three boundaries

http://www.pbs.org/wgbh/aso/tryit/tectonics/shockwave.html

Asthenosphere

• A plastic-like layer found below the lithosphere.

• The rigid oceanic and continental plates of the lithosphere sit on top

The Asthenosphere is heated by the hot Outer Core

Convection Current

• Hot material rises, cooler material sinks, creating a current, called a Convection Current

core

mantle

crust

When the asthenosphere moves, it carries the lithospheric plates

Convection currents cause plate motion

http://www.absorblearning.com/media/attachment.action?quick=12p&att=2775

http://www.youtube.com/watch?v=ryrXAGY1dmE

http://www.youtube.com/watch?

v=Kpoko_l34ZE

http://www.youtube.com/watch?v=lJiAUvB1vEU

Every time these plates move we get earthquakes, volcanic eruptions, and

possibly tsunamis