1.2 continents change position over time

7/27/2019 1.2 Continents Change Position Over Time

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Continents

ChangePosition

Over Time

Chapter 1

Lesson 2


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Continents Join Together and S

The Earths surface is constantly moving

We know this because of changing mapsover time

In 1912, German scientist Alfred Wegenerproposed a hypothesis called

This hypothesis stated that Earths continents

were once joined in a

and

gradually moved/drifted apart


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Evidence for Contin

1. Wegener learned

that the fossils of one dinosaur, wasdiscovered in both South America andAfrica. The fossils were NOT foundanywhere else in the world. This can beexplained if South America and Africawere once joined.


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Evidence for Contin

2. Greenland

today lies near the Arctic Circle and is

mostly covered in ice. However, fossils oftropical plants can be found on its shores.Another example is South Africa. We knowthat Africa has a warm climate, but itsrocks were deeply scratched by ice sheetsmillions of years ago.


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Evidence for Contin

3.

Wegeners best evide

make up the continenother. Rocks in Brazil mfound in western Africain the Appalachian MAmerica] matched thScotland.


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Pangaea and Contin

is the huge

supercontinent that included all of ourcontinents today

Long ago, all the continents were a singleland mass until they started to split apart[200 million years ago]

However he was unable to explain HOWthe continents moved


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The Theory of Plate Tectonics exp

plates and their contine

until the mid 1900s, whenscientists proved that tectonicplates moved!

arehuge underwater mountainranges; they are present inevery ocean and circles theentire Earth [seams of abaseball]


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Evidence from the

2.

Scientists drilled into t

obtained rock samplrevealed that the yothe ridge, while the oaway


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Evidence from the

3. Why isnt the

Earth getting larger if the sea-floor isspreading? The answer is OCEAN TRENCH.At these ocean trenches, dense oceaniccrust is sinking into the asthenosphere. Oldcrust is being destroyed at the same rateas the new crust forming.


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Causes of Plate M

Because tectonic platasthenosphere [hot taconvection; energy tramovement of a mater

SOFT ROCK in the asthcools, and sinks [denseheated and rises agai

inside a pot]

This sinking and rising m

transfers heat energy i

This is a VERY SLOW proyear]; but over a millio

distance!


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Causes of Plate M

also help

move huge plates

Slab pull occurs when gravity pulls a cool,dense plate down into the asthenosphere

Ridge push occurs when material from amid-ocean ridgeslides downhill FROM the

ridge


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Putting the Theory

Geoknoabomovthe

This Eartup oove

The

areAntIndiNazAmplat

Whetheyearerupmee

plat

1.2 continents change position over time

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