12.1 evidence for continental drift - mr.v's classes ... · pdf file12.1 evidence for...
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12.1 Evidence for Continental Drift
VOCABULARY
Word to Know
Resource Exploitation
Resource use
Sustainability
Land use
Native Species
Introduced Species
Continental Drift Theory
• states that the continents have not always been in their present locations but have “drifted” there over millions of years.
• proposed by German scientist Alfred Wegener • He suggested that, millions of years ago, all the continents were joined as a
“supercontinent = PANGEA
EVIDENCE OF FOR CONTINENTAL DRIFT THEORY
THE CONTINENTS FIT
• The continents looked as though they might fit together like puzzle
pieces.
THE CONTINENTAL SHELVES FIT
• The continental shelves actually fit together even better than
continents
• CONTINENTAL SHELVES = submerged original shorelines of
continents
THE CONTINENTAL SHELVES FIT
• The continental shelves actually fit together even better than
continents
• CONTINENTAL SHELVES = submerged original shorelines of
continents
MATCHING FOSSILS, GEOLOGIC FEATURES AND ROCKS
• Wegener also realized that other evidence also supported his theory
MATCHING FOSSILS, GEOLOGIC FEATURES AND ROCKS
o There were matching geologic features and rocks on different continents.
EVIDENCE OF GLACIERS ON WARM CONTINENTS
o Wegner noted mountain ranges that begin on one continent, end at the
coastline and then appear to continue on a continent across an ocean
EVIDENCE OF GLACIERS ON WARM CONTINENTS
o Similar rocks (same age, same type) and rock structures found in
Newfoundland, Greenland, Ireland, Scotland, and Norway
MATCHING FOSSILS, GEOLOGIC FEATURES AND ROCKS
• Wegener also realized that other evidence also supported his theory
o There were matching fossils, like Mesosaurus, on different continents.
MATCHING FOSSILS, GEOLOGIC FEATURES AND ROCKS
• Wegener also realized that other evidence also supported his theory
o There were matching fossils, like Mesosaurus, on different continents.
EVIDENCE OF GLACIERS ON WARM CONTINENTS
o There was evidence of different climates, (eg. such as glaciers) on warm
continents.
How Can Continents Move?
PLATE TECTONIC THEORY
• Earth is broken into large, movable slabs of rock that move around the
surface of Earth, sliding over a layer of partly molten rock.
• These slabs are called tectonic plates
How Can Continents Move?
PLATE TECTONIC THEORY
• Earth is broken into large, movable slabs of rock that move around the
surface of Earth, sliding over a layer of partly molten rock.
• These slabs are called tectonic plates
EVIDENCE for PLATE TECTONIC THEORY
• It was noted that earthquakes and volcanoes appear in certain
patterns along the edges of tectonic plates
o Volcanoes are openings in Earth’s surface, that, when active, spew out gases,
chunks of rock, and melted rock
o An earthquake is a sudden, ground-shaking release of built-up energy at or
under Earth’s surface.
EVIDENCE for PLATE TECTONIC THEORY
• A long mountain range running north to south down the length of
the Atlantic Ocean was discovered = Mid-Atlantic Ridge
EVIDENCE for PLATE TECTONIC THEORY
• Determination of the age of rocks of the ocean floor revealed that
the youngest rocks were found closest to the ridge and the layer of
ocean sediment—the small particles of silt and organic debris
deposited on the ocean floor — became thicker the farther it was
from the ridge.
EVIDENCE for PLATE TECTONIC THEORY
• Determination of the age of rocks of the ocean floor revealed that
the youngest rocks were found closest to the ridge and the layer of
ocean sediment—the small particles of silt and organic debris
deposited on the ocean floor — became thicker the farther it was
from the ridge.
EVIDENCE for PLATE TECTONIC THEORY
• Determination of the age of rocks of the ocean floor revealed that
the youngest rocks were found closest to the ridge and the layer of
ocean sediment—the small particles of silt and organic debris
deposited on the ocean floor — became thicker the farther it was
from the ridge.
EVIDENCE for PLATE TECTONIC THEORY
• Paleomagnetism shows that iron-based rocks along the ridges are
magnetically striped with reversing magnetic fields.
Hess’ Explanation
• Hess tied together all the data on the age of rocks, sediment
thickness and magnetic striping . He suggested that:
o Magma (melted rock) rises to the Earth’s surface
o It cools down and hardens when it breaks through Earth’s surface forming new
sea floor = SPREADING RIDGE
o As more magma rises to the surface, it pushes the hardened material aside =
FLOOR SPREADING