Getting an A in Science
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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)
How many continents are there?
7- North America, South America, Africa,
Europe, Asia, Australia, Antarctica
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?
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
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.
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
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
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/
Plate Tectonic Theory
• Theory of Plate Tectonics -Earth’s crust is broken into plates which float and move.
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
• 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/
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
Asthenosphere
• A plastic-like layer found below the lithosphere.
• The rigid oceanic and continental plates of the lithosphere sit on top
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