EARTH SCIENCE PLATE TECTONICS 1.
divergent
Made by: Ariani Dimacali 2. convergent
Source: PPT of Sir Russel Bacani 3. transform
“PLATE TECTONICS” ⎯ all plates are interconnected
The theory of Plate Tectonics divergent boundary
⎯ attributes earthquakes, volcanoes, mountains ⎯ hot molten rock rises from the mantle rises to the
formation, and related geophysical phenomena surface
⎯ how crust was formed, moved, and changed ⎯ new crust is formed - constructive boundaries
⎯ origin of volcanoes, earthquakes, and mountains ⎯ ocean can be formed
⎯ less occurrence of earthquakes weather would
be more uniform, landforms would be older convergent boundary
continental drift theory ⎯ one plate is being pushed under another-
subduction
⎯ large landmasses seemed to fit together ⎯ destructive boundaries
⎯ continents were moving or drifting away slowly ⎯ subduction zones - mountains and volcanoes
⎯ fit of continental shorelines, similar geologic ⎯ severe earthquakes - tern do pressure and
features, shifting of climate belts friction caused by the collision
⎯ southern hemisphere - rocks and fossils; ⎯ it surges upwards to produce volcanoes
Gondwana sequence ⎯ oceanic plates with continental plate
⎯ one giant landmass – Pangea ⎯ volcanic arc is formed
⎯ parts of Pangea drifted to their present positions ⎯ oceanic plate with oceanic plate
- continental drift theory ⎯ undersea volcano
⎯ scientists - solid mass; no evidences ⎯ continental played with continental plate
⎯ paleomagnetism, convection currents, seafloor ⎯ mountain range
spreading
⎯ conversation currents - movement of materials transform boundary
caused by the difference in their temperature
⎯ fault - deep crack in Earth’s crust
⎯ 1 to 5 per year - 50 million years
⎯ opposite direction - rocks are crushed
⎯ South Atlantic Ocean and Indian Ocean; Pacific
Ocean ⎯ Fault valley or undersea canyon
⎯ Australia – Asia ⎯ Earthquake - cracks and breaks at the boundary
⎯ Africa - Mediterranean Sea “ALFRED LOTHAR WEGENER (1880 - 1930)”
seafloor spreading ⎯ Wegener was a German meteorologist,
geophysicist and polar researcher. In 1915 he
⎯ better observations of the ocean floor
published ‘The Origin of Continents and Oceans’,
⎯ underwater mountain - ‘mid-ocean ridge’ - ‘rift which outlined his theory of Continental Drift.
valley’
⎯ Wegener was a member of four expeditions to
⎯ ocean crust spreads away from the mid-ocean Greenland. In 1930 he visited Greenland for the
ridges last time, where he died shortly after his fiftieth
⎯ volcanic and earthquakes activities birthday.
plate boundaries ⎯ Wegener’s theory of Continental Drift was met
with skepticism by many scientists. Although he
⎯ movement of Earth’s tectonics plates - forming had a lot of evidence to support the theory, he
different plate boundaries could not explain how the plates moved. It would
⎯ Asthenosphere - plates lie atop layer of partially be almost half a century before this problem
molten rock began to be solved.
⎯ continents or ocean ⎯ Wegener supported his Continental Drift idea
⎯ these types of plate boundaries - produces with 5 lines of evidence:
energies and tremors that change Earth’s surface
1. Jigsaw Fit ➢ Cynognathus is an extinct mammal-like
➢ The similarity in outline of the coastlines of reptile. The name literally means ‘dog jaw’.
eastern South America and West Africa
Cynognathus was as large as a modern
had been noted for some time. The best fit
is obtained if the coastlines are matched at wolf and lived during the early to mid-
a depth of 1,000 meters below current sea Triassic period (250 to 240 million years
level. ago). It is found as fossils only in South
➢ Any areas where there are gaps or Africa and South America.
overlaps may be explained by:
• Coastal erosion since continental 4. Geological Fit
separation ➢ When the geology of eastern South
• Coastal deposition since continental America and West Africa was mapped, it
separation revealed that ancient rock outcrops
• Rises in sea level (eustatic change) (cratons) over 2,000 million years old
since continental separation were continuous from one continent to the
• Changes in land level (isostatic other.
change) since continental separation 5. Glacial Deposits
2. Tectonic Fit
➢ Today, glacial deposits formed during the
➢ Fragments of an old fold mountain belt Permo-Carboniferous glaciation (about
between 450 and 400 million years 300 million years ago) are found in
ago are found on widely separated Antarctica, Africa, South America, India
continents today. Pieces of the Caledonian and Australia. If the continents haven’t
fold mountain belt are found in Greenland, moved, then this would suggest an ice
Canada, Ireland, England, Scotland and sheet extended from the south pole to the
Scandinavia. When these land masses are equator at this time - which is unlikely as
re-assembled the mountain belt forms a the UK at this time was also close to the
continuous linear feature. equator and has extensive coal and
3. Fossil Evidence limestone deposits. If the continents of the
➢ There are many examples of fossils found southern hemisphere are re-assembled
on separate continents and nowhere else, near the south pole, then the Permo-
suggesting the continents were once joined. Carboniferous ice sheet assumes a much
If Continental Drift had not occurred, the more reasonable size.
alternative explanations would be: ➢ More evidence comes from glacial
• The species evolved independently striations – scratches on the bedrock
on separate continents – made by blocks of rock embedded in the
contradicting Darwin’s theory of ice as the glacier moves. These show the
evolution. direction of the glacier, and suggest the
• They swam to the other continent/s in ice flowed from a single central point.
breeding pairs to establish a second
population.
➢ Remains of Mesosaurus, a freshwater
crocodile-like reptile that lived during the
early Permian (between 286 and 258
million years ago), are found solely in
Southern Africa and Eastern South America.
It would have been physiologically
impossible for Mesosaurus to swim between
the continents. This suggests that South
America and Africa were joined during the
Early Permian.
