In this lecture you will:
|The Earth is not stable and unchanging. There is a lot of movement. The major movement is called "plate tectonics". Earthquakes and volcanoes mostly occur at the boundaries of these plates as seen on right.|
The plates of the continents "fit" together.
|2. MAGNETIC ORIENTATION at sites
of newly formed crust
- the crust spreading alternates north
|3. Continuation of geological features
between Africa and south America.
|4. Continuation of fossil records|
|1. Sea floor spreading
.. sea floor is thinner, more likely to
occur where crust is thin rather than thick click on the link to see the
ages connected with the ages.
|2. Crust spreading at rifts
– Rift valley in Africa and Iceland where
new material is oozing up out of the mantle and spreading. These are known
as divergent boundaries
"The continent of Africa is thought to
have been split by a series of rift valleys in various states of development.
Those in East Africa are still in thick crust. Those in West Africa are
associated with thick oil-bearing sediments. In the Red Sea area the rifting
has gone so far as to form a narrow ocean. In the south-east Madagascar
has been completely separated from Africa by rifting. "
|3. Plate interactions||
http://www.ucmp.berkeley.edu/geology/tectonics.html has excellent animations of various eras... and includes a brief history of the eras and links to very interesting information
– plate tectonics is the driving force of continents drift. Without plate tectonics continental drift was an hypothesis with no explanation of a driving force.
-- Pangea began to break up about 200 million years ago.
– the boundary between the Triassic and Jurassic periods,
– middle of the age of dinosaurs.
-- 65 million years ago, end of the Cretaceous period and the age of dinosaurs,
North America was still attached to Europe and Australia to Antarctica.
– since then the continents have moved to their present positions, North and South America became attached, and India bumped into Asia.
– During the next 50 million years or so the Atlantic Ocean will get larger and the
Pacific Ocean smaller.
-- Baja and southwestern California will move north and split from the continent along the line of the San Andreas fault.
-- Eastern Africa will split away from Africa along the Great Rift Valley.
– Australia and New Guinea will move north. And India will move east.
|1. Two thin (ocean) plates
– 1 side dives under the other and melts
|2. one thin (ocean) and one thick (continent)
|3. two thick plates meet
– the Himalayan Mountains
|4. plates slide past each other going in different directions||
Discuss the theory of continental drift.
How is plate tectonics related to the drift theory?
How are continents and crustal plates different?
Why are some, but not entirely the same kind of dinosaur fossils
found in the major continents?
Why are there no mammals native to Australia?
Is the age of continental drift over? Explain why or why not.
Was Antarctica once in the tropics?
Why does the crust of Earth "ride" or float on top of the mantle?
Which part of the Earth's structure is responsible for its
Which part of the Earth's structure is essential for plate
tectonics to occur? Why do the plates move?
Is the crust the same depth everywhere
What supporting scientific evidence is there for plate tectonics?
Give two different lines of evidence.
What does the mid-Atlantic Ridge contribute to the theory of