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MOVING CONTINENTS
UNITE 2 , MODULE 1 , LESSON 1
PAGES 6-19
ENCOUNTER THE PHENOMENON
• Q: How do you use clues to put puzzle pieces together?
• Align text ( words)
• Align shapes
• Connect rejoins with the same color
INVESTIGATION
• A Surprising fit
WHY DO SOME CONTINENTS HAVE MATCHING
SHAPES?
•
Nearly 100 years ago, a scientist named Alfred Wegener began an
investigation.
• He wanted to know if Earth’s continents had always been in the
same place, or if they had moved.
WHY DO SOME CONTINENTS HAVE MATCHING
SHAPES?
• Wegener proposed that all the continents were once part of
a supercontinent called Pangaea.
• Over time, Pangaea broke apart, and the continents slowly
drifted to their present locations.
WHY DO SOME CONTINENTS HAVE MATCHING
SHAPES?
•
Wegener proposed the hypothesis of continental drift.
• The continental drift hypothesis suggested that continents are in constant motion on the surface of Earth.
WHY DO SOME CONTINENTS HAVE MATCHING
SHAPES?
• Wegener looked at the coastlines of continents that are
now separated by oceans.
•
He saw similarities in the shapes of the continents,
including the continental shelves.
•
For instance, Africa and South America seemed to fit
together like the pieces of a puzzle.
INVESTIGATION
• The continental drift hypothesis
WHY DO SOME CONTINENTS HAVE MATCHING
SHAPES?
• Wegener knew that he needed evidence to support his hypothesis of continental drift.
•
The most obvious evidence was the puzzle-like nature of the continents.
• But other scientists were doubtful of his hypothesis. Wegener needed more evidence.
•
To support his hypothesis , Wegner had Four evidence:
• Evidence from rock formation
• Evidence from Glacial formation
• Evidence from Coal formation
• Evidence from Fossils
(PARTNER) UP !
•
Q1: How did Wegner use the rock formation as an evidence of his hypothesis?
•
he suggested that if the rock formation was the same in two different continents , the meant that
they were one part in the past
• Q2: What were the mountain chains he examine to support his hypothesis?
• Caledonian mountain range, and the Appalachian Mountains
• Q3: According to his discovery , which continents were one part in the past?
• North America and Europe
• Q4: how did geologists know that different continents have rocks of common origins and were one
connected?
• By identifying the type and age of rocks
HOW DO ROCKS PROVIDE EVIDENCE THAT
CONTINENTS MOVE?
•
Evidence from Rock Formations:
•
Wegner supposed that mountain ranges had separated as
continents drifted apart .
• He believed that there would be areas of similar rocks on
opposite sides of Atlantic ocean.
MOUNTAIN RANGES
• it is a series of mountains arranged in a line and connected by high ground.
• Appalachian Mountains
• Caledonian mountain range
HOW DO ROCKS PROVIDE EVIDENCE THAT
CONTINENTS MOVE?
•
Evidence from Rock Formations:
• More evidence came from the rocks that make up two mountain
chains in Europe and North America.
• The Caledonian mountain range is in Northern Europe, and the
Appalachian Mountains are in Eastern North America.
• Rocks in these two mountain chains are similar in age and
structure.
•
Both are also composed of the same rock types.
•
If you could place North America and Europe next to each other,
these mountain chains would meet.
• They would form one long, continuous mountain belt.
HOW DO ROCKS PROVIDE EVIDENCE THAT
CONTINENTS MOVE?
•
Evidence from Rock Formations:
•
Many rock formations and mountain ranges on Australia, South
America, Africa, India and Antarctica all seemed to have formed
in the same way at the same time.
• Today geologists know that there were large-scale volcanic
eruptions on the western coast of Africa and on the eastern
coast of South America hundreds of millions of years ago.
• Geologists have studied rocks from these eruptions.
•
They determined that the volcanic rocks from both continents
were identical in chemistry and age.
GLACIAL FORMATION
• They are formations result from the presence of ice .
HOW DO ROCKS PROVIDE EVIDENCE THAT
CONTINENTS MOVE?
•
Evidence from Glacial Features
• When Wegener pieced Pangaea together, he proposed that South
America, Africa, India, and Australia were located closer to the
South Pole 290 million years ago.
•
He suggested that a large ice sheet covered much of these
continents. When the ice sheet melted as Pangaea spread apart, it
left rock and sediment behind.
•
Wegener studied the similarities of these sediments.
HOW DO ROCKS PROVIDE EVIDENCE THAT
CONTINENTS MOVE?
•
Evidence from Glacial Features:
• Wegener also studied glacial grooves.
• Glacial grooves are deep scratches in rocks made as
ice sheets move across the land.
• Wegener found glacial grooves on many different
continents.
• By studying these grooves, he was able to determine
the direction that the ice sheet moved across the
joined continents.
QUESTION
• Q1: What evidence did glacier features provide to Wegner?
• They provided patterns that connected different continents together
HOW DO ROCKS PROVIDE EVIDENCE THAT
CONTINENTS MOVE?
•
Evidence from Coal Deposits:
•
Coal beds are in Antarctica, a polar climate today.
•
Yet coal formed from fossilized plants that lived long ago in
warm, wet climates.
•
This meant that Antarctica must have been warmer and wetter
when these plants were alive.
•
Wegener used this evidence to conclude that Antarctica must
have been much closer to the equator sometime in the geologic
past.
FOSSILS
• They are the remains of animals or plant that lived once in the past .
HOW DO FOSSILS PROVIDE EVIDENCE THAT
CONTINENTS MOVE?
•
Evidence from Fossils
• Fossils of a plant called Glossopteris have been
discovered in rocks from South America, Africa,
India, Antarctica, and Australia.
•
Today these continents are far apart and separated
by oceans
• The plant’s seeds, which were large and heavy,
could not have traveled across the oceans.
HOW DO FOSSILS PROVIDE EVIDENCE THAT
CONTINENTS MOVE?
• Another fossils Wegner used are:
•
Mesosaurus ,a coastal reptile
• Cynognathus and Lystrosaurus , terrestrial
reptiles
• They have been found on continents that are
now separate by vast oceans.
• These animals could not have swan all this
distance
INVESTIGATION
•
Wegner’s thorn
WHAT WAS MISSING?
•
Wegener supported his continental drift hypothesis until his death in 1930. Wegener’s ideas were not widely
accepted until nearly 40 years later.
•
Why were scientists skeptical of Wegener’s hypothesis?
• Continental drift is a slow process. Wegener could not measure how fast the continents moved.
•
Wegener also could not explain what forces caused the continents to move. The mantle under the continents
and seafloor was made of solid rock.
• How could continents push their way through solid rock?
WHAT WAS MISSING?
• The evidence for drifting continents was hidden on the seafloor.
•
During Wegener’s lifetime, scientists did not have the tools to determine what happens beneath the oceans.
• Wegener also could not have known what the seafloor looked like.
• The evidence needed to prove continental drift was not discovered until long after Wegener’s death.
QUESTION
• Q1: how does Glossopteris provide evidence of continental drift ?
• Glossopteris fossils are found on different continents that are far apart from each other today.
• Q2: how did Wegner use fossil to support his continental drift hypothesis?
• The same fossil have been found on several continents that fit together like puzzle pieces
• Q3: Which of the continents would not support Glossopteris growth today ?
• Antarctica
QUESTION
• Q4: How did Wegner use as a further evidence of the continental drift hypothesis ?
• They all are found on continents that are now separated by great distance and since one lived in fresh
water and the other lived on land they could not have swum across the salt ocean water between the
continents .