Transcript Clues in the Crust - SD43 Teacher Sites

Clues in the Crust
Need To Know
Background Information
 The formation of Mountains is a slow
movement of Earth’s Crust where
earthquakes and volcanoes are much
more rapid and violent.
 Scientist can explain both types of
movement by studying cross sections of
the sea floor.
 A cross section is a drawing of what you
see when you cut through an object.
Ocean Floor Morphology
 Ocean Ridge – the raised floor, which can
become large enough to be considered an
underwater mountain range. ie Juan de Fuca
Ridge
 Continental Slope – a deep slope in the
seabed between a continental shelf and the
sea floor.
 Continental Shelf – a shallow underwater
ledge located between a continent and the
deep ocean.
Cross section
 Abyssal Plain – a large flat area on the
sea floor. Abyssal plains make up a large
part of the sea floor.
 Rift – an opening in the oceanic crust,
where molten materials from Earth’s
mantle can escape.
Cross section
How Does Earth’s Crust
Move?
 A scientist who searched for answers
was a German Meteorologist (studies
climate and weather), Alfred Wegener
(1880- 1930). Wegener noticed that the
continents almost fit together like a
puzzle.
Pangaea
 Wegener thought that the fit of the
continents was more than just a
coincidence. He suggested that all the
continents were joined together in a huge
land mass called Pangaea. He
suggested that Pangaea broke apart
about 200 million years ago.
Another Theory from
Wegener
 Wegener also proposed the theory of
continental drift. According to the theory of
continental drift, the continents change
position very slowly, moving over the surface of
Earth a few centimeters every year.
 Most of the scientists of Wegener’s time
strongly disagreed with him. Wegener could
not explain how the continents moved but
collected as much evidence as he could. He
collected fossils and rocks.
 As Wegener looked more carefully at the
climates suggested by the fossils and geology
in different areas, he saw unexpected
similarities between continents that are no
longer close together. He and Vladimir Koppen
marked all the climates on the continents and
then tried to put the continents together based
on their paleoclimatic evidence. They found
the continents fit together like a puzzle.
Wegener based his theory of continental drift
on biological, geological and meteorological
evidence.
Fossil Evidence
 Fossils of the reptile Mesosaurus have been found in
South America and Africa. Mesosaurus lived in fresh
water and on land and probably could
not swim between
continents.
Wegener
hypothesized that
this reptile lived on
both continents when
they were joined.
Evidence From Rocks
 The Appalachian Mountains in eastern
North America are made of the same
kind of rock as a mountain range in
Britain and Norway. There are similarities
between rock in Quebec and rock in
northern Britain. There are also
similarities between rock in South
America and rock in Africa.
Rock Evidence
Modern Day Evidence
 Technological advances have allowed
geologists to actually touch the sea floor
sediments that were found over 1000m
deep.
 Scientists have used Sonar, Seismic
Waves and Core Samples to confirm
Wegener’s theory of continental drift.